High Temp/High Pressure Readings in Boiler


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Old 11-18-14, 08:04 PM
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High Temp/High Pressure Readings in Boiler

We recently had a fill valve replaced (hot water boiler had low pressure). As the old valve was a dual fill/relief valve, we also had a new pressure relief valve installed on the boiler.

However, subsequently we have had several occasions where

1) the safety button on the furnace kicks off the burner. The temperature gauge on the furnace outlet never reads above 100F, but the inlet pipe is clearly quite hot to the touch. (High limit is set to 180F, low limit for the pump to turn on is 100F, we turned it down from 120F)

2) the pressure gauge on the furnace outlet reads as high as 36psi, but with no spill from the pressure relief valve. Can we trust the relief valve would have spilled if the pressure really was this high and this is just a faulty gauge reading?

We monitored by video tape and observed this pattern on several occasions.

As the cold pressure was about 18psi, we bled some water off through the expansion tank drain valve. Subsequently we heard the fill valve open (set to fill below 12psi). Cold pressure subsequently reads 14psi.

After several subsequent hours of operation, button tripped off the burner once again (high temperature?)

Pressure hasn’t gone above 26psi.

We don't want the boiler going out on us in the winter but more importantly we want to make sure we aren't unsafe.

Our furnace is an old Pennco hot water boiler 96,000 BTU with an old style (non-bladder) expansion tank and big red Bell & Gosset 1/2 HP Pump, some baseboard and some upright radiators.

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Old 11-18-14, 10:03 PM
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the safety button on the furnace kicks off the burner.
Can you show us the location of this safety button? (closeup of the control)

The temperature gauge on the furnace outlet never reads above 100F, but the inlet pipe is clearly quite hot to the touch.
You would be able to hold your hand on a pipe with 100F water in it for quite a long time. Above 130F and you would only be able to hold for a second. This is called the 'ouch test'.

Can we trust the relief valve would have spilled if the pressure really was this high and this is just a faulty gauge reading?
I would think so. Brand new relief valve, and as things go, relief valves are pretty darn reliable. They HAVE to be.

I think the first thing to do is verify your PRESSURE gauge.

Read this:

http://www.doityourself.com/forum/bo...ure-gauge.html
 
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Old 11-19-14, 12:45 AM
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Thanks for the reply. Here’s some more photos.

Hi/Lo settings above circulating pump are at 180/100.

Pilot safety switch is what we are referring to. (Pilot has never gone out, but safety switch is occasionally tripping; almost always corresponds to when temp gauge nudges above the 100 mark and when pressure gets above 30 mark, although we don't really understand why this would be the case. Unless when the thermostat is satisfied and the burner goes off the probe is not 'reading' the pilot?).

Alternatively, the limit switch on the pipe set at 180 is also wired into the pilot safety switch. Is it correct to think this would shut off the gas if the temp gets too high?

After resetting pilot button and 8 hours of otherwise apparently normal operation temp on gauge reads right at 100F (starts at 0 and slowly creeps to there and never above). Pressure just a hair under 30 with relief valve spillage.

Ouch test: Can grab the pipe, but only second or so.

Will get a gauge in a.m. and run pressure gauge test.

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Old 11-19-14, 05:52 AM
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The "How to verify a boiler pressure gauge" thread is great, thanks!

Local plumbing supply has the 0-30 psi gauge and we will have it in our hands shortly.

When we go to hook the 0-30 psi gauge up to the boiler or expansion tank drain valve, we were wondering if we should look at the pressure when the system is hot? cold? pump running? all of the above? can we safely leave it hooked up for awhile as we monitor the situation?

Update: It got down to 14F outside last night and the furnace ran continuously without tripping the red safety button tripping; temperature read around 100F on the outlet pipe (but you can't keep your hand on it, ouch!) and pressure stayed just a hair above 30psi but the pressure relief valve never spilled any water.
 
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Old 11-21-14, 06:51 PM
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Just a quick update to our last posting about observing occasions where boiler gauge pressure was reading as high as 36 (with no spill from the relief valve) and, usually associated, occasions where the pilot safety was tripping off without the pilot going off.

In the last two days we haven’t observed any pressure readings on the old boiler gauge above 24, nor has the pilot safety tripped off the burner (we’ve been running continuous time lapse video on the gauge).

We’re unsure whether to attribute the current appearance of normal functioning to less demand/call from the thermostat due to warmer weather conditions (the two days prior had been in the teens but the past two days being in the high 20’s low 30’s) OR due to our lowering our cold pressure a bit by bleeding off some water through the expansion tank valve (then letting the fill valve reset) and lowering our circulating pump temp from 125 to 100 (although now the pump circulates pretty much all the time). At any rate we’re not really convinced yet that we’ve solved the problem until we get another cold snap in the teens.

Meanwhile, we visited our ‘real’ plumbing supply store for a 0-30psi gauge and made an improvised pressure gauge as suggested (thanks for the link) just to see how it corresponds to the actual gauge and took a few preliminary readings. (We attached the improvised gauge to our expansion tank valve.)

Boiler Gauge = 20 PSI, Improvised gauge = 18.5 PSI
Boiler Gauge = 22 PSI, Improvised gauge = 20.5 PSI

So not that far off, at 20-22, but we don’t know how that relationship would hold at the higher end, as we were previously seeing occasionally up to 36 on our old gauge with no spill from the pressure relief valve (we can’t imagine we wouldn’t have seen the relief valve activate if the pressure really were this high, right?)

Any other thoughts about this?

And, because we had a coupon at another unnamed franchise, we also brought home a free tarp along with an infrared noncontact thermometer (range -27 – 482F) and took some readings of the pipe just above the old gauge at the same time we did the above PSI readings. (Our temp gauge needle seems to go to and stick at 100F and never go beyond it, but the ouch test was previously on the 1-2 second ‘ouchy’ side).

Boiler Gauge = 75 degrees, Improvised gauge = 119 to 122. “Ouch” test 4-6 secondish.

What is the normal/expected temperature range in a properly operating boiler? And what temperature is ‘too high’.

Also, what should the setting for the circulating pump be set at ideally? We’ve had one service person place it at 125 and another at 100, each with different rationale about efficiency of heating in terms of cost of heating vs. quality of heating.)

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Old 11-22-14, 09:31 AM
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not that far off, at 20-22, but we don’t know how that relationship would hold at the higher end
It's pretty common that the difference is non-linear and that the higher the pressure, the greater the error.

(we can’t imagine we wouldn’t have seen the relief valve activate if the pressure really were this high, right?)
Right...

brought home a free tarp along with an infrared noncontact thermometer (range -27 – 482F) and took some readings of the pipe
We just had a Grand Opening here in town and I got the tarp, my wife got the magnetic parts holder, with 'no purchase necessary'. Used to have to drive 25 miles, glad they're here now. Cheap stuff, but most of it is good enough quality for the occasional non-professional use.

What you should know about the IR thermometers is that they aren't always terribly accurate. This is due to the fact that different materials 'emit' IR at different rates.

From Omega website:

What is emissivity, and how is it related to infrared temperature measurements?

Emissivity is defined as the ratio of the energy radiated by an object at a given temperature to the energy emitted by a perfect radiator, or blackbody, at the same temperature. The emissivity of a blackbody is 1.0. All values of emissivity fall between 0.0 and 1.0. SOME infrared thermometers have the ability to compensate for different emissivity values, for different materials. In general, the higher the emissivity of an object, the easier it is to obtain an accurate temperature measurement using infrared. Objects with very low emissivities (below 0.2) can be difficult applications. Some polished, shiny metallic surfaces, such as aluminum, are so reflective in the infrared that accurate temperature measurements are not always possible.
And here a table of values of many materials.

Emissitivity of Common Materials

You can see that most copper won't give a very accurate reading, while heavily oxidized iron will be pretty good.

What is the normal/expected temperature range in a properly operating boiler? And what temperature is ‘too high’.
There are many 'it depends' in this type of discussion.

A HIGH LIMIT of 180F is generally accepted as a 'standard'.

This is the temperature that most radiator specs state the BTUH output of the products.

A designer should know the heat loss of the home on a room by room basis and install the proper amount of radiation in each room to meet the heat loss ON THE COLDEST DAY with 180F water.

Any days that are warmer than that coldest day (called the DESIGN TEMPERATURE) will require cooler water to meet the heat loss.

The direct answer to your question then is; The normal/expected temperature range depends on the outdoor temperature, the heat loss of the home, the amount of installed radiation, and to some degree the BTUH output of the boiler.

If your home requires 190F or 200F water to heat on the coldest day it means that there is not enough installed radiation in the home.

In my opinion, anything over 180F is 'too high', but some cases do require higher temperatures.

I would put a brick wall at 200F. If the home needed 200F or higher, more radiation should be installed.

Also, what should the setting for the circulating pump be set at ideally? We’ve had one service person place it at 125 and another at 100, each with different rationale about efficiency of heating in terms of cost of heating vs. quality of heating.)
More highly debatable questions... and lot's of differing opinions.

Most modern boilers run the circulator without any temperature control at all. As soon as there's a call for heat the pump(s) start.

These modern systems generally use fin tube baseboard which heats up quickly and the water returning to the boiler heats up quickly, allowing the boiler itself to run in a temperature range that it 'likes', which means hot enough so that the flue gases don't condense inside the boiler and cause excessive corrosion (because flue gas condensate is acidic and corrosive).

Systems with high mass radiators such as standing cast iron, and a large water volume require some 'protection' for the boiler, allowing it to heat up faster to avoid condensation issues. This is one of the reasons for holding off the circulators if the boiler isn't hot enough.

Your home has a mix of "some baseboard and some upright radiators". You don't specify if the baseboard is copper tube with fins, or cast iron. Which do you have?

It's generally not advisable to mix fin tube baseboard with cast iron as this can lead to uneven heating in the home. Since fin tube baseboard heats quickly, and cools just as quickly, and cast iron heats slowly and cools slowly, you can see how there could be imbalances from room to room.

I would say that 100F is too low in my opinion. I would suggest 120F without knowing the exact nature of the heating patterns in the home.
 
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Old 11-22-14, 09:35 AM
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Getting back on the subject track...

Your burner cutting out and needing reset should not have anything at all to do with boiler temperature or pressure. That BASO control is monitoring the THERMOCOUPLE that proves the pilot flame is lit. If the pilot goes out and the thermocouple cools, that control should 'trip'.

You could have a sketchy thermocouple, or the connection between the thermocouple and where it screws into the Baso control may be dirty or corroded. It's an ELECTRICAL connection and needs to be clean and tight.
 
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Old 11-22-14, 09:51 AM
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Pressure excursions above normal are caused by a couple things...

1. Expansion tank 'waterlogged'.

2. Pressure reducing (fill) valve leaking through internally.

3. If the boiler has an internal coil to produce domestic hot water (I don't think yours does?) that coil could have an internal leak and over pressurize the system.

I suspect that your expansion tank should be COMPLETELY drained as a next step.

That's an awesome tank by the way... love the rivets! Very Titanic! (I would probably stencil "TITANIC" on it myself as a joke... I've been know to do weird 5h1t, for example...)


Sadly, that steel that artwork is on is probably part of a new Toyota or LG refrigerator by now.



The tank may not be piped properly for starters. (it may be ok though, I just can't see it in the pic)

The pipe from the boiler must go UPHILL all the way from the boiler to the tank. It has to be this way so that any air coming up the pipe back to the tank where it belongs can make it's way there.

The picture is sorta dark and I can't see the piping to the boiler. The copper pipe with the ball valve is the water supply, isn't it?

Can you show me a clearer, brighter pic of the piping from the tank to the boiler please?

Is there a SHUTOFF valve on the line from the boiler to the tank?

After I find this out I'll detail what you need to do to COMPLETELY drain that tank.
 
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Old 11-30-14, 03:13 PM
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Thanks for the detailed response. This is really helping our understanding of this beast in the basement and our ability to troubleshoot in a more systematic, stepwise fashion. Now we’ve kind of gotten invested in the puzzle and are considering the possibility that the biggest thing wrong with our boiler may be our understanding of how to maintain it and respond to changes in functioning (although we are still doing our need-a-replacement-boiler homework just-in-case).

Still waiting for our next cold snap to get some pressure readings with the improvised gauge to see what is going on with those higher readings we observed during the last cold snap (teens-20’s). As for the infrared thermometer, our biggest disappointment was learning that we would not be able to use it on the Thanksgiving turkey. We of course still pointed it at it, as well as at armpits, and the refrigerator, just because we could and the pie was all gone. As for using it on the boiler, we are taking concurrent readings on each of the 2 large black (cast) outlet pipes from the same location each time, close, but no contact. If not accurate, the approximations are possibly more reliably informative than either our old gauge (which either sits at <60 or tops out at 100 and the needle won’t go further), or our ‘ouch’ tests. Just an update on the correlation between the old and improvised pressure gauge.

Meanwhile, it appears that the boiler knows we are watching it now and feels we have nothing else to do until it gets really cold again so it is presenting us with new questions. It seems that to keep the pump from circulating all the time, we have to keep making adjustments to the low setting on one of the 2 devices (aquastats?) mounted on one of 2 the outlet pipes. Presently we think it turns on when we close the refrigerator, and off when we go up the stairs. Not really but it does seem that kind of random to us; the gianormous mercury switch inside the cover (we peeked) seems to bloop all or nothing to left or right when we try to finesse any adjustments either way. We will post those questions and some photos on a separate thread.

As regards the current thread:

The 1.5 PSI difference between the old gauge readings and improvised gauge seems to hold for readings between 13.5 and 25 on the old gauge (maybe just slightly less difference at the lower end), but we don’t know what the relationship is for the higher pressures we previously observed.

Attached, some new photos showing more detail of the boiler piping and some photos with greater detail around the expansion tank and all the connections between.

Also below some info about 1) the boiler history/modifications, 2) our radiators, 3) the expansion tank, and 4) ‘what we’ve fiddled with so far’.

Some history we’ve learned/pieced together over time about our boiler: The boiler is a Pennco, serial 13437; size 323 WA; Sq.ft radiation 512; Input BTU/hr 96,000, made by Pennsylvania Furnace and Iron Company Warren, Pa.

You can see from the photos it originally had two returns on the bottom and two outflows near the top of the boiler and, as we understand it, originally convection/gravity-circulated without a pump. At some point a circulating pump was added on the return on the right of the unit and the return piping on the left was reconfigured to join the return on the right (you can see the copper piping running left to right above the boiler in the photos). (Our waterlines also run behind/above the boiler; the valves you see dangling down there belong to them, not the boiler)

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We are unsure of the boiler’s age, but it seems we are quite possibly contemporaries. We believe that it considerably predates the single story, single room addition that we think was completed some time in the 70’s, given the evident modifications to the piping in order to loop in the baseboard radiators that were placed in the addition. (At that time we also think that one of the original upright cast iron column radiators – or possibly a fireplace- in the adjacent first floor dining room was replaced with a baseboard radiator as well.)

So, as far as radiation goes, there are cast iron Base-Ray baseboard radiators in two rooms on the first floor; the remainder of the house has upright, cast iron column radiators, some 2 column/8” wide and some 3 column/10”wide and there is one conduction radiator in an upstairs bath. The house is 2 story brick, 1625 sq. foot, with wonderfully drafty original windows (many do however face south and east, with considerable effect when the sun is up). Qualitatively, heating in all rooms has been comfortable for us the several winter’s we’ve been here so far, although the addition is always clearly cooler. We experience Western Pa. winters. We usually don’t run the thermostat over 68; so we don’t know how it would perform if someone less warm-blooded cranked it up to 72.

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Now, about that expansion tank. That’s another story. You can see in the photo the nice bright expansion tank drain spigot (with our improvised gauge attached). You can also see in that photo the disastrous looking isolation valve between the expansion tank and the system with the ancient remains of a rag wrapped around it. Pretty clearly at one time it leaked. We’re terrified to touch that. Had we not been so ignorant about what it’s purpose/function was in relation to draining the expansion tank, we would have asked the HVAC guy to replace it when he drained the system to replace the fill valve. (To our credit we did in fact point to it and ask vaguely about replacing it, to which he replied something in the way of ‘if it’s not leaking probably not doing any harm.’) Sooo…although we had the new isolation valve between the boiler and the new fill valve shut when we recently drained a bucket of water off through the expansion tank, we’re now guessing that not closing that horrible looking valve between the expansion tank and the boiler means that the bucket of water we drained out through the expansion tank drain didn’t really ‘empty’ anything out of the expansion tank or introduce much if any air into it. (The expansion tank is, by the way, mounted between the joists and is higher than all the other piping in the basement; the pipe from the system to the expansion tank appears to us to be on about the same level) (that last photo of the cruddy valve is a view from the back side)

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Our rationale for draining off some water was:

1) To test the possibility that the corrosion around that valve between the system and the expansion tank was clogged, preventing the boiler from relieving pressure to the expansion tank, leading to the occasions during the last cold snap where we observed higher pressures. Since the fill valve opened and returned some water to the system after we reopened the isolator valve between the fill valve and the system, we think we ruled that out. Yes?

2) We had the vague notion that doing so might also introduce some air into the expansion tank. Since we didn’t attempt to shut off that corroded looking valve between the system and the expansion tank however; we are now gathering that was probably an erroneous notion. (Note that the expansion tank sounds empty to us when tapping on it, but maybe that’s not exactly a good test).

3) To reduce the cold pressure a bit since it was a good bit above 12 (we seem to recall it was 18) right after the service person installed the new fill valve and recharged the system, even prior to resuming boiler operation. Our thought was that maybe the higher pressure spikes we saw subsequent to the fill valve replacement may have been due to an overfilled system and the fact that we did a really excellent job of bleeding the radiators (which we have been less than diligent about in the past). After we took some water off cold pressure did refill and settle lower, at about 14 (on the old gauge, prior to building a test gauge)

Our highest observed pressure after that, as per our last post, has been 31 (this was prior to improvising a gauge to verify our readings) but it remains to be seen if this was due to our efforts or a slight warm up in the outside weather (teens to 20’s),. Since making the gauge, our highest verified pressure has been 23.5 (old gauge was reading 25), but again we’ve still been having warmer temps outside than when we saw the pressure spikes. So….we’re watching and waiting. (By the way, at the same time, the infrared temp on the outflow just above the old gauge was 133)

We’re mulling over the information about the mix of radiators. We’re now pondering if perhaps we were somewhat chronically running with lower than optimal boiler pressures prior to having the fill valve replaced and that the lower pressure was more or less ‘masking’ pressure swings in the system? We haven’t always been great at bleeding the radiators, and only discovered our recent fill valve problem when we bled them and pressure dropped to zilch.

So while we were mussing about, since we really couldn’t tell what the status of our expansion tank was or if removing a bucket of water has changed it’s status at all, we also took advantage of the weather while the boiler was off/cool and ‘undid’ a bit of our wonderful job of bleeding the radiators by reintroducing a bit if air into our tallest radiator on the second floor while we drained off a bit of water, then verified system refill to a cold pressure of 12 on our improvised gauge (about 13.5 on our old gauge). This might be a misguided notion, but if we can hear you laughing from here, it’s easy to ‘undo’.
 
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Old 11-30-14, 04:47 PM
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Howz, I gotta tellya, I like your style of writing!

I'm going to re-read the whole thing later with comments, but one thing I wanted to mention now... that old gauge might just be more accurate than you think.

It appears to be maybe 3-4 feet higher in altitude, is that a good approximation?

For ever foot of altitude a gauge will read 0.432 PSI LESS.

So, the 3-4' higher gauge would read 1.3 to 1.7 PSI less... and isn't that about what you are seeing?
 
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Old 11-30-14, 04:49 PM
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Looks like Mr. Snively and his plumbing company got to your expansion tank before I could!

If you are in western PA, northwest of Pittsburgh, it may be that the Snively family is still in the plumbing business in Southington, Ahia...

http://www.ehardhat.com/directory/pl...nively/1506240
 
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Old 11-30-14, 09:07 PM
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the gianormous mercury switch inside the cover (we peeked) seems to bloop all or nothing to left or right when we try to finesse any adjustments either way. We will post those questions and some photos on a separate thread.
I posted in the other thread, but want to add here... If you are turning the adjustment until the control 'changes state', you won't ever get it adjusted... because you are in effect going past the differential.

Just slightly adjust it up or down and wait to see what happens. I would probably set that circ control for 120F or so and leave it be.

piping in order to loop in the baseboard radiators that were placed in the addition.
Are the radiators in the addition also the BaseRay cast iron type? Or are they copper tube aluminum fin (fin tube) type?

----------------

I presume from the way it appears to be piped that the thing at the upper left on the boiler in the first pic of the last post is a pressure relief valve. Can you get a closer shot of that please?

If that's not a pressure relief valve, look around for one... you MUST have one! I want to see it.
 
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Old 11-30-14, 09:18 PM
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‘if it’s not leaking probably not doing any harm.’
It probably IS still leaking, maybe better stated as 'weeping'.

If the pipes are hot/warm, the water may evaporate before you see it, leaving only the mineral deposits you see behind.

That valve appears to have been leaking from the 'gland seal' around the stem.

As long as the valve is not completely corroded away, you may be able to repair it fairly easily.

I'll let Rich Trethewy explain:

What's Packing? | Plumbing | Plumbing, HVAC & Electrical | This Old House

Wire brush the corrosion off, see if you can loosen the gland nut (Rich calls it a 'bonnet').

Take some fine emery paper and give the stem itself a 'shoe shine'.

If you can loosen the gland nut, go to HD or Lowes and get some GRAPHITE PACKING

DANCO 3/32 in. x 24 in. Graphite Valve Stem Packing-80793 at The Home Depot

Slide the gland nut up the stem, wrap a few turns around the stem and tighten the gland nut again. That nut only needs to be tight enough to squeeze the packing around the stem, so go easy. If it weeps, tighten a little more.

After that, give it a try... see if it will close.

More tomorrow, gotta git.
 
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Old 11-30-14, 10:15 PM
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Pressure relief valve: yes that’s it and it was installed in September when the fill valve was replaced (and an old style pressure relief valve that was adjacent/built into the old fill valve was removed.) Reads 30, 510,000 BTU

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Autostat: yes, 120 is where we reset it earlier today.

Baseboard radiators: yes, all the baseboard rads are Base-Ray, cast iron. All are in the single story addition, with the exception of one that is in the adjacent dining room (which also happens to be one of two rooms closest to the thermostat). All other rads are the big cast iron column rads.

Old gauge/improvised gauge: Height difference is about 18”. The bottom of the expansion tank is just above the boiler pipes.

Snively Plumbing: Going to have to send that fella a photo of the expansion tank and see if rings any ancestral bells.

Corroded expansion tank valve: methinks that the degree of corrosion on this valve is not fully appreciated. More horrifying photos attached. PS - the temperature of the pipe on either side of this corroded valve has never been more than lukewarm to the touch.

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Old 12-01-14, 03:46 PM
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mulling over the information about the mix of radiators.
As long as everything is cast iron and not a mix of CI and fin tube, you should be OK.

reintroducing a bit if air into our tallest radiator on the second floor while we drained off a bit of water, then verified system refill to a cold pressure of 12 on our improvised gauge (about 13.5 on our old gauge). This might be a misguided notion, but if we can hear you laughing from here, it’s easy to ‘undo’.
Not laughing. You need some air cushion to keep the pressure under control and heat in the home, so as a temporary 'fix', it's not laughable at all... at least not to me!

Old gauge/improvised gauge: Height difference is about 18”. The bottom of the expansion tank is just above the boiler pipes.
OK, so expect the improv gauge to read just under 1 PSI lower then. In other words, that old gauge is still pretty dang close! Close enough for boiler work! The temp gauge on the other hand...

You should be getting pretty good readings off the cast iron fittings with your IR 'gun'.

Your relief valve is fine, thanks for clarifying.

Back to the expansion tank:

While the way it's piped may not be optimal for a (now) pumped system, it's not really all that bad. When it was gravity, it was probably fine, and the owners were used to bleeding the rads, I'm sure.

IDEALLY, there would be an 'air scoop' installed in the main flow path, and this scoop would have a port on top of it to which the expansion tank connected. In this way any air that was caught by the scoop would travel back up the pipe to the tank, where it belonged.

This really can't happen with the way your tank is currently piped, the air will just scoot on past that tee/elbow fitting. You will probably still have to bleed the rads yearly, and probably have to drain that expansion tank every other / third year. If you can live with that, there's no reason to change anything.

But you do need to do something with that shutoff valve. Unless you let the pressure out of the boiler you can't properly drain the tank.

Until I saw this picture:



I was like... "that's not so bad, I've seen worse that still worked" ...

What I see here is a bit of the casting broken out the bottom of the valve, and it appears that the pipe on the left is barely threaded into that valve at all. I'm really surprised it's not spraying all over the place! There should be approximately 7-8 threads into the valve and that would leave maybe 2-3 outside, like it appears on the other side.
 
  #16  
Old 12-01-14, 03:51 PM
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Do you by chance own a small air compressor that you can adapt a fitting onto the tank drain valve?

You don't want/need a monster compressor, even a tire inflator will work.
 
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Old 12-01-14, 04:32 PM
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Autostat: yes, 120 is where we reset it earlier today.
Please see my revised recommendation for the temp setting of the circulator control.

I'm now at 140F MINIMUM.

I'd like you to run with this setting and measure the temperature of the return water back to the boiler for a full boiler heat call cycle.

Can you do this and perhaps log the temp once a minute? Tedious I know, but I don't want you trashing your boiler because it's running too cool.

I've also posted a piping diagram in the other thread.

http://www.doityourself.com/forum/bo...nctioning.html
 
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Old 12-08-14, 04:41 PM
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UPDATE:

Current temps outside continue to be mild (40’s-30’s with an occasional dip into high 28 or so).

Still no occasions where outside temps have dropped into the 20’s and teens again (which is when we experienced PSI as high as 36 –with no spill from new relief valve; and shutdown of electronic gas valve, presumably triggered by concurrently exceeding the high temperature limit.). Meanwhile...

HIGH/LOW LIMIT SETTINGS:

High limit autostat is set at 180 (as before)

Low limit autostat setting for circulating pump: reset, per suggestion, at 140, where it has been running the last several days. Closely observed several firing and circulating sequences and took multiple infrared readings throughout.

At 140 setting infrared check shows pump pretty consistently circulates on at 132-ish and off at 105-ish

(Set at 130, infrared check shows pump circulates on at 123-ish and off at 96-ish)

Don’t know to what degree the infrared reflects actual temp.

HIGHEST PSI:

No readings above 21PSI since weather has continued to stay in the mild range or since raising low limit to 140.

CORRESPONDENCE BETWEEN TEMPERATURE ON OLD GAUGE VS. INFRARED TEMPS:

Keeping in mind that deciding where the needle on the old gauge is depends on if you shift slightly where you are standing when you look at it….it seems like there’s a ballpark of 50 degrees difference between gauges and infrared.

old gauge vs. infrared:

60 = about 105; 65 = about 112; 70 = about 119; 80 = about 126, 85 = about 134.

(Video shows us max of about 90 on the old gauge over the last several days; we weren’t there to take an infrared reading then, middle of the night.)

If that relationship holds, 100 on the old gauge is at least 150.

So when we were seeing shutdown when it nudged above 100 on the old gauge we very possibly were crossing past the high limit and tripping the electronic gas valve off.

EXPANSION TANK:

re: “Do you by chance own a small air compressor that you can adapt a fitting onto the tank drain valve?” We’re guessing that you are talking about attempting to directly pass air into the expansion tank via the expansion tank drain valve, (giving us a way around that funky corroded isolation valve) yes? We may have access to a little portable tank for inflating tires that we can borrow. If we’re barking up the right tree, more detailed guidance would be welcome.

BACK TO THAT CORRODED VALVE:

We poked around it a bit and we have serious doubts that we won’t end up with a leaking mess if we attempt to bugger with the packing nut further (but it looks prettier on the outside so that made us feel superficially better). We were thinking of just biting the bullet and having someone come and replace it. Is that likely to be a straightforward repair for someone competent or is this more like opening a whole new can of worms (you know, breaking adjacent pipes; stressing the boiler when refilling it with all that nice new cold water, or other some such nightmare). What should we know before we have someone do that?

(Expecting outside temps hi53/lo36 for several days next week; probably the last mild temperature spell for the winter; so we could have the boiler at cold temp beforehand). We attached additional photos that show the pipes and fittings adjacent to the valve, for a more ‘in context’ view. It looks all cast to us, but we dunno. (Maybe the little globe with the valve is brass????)

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Old 12-08-14, 05:16 PM
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We’re guessing that you are talking about attempting to directly pass air into the expansion tank via the expansion tank drain valve, (giving us a way around that funky corroded isolation valve) yes?
Exactly.

I was fooling with my drawing program this weekend and put this together. I've been wanting to do a 'sticky' for some time now that details how to drain those steel tanks... Still gonna do that, but for now, this drawing will have to do. Because you can't isolate your tank, the process is going to be a bit different than what's on the drawing. That sequence assumes an isolation valve between tank and boiler. Do NOT use the instructions in the graphic for this particular case.



I believe you can do a more or less 'opposite' process.

First, using dimensions of the tank, estimate how much water would fill that tank. It's probably a pretty good bet that it's almost full now with very little to no air up top.

You want to remove about a THIRD, but not more than HALF that water.

You don't want to take out too much water because when the boiler cools it may be possible that as the water contracts it will draw air into the system.

Make note of boiler gauge pressure before starting.

Introduce some air via B to increase pressure in system, watch boiler pressure gauge, stay below say 20-25 PSI.

Close B and Open A into a bucket until boiler gauge drops back down to starting point.

Keep track of how much water you remove.

Repeat as necessary until you've removed approximately a third of the water in the tank.

If you need to remove a little bit more in order to get the boiler pressure back to where you started, do so.

Sounds do-able?
 

Last edited by NJT; 12-09-14 at 06:42 AM.
  #20  
Old 12-08-14, 05:40 PM
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Is that likely to be a straightforward repair for someone competent or is this more like opening a whole new can of worms (you know, breaking adjacent pipes; stressing the boiler when refilling it with all that nice new cold water, or other some such nightmare). What should we know before we have someone do that?
A competent pipe fitter should have no issues with that.

Getting the nipples (which should probably be replaced with the valve) out of the tee fitting and the elbow would be the hardest part.

I believe that the reason the one nipple appears to be barely threaded into the valve is because the nipple is too short and couldn't be made to 'line up'.

A solution to that would be to replace the nipples with copper cut to correct length. Threaded adapters into the tee and the elbow, cut copper to correct length, assemble and solder.

A good pipe fitter with threading dies can cut and thread an exact length pipe though...

You'll allow boiler to cool so stressing the boiler is not an issue really.

What's going to be a PITA is when you put all that fresh water back in the system, you now have all that air that's going to need to be bled...

I would come up with a way to not have to drain the pipes completely.

For example:

Solder a threaded adapter and a pipe stub into one side of the new replacement valve, and a pipe stub into the other side of the valve, on the bench. CLOSE the valve.

Since you're replacing the cruddy valve anyway, I would CLOSE it also and break the union between the elbow and the tank loose. (did I mention that you will need to at least drain the tank?)

DEPRESSURIZE, but don't completely drain the system.

Loosen the old valve assembly at the tee fitting. Have the new one in hand ready to QUICKLY! screw in when you remove the old one.

Yes, some water will be lost... but if one has the proper rain gear and plastic sheets on the floor, cleanup shouldn't be too bad. To me, it's easier than draining and refilling the whole system!

When the new valve assembly is in place, complete the piping on the tank side of the valve.
 

Last edited by NJT; 12-09-14 at 06:45 AM.
  #21  
Old 12-08-14, 05:42 PM
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By the way... some guys have tools that use liquid nitrogen to FREEZE sections of pipe before disassembling. Don't know how risky that might be with that old pipe, but if you get a guy with the tool, he might use it.
 
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Old 12-08-14, 05:56 PM
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What about this approach. With the system cooled down, isolate the tank from the boiler. Open the tank drain valve until the tank is empty as proved by glub-glub-glub of air being sucked into the tank and water draining stopped. Shut the drain valve.

Open the valve between the tank and the boiler and open the isolation valve ahead of the automatic fill valve. When the tank fully refills and equilibrium pressure is reached, the tank will be about one-half full, cold (not one-third, which is ideal, but no special fittings or compressor required).

Why is it one-half full? The absolute pressure of the air cushion is initially atmospheric, say 14 psia. After the water is added, the gauge pressure will be, say, 14 psi, which is 28 psi absolute. For such conditions, air may be considered an ideal gas, P1 V1 = P2 V2.

A Bell & Gossett Airtrol tank fitting allows you to nail it right at one-third full, and is a bit simpler.
 
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Old 12-08-14, 05:59 PM
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With the system cooled down, isolate the tank from the boiler
Because he's afraid to turn that isolation valve, and I don't blame him.

This is a work around for a scary valve (that probably won't close anyway).
 
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Old 12-08-14, 06:05 PM
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some guys have tools that use liquid nitrogen to FREEZE sections of pipe before disassembling
The Navy called this a freeze seal. You fashion a cylindrical Styrofoam sleeve around the pipe and pour in liquid CO2 or nitrogen into a hole in the top of the sleeve. It never seemed to affect the pipe itself.
 
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Old 12-08-14, 07:30 PM
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About the possibility of putting too much air in.
One little point of head scratching we are having here is that although we assume that the higher pressures we saw during the last cold snap point to the possibility/likelihood that the expansion tank needs servicing/drained--we can't understand
1. why when we tap up and down it with a wrench it sounds convincingly hollow/empty.
2. when the temperature of the pipes, as they work from the boiler outlet pipe toward where they attach to the expansion tank they are always cool (or barely warm).
Example: if the temp of that horizontal section under the expansion tank is 110 at the side nearer the boiler, it immediately drops about 10 degrees at the junction where the waterline T is, then another 10 just at the cruddy valve, another 10 at the elbow up to the tank, and then another 10 at the tank itself. So at one end it's 110 and the point where it enters the tank it's 80.

During one of the nights in the teens when we were first seeing PSI of 36, the outlet pipes were pretty darn 'ouchy', while hand on ball at the bottom of that valve barely seemed to qualify as warm. (That's one of the reasons we initially pondered if the pipe around the isolation valve to the expansion tank was blocked. However, the fill valve activated after we drained water off through the expansion tank drain, this seems unlikely).
 
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Old 12-08-14, 08:01 PM
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First, thanks again for terrific help. Really.

Expansion tank is 30" long and 12" diameter....so about 14-15 gallon capacity?

Spiffy photo diagram by the way.
Don't have our heads totally around the pressure dynamics of this little maneuver but it's getting clearer. We looked at a nifty little thing on calculatorsoup that helps a little too.

Spoke to friend about loan of portable compressed air tank with a hose on it but no regulator.... Problematic? (Can we sort of 'regulate' the air pressure by only partially opening B?)
Got a million of those two way faucet adapters. Overzealous gardening.
 
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Old 12-08-14, 08:36 PM
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1. why when we tap up and down it with a wrench it sounds convincingly hollow/empty.
To tell anything from this you would need a 'reference' tank. One that you could fill and tap, then drain and tap, and hear the difference between the two. It's just not a valid test, water vibrates too.

2. when the temperature of the pipes, as they work from the boiler outlet pipe toward where they attach to the expansion tank they are always cool (or barely warm).
Which would make sense if the tank were nearly waterlogged because it shows that little, if any, hot water is pushing into the tank. Since air can be compressed, but water can not, if there is an air space in the tank to be compressed, as the water heats and expands it will push into the tank.

BUT, it's not a lot of hot water pushing in, at MOST a couple few gallons, and it goes in slowly so is able to cool as it slowly works it's way down the pipe.

That's one of the reasons we initially pondered if the pipe around the isolation valve to the expansion tank was blocked.
Further evidence... sure the pipe could be blocked, but no air in the tank would also prevent expansion of the hot water into the tank.
 
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Old 12-08-14, 08:49 PM
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about 14-15 gallon capacity?
Sounds about right.

Tank Volume Calculator

So if you took out 5-7 gallons you would be in good shape.

Don't have our heads totally around the pressure dynamics of this little maneuver
Main thing is that you need to get air into that tank. So say you start with the boiler at 15 PSI and pump air in until you are at say 25 PSI. Air goes to top of tank and stays there, while you drain pressure off bottom of tank as water. You are simply replacing some of the water volume with air volume.

portable compressed air tank with a hose on it but no regulator.... Problematic? (Can we sort of 'regulate' the air pressure by only partially opening B?)
Yes, you should be able to do that... you can use the boiler pressure gauge as indicator. You could even 'gang' two of the hose wye adapters and put your new gauge on one of the ports.

Remember that the air tank you use has to be large enough to replace about 5 gallons of water with air, and that the pressure in the portable tank has to be enough above the 15 or so PSI that you start with in the boiler. But if it's not large enough on a single charge you could always refill it.
 
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Old 12-08-14, 09:29 PM
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Which would make sense if the tank were nearly waterlogged because it shows that little, if any, hot water is pushing into the tank.
...

So it seems we can stop our superstitious tapping on it with a wrench and actually do something potentially more productive tomorrow.
 
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Old 12-08-14, 10:27 PM
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Just add air to the tank to bring the boiler pressure up to about 25 psi, turn off the air and then blow the water out either the tank drain OR the boiler drain, whichever is less messy. You might have to do it a couple of times. If you use the boiler drain it proves the connecting piping and valve are open.
 
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Old 12-09-14, 03:38 PM
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PUTTING AIR IN EXPANSION TANK WITHOUT HAVING/USING AN ISOLATION VALVE:

As far as difficulty factor (and considering our baseline plumbing experience is about as extensive as using a toilet plunger and tapping on the expansion tank with a wrench--with authority), accomplishing this task following the guidance here couldn’t have been more straightforward. The details in the mechanics of “how to” made it clear it was something we could do, and the information about “why to” allowed us to arrive at our own understanding that doing this made sense given the behavior of the boiler that we had observed. Some photos attached.

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And, as it turns out, a slow leak in the portable compressor (that the lender warned us about), was a bonus rather than a headache (as it was slow-leaking through the shut off valve into its own hose). Once we hooked it up to our little improvised adapter (also completely simple), we didn’t even need to open the compressor valve but just let it ‘slow leak’ into the expansion tank. Took longer (start to finish about an hour) but gave us a nice slow rise in system PSI to 22 (from baseline cold PSI of 14), at which point we closed the Y to the compressor and opened the Y to the hose until pressure dropped back to baseline of 14PSI. Repeated until we had displaced/drained 5.5 gallons of water and back at baseline of 14PSI.

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Re-engaged the thermostat, watched it run a few cycles without anything interesting to report by the time the thermostat was satisfied again. (We lucked out with outside temp reaching a higher than expected high of 44 today and lots of sun through the windows, so only lost 2 degrees from thermostat setting through the whole process even though we had the boiler off for about 3.5 hours. )

One change of note: Previously the run of connections/fittings between the boiler outlet to the expansion tank was always cool (or barely warmish) regardless of the temperature reading of the outlet pipe. Once we restarted the boiler, these pipes/connectors, warmed in tandem. So it would seem this is confirmation that the tank was waterlogged and now has some air cushion to expand into.

Finally, since the wrench wasn’t doing anything else and we are good at tapping on things with it, we tapped up and down the height of the expansion tank again just to see if it sounded ‘different’. Laughably, it turns out, to our subjective ears, it sounded ‘hollow’ before and it sounds ‘full’ now. So, we have been sufficiently schooled in our 180 degree misguided notions about that and will use the wrench for other things.

Will monitor and post back to see if this remedied the high PSI/temps and shutdowns we observed during the last cold snap (teens/low 20s).
 
  #32  
Old 12-09-14, 03:53 PM
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Awesome! I love a success story, especially one well written and illustrated too!
 
  #33  
Old 01-07-15, 06:05 PM
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Ignore, I somehow posted to the wrong thread.
 
  #34  
Old 01-07-15, 06:09 PM
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No, I was probably moving the posts and combining them into the other while you were posting...

Sorry bout dat!

Look for the newer thread, your posts are all there.
 
 

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