what would cause the high pressure valve to blow open ona V8 Burnham boiler

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Old 10-18-10, 05:16 AM
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what would cause the high pressure valve to blow open ona V8 Burnham boiler

I thought I had it fixed by replacing the expansion tank, looks now like the pressure is going up to 40 psi, it started out at around 30 with the new tank. I manually opened the autofill and thought it may have too much water and it was opening to get rid of the excess . Help
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Old 10-18-10, 12:46 PM
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40 PSI on a boiler gauge and the relief valve not opening generally indicates that the gauge is pooched... gauges 5uck.

Boiler COLD should be at 12-15 PSI, and with the expansion tank properly charged should not go much above 20 PSI when hot.

Your gauge being NG means that you don't really know what the pressure in the system is.

That's the first thing you need to know when troubleshooting problems such as these. So you need a way to verify your pressure gauge. Search this forum and you will find plenty of explanation how to do that.

Your problem sounds more likely to be that the pressure reducing valve (the one you calling 'autofill') is leaking through.
 
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Old 10-18-10, 04:22 PM
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v8 boiler

The pressure relief valve opened when the tank pressure was around 40PSI, I checked the expansion tank and it was full of water. Changed the tank and the pressure was around 30PsI, The pressure relief is opening again and the pressure is reading close to 40 again. The autofill has a little arm and I raised it allowing water in, I wasn't sure if it was working properly. I have now shut off the supply going thru the autofill valve to see iof it is leaking by.
Thsanks
 
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Old 10-18-10, 05:02 PM
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Tellin' ya, your gauge is bad... when there is a question between what a gauge says, and where the pressure relief opens, always go with the pressure relief. If the 30 PSI relief valve opens when the gauge says 40, the gauge is not to be trusted.

Did you check the new tank with an accurate tire pressure gauge before you installed it? It should have been between 12-15 PSI.

Again, a COLD system should be between 12-15 PSI, and the tank must match that pressure.

With the fill valve closed, you need to DRAIN some pressure, rather than lift the bypass lever and ADD MORE... you keep adding pressure and that relief valve is gonna blow every time.

You need to:

1. VERIFY THE PRESSURE GAUGE.

2. VERIFY THE ADJUSTMENT AND CONDITION OF THE FILL VALVE.
 

Last edited by NJT; 10-18-10 at 07:19 PM.
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Old 10-18-10, 05:29 PM
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Just wanted to add that you need to have the system pressure at zero to check the tank pressure when it is installed.
 
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Old 10-18-10, 07:24 PM
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True that Droop...

You absolutely can not get an accurate reading, or a proper air adjustment on the air side if there is ANY pressure on the boiler water side.

Thanks for pointing that out...
 

Last edited by NJT; 10-23-10 at 08:15 AM.
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Old 10-23-10, 05:14 AM
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still a problem

I let the boiler cool down to zero pressure reading from the front gauge, I checked the expansion tank and it reads 12PSI, the relief valve blew open and it did not shut off completely so i did what anybody would do I wacked it with a wrench and it shut off completely, then the system ran several times staying at 20 PSI.Should have left it alone but I had to find the real problem. SOO I changed the relief valve , now its opening again at 30 PSI when the front gauge reads 30 PSI. I shut the supply off that feeds water thru the autofill valve and the pressure is still up around 30PSI, it usually takes several calsl for heat beforte it opens. Do you think this is a pinhole like PETEREYE had ? The backflow does have a drip only a couple a day, would this cause the high pressure ? i did buy a new back flow and autofill but have not installed. SHOULD THE PRESSURE READ '0' AFTER COOLING DOWN OR STAY AT THE 12PSI EXPANSION TANK PRESSURE??
I have to shut it off when I leave for work as i don't want my floor flooded.
Thanks again
 

Last edited by Rickeyb; 10-23-10 at 05:45 AM.
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Old 10-23-10, 06:09 AM
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The system pressure should be 12 psi when cold. If you have too much water in your system, you will have to drain some out to lower the pressure. That means to check the expansion tank, you will have to drain water out until the system is at 0 psi. You should reread what njtrooper said, it answers many of the questions you asked and specifies what you should do.
 
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Old 10-23-10, 07:49 AM
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I am no expert by a long shot, but here is what happened to me last Spring. My oil boiler/furnace (i have steam radiators) relief value blew up and scared the crap out of me. Boy, was it loud. I began to dial 911 not knowing what hit my house. Then I heard it coming from the basement and opened the door. It was like 6 a.m. in the morning when the heat came up and I was just opening my eyes with a relaxing cup of coffee. The basement was filled with steam. Sure glad I was home and not away for 2 weeks. Several service people over a several visits did their thing - and the wrong thing - like changing values. The problem persisted. One service guy finally got the right answer - it was a clogged part (called the pig tail). He simply unscrewed it, and said it is clogged. He changed it and no problem since from that. I should add that the service company did the right thing and reimbursed me for the cost of some things I was responsible for (and not in the service contract).

[thanks netmouse... but: this poster does have a hot water system, not steam, and there is no 'pigtail' on a hot water system... good story though! I bet you hadda change yer underwear! NJT added this note... ]
 
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Old 10-23-10, 07:49 AM
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SHOULD THE PRESSURE READ '0' AFTER COOLING DOWN OR STAY AT THE 12PSI EXPANSION TANK PRESSURE??
No, absolutely should not read zero when cold. There always must be a minimum of 12 PSI in the system when COLD. That pressure will, and should, rise to something around, less than, maybe a little bit more than, say 20 PSI when the boiler is HOT.

But, you have NO WAY of being certain of this if you don't first VERIFY YOUR PRESSURE GAUGE!

i did what anybody would do I wacked it with a wrench
Anybody? I don't think so... sorry.

Do you think this is a pinhole like PETEREYE had ?
No, probably not, your symptoms are not the same.

Also, a problem such as his would only exist if you were heating your domestic water with a 'thankless' coil inside the boiler. Do you have a separate water heater?

The backflow does have a drip only a couple a day, would this cause the high pressure ?
No, not at all.

Now, pay attention to this... when you remove your old backflow and pressure valve, BEFORE YOU INSTALL THE NEW ONE, find a way to FLUSH THE WATER LINE TO THE BOILER ... run it FULL BLAST with a hose or something for a few minutes. There is almost always 'crud' in that water line, and if you put that crud into the new valve, you will be sorry. One tiny little piece of that crud gets under one of those valve seats and you are right back where you started, only more confused because... "it CAN'T be that, because I just replaced it" syndrome.
 

Last edited by NJT; 10-23-10 at 08:43 AM.
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Old 10-23-10, 08:09 AM
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IF and THEN's

IF a boiler system drops to zero pressure when cold,

THEN it means that there is not enough water in the system.

==============

IF that same boiler that is at zero PSI cold rises to over 30 PSI and blows the relief valve when hot,

THEN it means only ONE THING... that your EXPANSION TANK is either defective, waterlogged, or does not have the correct air charge in it, OR if there is a valve between the boiler and the tank that someone has inadvertently closed that valve.

==============

Brutally honest here, sorry.

IF you think you have a 12 PSI air charge in your expansion tank, and the above conditions exist,

THEN you are mistaken. You are doing something wrong.
 
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Old 10-23-10, 08:18 AM
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Pressure gauges 5uck

Rickey, I repeat:

VERIFY YOUR PRESSURE GAUGE!

If you do not, then you are pi55ing into the wind, and will be chasing ghosts all around your boiler room.

You MUST know that the gauge is ACCURATE!
 
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Old 10-23-10, 08:25 AM
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More IF - THEN

IF your VERIFIED pressure gauge reads zero with the boiler COLD,

THEN it means:
  • The manual water feed shut off valve is closed.
  • OR
  • the automatic pressure reducing fill valve or the water line leading to it is plugged.
 
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Old 10-23-10, 08:27 AM
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First

Verify your pressure gauge

If you have not, can not, will not done/do this, STOP.

You MUST KNOW that your gauge is accurate before doing ANY of the following!
 
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Old 10-23-10, 08:31 AM
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Second

VERIFY THE CORRECT AIR CHARGE AND OPERATION OF THE EXPANSION TANK

This procedure is STEP by STEP. FOLLOW IT EXACTLY!

1. Shut off boiler and allow to cool to under 100F.

2. Shut off water supply line to boiler.

3. Drain only enough water from the boiler drain to drop the system pressure to ZERO. DO NOT COMPLETELY DRAIN THE BOILER SYSTEM! ONLY ENOUGH TO DROP THE PRESSURE TO ZERO!

4. With an ACCURATE tire pressure gauge, check the air charge in the tank on the air valve opposite the end of the tank that's connected to the system. If ANY water comes out of the air valve, the bladder inside the tank is shot and the tank needs replaced. If no water comes out the air valve, and the pressure is less than 12-15 PSI, continue to step 5. If the pressure is OK, turn the water supply to the boiler back on and repressurize the system, turn the power back on to the boiler, no service is necessary.

5. Using a bicycle pump, or a small air compressor, add air to the tank until you have 15 PSI air charge.

6. Check the boiler pressure gauge again, and if it has risen off ZERO, drain some more water from the boiler drain until it is again at ZERO.

7. Check the air charge on the tank again. If it is below 15 PSI, add air to the tank until it is at 15 PSI.

8. Repeat steps 6 and 7 until the boiler stays at ZERO and the tank stays at 15 PSI. At this point, the tank is properly recharged and the water supply can be turned on to re-pressurize the system, turn the power on to boiler and return to service.
 
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Old 10-23-10, 08:34 AM
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Third

Verify the condition and adjustment of the automatic pressure reducing water fill valve.

If it is working properly, with the manual water fill shutoff valve OPEN, the pressure in the boiler will be 12-15 PSI when COLD.
 
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Old 10-23-10, 11:37 AM
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Thanks for all the info

I'll try again to find the problem based on the info given. I did lower the high limit and it is staying around 25PSI for now. I'll reply as to what I found.
Thank you
 
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Old 11-07-10, 09:25 AM
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I'm back from working out of state and the boiler pressure gauge reads around 13psi. I did test the expansion tank pressure with system cold and released all boiler pressure , Tank was around 15psi.
I replaced the pressure relief valve and the Combo Fill valve with the back flow preventer. I ran the water from the fill line and then brushed the insides and ran the water again to clean any debris from the line. I did this before leaving.Yesterday when I returned I turned on the boiler and the pressure went up to 29psi, second cycle went to 30psi and opened the pressure valve. I looked for a thread on "How to test the front pressure gauge " and didn't find one I May have worded it wrong, I did check "Boiler pressure gauge testing " and again didn't see how to do this. The front pressure gauge was at 30psi when the valve opened. I checked the valve that is in line and over the expansion tank , it had no air to release. After the system valve opened and released some water it is now operating around 21PSI. i HAVE NO IDEA WHAT IT COULD BE. I will check the pressure gauge as the system cycles and shut it down if it gets close to the 30psi .
Thanks,
Rickeyb
 

Last edited by Rickeyb; 11-07-10 at 09:28 AM. Reason: bad spelling
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Old 11-07-10, 11:38 AM
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Hi Rickey, welcome home! Let me clarify the timeline a bit...

You are saying that BEFORE you left for work days ago, you replaced the fill/backflow combo, and left the manual fill valve OPEN while you were gone. Is that correct?

Was the boiler ON, or OFF, while you were gone?

You returned from work, and COLD the pressure was sitting at 13 PSI?
(ifso, perfecto)

You successfully verified that the air charge in the tank is correct and that there are no closed valves between the system and the expansion tank?

And yet, upon firing the boiler up on your return, the pressure rose to 30 PSI and opened the relief valve...

It sounds to me now that the gauge is agreeing with both the preset pressure on the new pressure reducing valve, AND is also agreeing with the preset pressure on the pressure RELIEF valve...

Is this scenario exactly correct?
 
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Old 11-07-10, 11:45 AM
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I can't explain why the gauge seems to have repaired itself, but it appears reasonably accurate based on your last assessment of the relief opening at 30 PSI.

When you replaced the expansion tank, did you replace it with the SAME SIZE tank?

Too lazy to read back in the thread, so please tell us, or tell us again,
What type of heat emitters are in your home? Fin-tube baseboards? Big ole cast iron radiators?

How big are the pipes between the boiler and the heat emitters in the home?

I'm trying to get a feel for the volume of water in your system.

I think it might be time to ask you to set up a free account at Image hosting, free photo sharing & video sharing at Photobucket and upload your pics there. Drop a link here for us to view... show us EVERYTHING that is connected to your boiler system.
 
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Old 11-07-10, 03:44 PM
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Trooper is on the right track. What size boiler and what type of radiation?
 
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Old 11-09-10, 03:20 AM
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I have a small single floor home with baseboard. A new tankless V8 Burnham boiler with a beckett burner. I replaced the expansion tank with the same size. Your last reply is correct. I left the boiler turned off, fill valve open, and the pressure on the boiler gauge read aroung 12-15. When I removed the old fill valve with the back flow the insides did look crudy. I did as you said and flushed the line and even brushed the inside of the supply and flushed again. Fired up the boiler and the pressure went up to around 28-29, the second firing pushed it up to 30 and opened the valve. I'll try to send pictures tonight,
Thank you again
Rickey
 

Last edited by Rickeyb; 11-09-10 at 03:22 AM. Reason: added more info
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Old 11-09-10, 03:25 PM
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You replaced the expansion tank with one of the same size - I assume it's a bladder-type tank.

What does the pressure guage indicate now with the system completely cooled down to room temp (like it was when you re-filled the system)? If the pressure when cooled down is now about equal to your refill pressure, the problem is that the exp tank has lost some or much of its air cushion or the tank is too small. Did you pump up the air side of the tank to 12-15 psi BEFORE you filled the system? If not, you'll have to depressurize the water side of the tank to atmospheric, and pump up the bladder with a bike pump and tire gauge. Depending on your valving, this may require draining the system.

If the pressure when cooled down is now much higher than your refill pressure, the problem is the pressure reducing valve leaking past the seat - replace it.
 
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Old 11-09-10, 03:59 PM
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Rickey, OK, the tank was the same size... but that leads me to ask, WHAT size? Typically they are '15', '30', '60' ... and MOST systems similar to yours would take a 30... some might get by with a 15.

Mike, the pressure reducing valve has been replaced, and Rickey seems confident that there was a 15 PSI charge in the tank with the boiler at zero.

So, the next and nearly last thing to do is as Mike said, let the system cool all the way down again, and see that the pressure returns to the 13 PSI you saw when you returned from work.

IF that happens, and it holds there, the new pressure reducing valve is OK. Also, then there is only one thing the problem can still be... with the expansion tank. The confidence seemed high that there was in fact 15 PSI in the tank with the boiler at zero, so the only possible thing left is that the tank is too small!

But IF the tank is too small, then why wasn't the OLD tank of the same size also too small?

Rickey, are you SURE that your tank really has 15 PSI? are you SURE that your tire pressure gauge is accurate?
 
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Old 11-10-10, 05:38 AM
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Hello, I shut the supply off and drained the water so I had no pressure reading on the pressure gauge. it did read 15psi when it was cold and i then checked the expansion tank , which is a Watts 30 and had 15psi, tested several times with a good tire pressure gauge. This is a tankless V84 burnham boiler
Fired thge boiler up and the pressure went up to 25psi. Let me ask you this, if I release some pressure from the exp. tank should the pressure gauge lower ? I tried to let a little air out and saw no change in the pressure gauge. I set up an account on PhotoBucket and uploaded pics of the boiler , how do I get them to this forum ? Tonight I think I will do the same test and let all the air out of the tank and try a recharge.
Thanks again,
Rickey
 

Last edited by Rickeyb; 11-10-10 at 05:39 AM. Reason: more info
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Old 11-10-10, 03:52 PM
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if I release some pressure from the exp. tank should the pressure gauge lower ?
Theoretically, yes, but in reality, no, I doubt it. If it does move at all it will probably be nearly imperceptible.

I set up an account on PhotoBucket and uploaded pics of the boiler , how do I get them to this forum ?
You need to copy a link to your photobucket album here so we can click on it and go view your pics.

Tonight I think I will do the same test and let all the air out of the tank and try a recharge.
I guess it can't hurt, but unless you are unsure that you did it correctly, what's the point? If you drained the boiler to zero, and had 15 PSI air charge, then what more can you do?

Wait until we see the pics... maybe something will jump out at us, and we'll have one of those " AHA! " moments...
 
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Old 11-12-10, 04:42 AM
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Pictures by Gulfstar76 - Photobucket

I have some pictures of the boiler and controls, Not sure if I linked it correctly, not the best with computers.

I drained the expansion tank of air and recharged to about 13 PSI, I think I will buy a digital pressure gauge today and retest, they look too be more accurate. Fired the boiler and it went to around 25psi, second firing it went to 30 and shut it off before it opened the relief valve.. If i lower the tank air below 10psi will this cause another problem ?
I will run the boiler on Sat and monitor it as i cycle the call for heat . I have not had time to cycle it more than twice as I'm working long hours.
Thanks,
Rickey
 

Last edited by NJT; 11-12-10 at 05:55 PM.
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Old 11-12-10, 12:09 PM
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Pictures by Gulfstar76 - Photobucket
 

Last edited by NJT; 11-12-10 at 05:54 PM. Reason: thanks Furd for fixing link!
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Old 11-12-10, 05:16 PM
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Why?

Rickey, the pic of your aquastat... those TEMP settings? WTH ?

I know that those tankless water heat coils really bite the big one, but cranking that LOW setting up to 170 is ... well... kinda nutz!

That high setting coupled with the fact that you have a NON thermostatic tempering valve [edit: I think I'm wrong about this... that may be a Watts 70 series, and possibly IS thermostatically controlled] means that it is possible for dangerously HOT water to enter your domestic system.

I would highly recommend that you consider turning that down to not higher than 150 AND replacing that tempering valve with a thermostatic type that will actually regulate the water temperature. [but even if it IS a thermostatic type valve, 170 LOW setting is STILL too high, waste of fuel!]

When you turn down the LOW setting, ALSO turn down the HIGH setting. I highly doubt that you need 195 water to heat your home. Back it down to 180. On top of everything else, you should see some fuel savings.

Ultimately, the RIGHT thing to do is abandon that tankless coil and go with a real water heater, an indirect type is very efficient, and you won't have to worry about your housemates being scalded by super hot water... DANGEROUS!

OK, back to study your pics some more...
 

Last edited by NJT; 11-12-10 at 05:52 PM.
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Old 11-12-10, 05:25 PM
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I can't see anything in the pics that might suggest why it's over pressuring...

Can you step back and get a wider angle shot of the system?
 
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Old 11-12-10, 05:58 PM
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If i lower the tank air below 10psi will this cause another problem ?
It will make the problem WORSE, and raising the pressure won't help either.
 
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Old 11-13-10, 06:55 AM
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Hello again, I posted 4 more pic's as requested. I bought a digital pressure tester and performed the expansion test . Close off supply, drain pressure valve only about 2 cups of water ) and tested it read 11.5 PSI, I pumped it up to 14.5 psi. One question do I have to open the fill valve or will it automatically pull in the amount of water needed ? Would I open it until I don't hear any more water entering the boiler ? I turned on the Boiler and agin 1st cycle it stopped around 25 PSI, 2nd cycle it went up to 29psi, 3rd cycle water was starting to exit the pressure release valve. I lowered the high limit to 180 and low limit to 150 . Does the High and low limit have any bearing on the boiler pressure ? Could this be my prtoblem ?
Trying
thanks for your patience
Rickey
 
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Old 11-13-10, 11:44 AM
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I dunno Rickey... there has to be some sort of a misunderstanding here... somewhere... either I'm missing something you are telling me, or you are missing something I'm telling you... because if you are starting out at 13 PSI COLD on a system with a brand new properly charged tank and a new pressure reducing valve, there is NO WAY it can be doing what it's doing.

Here are the final steps...

1. Turn off the boiler and allow it to cool to 100 F or less.

2. READ AND REPORT THE PRESSURE GAUGE AT THIS POINT.

A) If the boiler returns to 12-13 PSI when cold, CLOSE the manual shut off valve on the water feed line and LEAVE IT CLOSED FOR NOW. Skip B and continue to 3.

B) If the boiler pressure does NOT return to 12-13 PSI when cold, STOP HERE and tell us what it returns to.

3. CLOSE THE COLD WATER VALVE that feeds the tankless coil on the boiler. You will have NO HOT WATER PRESSURE IN THE HOUSE FOR THE DURATION OF THIS TEST. LEAVE THAT VALVE CLOSED FOR NOW.

4. Turn the boiler on and REPORT WHAT YOU FIND. Tell us BOTH the PRESSURE AND THE TEMPERATURE at various points as the boiler is firing.
 
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Old 11-13-10, 12:50 PM
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Originally Posted by Rickeyb View Post
I drained the expansion tank of air and recharged to about 13 PSI,
Maybe you told us this, but before your pumped up the air to 13 psi, did you drain the water out of the system and open it up to atmosphere? That step is essential.
 
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Old 11-13-10, 01:00 PM
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Mike, Rickey said that the procedure I posted was followed... and that procedure has been tested, so I know it works... IF and ONLY IF it is followed EXACTLY, and I am re-posting it here:

===================================

This procedure is STEP by STEP. FOLLOW IT EXACTLY!

1. Shut off boiler and allow to cool to under 100F.

2. Shut off water supply line to boiler.

3. Drain only enough water from the boiler drain to drop the system pressure to ZERO. DO NOT COMPLETELY DRAIN THE BOILER SYSTEM! ONLY ENOUGH TO DROP THE PRESSURE TO ZERO!

4. With an ACCURATE tire pressure gauge, check the air charge in the tank on the air valve opposite the end of the tank that's connected to the system. If ANY water comes out of the air valve, the bladder inside the tank is shot and the tank needs replaced. If no water comes out the air valve, and the pressure is less than 12-15 PSI, continue to step 5. If the pressure is OK, turn the water supply to the boiler back on and repressurize the system, turn the power back on to the boiler, no service is necessary.

5. Using a bicycle pump, or a small air compressor, add air to the tank until you have 15 PSI air charge.

6. Check the boiler pressure gauge again, and if it has risen off ZERO, drain some more water from the boiler drain until it is again at ZERO.

7. Check the air charge on the tank again. If it is below 15 PSI, add air to the tank until it is at 15 PSI.

8. Repeat steps 6 and 7 until the boiler stays at ZERO and the tank stays at 15 PSI. At this point, the tank is properly recharged and the water supply can be turned on to re-pressurize the system, turn the power on to boiler and return to service.

========================================

Rickey, the reason we keep going back to the tank is because it is the single element here that can/will cause what you are seeing.

If your fill valve is working properly, and the COLD boiler is between 12-15 PSI, and HOLDS there, then the ONLY other thing that can cause what you are seeing is an improperly charged expansion tank. (or one that is too small, but you said you have a small home with fin-tube baseboard, and a 30 should be fine for that)
 
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Old 11-13-10, 01:08 PM
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Originally Posted by Rickeyb View Post
I lowered the high limit to 180 and low limit to 150 . Does the High and low limit have any bearing on the boiler pressure?
The high-limit, Yes - and the photo of your boiler gauge shows 205 deg F (which is too high, although before you turned it down).
 
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Old 11-13-10, 01:22 PM
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Originally Posted by NJ Trooper View Post
3. Drain only enough water from the boiler drain to drop the system pressure to ZERO. DO NOT COMPLETELY DRAIN THE BOILER SYSTEM! ONLY ENOUGH TO DROP THE PRESSURE TO ZERO!
I would feel better, under the confusing circumstances and the reported pressure gauge irregularities, if the system were vented to atmosphere while draining - perhaps at a bleeder. Not drained bone dry, but making sure there isn't something weird going on.

What if the air in the tank is almost depleted? Draining a dab of water from the system, combined with a bad gauge, might fool us and produce some of the strange results that have been reported.
 
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Old 11-14-10, 04:38 AM
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Sometimes you can't see the steam thru the water, by having me change the high limit the pressure now is stable around 20-22 PSI. I let it run all day yesterday and it never went any higher . I think originally it was around 185 and I might have put it up to 190/195, with the Diff that is around 13 the hotter water was creating more pressure. The pressure gauge was reading high at around 210 very close to boiling water. I only drained enough water to drop the pressure to zero. I will monitor and report if these conditions change. You mentioned a superstore tank. since oil is now at 2.69 a gallon in my area. I would install an on demand electric water heater, only my wife and myself are presently in the home. Home depot superstor tank was pricing at $800.00 too much for me right now.
I can't explain the pressure gauge , it was pitted and looked cruddy on the inside.
Happy Sunday, thanks again
Rickey
 
  #39  
Old 11-14-10, 08:56 AM
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The diff setting doesn't have any effect on the high limit... only on the LOW... and I would actually increase that to 20...

Hopefully it's all good to go now, thanks for letting us know!
 
  #40  
Old 11-15-10, 04:53 AM
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No , thank you and all who contributed. I learned alot about my boiler because of you.
I will set the diff to 20 as recommended.
Happy days,
Rickey
 
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