Bleeding radiators doesn't seem to work


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Old 11-03-09, 04:36 PM
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Bleeding radiators doesn't seem to work

Hey everyone, I'm having trouble bleeding my radiators. I also don't have a good understanding of this boiler system I have (it's a new house to me).

So let me start with the bleeding issue...sorry, this is gonna be long...

I had an HVAC guy come out and take a look at the system to make sure everything was good for the winter. Unfortunately, I don't think this guy knew much about hot water heating, and was possibly lazy. When running, the radiators sounded like water was "sloshing" through them. So I asked the HVAC guy if the system needed to be bled. He put his hand up to the radiators and said "no, they are putting out enough heat." I responded by saying/asking "well, does that mean the system could be putting out more heat if it were bled?" He said everything is fine. I even asked him to bleed it and show me so I knew the proper way to do it. He basically said that was not necessary. So he left.

I then decided to bleed them myself by starting at the radiator furthest from the boiler. I made sure the circulator was running and opened the valve on the radiator. As I had thought, there was air in there. Air came out constantly for about 10 to 15 seconds! I continued down the line letting air out of each one.

I thought all was well, but then I started hearing another noise. Now there was a clicking and popping noise coming from the boiler room. I had the HVAC company send someone back out to see what was going on.

They sent the same guy back... I told him that I bled the system and that there was a lot of air in the system, but now there's a new noise. He went and looked at the boiler and said "you shouldn't have bled the radiators because that can let more air into the system, and that noise I was hearing was the floater valve." He said it was making noise because of air bubbles in the system. He then said that there is no problem and that the air bubbles will eventually make their way out in a couple days.

Well, a week and a half later...the noise is still there. From the research that I've done, it seems as though everything isn't "fine." The HVAC guy said water will come into the system as needed, but it doesn't seem like that is happening...maybe I'm wrong.

The pressure reads about 14psi when cool and about 16psi when hot.

So what should I check? Or does this really seem fine? Am I always going to hear that clicking, popping and sloshing? It just doesn't seem right.

Here are pictures of what my system looks like: Photos

If you all could help me understand how this system works and what the different components are/do, then that would be amazing. Let me know if you need more information about anything or need any additional pictures.

Thanks in advance.
 
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Old 11-03-09, 04:54 PM
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I'll start by putting some comments on the pics in your album...

then more later... sounds like din-din is served. Yummm. FOOD!
 
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Old 11-03-09, 05:54 PM
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Hey NJ Trooper

Thanks for the info so far. I'm following so far.
So the second valve in the back to the left of the reducing valve is in fact another reducing valve. It's not identical, but has very similar specs on the label. It seems like there is one for each expansion tank???
About the missing drip leg...Is that something that should be remedied asap?
About the extra gauges...
I live in a townhouse that was once (probably about 15 years ago) a business joined with the neighboring unit. It seems as though the existing pipes supplied heat to both units possibly (and maybe had 2 zones then). Then when they units were separated and renovated, I bet they modified the system to heat just this unit. That's my best guess.
Well, I'll wait to hear what else you have to say. keep it coming. I really enjoy learning about this stuff.
Thanks again.
 
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Old 11-03-09, 08:32 PM
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Sorry I got sidetracked with food and spirits... and TV...

It seems like there is one for each expansion tank???
I would hazard a guess that at one time there were actually two boilers, operating independently of each other, thus two tanks, two reducing valves, two gauges, etc...

He went and looked at the boiler and said "you shouldn't have bled the radiators because that can let more air into the system, and that noise I was hearing was the floater valve."
That heating guy is selling you a line of BS... what the heck is a 'floater valve' ? There IS such a thing as a 'float valve' but that's in your terlet tank, or on a sump pump. There IS such a thing as an 'automatic air vent', and they have floats in them, but I don't see one in your pics, and in any case, it's not appropriate on a system that has the type of expansion tanks that yours does. Either he is lazy as you suspect, or doesn't know wtf he is talking about, or whatever, I would either ask that they send someone different next time (you might get worse!), or use a different company (you might get worse!)... it's a real crap shoot these days finding someone who knows what he's doing, and CARES enough about what he's doing to not BS the customer and take the easy route to the door.

The HVAC guy said water will come into the system as needed,
That part is supposed to be true, presuming that the pressure reducing valve(s) is(are) working properly, and the shut off valve(s) leading to it(them) are open, and it(they) is(are) properly adjusted.

The pressure reads about 14psi when cool and about 16psi when hot.
No problem with that. I would even expect the pressure to be a bit higher when hot, but with two tanks online, it seems likely that the hot pressure is not as high as some systems. This would also indicate that the expansion tank(s) are NOT waterlogged, which is a good thing.

more...
 
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Old 11-03-09, 08:45 PM
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You may indeed still have some air in the system. Maybe what you are hearing is the air bubbles going through the pump...

What I can't see in the pictures is how the expansion tanks are connected to the system.

Ideally, they are connected in such a way that air traveling through the system is trapped by an air separator, or by the boiler itself, and sent up the pipe to the expansion tank.

Whether or not the air will eventually work it's way to the tank is a funtion of how/where they are piped in.

Can you follow those pipes and tell me, or show me in a pic, how they are connected?

Are there any more of those zone valves that can't be seen in the pics?
 
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Old 11-04-09, 08:10 AM
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The two boiler idea definitely seems plausible.
About the HVAC guy...I'm done with him and his company. I consider my $100 service charge a donation for them to buy some textbooks...chances are that they won't change though...
I agree with the crap shoot statement. I really wish it were easier to find more people in general that cared about anything, but that's another forum I'd suppose...

I'll get back to you later about the specs on those reducing valves...I can't remember the pressure spec on them...probably useful info for ya...

When listening to the sound, it definitely seems to be coming from the zone valve and not the pump. I can definitely hear the pump doing its job and it sounds pretty smooth. Could the zone valve be going bad?

So I've added a diagram to my photobucket page (Photos). Please excuse the lack of proper symbols for the different components. I'm an electrical engineer. So HVAC stuff is uncharted territory for me.

Let me know if the diagram isn't sufficient and I'll try and get pics that adequately show what's going on (it's just hard to do in the small space).

Thanks again and if you ever move to VA and decide to do HVAC work, then you've got a customer (although, my hopes are that I can learn enough about this system to take care of things mostly myself).
 
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Old 11-04-09, 01:02 PM
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I forgot to add that there are no more zone valves...just one.
 
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Old 11-04-09, 02:26 PM
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So the reducing valves say max psi: 125, max temp: 225deg, set at: 12lbs (i would assume that should technically say 12psi). Now does this mean they won't let new water into the system unless the pressure falls below 12psi?
 
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Old 11-04-09, 03:27 PM
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Hey, now that's not a bad drawing for an EE! J/K

Yeah, I'm gonna stick with my story that there were once two boilers side by side there. There's no other explanation for the redundant devices. I wonder why they didn't just cut out the extras and slap on a few pipe caps...

You might not even NEED that zone valve... not sure what function it serves in your system. It does look as though there are wires on it though... do you have more than one thermostat in the home? Are the two pipes with the gauges on them leading to different 'zones'?

It is possible that air bubbles in the system are causing the zone valve to make noise...

It's difficult to tell from the graphic (or the pics) how the pipes are 'physically' configured, but I am doubtful that any air in the system has any hope of finding the expansion tanks.

Ideally, the tanks would be piped to an air collection device that is in the main stream of water, and would pass the air to the tanks as it collects it. It appears that your tanks are piped off a tributary... they will still do the job of controlling the pressure increase when the boiler heats, but probably won't collect much of the air in the system.

Depending on the location of your air bleeds at the radiators, sometimes they are best bled when the system is hot and the pump is running, and sometimes they are better bled when the system has been off for a while with the pump not running.

If the bleeds are at physical 'high spots' then bleed with the pump off. If the bleeds are at the downstream ends of the rads/baseboards, then usually better to bleed with the pump running. Try it both ways... and keep at it for a while, you may eventually get enough air out to quiet the system down.

Short of ripping out the near boiler piping and re-doing it, you may never be able to get it ALL out.

One thing that's worth keeping in your mental notebook... on a system with the steel tanks such as yours, it is possible under certain conditions for the tanks to become waterlogged if the system is continually bled of air. I'm sure you know that there is supposed to be a big air bubble trapped in the tanks, and that's what compresses and controls the pressure. But, since the water is in contact with the air inside the tanks, some of the air will dissolve back into the water and float around the system. If you keep bleeding the air out, eventually the air bubble in the tank disappears and you have pressure control problems. If you are only seeing a few pounds of difference between cold and hot, you have a ways to go before that happens, but what you will notice is that the cold pressure is fine, and the high pressure will start creeping upward...
 
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Old 11-04-09, 03:36 PM
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Originally Posted by Kfahrend View Post
So the reducing valves say max psi: 125, max temp: 225deg, set at: 12lbs (i would assume that should technically say 12psi). Now does this mean they won't let new water into the system unless the pressure falls below 12psi?
12 lbs (PSI) [and even more technically correct I believe would be PSIG] is the factory setting. They are adjustable from around 10 to 25 or so...

Correct that they add water when the pressure drops below the setpoint.

The Pressure Reducing Valve sets the MINIMUM pressure in the system when it is cold. The MAXIMUM pressure is a function of the size of the expansion tank relative to the volume of water in the system. The tank(s) need to be sized such that they will accept the approximately 4% increase in volume of the water as it is heated from room temp to appx 180F.
 
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Old 11-04-09, 04:34 PM
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do you have more than one thermostat in the home?
There were two until this last week. I consolidated the old analog mercury switch stat (for boiler) and the cheapo digital stat (for AC) into a single programmable stat.
Are the two pipes with the gauges on them leading to different 'zones'?
This brings up a question in my mind... All of the arrows on the valves indicate that the piping with the zone valve on it is the return line to the boiler and the other piping with the gauge alone is the sending line from the boiler. Does this seem correct? That would mean the the pump I have right next to the boiler is driving water down into the boiler. So to finally answer your question directly, no, I don't believe they are leading to different zones.

I have a small two-story townhouse with two rads downstairs and 4 upstairs. I have 1 older cast iron rad in the bathroom (it get hot, it's nice). The rest of the radiators are tube and fin units with tall housings. The radiators downstairs do not have bleeder valves, but all of the upstairs units have bleeder valves. Also, all of these valves are physically higher than the piping. So I take it that I should try bleeding the system when off and cold.

So the clicking and popping has actually subsided a little. Should I be careful to not let out much water when bleeding? Also, it doesn't appear that there are valves on the expansion tanks to allow me to pump air into them if necessary. Does that seem fine?

Oh yeah, about that missing drip leg... what's your take...should I get one in there soon?
 
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Old 11-04-09, 05:27 PM
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There were two until this last week. I consolidated the old analog mercury switch stat (for boiler) and the cheapo digital stat (for AC) into a single programmable stat.
OK, I think that means that now you have one stat that now controls both the A/C and the heat...

I looked again at the pics and traced the piping to the extent possible and now see that the gauges say "Z1 S" and "Z1 R" ... and I take that to mean "Zone 1 SUPPLY" and "Zone 1 Return". But that's puzzling, because if there is a "Z1", one would think that there would also be a "Z2" and perhaps more... what's more puzzling is why someone thought they needed a pressure gauge on both the supply and the return, like they would somehow be different? weird... I'm gonna guess that maybe at one time, they were TEMPERATURE gauges, OR that there was some other piping changes made when the other boiler was removed that somehow 'tied together' more than one previous 'zone'...

So, the HOT SUPPLY coming off the boiler is the pipe to the rear, and the cooler water returning to the boiler is the front pipe.

The zone valve could possibly be there as a 'legacy', OR it may be being used to prevent 'gravity flow' when the system is off and not heating. 'Gravity flow' or 'thermo-siphon', etc, describe what happens when heated water rises in a piping system due to the different bouyancy of different temp water, and can cause the system to continue to heat the home AFTER the thermostat is satisfied. The same thing can be accomplished passively with a 'Flow Check' valve...

How is the zone valve wired? Which terminals are being used, and where do the wires go?

There should be a pair of low voltage (24VAC) wires coming off the T T terminals in the aquastat, where do they go?

Yes, your pump appears to be pumping on the return, back into the boiler.

On the 'drip leg', it's something that should be done, but it has probably been that way for a while... I would say not a show stopper, but get it done when you can. Hopefully you won't get a bit of dirt or rust fouling the gas valve...

more on the tanks and bleeding in a while...
 
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Old 11-04-09, 06:29 PM
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The Z1 Supply and Z1 Return make sense except that the Z1 Supply gauge is the one in-line with the zone valve that has an arrow on the fitting pointing down to the pump. It seems as though things here are a little out of wack.

About the two gauges... They in fact do read different values. The one labeled Z1 R reads about 12.5 and Z1 S reads about 14 (it is cold now). Interesting...

Another interesting note for ya. When the system is running and hot, the Z1 R gauge needle stays very constant, but the Z1 S gauge needle flutters to the "beat" of the noise coming from the zone valve (unless the noise is somehow being generated by the gauge...that would be quite strange).

About the wires on the zone valve... The TH and TR terminals are being used (I took a picture of that for ya too and added it to the photos). So I'd have to move my washer and dryer to be able to really get to the aquastat and open it up...
But without the details of how it's hooked up in the box, I can see from the outside that the thermostat signals are going into the aquastat. From the aquastat, I have a pair of wires going to the zone valve. All other controls lines for flue damper, pump, and ignitor I guess are coming from the aquastat as well.

Back to the two boiler idea... more evidence here. There are two sets of thermostat wires, but one pair is cut.

If you need to know the actual wiring inside the aquastat I can probably get that to ya this weekend.
 
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Old 11-04-09, 07:14 PM
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I just thought of something regarding the expansion tanks not having schrader valves... I guess the tanks don't need to be pressurized. They just act as a mass of air to act as a damper. So the only service necessary for them would be to drain them if they became water logged and then you'd recover you adequate volume of air. Am I thinking correctly?
 
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Old 11-04-09, 07:33 PM
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Should I be careful to not let out much water when bleeding? Also, it doesn't appear that there are valves on the expansion tanks to allow me to pump air into them if necessary. Does that seem fine?
It doesn't make sense to even bleed if all you are getting is water... it's the air you want out, right? So if you do get only water, might as well close the bleeder.

You asked about bleeding with pump off... versus on... I would try it both ways, cuz ya won't know where the air is hiding until you try it. Before you bleed with the pump off, just let it sit for an hour or so ... if the bleeders are at the high spots, it may take a little time for the air to float up there.

You don't need to pump air into the steel tanks that you have. When (IF) they become waterlogged, you would close the valve in the line leading to them, hook up a hose to the drain, and get ALL the water out. There are lots of threads around here that talk about how to get the water out... because what happens when you drain them is that a vacuum builds inside and the flow will stop, leading you to think they are empty, but they probably aren't. It's like he finger over the end of the drinking straw thing... lift it out of the glass and the liquid stays in the straw... same thing happens with those tanks. So, you have to 'break' the vacuum. Some guys blow into the end of the hose... yuk... some guys might use a small air compressor to blow into the end of the hose instead... If you use a short, large diameter hose into a bucket, and leave the hose fitting a bit loose at the drain, you might not need to resort to blowing into the hose, but whatever means you use, the tank should be emptied.

Then, you close the drain, and open the inline valve. The pressure from the system will fill the tank about halfway or so, and compress the air inside...

But if you've got no problem with high pressure, I'd not bother with them.
 
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Old 11-04-09, 07:36 PM
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Originally Posted by Kfahrend View Post
I just thought of something regarding the expansion tanks not having schrader valves... I guess the tanks don't need to be pressurized. They just act as a mass of air to act as a damper. So the only service necessary for them would be to drain them if they became water logged and then you'd recover you adequate volume of air. Am I thinking correctly?
Yes, exactly...

There are two types of tank in use... the older variety you have is just a plain steel tank, and a bubble of air inside.

The newer variety with the schrader valve is a 'bladder' tank, and there is a rubber membrane between the air and the water. This type of tank IS precharged with air which is supposed to be 'captive' in the tank. They are generally better liked, because they are smaller, etc, but the fact is that your tanks are fine, and if they are doing the job, no need to do anything with them at all.
 
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Old 11-04-09, 07:47 PM
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I see what you mean about the S and R being reversed on the gauges... someone may have swapped them... or just wrote the wrong thing on them... maybe it was your 'heating guy' who probably didn't know the difference! ha ha ...

About the two gauges... They in fact do read different values.
I'd probably wager that one or both of the gauges are slightly out of cal... and that if you swapped them, you would see that they still read nearly the same, +/- a half PSI or so due to the foot or so difference in altitude.

If you need to know the actual wiring inside the aquastat I can probably get that to ya this weekend.
Probly not necessary... I've got a good idea of how they wired that. My guess is that the wires to TH and TR are going to the T and (W,Z) terminals. I bet the aquastat is an L8148E model. Wiring the zone valve in that way puts the motor in parallel with the relay coil, and both are being switched by the thermostat which is wired to the T and TV terminals.
 
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Old 11-05-09, 08:03 AM
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Good, good. I'm learning here. Thanks for all of your input, it is much appreciated.
Back to the noise I was/am hearing... If the noise is in fact coming from the zone valve, is that something to worry about? Do those things make noise before they fail?

Another question... Given the information you have on my system, what would you say is the psi point at which it is getting too high and may indicate water in the tanks? I'm just curious.
 
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Old 11-05-09, 02:35 PM
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The noise you hear could just be air bubbles shooting through the valve. Inside that valve is a composite material 'ball' on the end of a lever arm. When air shoots through, it could be 'rattling' the ball on the arm. Just a guess without actually hearing the noise.

Is the noise very random? or very regular? If it's a regular rhythmical noise, it might be that the gears are stripped and what you are hearing is the gears ticking... you could pop the cover and take a look. Inside you will see a synchron motor, a bunch of gears, and a 'microswitch' endswitch.

what would you say is the psi point at which it is getting too high and may indicate water in the tanks?
When the boiler is cold, 12-15 PSI is the norm, only higher if the system is very 'tall', as in a 3 story home. Then you might want the cold pressure a few PSI higher.

With two expansion tanks on line, I would not expect to see more than 5 PSI differential between room temp and 180, if the tanks get waterlogged, the cold PSI will/should stay the same as long as the pressure reducing valve(s) are functional, but the high side will begin to creep higher... I think you said that you are only seeing like 2-3 PSI differential between cold and hot, so you are good to go there.
 
 

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