Hydrotherm boiler is building to much pressure

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Old 01-14-12, 07:45 PM
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Hydrotherm boiler is building to much pressure

Some history. This is a gas fired 30 year old cast iron unit. Taco circulator 1 zone. I changed the watts auto feed valve- pressure regulator 1156 i beleive, factory set at 14-17 pounds, supply house said no need to adjust it. I changed this because i checked if it was workng by raising the lever and nothing happened. Before I did this the system worked fine.

The old valve was crusted nicely inside, but the gate valve or shut of valve before it was totally clogged jup as if it was welded shut. New ball valve, new watts 1156 also new tridicator, old one did not move. Refill the boiler and it auto fills to 25 psi cold. That should not be. Maybe its alot of air. Turn the system on, bleed the radiators and we have heat so we are good. Well no, the next day it blows the pressure valve. When i checked the gauge it was at 45 psi, not kidding. I reduced the the watts valve as much as you can by turnng the screw out, changed the expansion tank 30lb and the made o mist air bleeder. Now it starts out at 20 psi which should not be since i turned the valve all the way down and it climbs to slightly over 30 psi and the blow off valve drips. The exp tank is at 16-17 psi out of the box i did'nt add any air to it. What am i missing, what should i do?
 
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Old 01-14-12, 10:30 PM
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auto fills to 25 psi cold
Did you flush out the water line real well before attaching the new valve? You mighta got crud in the new valve...

Maybe its alot of air
Will not cause high pressure by itself.

the gauge it was at 45 psi,
New gauge, probably OK... and relief valve didn't blow?

Did you do all this work and NOT replace the relief valve?

starts out at 20 psi which should not be since i turned the valve all the way down and it climbs to slightly over 30 psi and the blow off valve drips
See first point above... new valve might be toast.

The exp tank is at 16-17 psi out of the box i did'nt add any air to it
I question the accuracy of your tire gauge.

what should i do?
1. Change the relief valve.

2. Verify the accuracy of the tire gauge you used and be certain that the new expansion tank is at 12 PSI.

3. Fill the system to 12 PSI with boiler cold. CLOSE the manual fill ball valve and run system. Monitor pressure. As long as the system isn't losing pressure somewhere (leaks), you can run it with the valve closed. After all, how long was it running with the plugged valve? Some valve manufacturers recommend running with the valve closed (Bell & Gossett for one).

You may see the pressure drop some as the air is removed from the system by the auto air vent, so keep an eye on the pressure and add a little if needed to keep it at 12 minimum.

If the pressure remains in control, then you know the new valve is NG.

Does this boiler also produce domestic hot water? i.e. does it have a tankless coil in it?
 
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Old 01-15-12, 08:45 AM
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I did not flush the feed before I installed the new pressure regulator but I had to change the shut off valve before it and the inside of the pipe looked fine. Flushing it would have been a good idea.

The pressure relief did blow at 45 psi and starts dripping at 30 so it seem to be working fine. I did not change it.

it is a cheap tire gauge but would 16 PSI on the tank cause the pressure to rise???? The 16 measure was after it had run for a while. FYI the old one was at 0 psi after I took it off, did not check before I took it off. there was no water in the tank but it is installed upside down with the air feed-gauge fitting on top so if there was water in the old one it could have just dripped back into the piping.

Number 3, I was thinking the same thing, further since the tridicator was not working I had no idea what the system was operating at. I have a fealing it was low on water since the tenant said wow the radsiators are really nice and hot now. If I shut the valve how do I know if the system has a low water shut off as a saftey?

How many days should I monitor this pressure? The reason I ask is it starts at say 20 and cycles fine for a few hours but after a solid day the pressure builds.

I'm thinking I will pull this auto fill valve off and get a new one

This system does not produce domestic hot water.
 
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Old 01-15-12, 09:48 AM
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OK, sorry, but yer confusifying me...

You said this:

The exp tank is at 16-17 psi out of the box
and then you said this:

The 16 measure was after it had run for a while.
So, which is it? 16-17 out of the box? or 16 after it ran a while?

You can only get an accurate measure of the tank's air charge if there is ZERO pressure on the water side of the tank. You need to clarify this a bit.

would 16 PSI on the tank cause the pressure to rise????
No... not really... it WOULD limit the maximum amount of expansion room inside the tank a bit, but in general, no. If the tank is marginally sized for the system, it COULD cause a pressure problem.

But, like I said, if you have pressure on the water side, you can NOT get an accurate measurement.

The pressure relief did blow at 45 psi and starts dripping at 30 so it seem to be working fine. I did not change it.
Is the relief valve more than five years old? CHANGE IT.

since the tridicator was not working I had no idea what the system was operating at.
I was under the impression that you replace the tridicator at the same time you changed the tank?

What was the exact sequence of events?

If I shut the valve how do I know if the system has a low water shut off as a saftey?
You should be able to see it... should be attached to a tee fitting on the hot supply pipe out of the boiler. It certainly should be labeled as such...

How many days should I monitor this pressure? The reason I ask is it starts at say 20 and cycles fine for a few hours but after a solid day the pressure builds.
I dunno... a week or two... or maybe even only a day or two, since you are seeing the problem pretty much within a day.

This is very symptomatic of the fill valve leaking through.

I'm thinking I will pull this auto fill valve off and get a new one
Why not do the diagnostics to be sure?

Again:

1. REPLACE THE RELIEF VALVE.

2. VERIFY 12 PSI in the new expansion tank. You MUST drop the boiler pressure to ZERO in order to do so. Here is a 'step-by-step' that you can use:

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

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. REPEAT: DO NOT COMPLETELY DRAIN THE BOILER! 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 12 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 12 PSI, add air to the tank until it is at 12 PSI.

8. Repeat steps 6 and 7 until the boiler stays at ZERO and the tank stays at 12 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.


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

3. Fill the system to 12 PSI with boiler cold. CLOSE the manual fill ball valve and run system. Monitor pressure.
 
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Old 01-15-12, 11:43 AM
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NJ Trooper, are you in North Jersey?

sequence of what I did. auto feed and new ball valve, refill system all is working, next day pressure relief blows, water on the floor, gauge at 45 ish. drain water out and i hear the auto fill adding new water in, wtf? swearing at supply house because who else can I blame, certainly not myself. adjust auto fill now we auto fill to 20 but next day it still blows, change expansion tank and air eliminator little made o mist thing. FYI THE EXPANSION TANK SEEMS TO BE INSTALLED UPSIDE DOWN FROM OTHERS I HAVE SEEN, NOT SURE IF THIS REALLY MATTERS AS i HAVE SEEN SOME SIDEWAYS AS WELL. It still blows but now it only gets to about 30-35 psi

Out of the box, I mean I did'nt add any air to it or take any out. Box said set at 12 PSI but I did'nt check it until it was running and was already hot and it was at say 16 PSI. I appreciate your steps on getting this straight. Question, I totally drained the system and the feed valve should not have added more than 14-17 PSI to the system as the tag reads, max 25 PSI. It auto filled to 25 psi the first time then I turned out the set screw counter clockwise actually backed it all the way out not knowing it would actually come out. By screwing out, does that reduce the set pressure? regardless it should not get above 25 psi.

relief valve is probably greater than 5 years old, yes. But it is working as it starts dripping at 30 and runs at 35-40 but it does not bring it back down to 30 so I see your point in changing it.

I don't think this system has any other saftey shut off besides the aquastat thing that sets the max at 180 degrees. That seems to be working but at first it did fire to about 200 degrees. Now it's working fine, I did not touch it. Would it look similar to a zone valve ie where it has a sensor in the pipe and a box on the outside?

Changing the pressure valve should be easy since I now discovered that the system actually has 2 isolation valves.
 
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Old 01-15-12, 02:51 PM
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LWCO could look like this:


image courtesy taco-hvac.com

or this:


image courtesy completewatersystems.com (formerly Bell&Gossett)

or this:


image courtesy hydrolevel.com

Would it look similar to a zone valve ie where it has a sensor in the pipe and a box on the outside?
I guess you could say that...

who else can I blame, certainly not myself.
... I guess some things are just universal, aren't they!

FYI THE EXPANSION TANK SEEMS TO BE INSTALLED UPSIDE DOWN FROM OTHERS I HAVE SEEN, NOT SURE IF THIS REALLY MATTERS AS i HAVE SEEN SOME SIDEWAYS AS WELL
Well... they aren't 'supposed' to be installed upside down or sideways, but they often are, and they will still work... maybe not for as LONG as they are supposed to, but it's really not a 'show stopper'.

Box said set at 12 PSI but I did'nt check it until it was running and was already hot and it was at say 16 PSI.
OK, I understand now. You WILL see a higher pressure on the air side if the tank has a higher pressure on the water side when the boiler is hot. If the tank has the correct factory air charge of 12 PSI, when the boiler pressure rises ABOVE 12 PSI, you will read the higher of the two pressures on the air valve. As long as you didn't let any air OUT, then you should be good to go.

I'm quite sure that the new valve has some 'crud' under the valve seat and is slowly leaking into the boiler... that's why it takes some time to build up the over-pressure. It's like a dripping valve... slowly... raising the pressure too high.
 
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Old 01-19-12, 07:27 PM
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Thanks nj trooper

I have shut off the water supply to the boiler for the past several days. Pressure started at 20 and has stayed at 20. Bought a new fill valve and will be looking to swap it out. I guess the new valve got clogged by debris in the pipe or it was bad out of the box.

Anything special i should be doing when swapping this one out?
 
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Old 01-19-12, 08:05 PM
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Anything special i should be doing when swapping this one out?
Figure a way to flush the line out real good before installing...

Rig up a hose somehow... and turn it on full blast for a minute or so.
 
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Old 01-19-12, 08:58 PM
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Will flush out first

A old shop vac hose should work nice for that. You never answered if you are from North Jersey
 
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