Anybody here knows water boiler heat systems?

Jay H · 03-08-2006, 07:04 AM

I have a gas-fired water boiler with hot water baseboard heating system in my house. Last week I had a zone control valve die (a Bell&Gossett valve) and had a local HVAC guy replace the valve with one from Honeywell. When the heat stopped on the first floor, I tried to replace the valve with a spare but the spare that I replaced must of been bad. When the HVAC guy replaced the valve, he had to drain the system and refill it, however, since then, there has been very slight dripping from the overflow pipe. I am trying to figure out what cycle it is from but I figure it must be when the boiler is firing and the water is heated due to expansion.

I have a newer expansion tank with diaphram, I'm assuming it's still has enough air in it to allow for the water to expand. The boiler also has a pressure gauge and looking at it, it reads 40psi. However, how do I tell what is "normal" and how do I find out at what pressure the pressure valve is supposed to trigger? If the dripping doesn't stop, I'm going to have to look further why it is doing it. I've read that you can put more air in the expansion tank via a simple shraeder bicycle pump but I don't think that is the problem.

Jay

brac · 03-08-2006, 07:43 AM

Hey,
I don't know how old your system is but it sounds like uou have a problem. pressure on these systems is usalluy around 10 - 15 psi.
Here is what I would look for. There should be a pipe that runs to your plumbing system (make up water) this pipe will have a valve that sets the pressure at a fixed point. There is usally a bypass there for filling the system this valve should be closed but sounds like it's open 40 psi is likely what your plumbing system runs at. anyway look for a valve and close it then use the handle on the overflow or one of the faucet type valves to let out some water..i.e lower the pressure. probally around 15-20 pounds should solve your problem and when it gets low enough to need some water the make-up valve will set the pressure where it should be..
Hope this helps..
Brac

Jay H · 03-08-2006, 08:01 AM

Thanks!

The main water supply intake for the heating system has a pressure valve on the backside that is supposed to regulate the pressure of the closed loop. If this valve is bad and the valve is stuck open, wouldn't I have a problem again when I drain the water to lower the PSI to 10-15psi and then open the main water intake? Unless the valve is just temporarity stuck open.....

P.S. I don't see any bypass for the main water supply, the main water supply runs to the shut-off-valve, then the pressure sensor valve and then straight to the return side of the boiler.

Jay

brac · 03-08-2006, 04:03 PM

The repaie guy might have refilled with a hose to bypass the vavlve, if this is the case letting out some water would solve the prob.

Also I would look on the regulator to see what its operating pressure is.

If it seems stuck try taping it with a piece of wood.

Hope this helps
Brac

Jay H · 03-09-2006, 07:34 AM

Hey, I think I misread the pressure in the first post, it's a combination pressure/temperature reading in both Bars/Psi and degF/degC, I think when I was reading 40psi, I was actually reading 40degC... Last night, I checked again (and dusted off the gauge cover!) and it reads 13psi which appears totally normal. After a complete heating cycle, it goes up to 29psi and 170degF. However, I notice that the pressure relief valve drips even when the boiler is off so I think it is simply a bad TPR (as it is called I think). I rapped on the diaphram expansion tank, sounds OK, sounds like it has air in it. I don't have domestic water coil going into the boiler and the pressure regulator valve seems OK (aka I don't hear water going into the system nor does the PRV getting cold (from the main water supply).

So I think I'll eventually replace the TRP which is cheap or simply use the water that overflows to water the plants! It's not much water really..

Jay

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Chu Gai · 03-09-2006, 10:03 AM

Did the valve itself die or just the actuator?

Jay H · 03-09-2006, 12:30 PM

OK, I had to look up what an actuator is... Not sure if ever got a good description but here is the history:

Well, when my zone control valve died, it triggered off an over pressure situation and eventually the 30psi was exceeded and water came spitting out of the overpressure pipes. (unbeknowst to me who found out after) Not much water but a puddle formed and ever since then, the valve must of not set well anymore so now it drips out of it.

From doing research on the internet, many folks do not test these pressure relief valves because many old ones will develop a leak and this one is fairly old I think.

The valve from what I've learned is also simply a screw on type thing, it has a small lever on the top that if I move it, it opens the seal and water comes out. I can sort of rotate that lever but not sure if that does anything (could that reseat the seal, perhaps I need to play with that to see if I can get a better seal and stop the leak)... Otherwise, the valves are only like $11-$15 and seems easy to physically replace. I would have to drain the boiler and purge the new water though...

Jay

Chu Gai · 03-09-2006, 01:59 PM

I'm assuming your system is more or less like mine. One of the zones is also wired such that if the boiler were to decide to generate excess pressure, that the zone that feeds the greatest radiated area would automatically open, even if it's summer, to releave some of the pressure. I've had to replace a couple of zone valves over the years and never have I had to replace the actual valve. Just the actuator (that round thing with the wires).

However, I did have a leak one time which necessitate my draining the system. While it was drained, I removed the captive air tank and checked the pressure using a pressure gauge. I also replaced a couple of older valves on the boiler with ball types. A little more expensive, but much more reliable seating. I also replaced the pressure relief valve for no other reason than it was old.

Refilling and getting heat to all zones though was a problem for me. One of the problems I had was this spitting that you observed. This was traced to air in the lines. Too much air (I guess from the cold water feed) such that it was locking the system up. The manual for the boiler I had was pretty old and it was unclear what the correct sequence of steps was. I contacted the manufacturer who provided a schematic of the inner workings. A couple of trial and errors on my part and eventually I got the entire system filled correctly and was able to bleed off the trivial amount of air in the lines over a few days of running. You might have better luck than I since my boiler came from Sweeden.

I know I also referred to a website that dealt with plumbing and boilers, but I no longer have the link. People there were pretty helpful.

Jay H · 03-09-2006, 02:13 PM

I have found ths.gardenweb.com which has some really good forums on all things "house", including HVAC.

Re: Zone Control Valves. yes, I had a stock pile of spare ZCV parts from the seller and a spare actuator itself. When my zone stopped working, I replaced it with the spare one, but it didn't help anything and I kind of worried about the pipes freezing so I called the HVAC guy. I have spare parts for the ZCVs but I have to learn how to fix them. The HVAC guy says that the honeywell ones are good and should be more reliable. The ones I had were Bell&Gossetts.

Anyway, don't seem to have an air problem in my small system, but the PRV leaks due to just age. It drips even when the boiler is at normal PSI (13psi). It's only supposed to trigger at 30psi so I think it's a clear case of an old seal.

There are cases where the PRV is actually correct in letting water out which could be caused by many scenarios, from what I've read:

: Leaking Domestic hot water coils if you have a shared boiler for heat and hot water which I don't have
: lack of air in the expansion tank. No problem from my testing
: leaking pressure reducing valve on the intake, Doesn't seem to be bad to me.

I have one bleeder valve right inline with the expansion tank. I figure to drain the boiler, I can just turn off the two ball valves going to each zone, then below the circulator there is a hose bib I can connect to a hose and open the valve there after the water has cooled in the tank and power is all off. Refilling it would be reversing the process and then purging the air from the bleeder valve.

Jay