Oil buner pressure problem

My 20 year old oil fired boier for baseboard hot water heating system is building up excess pressure. I figured that the water inlet valve (manual, not auto-fill) was bad, thereby allowing curb pressure into the system, I replaced that valve. That did not solve the problem. I then turned my attention to air issues. I drained my expansion tank (old steel type) and it was not full. I installed new bleeders on all of the baseboard units and the bled as expected. I am confident that I do not have any airlocks.
I filled the system to 13# of pressure. It seems to work fine for a few days and then it creeps up to 25# or more. It has reached 30# and blown out of the PR valve. I've let water out several times to lower the pressure and somehow it seems to creep up again. Does anyone know of a possible source for this pressure increase? It's a closed system with no apparent leaks, well bled, and has a new water input valve. I cannot figure this out. Thanks. RNR
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13 pounds pressure? I have a 3 story house and the boiler is in the basement so its 4 levels and only needs 13 lb pressure, its an old gravity feed that now has a pump. Is water actualy going into the expansion tank, try www.heatinghelp.com all boiler pros there. Just an uneducated bubba guess, water is still filling it, the new valve is no good , or its the expansion tank.
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On Fri, 21 Nov 2008 07:11:29 -0800 (PST), ransley

I'll try that site, thanks. I understand your line of thinking because these are the same areas that I've been focusing on. I have full confidence in the valve. I didn't remove the old one, which probably wasn't bad anyway. I now have two valves (one gate, one ball), both of which are firmly closed. I can't imagine that any water is getting in. I did a rough calculation of the volume of the expansion tank and came up with 15 gallons. When the boiler was at very high pressure, I drained the expansion tank to see if it was too full and only got 5.5 gallons out, which I think is fine. I'm not saying that you're wrong, I'm just saying that I have been poking around these areas and getting nowhere. Thanks. RNR
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rnruss52 wrote:

If you're sure that no water is coming in from your series of two fill valves, and if you've drained the expansion tank and relieved pressure enough to account for the normal expansion of cold fill water expanding as it comes up to temp, the only possibility left would be a leak in your tankless domestic hot water coil. If there is a leak in this coil which sits inside the boiler, it will be adding water to the boiler volume up to the water system pressure.
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wrote:

It would not surprise me at all if that coil was leaking. I had wondered about that and was told that there was not direct route into the heating loop from that coil. I don't have any first hand knowledge on how that stuff is configured in there. Is that coil actually immersed in the water that goes through the heating loop? If so, that would certainly explain my problem. My heater does make domestic hot water, but I don't need it. It could not keep up, so 5 years ago I installed an electric water heater and I have the ouput from the boiler feeding pre-heated water to the input side of the electric heater. I could put a valve in the water line before it goes into the heater and just run a clean cold water line into the electric heater. Does that sound reasonable? Thanks for pointing me back to this possiblility, before I go nuts. RNR
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rnruss52 wrote:

As far as I'm aware those DHW coils do indeed sit in the main boiler water. If you don't need it, bypassing it and capping off the coil connections should do the trick.
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Might not be a concern on boilers. But on wood stoves, you have to drill a little hole in the cap. Or the heating coil over pressurizes and ruptures. Boom!
--
Christopher A. Young
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Stormin Mormon wrote:

Not a concern, if it already has an internal leak that is the reason for the capping.
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wrote:

This has me a little concerned. If I am wrong about the leak in the domestic coil, could this explode. I also thought about valving off the input on the coil and just cutting the output pipe and leaving it ot vent to the air, just in case. But then I thought that if there was indeed a leak, when the domestic coil pressure became lower than the boiler pressure, I would lose boiler pressure through the coil and out the vent that I created. Not sure what to do now. RNR
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Call a pro. Get it checked out and corrected.
The good news is that water does not explode if there is a leak. The bad news is that steam can explode with great force. Find the problem and fix it.
If you have to replace the boiler, be sure to get an energy efficient one and an indirect water heater. Look at System 2000, Crown, Buderus, Peerless, and a few others.
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rnr wrote:

It's really simple, just turn off the water supply to the DHW coil and do your pressure tests. If that is indeed the source of that water (and there isn't any other possible source its there?), then with that supply turned off you won't have any pressure increase beyond normal stabilization. Alternatively, disconnect the DHW coil and leave it uncapped and watch the boiler pressure drop and water run out from the leak.
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rnr wrote:

Well, did you fix it?
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wrote:

I chickened out. I'm still draining water out every other day, or so. While I cannot imagine where else the pressure could be coming from, I can't help but think that I may be creating a dangerous situation that may manifest itsef when I'm not home. I still want to do something. The leading possibility is shutting off the input to the DHW coil and cutting the output line and leaving it open to vent. If there is not leak, it should vent until empty, then stop. In that case, I would reconnect it and go back to square one. If it vents continually, and the pressure in the boiler goes down, I would feel much more comfortable with capping it off, as this would indicate a leak. If there was a leak, and I capped off the lines, then the pressure should equalize between the boiler and the coil and all will be well. I'm not usually this indecisive but I cannot afford a new heater right now and I don't want to inadvertently disable by causing collateral damage. I will have to do something soon, as this is likely to get worse. RNR
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wrote:

You have provided me with my first ray of hope. I can bypass the coil for $10 and a half hour of work. That will be done tomorrow. I have nothing to lose. Thank you very much. RNR
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rnruss52 wrote:

Your water pressuer regulater on the water feed line is defective. Replace it.
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On Fri, 21 Nov 2008 12:24:49 -0500, Claude Hopper

I do not have an auto-fill valve. There is no regulator. The only time water goes in is when I manually open the valve.
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rnruss52 wrote:

Then your expansion tank is plugged.
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Claude Hopper :)

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