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Boiler identification and PRV

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by kohj1978, Oct 19, 2012.

  1. kohj1978

    kohj1978 New Member

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    I have an old Kerr wood boiler and we seem to have gotten everything to work but the prv drips when I load it for over night. It seems once the dump zone pipess are hot and the other zones are notcalling for heat the prv startsa to leak. I've looked around and can't find any model or other info on the boiler there is a ul code for maine on it and a kerr plack. There wasa a 40 psi prv on it but our plumber changed it to a 30 and now were getting the drip. I'm nervouse about running when icant watch it the 40 psi blew off when we first bought the house. My fualt had furnace off. And Started the boil not knowing that I shut off the circulators as well. I'm new to this

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  2. Eric Johnson

    Eric Johnson Mod Emeritus

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    You can try flushing the relief valve out by opening it a couple of times in hopes that it will flush out any debris that may be holding it open. If that doesn't work, then you either need to replace the PRV (they're not terribly expensive) or adjust your system pressure so that it runs at something like 15 psi instead of 30. If pressure is the problem (i.e., it gets up to 30 psi) What kind of expansion tank do you have? Do you know if it's working properly?
  3. kohj1978

    kohj1978 New Member

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    the pre set the on the oil boiler is says preset to 12psi and max of 75 but im not sure how to check that, and i dont know if this makes a differance but the oil boiler prv is a 40psi. As far as if its working im not sure i would assume so but once again i dont know how to check. the oil boiler was just serviced so im guessing its working. I dont mind replacing the prv thats on it im just not sure what psi should be there
  4. Eric Johnson

    Eric Johnson Mod Emeritus

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    30 psi is standard in this country, as far as I know. That's what you should go with. Don't confuse it with a domestic hot water PRV, which looks similar and will fit, but the pressure is much too high. You should have a pressure gauge somewhere on your boiler that will show you what the pressure is at any given time. They're cheap and not hard to install, so if you don't have one where you can see it, by all means, have one installed. Any 1/2-tap into the boiler or its piping will work. As I said, your system pressure at the boiler should be around 15 psi--maybe slightly higher when it's hot.

    The fact that your PRV starts to drip when you bring the system up to temp tells me that you have a problem with your expansion tank. If it's a more modern (read: small) tank, then it's probably a bladder tank and the bladder may be shot, which would allow the system pressure to rise as the temp increases. If you have an older (read: big, hanging from the rafters) expansion tank, then it's probably full of water and needs to be drained for it to work properly.

    Either way, it doesn't sound like a serious problem, but you should get it fixed before the heating season begins in earnest.
  5. Morgan

    Morgan Member

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    Around here PRV is usually an acronym for Pressure Reducing Valve, relief valve is usually called just that. Around my parts anything over 30psi is considered high pressure and requires addition inspection. Any residential relief valve should be set at 30psi. Most systems should be running in the 10-20psi range. If you relief valve is dripping there are only a few things that could cause this. Relief is bad (should be changed every few years anyway) Expansion tank is bad (bladder gone), or waterlogged (common of the older galvanized/steel bladerless tanks usually hanging from the ceiling), your waterfeeder could be bad and overpressuring your systme (this is the valve that allows water into your heating system, and should be set at or around 12psi. I always turn mine off after filling, if your system needs water after the fact it has a leak, install a LWCO and close the waterfeeder after initial filling in my opinion) Other than that you could check your tankless coil or indirect water heater coils for leaks, its rare but it does happen.

    Where are your circ pump(s) on the boiler supply or return?
  6. Eric Johnson

    Eric Johnson Mod Emeritus

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    + Word
  7. Morgan

    Morgan Member

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    One other thing that just crossed my mind, I was on one of the few service calls that I do for a problem just like this one. Couldn't figure out what was causing the system to over pressure and weep at the relief valve. I was sure the indirect coil was leaking but after isolating it the problem was still there. Water feeder and relief had been replaced by an earlier plumber so I knew these were good. Turns out the bypass around the waterfeeder (used for fast-filling and purging) had a globe valve installed backwards. Whatever happened over time caused this globe valve to pretty much disintegrate on the inside and was leaking by. Yup turns out a 2 hour call could have been fixed in 15 mins...........sometimes I wish I did some more service work, although more times than not I am glad to stick with the commercial stuff :)
  8. kohj1978

    kohj1978 New Member

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    OK i do have an expantion tank with a blader, and looking around i did find the pressure reducing valve (dont know if thats correct) it says 12-15psi and looks to be in ruff shape, i also noticed that when the ciruclator next to the wood boiler kicks on there is a 2-4 psi increase but the whole system including the oil boiler read 30 psi, and the pumps are on the return i believe, there on the line coming out of the bottom of the boiler, and the pumps flow arrow indicates that it would be pushing into the bottom of the boiler and hot water coming out of the top to the zones
  9. kohj1978

    kohj1978 New Member

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    So i just changed the expantion tank and the pressure reducing valve, after filling the system the pressure is about 16psi i just lit the wood boiler so i guess ill see in about an hour or so iff it worked, also i dont have an LWCO there is a valve before the pressure reducer should that be closed after its filled.

    This is the old valve
    IMG-20121021-00188 (1024x768).jpg
  10. kohj1978

    kohj1978 New Member

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    its up to temps (180) and the dump zone kicked on the psi at the oil boiler is reading 15psi but the wood boiler looks to be closer to 18psi still not 12-15 but far from 30+ which is nice but im guessing something else is wrong,
    we had an electric water heater installed back in april when we bought the house and i see no signs of leaking around or on that. any other ideas on it would be great
  11. kohj1978

    kohj1978 New Member

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    After burning for a day i noticed that the wood boiler psi was up to 28psi, and then this moring with a cold system it was back down to 12-15psi, In my mind (which is usualy wrong) heat from the boiler would increase the pressure to some extent since its a closed system and the pressure on the feed side of the pressure reducing valve is higher so it allows the bioler pressure to rise, any idea whats could be cuasing this after i replace the valve and tank,
  12. maple1

    maple1 Minister of Fire

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    Expansion tank not big enough?

    Is it a bladder tank? Pre-charged too high?

    The valve between the tank & system is open - right?
  13. kohj1978

    kohj1978 New Member

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    it is a new blader tank that we put in over the weekend but i didnt check charge on it ill do that tonight

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