boiler emerg. relief valve activated

Mitch_6

Sounds like you already know the answer, you need an expansion tank sized for your system, 165K out would be a floor mount SX-30 or extrol 90 at minimum sized by an extrol chart. What is your boiler pressure should be 15 to 21psi. Circulators on the feed or return are not critical. The bypass will help extend the life of the boiler by allowing it to run at higher temperatures, if you have a large water content and over sizes by btu output. You really want your boiler to cycle 160 to 180. If you can just change the expansion tank, relief valve and maybe the auto feeder (basic high pressure tune up when you have it drained down)it should get you by.

Since the boiler is almost 25 years old if you are going to do any major refit you may as well install a new more efficient and properly sized system.

Mitch

D107

Valve opened hours after 160 to 180deg aquastat adjustment

Under pro advice I've had my 1981 Weil McLain CGM-7P1 Series 7 gas boiler water temp setting at 160. Due to the colder weather last night I upped it to 180. This morning I found some water on the floor, maybe a quart's worth. First feared it was the boiler seals, then I checked and found water in the relief valve pipe. No wetness as far as i can tell from the boiler underside itself. As a side note, when I moved the aquastat setting up, I heard a click but boiler didn't activate to make the new temp which I thought was unusual. Also though we keep the heat very low daytime (58F) I never hear it going on on aquastat which makes me think it's not functioning and boiler is actually cold-starting. (Our top indoor room setting is 65F.)

I've been told by pros that this boiler has a number of built-in problems: no bypass, pumped on return side, 3/4" circulator lines going into 3/4" manifold--instead of 1"--going into boiler--(3 ciculators, three zones, mostly cast iron rads.)--ET 5 undersized Amtrol expansion tank which is inline on supply side at start of main zone. Boiler input 210K, gross output 165K. Actual house heat loss probably around 55K, existing radiation around 75K.

Any opinions welcome and Happy Thanksgiving everyone. (I'm giving thanks I may not have a boiler seal leak.)

David

Timco

Could be several things... Bad expansion tank, pressure too high, for starters. The extra heat builds up extra pressure that has to go somewhere, and will at 30#, and may seep a bit at 28-29#. 10# cold is pleanty for a single story home, maybe 15# for 2-3 story application. Expansion tank should give a hollow ping if tapped with a key or scrwdriver, not a thud to indicate it has water in the air side. Aquastat would have bumped the heat up when turned up only if there was a call for heat, or if the temp fell below it's 'range'. Also, pumping away from the expansion tank reduces system pressure by putting a vacuume on the expansion tank, rather than forcing water into it. HAs nothing to do with pumps on the return side. You will get better flow / performance by putting the monifolds and near boiler piping in 1".

T

Uni R

If...

If your expansion tank is undersized as you say (an ET 5 is a tiny tank) then by upping the temp from 160 to 180 you exceeded what little expansion room you had and that caused the pressure release valve to get tripped. In my non-professional opinion, I'd get a properly sized tank on there right away, because it is as much of a safety device as the relief valve and if you keep tripping that valve it can easily stick open on you. The rest of your problems need to be properly addressed as well but that tank size needs to be increased right away.

D107

Thanks

so much guys. yes it's a matter of how much $$ to put in to an old warhorse. Expansion tanks are fairly cheap but i think with the draindown, labor etc. it adds up. Perhaps keeping aquastat at 180 for now instead of manually up and down from 160 --now that it's purged--will avoid the problem until I can get a new one. I guess I could bleed another quart from the near-boiler flush valves just to lower pressure a bit in the interim, and though this is not any long term solution, if the weather really warms up and I feel i need to go down to 160 again, I should flush a quart out or so before I return to 180deg. My local pro has recommended a Buderus condensing boiler with indoor reset and I'm inclined to agree. Can't see throwing good money after bad.

FYI three zones are basement, main and 2nd floor.

As for aquastat, seems like if setting is raised from 160 to 180, it would activate boiler to raise water temp by those 20 deg.

Enjoy they turkey and the family,

Best,

David