Too much Heat

Sento

I'm a homeowner. I have a Utica Boiler with Honeywell Triple Aquastat L8124. Only one zone. The unit was installed in 1997 and has worked fine until recently. My problem is that my house Temp won't go below 72F. I replaced my digital Honeywell with a cheap mechanical (Oil-Tech made a face when I told him I had digital).) Tested it - it's fine. (As was the original). After two visits from State Utilities(on Long Island) the conclusion is that I am getting hot-water circulation even when the house is hot. (even when the circulator is not on). The tech cleaned the flow valve and bled the system. (Didn't help). The next visit they will either put in a spring check valve to prevent the water flow or replace the flow valve.
I have a couple of questions for anyone sympathetic enough
to answer:
1.Can anyone explain the low and high and temp difference controls on the Aquastat. I've done a little reading, have experimented a little but I don't quite get it.
2. Do you think the service guys are doing the right thing ?
(Why would you want to put a check valve in, isn't this not addressing the problem directly which I guess could be the control valve or circulator).

Thanks all in advance.

John@Reliable

Too much heat?

Sounds like they are on the right track, a sticking flo-check can cause your problem. Has any work been done on water side of system before this happened? Has anyone drained water out of system or has any water been leaking out from relief valve? both which could dislodge something in system and now that something is holding flo-check open and causing "runaway heat". Also if 8124 wasn't working on hi limit it too could cause overheating,what is temp on gauge? if under 190-200 flo-check is most likely.

Unknown

The quick answer to the triple aquatat

When there is no call for heat the boiler will stay at the set temperature on the low limit side ( give or take for the differential ) . When the zone calls for heat , the boiler temp will be knocked up to the high limit setting . If you have a coil in the boiler , we usually keep the settings at 180 high side - 160 low side . If theres no coil we will keep it at 180 high - 140 low .

We have run into the problem of heat bypassing through the flowvalve . What we will do is change the flowvalve to the next size up , and if that doesnt work , we will install another flowvalve on the return pipe . Good luck .