Quirk with hot water heat system.

[mrsilv04]

I have a system with 2 hot water heat boilers. The thermostat has been calling for heat for hours and hours (the thermostat is on 68, and the room with the thermostat is at 64). However, even though there's a constant call for heat, both boilers are cycling on and off.

My first guess is that the boilers are hitting some sort of an upper heat/temperature limit setting (a safety), and are shutting down. Once they cool off, they refire and heat up again, until they get too hot again....?

When I found them this morning, both boilers were off, but the water in the system was still quite hot. Within about 10 minutes, they both eventually re-fired, and were heating the water in the system again.

It was 12 below this morning, which is about as cold as it normally ever gets during the winter in this area. This is about the coldest time of the year here, with a "normal" low temperature of around 14 degrees... so we're a good 25 degrees below normal right now.

 

[ARCOgraphite]

There is a low and high setting on the boiler. The low setting is for the circulator cut-in point AND the low boiler temp. The HIGH is the "call for heat" NOMINAL temp which will vary in a constant call for heat around your differential setting - usually 15-20 degrees delta. My typical conservative setting on my Honeywell unit is 160 LOW, 180 HIGH, diff 15. You cant just keep heating the water up or the boiler will explode! On call, It heats up to around 180 +/- and then stops firing around 195 - 200. Then it'll start firing again when it hits the lower differential around the 180 setting - lets say 170. All normal. Is your boiler oil fired(?) and why is the heat set at so high a temp(?) - we run ours below 64 - but I'm in an un-insulated logcabin and dont like to spend over $150 a month on #2 oil.

 

[ARCOgraphite]

BTW my elderly mother is in a condo in FL and the heating system cant heat the house to a 75 set point - in Florida! Shows you how cold it is down there even. Of course the heating system is supplemental to the AC and undersized.

 

[fdcg27]

I assume that the system has circulator pumps.
Are they working?
If not, the boliers will quickly reach their temp shut-off.
If the themostat calls for heat, and the boiler is already past its temp shut-off level, then the circulator pump(s) should run until the boiler temperature is low enough to let the boiler(s) fire.
If the pumps are not working, then the system relies only upon convection, and it will take some time for the boiler(s) to get cool enough to fire.
Finally, are you sure that there is not air trapped in the system?
Open some bleed valves, and see whether you are getting any air out.
Also, was the system set to the correct static preassure?
With mine, at least, you should see 10-11 psig with no boiler heating applied.

 

[duaneb9729]

is this a residential system or commerical system?

do you have low modern baseboard radiators or old cast iron radiators?

 

[ARCOgraphite]

Gee it was -12, you expect an efficieny hydronic system of 120K BTU to reach a room temp of 68deg? Then again maybe he had a zone freeze - but I doubt it if the room was 64. I think the OP is just noticing the mormal operation of the system - with a little - "I'm goonna freeze ta det" panic thrown in. Hope all is well in the OP house - sound like an apartment duplex.

 

[duaneb9729]

to me it sounds like the system is air locked or he has a bad pump, I highly doubt two bad pumps, but this is just a guess at this point.

 

[crazyoildude]

did you try bleeding the system? And if you have an expantion tank is that functioning correctly?

 

[ARCOgraphite]

Op didnt say he we not getting heat. Just that that system was not achieving 68deg and not firing constantly. You guys must have big boilers and well insulated houses to hit 68 on a sub zero night! -

to the OP any update - everything OK or are you an Ice Cube?

 

[ARCOgraphite]

I guess Mr Silverado froze to death ...

 

[mrsilv04]

Sorry guys.... it has been a busy couple of days. Had to turn the Silverado in to the body shop yesterday, and there was a few issues with my "substitute transportation", so what should have taken an hour of my time... ended up taking a half of a day.

Plus, I'm regularly seeing the Chiropractor because of the accident, and therapy sessions as well.

*****

I made a phone call this morning, and a local HVAC outfit that I've done business with in the past will send a technician out, who will inspect/test the entire 2 boiler system for a flat fee of $160.

Since there's a lot of different variables to be checked out on this system, that's the route I'm taking. It should be money well spent.

The last time that this system was inspected/repaired was about 5 years ago, when one of the three circulation pumps was replaced.

If the system is not running at peak efficiency (and I know right now that it isn't), it is likely that we'll recover the $160 by the end of the heating season in savings on the utility bill.

 

[ARCOgraphite]

Is it an oil burner/ boiler setup? That $160 should be for a complete cleanout and tuneup - not just a "check". You are supposed to have yearly maintenance doen on oil burners. I suppose you must have gas fired burner? BTW the chiropractor is a waste of money and are clowns. All you need is a good stretching and workout regimen with some shiatsu massage therapy and some NSAIDS to help reduce swelling. A local gym with an good PT would be my course of ation. This is from someone who could barely walk or get up off the floor at one point.