Hi,

I have a 20+ year old HydroTherm HC-100 boiler connected to radiators. The boiler temp is set at 180 but seems to only heat between 110-150 degrees. Any ideas on what could cause this? Should I bleed each radiator(when Hot or cold)?

Thanks,
Steve

 

You can bleed it any time.

What is your boiler pressure?

 

You could have any of several problems. The most likely is a room thermostat with a bad heat anticipator. Try turning up the themostat all the way & see what the boiler temp does. If it gets as hot as it should, the thermostat is almost certainly the culprit.

 

Jay11J,

Boiler pressure runs about 20 lbs.

Thanks,
Steve

 

Are you saying it shuts off at 150 degrees or it runs and runs and never gets any hotter than that?
Bleeding the rads isn't going to help, I don't think, you'd have a hot boiler and cold rads if that was the problem (if you had airbound radiation).
You don't say if it's gas or oil, or if it's got a domestic coil for hot water. Does the thermostat operate the boiler? Does it run in the summer to heat water for showers? Sounds like a capacity issue, like you don't have the BTUs needed due to combustion related issues but more info is needed. You could also have a control problem if it's shutting off at too low a temp.

 

OR... there could be no problem at all!

Not knowing where you are located I can't say for sure, but with the unseasonably warm weather we are having here on the east coast it wouldn't surprise me if nobody's boiler is getting up to temp before the t'stat is satisfied and shuts off the system.

When it's 45-50 * outside, my boiler fires, runs for a while, temp gets up to about 150-160 * and then ... shuts off ... because the thermostat is happy .

Listen to your circulator pump when the boiler shuts off.

Does it stop running also ?

If so, the thermostat has ended it's call for heat and shut down your boiler normally.

If the circ continues to run, and only the BURNER shuts off, then you may have issues.

So, before you pull yer hair out, make sure it's not doing exactly what it's supposed to be doing!

HAPPY NEW YEAR!

 

It could be a few things. Does the gauge work? Feel the pipe on the top of the boiler **CAUTION: IT COULD BE VERY HOT** What kind of aquastat do you have? If this is a high limit aquastat (cold start boiler), it will only allow the burner to fire if the thermostat is calling and the boiler temp is below 180. This is a gas boiler, so the hot water does not come off the boiler, and this is most likely the case. If you turn the thermostat way up, I think you will find that the boiler will get up to high limit. This is normal operation.

 

And, thanks to all on helping me out!!

I guess I was a little sparing on the facts so here goes:

-I live north of Boston in Massachusetts
-The boiler is gas
-Aquastat is a Honeywell L4006A1017
-The temp guage seems to be working-110 degrees and can touch the pipe
-Hot water is totally seperate via individual hot water tank
-From what I noticed the system won't go much hotter than 150 degrees.
-System runs off a thermostat in Living Room.

-the flame has about 1/2 inch blue and more yellow-I'll try to adjust tomorrow?

The system might be OK since the weather has been mild so the demand for heat has been minimal. But, I'll check for burner firing and circulating pump running or not.

Is there a way to check the aquastat? What happens if I disconnect it and join the 2 wires?

Thanks,

Steve

 

Don't do it. Any adjustments to the air or gas pressure could result in a hazardous situation. This is something best left to a pro with test equipment. When was the boiler last serviced?

 

The aquastat is a break on temp rise. It is a safety device that prevents the boiler from getting too hot. If you jump it out, it could cause the boiler to make steam and blow off the relief valve. If you were in the way of the relief valve outlet, it could cause 2nd degree burns. I'm sure you wouldn't look better with giant blisters and skin peeling off. If you want to test it, turn your thermostat all the way up and see what the temp gets up to. Turn the aquastat down to whatever that temp is (or till the burners shut off), then turn it back up to 180. If the burners shut off when you reach the temp the boiler is at, then it is working right. You may want to have the burners cleaned and inspected by a proffessional, and have them perform an efficiency test. Be sure the equipment they have checks the CO levels, and that it is below 50 ppm.