burnham boiler keeps running if thermostat is set over 70 degrees

mercrunner19975

I hope someone can give me some sound advise. We recently left our forced air home and bought a 1950's home with a burnham propane converted boiler, approx. 2002 mfg, date. I have had a local company out 3 times and no results. The boiler was unused for about 7 years while the home was vacant. The first thing we did wad drain and bleed the system which worked great. In the course of three weeks we went through $400.00 in propane. All the baseboards are warm, the water circulates fine, but the furnace will run....shut down..and refire minutes later. The return water is still hot. The last service tech told me that that is indicative of that boiler when the thermostat is set above 70 to 72 degrees ? I am a 40 year marine service technician, so I have a pretty good basic understanding of how things work....but I am at a loss here. The thermostat is an older mercury unit, but I cant see that as the problem. When the area the thermostat is located gets warmed up (by the nearby fireplace) it shuts down for a longer period of time, but I find it hard to beleive that it was designed to operate at 68 degrees. Any Ideas ? I suspect a bad component, all the temps and pressures are as recomended in the manual ??

Docfletcher

Greetings and welcome. I am a homeowner not a pro. Is the thermostat the old style Honeywell round type? Drafts can and will affect thermostats. The boiler will fire and circulators will run whenever the thermostat calls for heat. You may be able to remove the thermostat cover and watch the mercury in the bulb make connection when calling for heat and open the connection when satisfied. Once you reach the room temp the thermostat is calling for (say 70F) the thermostat should break connection and stop calling for heat. At this point the boiler should shut down and all circulators should stop. Why did you drain your boiler system? You should never do that because the older the boiler water the better it is for the system. Thank you for your service.

KC_Jones

Is this steam or hot water? You posted in the steam section, but you mention water circulating and bleeding the system which are functions of a hot water system.

mercrunner19975

apparently there was a leak at some point in time and there was very little water in the system. A good friend who has a summer home here has a heating and air service company in the Baltimore D.C. area is who helped me thus far. He told me the same thing about draining, but also recomended it to bleed the air, as well as as to see if there was in fact any debris in the system due to our being on well water. I was leaning toward thermostat replacement, but it seems to be doing what it supposed to

mercrunner19975

Hot water,,sorry,,,this is unexplored territory for me

nicholas bonham-carter

Is this system steam or hot water? If it is hot water, then it would be better to continue this post in the main wall.
If you short out the thermostat wires to simulate a call for heat, will the boiler run continuously? If so then maybe the anticipator of the thermostat is wrongly set.
Most of us use Honeywell digital thermostats, which can be set for the type of system, on which they are used. We try to make whatever adjustments necessary to prevent the type of short-cycling you are experiencing.--NBC

mercrunner19975

Not at home, had to work, it is a honeywell though, the high and low are set to the specs in the manual as well as the variable set to 15

mercrunner19975

If I were to replace the thermostat with a newer type, which seems like the first most likely cause in my mind, will it wire right in or does it need a seperate power supply ? Guess you can tell I am not even a rookie at this yet..lol

Jamie Hall

If the mercury bulb in the thermostat tilts properly -- you can see which end has the contacts -- and opens the circuit, I wouldn't bother to replace the thermostat unless you want the advanced functions of a digital. Then I'd go with a Honeywell VisionPro -- but the old round ones are fine.

What should happen, as has been said, is that when the thermostat is satisfied it should open the circuit and the the circulator(s) should stop.

The boiler, however, should be controlled by an aquastat on the boiler or on the boiler outlet pipe, and it may be that that aquastat is not functioning properly.

mercrunner19975

Well...I thank all of you for your thoughts...Guess I am gonna close up shop for the afternoon and get home, and check the thermostat mercury as you have recomended. I certainly do appreciate the help, guess I will see how that works out,
Thanks again !!!!!!