Boiler Shuts Down

[John F.]

When the outside temps (I'm in upstate NY) get down to the teens and single digits my boiler can't keep up with the heat loss. There is baseboard cabinet (7 inch cabinet) running the entire perimeter of the first floor exterior walls of the four rooms (each 13x13) the zone covers. The rooms are 8' 9" and all walls are insulated to R-13. The windows are dbl insulated glass and the basement ceiling below is insulated as well. The heat pipes are also fully insulated in the basement. The boiler (oil fired baseboard hot water 2 zone system) rated at 150,000 btu shuts down when it reaches the 180 deg boiler/water temp. I've been told that the 180 deg is the proper shut down. The thermostat calls for heat with a 2 degree drop in temperature. Right now it only runs for about 10 minutes before it reaches its 180 deg mark and then shuts down for about 15 mins. The result is a net loss of room temperature especially at night of upwards of 6 to 8 degrees resulting in a room temp of 60 to 62 degrees by morning. If temps go into the below zeros then the boiler never catrhches up even in the daytime. So my question is what if anything can I do or have the oil burner service company do to have the burner deliver heat for a longer peiod. Your usual good input would be appreciated. Thanks. John

[Speedy Jim]

It doesn't sound like a burner/boiler problem to me.

If the boiler is easily maintaining ~180F, the problem seems to be that the circ pump and radiation can't *remove* enough BTU from the water.

For example: Although the boiler has a rating of 150,000BTU/Hr, let's say that the rads can only unload 50,000BTU/Hr. The burner would only need to run 1/3 the time .

But the house needs 100,000BTU/Hr in coldest weather (example). The boiler *could* produce that easily, but the rads can't pump the BTU's into the house fast enough. So...house gets cold.

You may have to have someone re-calculate the fin-tube area required and/or the pump capacity to deliver enough water velocity.

Jim

[m Ransley]

You can raise the boiler temp to 190, the circulator pump could be weak, but it doesnt sound right, are the radiators extremely hot, have they been bled of air, does the circulator pump continue to run when the boiler is not firing and thermostat is not satisfied, it should. How many sq ft and what is your attic insulation. Are the baseboards retrofit.

[RBM]

If I'm reading your post correctly, it sounds like the entire system shuts down when the boiler reaches 180, which it shouldn't. You have two zones and I don't know if they are zone valves with one circulator or two circulators but, in either case, the thermostat should control the circulation of the hot water, and should keep it circulating until the thermostat is satisfied.

[spamTHISbrp]

John, it can be tough to tell on some units if the circulator is running, or not.

If the thermostat is closed, the circ pump should be running, and the burner itself will run or not as needed to keep the water in the boiler hot.

The only thing I can add to the replies here is to make sure the thermostat doesn't have its anticipator set to give absurdly short cycles.

Don't know how to check it on an electronic thermostat, but on a good ol' mechanical one remove the cover and look for a little dial in the middle of the metal coil, and see if its labeled. If its set far into the 'shorter cycles' zone this could cause the thermostat to shut off too quickly. This is actually a little heater that is adjusted such that the thermostat shuts off as the proper temp is approach so the temp doesn't overshoot by a wide margin.

Dave

[John F.]

The radiatorshave been purged they are not retrofits) are pretty hot but they don't seem excessively hot; don't know if circulator keeps running but will try and check that. The thing about the circulators though is that they are the small water lubricated type. Many years ago I had these same type and they would fail if they weren't used or run periodically during no heating months. Attic insul is approx. r-25. The upstairs is very warm. Thanks.

[John F.]

Thanks for input. That cicrulator is sounding supicious now that it has come up. I'm sure the burner people will not like it as my conract includes circulator replacement. Is there some easily done test without dismantling system to see if the pump is weak or really bad?

[John F.]

There are 2 zones each with it's own circulator and I just noticed up in the insulation near the boiler on the return side there is a non-electric flow control valve. If by "the entire system shuts down" you mean the boiler that is correct.I believe I detect the circulator for the zone involved running when I place my hand on it. When the boiler temp reaches

180+ boiler shots off and comes back on about 10-15 minutes later as room temp causes the thermostat to still call for heat. I'm beginning to believe that the total run of the heat loopis way too long. I don't know what limitations there should be. A quick calclation gives me 200 plus feet some of it is 1 and 1/4 inch pipe. The more I examine everything the more questions I have. Time to make a call. Appeciate exeryone's expertise. John

[Edwin Pawlowski]

Circulators do fail and they are about $50 to $70 to replace (for the parts). One thing that I did not see was if the problem was new or if it has always been that way. If it is new, I'd suspect poor circulation. If it has always had lack of heating, I'd suspect poor design of the baseboard setup. There may be not enough finned sections in each room.

[John F.]

Have been in the house only 2 years. I became vaguely aware of the heat loss last heating season but can't say I was aware of the frequency of boiler on/off situation. There are no walls left on which to put finned sections. As I mentioned in one of my replies there is some 200 feet and more of heat loop but only about 100 feet of that is actual heat fin. The rest is insulated piping in the unheated basement. I wonder if this length of run is too long or does it matter. I'm wondering if cutting into the current run and adding another zone would solve the problem assuming it's not a cirulator problem.

[Ben]

Do you have zone valves, or pumps that are controlled by "there should be 2" thermostats 180 degree temp sounds OK. When the boiler reaches

180 degrees the burner should shut off but the pump or pumps should stay running until the room temps have reached the setting on the t-stat. Check to see if the zone valves are open all the way (there is a dial on the body of each zone valve) so you can open these manually. The pumps could be bad or the Zone Valves could be bad!!! Good Luck

[Edwin Pawlowski]

In most cases, the baseboard enclosure runs the entire lingthof hte wall, but it mayh only have a portion that is finned, the rest is copper tubing. The amount of finned tubing is determined by the heat loss calculations done for each room. You can do more fine tuning of the heat from rom to room by closing the dampers on roms yo want cooler, thus allowing the temperature of hte circulating water to remain a bit hotter as it travels to the next room on the loop. In my case, some of the rooms have only 50% of the sections finned, the rest plain tubing.

As I mentioned in one of my replies there is some 200 feet and

Splitting the run to two zones may help in some cases. The water is giving heat to the tubing, that is giving heat to the fins, that are giving heat to the air. As the water runs each foot, it is cooling down. It just may not be hot enough by the time it gets to the last room. Running a section of insulated tubing to the further zone will help as it will be a shorter section.

If the boiler is cycling off and on, it has enough capacity to heat the house. It is shutting off because it can make more heat than the rest of the system can take away. Check to see how hot the return pipe is too.

If you are not getting enough heat in the house, the potential problems are: Not enough finned sections of baseboard Missing or insufficient insulation. Poor or no circulation (some circulators have speed controls so check for them) Poor layout of the zones

[John F.]

Thanks for all the input. All the tubing is finned except of course what's in the basement. I'm calling the oil company and will have them come and test circulator and review the system so that by next winter's major heating need I will be OK and maybe get some benefit this season.