I have been heating an old farm house (no insulation) with a 240 gallon OWB. I have cast iron radiators on the first floor and second floor, pressurized system with HX. I also am heating a shop about 150 feet away. I have 1 inch insulated pex underground. 1 pump to the house, 007, and one 007 pump sending water 150 feet one way, to the 3 radiators in the shop. I bought into the 1 inch theory, as being big enough to make the trip to and from the shop. I only need the temp high enough to keep the water from freezing in the shop. The boiler keeps up fine until the shop calls for heat. Then I get a 30 to 40 degree loss in them at the boiler. The boiler never gets a chance to fully recoup. Then the shop calls for heat again. For some reason my mind keeps thinking that the slower the water comes back to the boiler, the easier it will be to get heated back up to temp. That's why I only have one pump doing the work. Would another pump on the return at the shop help cure this problem? Or are there any ideas that can help eleviate the huge heat loss in the water? If the shop does not call for heat I can keep up just fine in the house, but when heating both, I am having huge problems, besides blowing through the wood.
30 to 40 degree water temp loss
- Thread starter adcman
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Sounds like you would be doing great just heating a big old uninsulated farm house. Is the shop insulated and how big an area is it?Is this the first year you've tried heating the house and shop?
I'm not very smart but if the shop isn't geting heated up I would think it would be better for the circulator not to run until the water got hotter rather then continue to slowly circulate the water. Just a waste of electricity for the thermostat to keep calling for heat before the water gets hot enough.
Might want to try heating the shop with its own dedicated stove or whatever. Or turn the thermostat down in the house when you will be in the shop and vice versa.
Hopfully someone else will have a better more intelligent answer. I just wanted to share my thoughts.
When I was a kid Dad bought an old farm house with an old oil boiler hot water baseboard. The house seemed always cold. Dad would get upset with Mom because she would turn the thermostat up higher and the circulator kept running but the water never really got hot enough. He would turn the thermostat down for a while and let the boiler catch up.
I suppose if we had a bigger boiler , bigger furnance that would have fixed the problem. Maybe the only way for you to go is bigger.
I'm not very smart but if the shop isn't geting heated up I would think it would be better for the circulator not to run until the water got hotter rather then continue to slowly circulate the water. Just a waste of electricity for the thermostat to keep calling for heat before the water gets hot enough.
Might want to try heating the shop with its own dedicated stove or whatever. Or turn the thermostat down in the house when you will be in the shop and vice versa.
Hopfully someone else will have a better more intelligent answer. I just wanted to share my thoughts.
When I was a kid Dad bought an old farm house with an old oil boiler hot water baseboard. The house seemed always cold. Dad would get upset with Mom because she would turn the thermostat up higher and the circulator kept running but the water never really got hot enough. He would turn the thermostat down for a while and let the boiler catch up.
I suppose if we had a bigger boiler , bigger furnance that would have fixed the problem. Maybe the only way for you to go is bigger.
It sounds like the boiler cannot keep up with the house and shop load. Does it catch up on warmer, milder days? Do you know what the heatload for the house and shop actually are?
You could prioritize the house, and have the shop come on only when the house load is satisfied.
Does the boiler ever cycle off when both loads are calling?
hr
You could prioritize the house, and have the shop come on only when the house load is satisfied.
Does the boiler ever cycle off when both loads are calling?
hr
On the milder days the boiler keeps up fine. Most HVAC folks tell me to add the other pump on the return line, thus making the water flow faster. Theoretically that would satisfy the shop faster, thus making the boiler recover faster. I do not know how much heat loss I am experiencing in the shop, but it is fairly well insulated. The house is loose, and on very windy days it's hard to keep warm. The house is about 1500 sq. the shop is about 1000 sq. According to what I have read, 240 gallons should be enough to heat both buildings, but it seems I might be wrong. I did heat them both last year, but had the same problem, it just seems to be worse this year.
It's not so much the water capacity of your boiler but the size of the fire, and the efficiency of the unit. The horsepower so to speak. And the ability of your OWB to turn the wood into thermal energy. Wet or green wood makes that energy conversion much worse. You could be running a wood to water conversion of 50%, maybe less.
If you don't have enough horsepower to cover the load, moving the fluid faster will not change that. Lets assume the shop has a 25,000 BTU per hour load 1000 square feet times 25 BTU/ ft load. Your 1" pex should easily move the load from the boiler to the shop, even with 150 feet of pex. I suspect you do have some loss from the boiler to the shop. regardless the 007 should be enough pump for the job.
Maybe the house load is higher 30 BTU/ ft times 1500 = 45,000 BTU/hr. It sounds like the home has a lot of loss (infiltration) on windy days? Maybe the load of the house is considerably more under windy conditions? If you can, have someone do a Blower Door test on your home , find and eliminate as many "leaks" as possible. That is the best way to make a heating system perform better, and a more comfortable home.
The infiltration or losses the home experiences under windy conditions are often much larger than you would imagine, especially in an older leaky home.
You know what a wind chill can do when you are outside, inside it is called drafts! Even with a thermostat set, and the room at at 70F, drafts make you feel cold and uncomfortable.
IF the boiler can catch up and shut down on the coldest windy day then it is sized correctly. If either building is still too cold then you do not have enough distribution. Either not enough radiators or large enough piping supplying them from the OWB.
Perhaps you had a fossil fuled boiler previously with enough horsepower to supply 180F to those radiators. I'd guess the OWF struggles to maintain a 180F supply on cold, or windy days.
You could increase the pump size to overcome a distribution shortfall, but if the boiler is not keeping up with one, or both loads, the larger pump will just get you to the "not enough heat" condition faster.
It is easy to mis-size a boiler on those older leaky homes. I sold my neighbor a 145 Aquatherm for his 1500 sq. ft 80 year old farm house. Next winter I had to up-size it for him. Seems he is happier "feeding the beast" than upgrading the building envelop, and he burns green wood as he cuts it up. Oh well.
hr
If you don't have enough horsepower to cover the load, moving the fluid faster will not change that. Lets assume the shop has a 25,000 BTU per hour load 1000 square feet times 25 BTU/ ft load. Your 1" pex should easily move the load from the boiler to the shop, even with 150 feet of pex. I suspect you do have some loss from the boiler to the shop. regardless the 007 should be enough pump for the job.
Maybe the house load is higher 30 BTU/ ft times 1500 = 45,000 BTU/hr. It sounds like the home has a lot of loss (infiltration) on windy days? Maybe the load of the house is considerably more under windy conditions? If you can, have someone do a Blower Door test on your home , find and eliminate as many "leaks" as possible. That is the best way to make a heating system perform better, and a more comfortable home.
The infiltration or losses the home experiences under windy conditions are often much larger than you would imagine, especially in an older leaky home.
You know what a wind chill can do when you are outside, inside it is called drafts! Even with a thermostat set, and the room at at 70F, drafts make you feel cold and uncomfortable.
IF the boiler can catch up and shut down on the coldest windy day then it is sized correctly. If either building is still too cold then you do not have enough distribution. Either not enough radiators or large enough piping supplying them from the OWB.
Perhaps you had a fossil fuled boiler previously with enough horsepower to supply 180F to those radiators. I'd guess the OWF struggles to maintain a 180F supply on cold, or windy days.
You could increase the pump size to overcome a distribution shortfall, but if the boiler is not keeping up with one, or both loads, the larger pump will just get you to the "not enough heat" condition faster.
It is easy to mis-size a boiler on those older leaky homes. I sold my neighbor a 145 Aquatherm for his 1500 sq. ft 80 year old farm house. Next winter I had to up-size it for him. Seems he is happier "feeding the beast" than upgrading the building envelop, and he burns green wood as he cuts it up. Oh well.
hr
I had the shop shut down from the boiler and ran it on propane for a few weeks, when it was cold last year. The house kept up fine until it got to -30 wind chills, then I needed the pellet stove to compensate. On windy days before the boiler, the furnace never shut down, 5 min cycle times at best ($6300.00 propane bill to heat both, on a very cold year). So I am happy with the way the boiler handles the house. It will hold temp for about 30 min before the blower kicks on, and recoup in about 15 to 20 minutes. It's the shop that is goofing things up. I might try just keeping the temp up around 70 to see if that stabilizes the water returning, (less temp loss) and causes less of a shock to the system. I just don't want to have to fill every 6 or 7 hours. I thought about adding a pellet stove , but the budget won't allow this right now, but it is a thought in the future. I guess the thought of another pump on the return line won't accomplish anything then. I'm perplexed.
You don't get something for nothing, raising the shop set point losses you more heat because of the building loss. Those OWB's don't much care about return water temps IMO. we have done some in the past where the return water from the house was the supply water to the shop, then back to the boiler. This can/could give you the hottest water to house and lower temps in shop. This can help on both ends. baseboard higher temps -set point higher in house -- shop lower water temp, lower set point. This means you get the best use of your heat transfer. The down side is the split across the boiler is big. Keep shop as cool as possible when not in use. Wood is super important [for a different reason than gassers, OWB'S run so cold wet wood magnifies the issue] unless you want to baby sit the thing and spoon feed it. Cut up some oak pallets and burn those if you see a large increase in heat, the wood is your problem
I have been burning 2 year old oak, so I doubt wet wood is the problem. Once in a while I toss in some wet wood, but not very often. The water temp is set at 175, so when the shop calls for heat I see a steady drop on the inside thermometer. I can keep the shop at 45, but wouldn't just make the colder water returning more of a problem? I have 3 cast iron radiators in the shop not baseboard, which might be an issue. They are run i series. the last one takes a bit to get warm, but seems to heat ok. The radiators are lower than the boiler, so they are not pressurised, the boiler water is going directly to the radiators and then back to the boiler. I am concerned about leaving the shop too cold because If the water does not circulate and stands idle too long they might freeze. One time I forgot to turn down the propane thermostat and the radiators never called for heat, freezing the lines at the boiler.
adcman said:
Sounds like the boiler is a little undersized. Its like my S-10 pulling a trailer load of wood. I go down the road just fine and it moves the wood to where I need it. My problem is when I get to a sizeable hill, I don't have enough horsepower to keep up the speed and everyone passes me. The super cold windy days are like that big hill. Just not enough horsepower in the 240 gallons to make up for the two heat loads at the same time. Depending on how ofter this happens, maybe a suplemental heat source in the shop to cover this.
I used to have to clean the vanes on the fan for my OWB. It doesn't take much the loose efficiency there that will have a big impact on output.
I used to have to clean the vanes on the fan for my OWB. It doesn't take much the loose efficiency there that will have a big impact on output.
Rob C you hit it on the head! Somehow, when I was insulating the pipe some fiberglass got sucked into the blower clogging up the vanes. I did not even think about that possibility until I read your post. Temps are keeping up fine now. I stil have a 30 degree loss, but the recovery time is only about 15 minutes instead of 90 minutes. Thanks to all for the help!
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