How long should my boiler run......

Uni R_3

It's really quite simple.

At any given outside temperature, there is a corresponding temperature your rads need to be to maintain a comfortable indoor temperature. As the temperatures drop, the temperature of your rads needs to go up because your house is shedding heat at a faster rate.

There is a control called an OutDoor Reset controller (ODR) that has a scale in it that you dial in. It is connected to a outside temperature sensor. When the temperature outside drops, it automatically raises the water temperature limit the right amount and vice versa when the temperature outside starts climbing.

What ODR doesn't do well is work with a setback t-stat. If the heating system is supplying just enough heat to maintain a comfortable indoor temperature, there isn't any excess heat to help the house heat up quickly - it is simply given just enough heat to hold steady - or close to it.

********************************

In your current situation, the 150° actually sounds like it would work if you didn't set the thermostat back. With 175°F water, you can warm the house up quicker, but there is an efficincy hit doing that.

175° water can heat the house much quicker, but 150° heat can heat the house much steadier. In houses, steadier is better as a rule, especially for comfort.

Ben_11

How long should my boiler run????

Hello,

I've been told that my HWBB boiler should run between 5 and 15 minutes a couple of times an hour. Mine is consistenly running for 30 - to an hour and sometimes longer depending on outside temperature. I recently discovered that the temp for the hot water itself was set at 150 and have since turned it up to 175. Is it okay for the boiler to run that long or is there something else I need to check??

jp_2

return temp?

what was the return temp when the boiler was running at 150F?

longer run times equal better or highest efficiency, that is, highest eff. that particular boiler can acheive.

was the house comfortable before you changed temp? or did it seem cold?

Ben_11

I'm not sure what the return temp was. The house was not comfortable before the temp change and it concerned me that it would take so long to jump three or four degrees in the morning. Sometimes is takes near an 1.5 hours. My relay doesn't have a minimum temp setting so I guess that means the water temp will drop until the actual house temp kicks the boiler back on?

Uni R_3

Ben

Your house probably didn't feel comfortable because of the nightly setback. You might want to look into getting an outdoor reset controller.

Ben_11

I'm sorry.....I'm not really familiar with a lot of this stuff. What woudl the reset controller do for me. Also, is it normal for it to take that long to jump up to temp? and is it normal for it to run for more that 10-15 minutes in the middle of the day to keep the temp at 65.

Ben_11

So you think my system is running okay......not too long??

jp_2

could try

you could try running at 160-165F and see if that works?

as unir said, the higher your water temp the low the efficiency and the higher the cost of heating your house.

the goal is to replace JUST the amount of heat that is being lost out of the house, therefore you need to run 24 hours, thus you use the lowest water temp to make this work.

Ben_11

Should I not be setting the temp to fall back a a couple degrees while i'm at work or sleeping?

Uni R_3

Depends

In order to do so, you have to have enough excess heating capacity at whatever water temp you are using. You'll save a few bucks, you might not be as comfortable and the colder it is outside, the longer it will take your house to recover.

When you set the temperature back? Does your house cool down fairly quick? If you have a draftier or less well insulated house, setback will save you much more than it would with better construction.

Ben_11

Setback

How quickly it cools down depends on how cold it is out. During the day it seems to hold for close to an hour. In the morning or evening it seems to drop more quickly. The house is very drafty and not well insulated. I have recently put plastic on the windows. Its seems like when it switches to setback.......it really has to work hard to get itself back in the morning. Wouldn't that take the efficiency down?

Mark Hunt

Sounds ok


but keep in mind, as it gets colder the boiler will need to run longer.

If you have a boiler with a BTU output capactiy of say, 100,000 btu's per hour and on the coldest day of the year your house loses 100,000 btu's per hour then the boiler would run continuously. As it warms outside, the heat loss for your home drops and the boiler would cycle on and off. Cycling is a sign that the heat generator has a higher capacity than is actually needed at certain conditions, i.e. over-sized.

On a fixed firing rate heat generator, there is not much you can do about this. The generator has only two options, on or off and when it's on, it fires at full capacity even though you may only need a small portion of the full capacity.

Longer run cycles are better because it is then that we achieve "steady state efficiency". On and off is like driving in the city, start, stop, start, stop. Your fuel mileage drops in the city and it's the same with your combustion appliance.

Sorry to be so long, but I hope this helps.

Mark H

Uni R gave a great description of ODR and how it works.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Ben_11

Mark,

So you think it si alright to leave my setting on the programmable? I adjusted the water temp and after reading my boiler manual online I think that was probably a good idea. I was set at 150 and the manual calls for at least 180. Also a plumber I had talked to a while ago suggested not using programable because they do not work will with baseboard. He said they are more effecient with forced air. What is your opinion on that?

Mark Hunt

Ben


Depending on the model T-stat you have, there is a setting that allows for the stat to set for HWBB. Some of the "smarter" stats will actually "learn" how long it takes to bring your house from the set back point to the desired "run" point and will adjust accordingly. So if you set back to 60° at night and want 70° at 7:00 am, the stat may decide it needs to bring the system on at 5:30am.

Your plumbers opinion is just that, an opinion. Set-back can and does work well with baseboard.

It is probably a good thing that you turned the water temp up on your boiler. If it is cast iron, those low return temps would have wrecked havoc on the sections when the flue gasses condensed inside the boiler.

I think you are all set now, but ODR is a good idea as well. It can also lower your fuel consumption.

Best wishes!

Mark H

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Jim_109

How Long Should My Boiler Run

I would like more feedback about combining setback thermostats with an outdoor reset. A comment in this thread says combining outdoor resets and programmable thermostats are not a good match.

I have a two zone oil fired system with cast iron radiators and baseboards on the main floor. Slant fin baseboard on the second floor. Honeywell thermostats.

I am considering upgrading my system to an indirect and high efficiency boiler with outdoor reset. I enjoy the comfort and (hopefully)cost savings by using the setback. THANKS!

Jim_109

How Long Should My Boiler Run

I would like more feedback about combining setback thermostats with an outdoor reset. A comment in this thread says combining outdoor resets and programmable thermostats are not a good match.

I have a two zone oil fired system with cast iron radiators and baseboards on the main floor. Slant fin baseboard on the second floor. Honeywell thermostats.

I am considering upgrading my system to an indirect and high efficiency boiler with outdoor reset. I enjoy the comfort and (hopefully)cost savings by using the setback. THANKS!

D107

t-stats with outdoor reset's OK

homeowner here--I must have missed the comment that said it wasn't. It's done all the time. There are other kinds of room sensors out there though that may or may not work better depending on your system.

What was said on this thread was that night setback and outdoor reset can be problematic if there's too large a setback--10 degrees is alot--and no morning boost function on the control that runs the boiler full fire until day temp is reached, then reverts back to regular curve.

Some controls literature suggests that if a large setback with outdoor reset is required, then while the night t-stat may be set at 60, the night water supply temp on the control can be set a few degrees above that, to bring temp up more quickly in the morning.

David