Any Home Heating Experts Here?

[CallMeKate]

I have a question about our radiant heating system. Bottom line, it's oil heat and the furnace is also used for heating the water. The furnace runs for 7 minutes about every 2.5 to 3 hours for regular water heating (unless there's heavier use like showers.) So the question is, would turning the furnace off for 12 hours (overnight like 5 p.m to 5 a.m.) save oil... or not since when I do that, it runs *20* minutes in the morning?

It's driving me batty because every time I try to research it, there are so many opposite answers. Run 24 hours with furnace kicking on every 7 minutes, or run 12 hours with it running 20 minutes to heat the water in the morning? Any difference at all?

 

[CallMeKate]

... Or non-experts? With it getting colder now, I worry that what seems to be a good idea may actually be wasting oil. Call me confuzzled.

 

[Paco Dennis]

Can you set the time and temperature on your water heater? 120F is recommended. Maybe you could get a timer for it.?

 

[CallMeKate]

Can you set the time and temperature on your water heater? 120F is recommended. Maybe you could get a timer for it.?

The temperature is set... but what I need to know is if it's actually saving oil to manually turn it off for 12 or 14 hours overnight when we don't use hot water then anyhow. Because of taking 20 minutes to bring it back up to heat.

 

[Paco Dennis]

I found this...

5

Electric water heaters lose very little heat. Putting a blanket on them or putting them on a timer won't save much money.
NG/propane/oil water heaters, on the other hand, lose significantly more heat, as they not only lose heat through their outside surfaces, but also even more heat via the flue. Putting a blanket around the outside will prevent perhaps 10% of the standby losses -- worth it if you're using propane but not NG.

Turning the water heater off will lower the temperature difference between the water inside the tank and the air outside the tank, so it can save you a significant amount of money ($3-4 for propane; I'm not sure how oil compares to propane) if you go out of town for a week and turn the water heater off (because after a few days, the temperature difference for the disabled water heater will be nearly zero and standby losses, being proportional to the temperature difference, will also be nearly zero.)

Turning the water heater off for only 12 hours a day will probably only save you ~40 cents a week if you have propane. Perhaps worth it if you can find a cheap device to do it for you, but not worth the trouble of doing it manually.

NOTE: By mentioning that lowering the temperature difference between water inside the tank vs. air outside the tank, one might be inclined to lower the setting on water heater to ~115 degrees Fahrenheit. While this will indeed decrease your standby losses, this is not safe. At lower temperatures, bacteria commonly known as "legionella" will grow, which is particularly dangerous to elderly and children, and sometimes causes death. If you would like to lower the setting on your water heater, you must raise the temperature on the water heater to 135-140F for at least one day each month.

and

If you have a tank -type heater, it would be an hour or so before you got hot water in any quantity if you shut it off between uses. Leave it on.

I hope this helps.

 

[Chet]

I would just let it run as usual. If you shut it off, it will only run longer than normal to heat up the water and bring it to temperature, and you end up saving nothing. Restarting every day might put some unnecessary wear and tear on the system too.

 

[CallMeKate]

I would just let it run as usual. If you shut it off, it will only run longer than normal to heat up the water and bring it to temperature, and you end up saving nothing. Restarting every day might put some unnecessary wear and tear on the system too.

Thank you, @Chet ... after I'd done it for a while, I started wondering about the wear & tear, too... it's not even remotely "new." I think you're right and I'll have to just let it run. Secondary to the guzzling oil issue is the fact that it's so very loud when it comes on and it wakes me every few hours during the night, so that was the selfish part of the reason.

 

[Chet]

Another thought. The water might be heating up hotter than necessary. You could try measuring the water temperature with a thermometer. If it's very hot, lowering it a little and using less cold water might work just as well when it comes to comfort.

120 degrees Fahrenheit is the safety recommendation against scalding, but 140° is the common default setting. Most experts agree that anything below 120 degrees creates a risk for bacteria to develop inside your water heater from stagnant water, such as legionella that causes Legionnaire's disease.