MM question about heating

[Deleted]

We have a programmable thermostat and forced air heat. I've heard that it's not good to have wild swings in temp. because that ends up costing more. I'm sure there are lots of factors here (outdoor temps, size of house, type of heat), but this is what my schedule looks like and has for a couple of years. Am I defeating my purpose of saving energy/money? You'll notice this all revolves around me. I'm fairly certain DH would go without all the time; he loves cold.

10 p.m.-6 a.m.: 45. But it almost never gets there. I'm guessing it gets into the low to mid-50s most winter nights. However, once or twice a year, we will hit 45. I freaking love a cold cold bedroom. I have the thickest down duvet I could find, and that's the ideal room for me, so this is more about comfort than saving energy/money.

6 a.m.-6:30 a.m.: 63. Basically it runs for 20 mins. or so straight to make it up to 63.

6:30 a.m.-5:00 p.m.: 45 (we're not home). Probabaly hovers in the high 50s low 60s all day in most of our winter, but on a few days I imagine it drops to the low 50s or even high 40s.

5 p.m.-10 p.m.: 62. It's cut off by the time I get home at 5:20, then just runs infrequent, shorter cycles until 10 p.m.

[SusanBAnthony]

I am no expert, but from what I remember, that is fine. You are not talking about it having to run for hours to get up to temp. 20 minutes seems reasonable to me.

[Deleted]

Great! I truly don't want to have heat on at night because I'd feel like I was smothering, but 63 is about my limit for showering/dressing, so I'm glad to hear 20 mins. probably isn't too much.

[SusanBAnthony]

Pretty much everyone who has a programmable thermostat does this though, right? We dont keep ours quite as cold as you since having kids, but the heat usually doesn't kick on until 4 or 5 am most nights.

[kyliek29]

When we got ours, my dad told me that the most temp shift you should have regularly is 7 degrees - anything over that is overloading the system. Not sure how true that is? I think our biggest shift is from 63 when we are gone during the day to 70 around the time when we will be getting home from work.

[Deleted]

Nov 15, 2012 11:10:03 GMT -5 kyliek29 said:

When we got ours, my dad told me that the most temp shift you should have regularly is 7 degrees - anything over that is overloading the system. Not sure how true that is? I think our biggest shift is from 63 when we are gone during the day to 70 around the time when we will be getting home from work.

Yeah, I knew I had heard something like this. But it seems like it would depend on the size of the space. It seems like if you were bringing the temp of a small space up by that much it wouldn't take long (we're only 950 sf and I block off about 90 of those in winter so they aren't heated). But maybe if you have a smaller space, you also have a smaller system, so it's still overworking?

[sjh722]

I've heard 8 degrees as a max temp shift before. That's probably a better question for someone much more well-versed in HVAC than I am. Where's fox?

[FoxInFiji]

LOL well only in your mild climate would a unit only have to run 20 minutes to make up an 18 delta T! You're fine. If you're uncomfortable mix it up. If you're not you're not wasting energy.

Yes in a cold climate people generally say anywhere from 6-8-10 degrees is the delta you should use but that depends on your system as well. In general if you're running more than an hour to reheat your space you probably should decrease the setback delta T. For example our geothermal heat pump gives us low temperature heat in our climate and scroll compressors work best when they are at a low continuous speed vs high speed on and off all the time. Our set back isn't much because of that but the average natural gas or LP furnace works the other way around because they burn hot. A quick on and off isn't a big deal for that type of system.

[Deleted]

Yea! An hour. Got it. Nowhere near that.

[wawa]

Nov 15, 2012 11:53:15 GMT -5 FoxInFiji said:

LOL well only in your mild climate would a unit only have to run 20 minutes to make up an 18 delta T! You're fine. If you're uncomfortable mix it up. If you're not you're not wasting energy.

Yes in a cold climate people generally say anywhere from 6-8-10 degrees is the delta you should use but that depends on your system as well. In general if you're running more than an hour to reheat your space you probably should decrease the setback delta T. For example our geothermal heat pump gives us low temperature heat in our climate and scroll compressors work best when they are at a low continuous speed vs high speed on and off all the time. Our set back isn't much because of that but the average natural gas or LP furnace works the other way around because they burn hot. A quick on and off isn't a big deal for that type of system.

I love when you talk all engineerey.

[noodleoo]

Huh, I had never heard that rule before. I'll have to check what ours is set to. I think we leave it at 55 at night and while we're at work and then it goes up to 66 when we get home/wake up. Do you think that's okay? It is definitely COLD in the winter in MA.

[FoxInFiji]

Nov 15, 2012 12:10:31 GMT -5 wawa said:

Nov 15, 2012 11:53:15 GMT -5 FoxInFiji said:

LOL well only in your mild climate would a unit only have to run 20 minutes to make up an 18 delta T! You're fine. If you're uncomfortable mix it up. If you're not you're not wasting energy.

Yes in a cold climate people generally say anywhere from 6-8-10 degrees is the delta you should use but that depends on your system as well. In general if you're running more than an hour to reheat your space you probably should decrease the setback delta T. For example our geothermal heat pump gives us low temperature heat in our climate and scroll compressors work best when they are at a low continuous speed vs high speed on and off all the time. Our set back isn't much because of that but the average natural gas or LP furnace works the other way around because they burn hot. A quick on and off isn't a big deal for that type of system.

I love when you talk all engineerey.

Bwahahaha! You should meet me in person I'm way more engineery than that! I bet you are too!