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tschmidt
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join:2000-11-12
Milford, NH
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tschmidt to haroldo

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to haroldo

Re: Central air conditioner on/off? Old wives tale?

This topic has been beaten to death here.

If the temperature inside the house is different then outside then heat flows between the two. The greater the difference the faster the flow.

Turning off the AC or heat means for that period of time you are using no energy. When the AC/Heat is turned back on it has to work longer to get the higher/lower inside temp back to comfort zone. However that takes less energy then maintaining the set point temperature during that period.

Do a thought experiment, if you were going to be gone a week do you think you would save energy by turning it off or changing the set point compared to leaving it at the normal temperature?

/tom

Jack_in_VA
Premium Member
join:2007-11-26
North, VA

Jack_in_VA

Premium Member

said by tschmidt:

This topic has been beaten to death here.

If the temperature inside the house is different then outside then heat flows between the two. The greater the difference the faster the flow.

Turning off the AC or heat means for that period of time you are using no energy. When the AC/Heat is turned back on it has to work longer to get the higher/lower inside temp back to comfort zone. However that takes less energy then maintaining the set point temperature during that period.

Do a thought experiment, if you were going to be gone a week do you think you would save energy by turning it off or changing the set point compared to leaving it at the normal temperature?

/tom

In winter unless you want to freeze for a long time while the heat pump restores the temperature to set point the heat strips will come on negating any savings from lowering the thermostat and more than likely increasing the cost.

I never change mine winter or summer unless we're going to be away for extended periods like a vacation. Lifelong experience in instrumentation and process control business gives me a different perspective on issues like this. The savings (if any) aren't worth the effort and discomfort.

cowboyro
Premium Member
join:2000-10-11
CT

1 recommendation

cowboyro

Premium Member

said by Jack_in_VA:

In winter unless you want to freeze for a long time while the heat pump restores the temperature to set point the heat strips will come on negating any savings from lowering the thermostat and more than likely increasing the cost.

I never change mine winter or summer unless we're going to be away for extended periods like a vacation. Lifelong experience in instrumentation and process control business gives me a different perspective on issues like this. The savings (if any) aren't worth the effort and discomfort.

A central A/C has a single source of energy so it will cost pretty much the same regardless of the difference between actual temperature and set point. The heat pump is a bad example for this.
Decent thermostats allow for automatic start earlier so that the set point is reached at the desired time.
I could dump a couple of years worth of hard data which shows without any trace of doubt that keeping the unit off during the day saves energy vs keeping it on. Energy, not necessarily money. Rates may be higher at certain times.

Draiman
Let me see those devil horns in the sky
join:2012-06-01
Kill Devil Hills, NC

Draiman

Member

said by cowboyro:

said by Jack_in_VA:

In winter unless you want to freeze for a long time while the heat pump restores the temperature to set point the heat strips will come on negating any savings from lowering the thermostat and more than likely increasing the cost.

I never change mine winter or summer unless we're going to be away for extended periods like a vacation. Lifelong experience in instrumentation and process control business gives me a different perspective on issues like this. The savings (if any) aren't worth the effort and discomfort.

A central A/C has a single source of energy so it will cost pretty much the same regardless of the difference between actual temperature and set point. The heat pump is a bad example for this.
Decent thermostats allow for automatic start earlier so that the set point is reached at the desired time.
I could dump a couple of years worth of hard data which shows without any trace of doubt that keeping the unit off during the day saves energy vs keeping it on. Energy, not necessarily money. Rates may be higher at certain times.

Does that hard data take into account what the humidity can do to stuff in your house? Your comfort level? Life expectancy related to the extra stress a hot house can cause? A pissed off significant other or kids? Stall air on allergies? Way to many things to take into account for hard data to give a realistic answer to the OP's question. It's more of a personal choice given then situation and desired outcome.

cdru
Go Colts
MVM
join:2003-05-14
Fort Wayne, IN

2 recommendations

cdru to tschmidt

MVM

to tschmidt
said by tschmidt:

This topic has been beaten to death here.

Oh come on. We haven't beaten it to death this week. Maybe we can add in smart meters, government subsidized devices, and building/electrical codes into the mix to get a real discussion going.

dosdoxies
Premium Member
join:2004-12-15
Wallingford, PA

1 recommendation

dosdoxies

Premium Member

said by cdru:

said by tschmidt:

This topic has been beaten to death here.

Oh come on. We haven't beaten it to death this week. Maybe we can add in smart meters, government subsidized devices, and building/electrical codes into the mix to get a real discussion going.

Don't forget whether to put electrical tape on wire nuts or not.

Jack_in_VA
Premium Member
join:2007-11-26
North, VA

Jack_in_VA to cowboyro

Premium Member

to cowboyro
said by cowboyro:

example for this.
Decent thermostats allow for automatic start earlier so that the set point is reached at the desired time.
I could dump a couple of years worth of hard data which shows without any trace of doubt that keeping the unit off during the day saves energy vs keeping it on. Energy, not necessarily money. Rates may be higher at certain times.

Yes and when it's cold the recovery has to start early in the time that's supposed to be saving energy in order to keep the strips off if it's able to do it without strips. When it's cold a heat pump relies on strips to supplement the heat that it can't provide. Turning the entire unit off in most cases would cost far more than just keeping it running.

Example in my case the heatpump pulls 1.4 kW running which is about 14 cents/hour. 8 hours would be $1.12. Heat strips 15kW cost about $1.58/hr to operate.

I would be interested in seeing your hard verifiable data.
Jack_in_VA

Jack_in_VA to cdru

Premium Member

to cdru
said by cdru:

said by tschmidt:

This topic has been beaten to death here.

Oh come on. We haven't beaten it to death this week. Maybe we can add in smart meters, government subsidized devices, and building/electrical codes into the mix to get a real discussion going.

OH COME ON you must be reading the posts

Given that people are posting to this thread means that some are interested. You realize you don't have to read them. Does this mean that a couple of people have the power to determine a subject has been "beaten to death" therefore choking it off?
Jack_in_VA

Jack_in_VA to dosdoxies

Premium Member

to dosdoxies
said by dosdoxies:

said by cdru:

said by tschmidt:

This topic has been beaten to death here.

Oh come on. We haven't beaten it to death this week. Maybe we can add in smart meters, government subsidized devices, and building/electrical codes into the mix to get a real discussion going.

Don't forget whether to put electrical tape on wire nuts or not.

N/M

cdru
Go Colts
MVM
join:2003-05-14
Fort Wayne, IN

3 recommendations

cdru to Jack_in_VA

MVM

to Jack_in_VA
said by Jack_in_VA:

Given that people are posting to this thread means that some are interested. You realize you don't have to read them. Does this mean that a couple of people have the power to determine a subject has been "beaten to death" therefore choking it off?

Lighten up Jack. It was in posted in humor.

djrobx
Premium Member
join:2000-05-31
Reno, NV

djrobx to Jack_in_VA

Premium Member

to Jack_in_VA

I never change mine winter or summer unless we're going to be away for extended periods like a vacation. Lifelong experience in instrumentation and process control business gives me a different perspective on issues like this. The savings (if any) aren't worth the effort and discomfort.

So says the man with the low electric rates.

If you had the punitive tiered electric rates that we have, you'd be looking for ways to cut a few percent off the top, as small reductions in usage result in more significant changes on your bill.

Jack_in_VA
Premium Member
join:2007-11-26
North, VA

Jack_in_VA to cdru

Premium Member

to cdru
said by cdru:

said by Jack_in_VA:

Given that people are posting to this thread means that some are interested. You realize you don't have to read them. Does this mean that a couple of people have the power to determine a subject has been "beaten to death" therefore choking it off?

Lighten up Jack. It was in posted in humor.

I know yours was. This is an interesting topic as there are so many facets to consider.

cowboyro
Premium Member
join:2000-10-11
CT

1 recommendation

cowboyro to Jack_in_VA

Premium Member

to Jack_in_VA
said by Jack_in_VA:

said by cowboyro:

example for this.
Decent thermostats allow for automatic start earlier so that the set point is reached at the desired time.
I could dump a couple of years worth of hard data which shows without any trace of doubt that keeping the unit off during the day saves energy vs keeping it on. Energy, not necessarily money. Rates may be higher at certain times.

Yes and when it's cold the recovery has to start early in the time that's supposed to be saving energy in order to keep the strips off if it's able to do it without strips. When it's cold a heat pump relies on strips to supplement the heat that it can't provide. Turning the entire unit off in most cases would cost far more than just keeping it running.

Example in my case the heatpump pulls 1.4 kW running which is about 14 cents/hour. 8 hours would be $1.12. Heat strips 15kW cost about $1.58/hr to operate.

I would be interested in seeing your hard verifiable data.

Again you are giving a BAD EXAMPLE THAT DOES NOT APPLY.
An air conditioner runs with pretty much the same efficiency regardless of where the thermostat is set at. The efficiency of the heat pump + strips assembly is not constant and highly depends on which is running. You simply cannot compare the two.
cowboyro

cowboyro to Draiman

Premium Member

to Draiman
said by Draiman:

Does that hard data take into account what the humidity can do to stuff in your house? Your comfort level? Life expectancy related to the extra stress a hot house can cause? A pissed off significant other or kids? Stall air on allergies? Way to many things to take into account for hard data to give a realistic answer to the OP's question. It's more of a personal choice given then situation and desired outcome.

It does nothing in a daily scenario. We are not talking about leaving the A/C off for a week, we are talking about leaving it off for few hours when nobody is home. No stress, no pissed off "others". If humidity becomes an issue then it's likely a cat can escape too...

cdru
Go Colts
MVM
join:2003-05-14
Fort Wayne, IN

1 recommendation

cdru to cowboyro

MVM

to cowboyro
said by cowboyro:

Again you are giving a BAD EXAMPLE THAT DOES NOT APPLY.
An air conditioner runs with pretty much the same efficiency regardless of where the thermostat is set at. The efficiency of the heat pump + strips assembly is not constant and highly depends on which is running. You simply cannot compare the two.

When considering cooling only, heat pumps and air conditioners operate the same because AC is a one-way heat pump. And neither type remain at a fixed efficiency, that's why there are set standards to specify how the efficiency is measured.

Draiman
Let me see those devil horns in the sky
join:2012-06-01
Kill Devil Hills, NC

Draiman to cowboyro

Member

to cowboyro
said by cowboyro:

said by Draiman:

Does that hard data take into account what the humidity can do to stuff in your house? Your comfort level? Life expectancy related to the extra stress a hot house can cause? A pissed off significant other or kids? Stall air on allergies? Way to many things to take into account for hard data to give a realistic answer to the OP's question. It's more of a personal choice given then situation and desired outcome.

It does nothing in a daily scenario. We are not talking about leaving the A/C off for a week, we are talking about leaving it off for few hours when nobody is home. No stress, no pissed off "others". If humidity becomes an issue then it's likely a cat can escape too...

I didn't think you'd have a good way to wiggle out of that and you don't. I'm just glad it's all public so everyone can see your response.

cowboyro
Premium Member
join:2000-10-11
CT

cowboyro to cdru

Premium Member

to cdru
What I mean is that with 80F inside (for example) the efficiency is the same whether the thermostat is set at 78F or at 65F. As opposed to heat pumps where if you have 74F inside the efficiency may dramatically decrease is you change the thermostat from 75F to 76F and it starts the auxiliary heating.

Snakeoil
Ignore Button. The coward's feature.
Premium Member
join:2000-08-05
united state

Snakeoil to cowboyro

Premium Member

to cowboyro
quote:
Rates may be higher at certain times.

I don't know about rates, but demand varies through out the day. When I lived in GA, the power company was offering a discount on the electric bill. All you had to do was allow them to install a remote "kill" switch to your AC unit. If they triggered the kill switch, you got a discount that month on your power bill. I think it was 25, maybe 50 bucks. That was so that during the peak hours during the say, the risk of "brown outs" was reduced/prevented.
Our current power company in Ohio hasn't made that type of offer, though even so often they offer to buy the old "inefficient" basement/garage refrigerator/freezer. They offer 50 to 150 bucks, plus hauling it away. I guess they want to lure people into buying more energy efficient appliances.

KrK
Heavy Artillery For The Little Guy
Premium Member
join:2000-01-17
Tulsa, OK
Netgear WNDR3700v2
Zoom 5341J

KrK to Draiman

Premium Member

to Draiman
said by Draiman:

Does that hard data take into account what the humidity can do to stuff in your house? Your comfort level? Life expectancy related to the extra stress a hot house can cause? A pissed off significant other or kids? Stall air on allergies?

Um... NOBODY'S HOME.... and it's only for a few hours, not enough for everything to start falling apart.... if you don't want it completely off, just turn up up to 85 or so.
Critsmcgee
join:2011-12-02

Critsmcgee

Member

said by KrK:

said by Draiman:

Does that hard data take into account what the humidity can do to stuff in your house? Your comfort level? Life expectancy related to the extra stress a hot house can cause? A pissed off significant other or kids? Stall air on allergies?

Um... NOBODY'S HOME.... and it's only for a few hours, not enough for everything to start falling apart.... if you don't want it completely off, just turn up up to 85 or so.

And?!?!?!? 9 to 11 hours a day isn't a 'few' hours for a typical person. That's 1/3 to 1/2 the day! It's enough time for a house to go from 71 to 90+ and that's not significant? Humidity can go from 45-50% all the way up to 65-70% in that time as well. Not sure about you but that's significant to me!

KrK
Heavy Artillery For The Little Guy
Premium Member
join:2000-01-17
Tulsa, OK
Netgear WNDR3700v2
Zoom 5341J

KrK

Premium Member

You know houses survived for decades without air conditioning. It's not like suddenly they will fold up into a pile of rot and mold because the AC is off for 6 hours a day.

Like I said, if not off, just up. You can have it turn back on before anyone gets home and cool back down. It's not rocket science.
Critsmcgee
join:2011-12-02

Critsmcgee

Member

said by KrK:

You know houses survived for decades without air conditioning. It's not like suddenly they will fold up into a pile of rot and mold because the AC is off for 6 hours a day.

Like I said, if not off, just up. You can have it turn back on before anyone gets home and cool back down. It's not rocket science.

They didn't have the same content decades ago so that doesn't hold any weight as an argument. Not worried about the house itself either.

KrK
Heavy Artillery For The Little Guy
Premium Member
join:2000-01-17
Tulsa, OK

KrK

Premium Member

I give up. Obviously you're just trying to argue.

I guess you live in fear of a power outage.

mattmag

join:2000-04-09
NW Illinois

1 recommendation

mattmag to Draiman

to Draiman
said by Draiman:

A pissed off significant other or kids?

'nuff said right there, end of discussion and Amen to that!