Leave heat pump on or switch on as required (weekends)

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timmmay

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#116830 11-May-2013 12:25

On the weekend we're typically home, but in and out a bit. If we go out for an hour or so I just leave the heat on. I'm trying to work out if I should leave it on low when we go out for 3-4 hours or switch it off.

I have a well insulated but older house. If it's 8 degrees outside overnight and it's 21 degrees inside at 10pm it usually drops to around 18 degrees by 6am. That's pretty good for an older house, I think.

If we leave the heat pump on the it runs slowly, in economy mode, where it's most efficient. The air and all the contents of the house stay warm - we're not just heating the air remember, the furniture, walls, etc all have to be heated.

If we turn it off everything cools down a bit, and when we get in (or on a timer just before) it runs at higher power, less efficiently, to warm the place up again.

Thoughts?

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#815718 11-May-2013 12:26

During the winter months we put our heatpump on 16-20c and it just hums away nicely, we never turn it off during that time.

Klipspringer

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#815738 11-May-2013 13:19

Leave ours at 23 in winter. If we going out for longer than say 3 hours we generally switch it off.

vexxxboy

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#815739 11-May-2013 13:29

we have a heatpump but its more off than on , we turn it on for 3-4 hours at night and an hour in the morning during the week. Cant see the point of warming the house when im not there.But we have excellent insulation so the house never feels cold.

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Niel

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#815755 11-May-2013 13:48

Ours is on whenever we are home. The windows and outside doors stay closed (also to keep flies/mosquitoes out). We switch it off if we go out for more than an hour, but it stays on when just quickly dropping kids off somewhere or getting e.g. milk. House is well insulated with rib raft concrete floor. A week ago we changed the heat pump from cooling-only to heating-only (don't like the faint smell you get when it reverse cycles).

This is our first Winter with the heat pump, still need to figure out how to manage the little bit of condensation we are getting now but it is mostly due to some of us showering at night. Maybe I just have to set the aircon to reverse cycle so that the occasional cooling will dehumidify the air.

Summer setting is 21 during the day, 23 at night. Winter setting is 23 to 26 depending on how we feel. For health reasons you should keep it above 18.

To save the most power, switch off when you are not home. For the best comfort and evenly spread temperature, leave it on all the time.

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#815759 11-May-2013 14:00

if you go away for less than half a day keep it on at a lower temp

if you go away for more than a day turn it off

between half a day and a day I don't know the cost effectiveness of either

but that's my uneducated guess ... i'm not a thermal-electro-physicist

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#815774 11-May-2013 14:49

An extract from the EECA website (http://www.eeca.govt.nz/news/getting-most-your-heat-pump):

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Fact: There's no benefit to running it when you don't need it.If you're leaving your home, or not using the room being heated, it's cheaper to turn your heat pump off. A properly sized and installed heat pump shouldn't take long to reheat the room once you turn it back on.
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I know from experience that the one we installed for my mum only takes 5 mins or so to heat up the room. So I guess they're saying in most cases it is more energy efficient to turn it off when you leave - but if you're only away for an hour you might like to return to a warm house - especially on a day like today on the Kapiti Coast

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Niel

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#815797 11-May-2013 15:45

There are more factors than only temperature, there is also getting circulation in the house and a number of other benefits. Humidity is also an issue for electronics reliability and health. The EECA takes a simplistic view looking at only the energy aspect.

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timmmay

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#815890 11-May-2013 19:29

Thanks all. Heating the air is easy. Heating all the other things inside the insulated envelope is probably what takes the real effort, and takes many hours say to heat a sofa or a big solid bed through.

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#815949 11-May-2013 20:44

If you're going out switch it off. It's just wasting energy. With a commercial system we typically stage it in 30 minutes before occupancy and if it's properly sized then it will get the space to setpoint in 20 minutes pretty easily.

You're also saving yourself compressor starts as well as energy so you are not putting wear on the unit. There is no justification for running air con when there is no load.

Also FYI Niel reverse cycle refers to the reverse cycle of refrigerant - i.e. The forward cycle of refrigerant is in cooling, the reverse cycle is heating. There is a reversing valve in the refrigerant circuit which provides this functionality.

timmmay

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#815953 11-May-2013 21:08

Thanks :) Good points.

kiwitrc

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#816056 12-May-2013 07:28

Niel:

This is our first Winter with the heat pump, still need to figure out how to manage the little bit of condensation we are getting now but it is mostly due to some of us showering at night. Maybe I just have to set the aircon to reverse cycle so that the occasional cooling will dehumidify the air.

.

Niel, I think heat pumps are pretty crap at dehumidifing, but possibly that has changed with newer ones. As for the shower, if you can install a shower dome, they have worked miracles in our place, no more foggy mirrors wet walls in winter or mould on the ceiling and walls etc and they keep warm after you turn the water off, so nice and warm to dry yourself. Sorry for going OT Timmmay

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timmmay

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#816070 12-May-2013 08:38

I don't know if heat pumps are any good at dehumidifying, my place never gets damp since I use a DVS and good extraction. I have to say though when my partner dries her clothes inside on a rack I sometimes turn that cycle on, it never seems to do much.

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#816370 12-May-2013 19:32

try it both ways, on similarly cold days/nights, and measure your power consumption over the 24 hour period. Do it for both dry and wet conditions.

It may well depend on how well the house holds heat as to whether one way or the other is more efficient. If you leave windows open etc, that might make a difference too.

I have a gas unit that heats up the whole house really really fast, so its better for me to leave it off when i',m out. The heat pumps are a bit slower, but if your house only drops to 18deg overnight then switching it off might not be a bad option cause you wont have to lift the temp much when you switch it on...

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Regs

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#816374 12-May-2013 19:34

kiwitrc:
Niel:

This is our first Winter with the heat pump, still need to figure out how to manage the little bit of condensation we are getting now but it is mostly due to some of us showering at night. Maybe I just have to set the aircon to reverse cycle so that the occasional cooling will dehumidify the air.

.

Niel, I think heat pumps are pretty crap at dehumidifing, but possibly that has changed with newer ones. As for the shower, if you can install a shower dome, they have worked miracles in our place, no more foggy mirrors wet walls in winter or mould on the ceiling and walls etc and they keep warm after you turn the water off, so nice and warm to dry yourself. Sorry for going OT Timmmay

if the condensation is as a result of the showering, try installing a [bigger] extractor fan in the bathrooom?

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Niel

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#816382 12-May-2013 19:45

Handle9: Also FYI Niel reverse cycle refers to the reverse cycle of refrigerant - i.e. The forward cycle of refrigerant is in cooling, the reverse cycle is heating. There is a reversing valve in the refrigerant circuit which provides this functionality.

"Reverse cycles" plural as in all the cycles. Unless you have an old system, an aircon can be set to heating only, cooling only, dehumidify, or automatically reversing cycles between heating and cooling as needed. The issue is that after cooling there is condensation on the element so when it reverse to heating you get a faint metallic smell.

The dehumidify cycle:
The dehumidify cycle is just a slow cooling cycle with constantly blowing air (possibly with vents set to high angle) so that humidify condenses on the element. A dehumidifier does the same except that the waste heat is used to heat the air up again and you get a net temperature increase.

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