Should Heat Pump be on Constantly?

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#337729 3-Jun-2010 12:04

vexxxboy:
vexxxboy: not sure if people have seen this yet but it looks quite good if you have the devices

http://www.google.com/powermeter/about/

heres the site that has the devices for nz and they are not that expensive

http://www.smartnow.co.nz/

Will be interesting to see the cost the bridge will will send your data to google automagiclaly saving you time and effort.

http://smartnow.com.au/current_cost_bridge.html

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#337757 3-Jun-2010 12:45

Nety:
IlDuce: You should get rid of your oil column heaters. You should replace them with Dimplex "Drytech" oil free "eco" column heaters. These are miracle heaters, just that people don't know it!

They claim for 1kW of electricity input, they put out 30% more heat than a 1.5kW oil column heater, and up to 8 (yes EIGHT!) times faster too! Thats amazing!

I'm sorry but this is just not true. Other then heat pump's NO electric heater can put out any more heat then the power that is put into it. Both heaters will be outputting 1kW worth of heat.

Heat pumps are?different?because they do not use the electricity to create the heat. They pump a special gas between the outside unit and the indoor unit taking heat from outside and releasing it inside.

Dimplex eco heaters are the exception apparently. I have measured their power input, they use 1.0kW electricity input (rounded to nearest 100 Watts), yet the box states 1.5kW heat output. That doesn't make sense to me, and my understanding of the law of thermodynamics. I wrote to Dimplex to explain, and to quote the response to why from the Marketing Coordinator:

"I have also further investigated about the power input drop ? this basically means that the ECO range oil free radiators does not require a continuous 1.5kW of power consumption to output 1.5kW of heat. Once the elements reach its peak temperatures it will drop power consumption to 1kW and will only require this amount of input to maintain a maximum temperature of 1.5kW heat output."

A complain was made to the Advertising Standards Authority last year, and it got thrown out.

Apparently because heat output is not measured in Watts or Joules, its measured in Degrees, and these heaters put out more Degrees of heat in a fixed size room within a 1 hour period, by 30% more, and also whilst using 33% less power input than an ordinary column heater.

Nety

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#337791 3-Jun-2010 13:30

Awesome they have managed to create something that creates more energy then it uses!! I am amazed that their not having masses for scientists breaking down their doors to find out just how....
IMHO that is just marketing speak (and very dodgy marketing speak at that).

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#337796 3-Jun-2010 13:37

Interesting thread here.

http://forums.whirlpool.net.au/forum-replies-archive.cfm/1422959.html

Sorry for getting off topic.

Edit
Looking into it more the logic they use in their test is seriously flawed.

They heated a room for a set amount of time (one hour) using a oil heater and their oil free heater and then stated that it was 30% more efficient because the room was approx 30% hotter at the end of the hour. Well of course it was. The heater takes significantly less time to get up to its maximum operating temperature as would a fan or bar heater when compared to a oil column heater. That does not mean it is more efficient it just means it takes less time to heat up.

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#337872 3-Jun-2010 15:23

Ah....

I did wonder if you were serious.

http://www.geekzone.co.nz/forums.asp?ForumId=48&TopicId=59405

beforenightfalls

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#337890 3-Jun-2010 15:51

just checked my power use for last 24 hours since turning heat pump off at night, and it has dropped to 50 units, compared to 59 to have it going all night. it obviously works better for us to have the heat pump off at night. i think my question has been answered now. thanks.

minimoke

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#337900 3-Jun-2010 16:00

I asked the exact same question after our heat pumps went in. The short answer, I've concluded, is "yes" - we now leave the heaters on all the time. When people are around the thermostats get set to 19, when no one is aroud they are set to 16.

There is tons of info and it gets a bit confusing when you are looking at convected and radiant heart etc. But the basic theory is that you are aiming for constantly warm surfaces.

Heat pumps draw a large amount of energy when first turned on as they try to quickly build the temperature up to the thermostat - thats why your lights might dim if you switch it on in a frosty morning. But once the temperature is reached it only takes a small amount of energy to maintain - especially if you let the sun do warming during the day; keep out the cold and allow for bodies generating 1kw of heat each at night. Once the thermostat is set and the room warmed the pump only turns on to maintain temperature - not to heat.

When I switched from on/off mode to "on all the time" mode there was no discernable difference in power bill. it was a bit hard to tell exactly over the 12 month period as the rates changed and I got a freezer. But the big difference was a constantly warm house - so that made it totally worth while.

But just to be clear the house has double glazing and extra layers of insulation and very well built for the sun - what works for me may not work for others.

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mentalinc

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#338022 3-Jun-2010 20:02

beforenightfalls: just checked my power use for last 24 hours since turning heat pump off at night, and it has dropped to 50 units, compared to 59 to have it going all night. it obviously works better for us to have the heat pump off at night. i think my question has been answered now. thanks.

So 9 units works out to be about $2 extra per day (at 23c KwH) to have it run 24/7.
Plus if you did anything different this day, e.g. cooked a roast the 59 unit day but not the 50 unit day you're going to have a variance.

In comparison to heat your daughter each night (12 hours) based on 1Kw heater at 23c KwH works out to be $2.76 per day.

So the heat pump 24/7 costs you an extra $2 per day but the other 2 heaters are costing you close to $5.50 per day.

Can the heatpump do the whole house is my question?

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beforenightfalls

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#338031 3-Jun-2010 20:13

no the heat pump can't do the whole house. not even the fire can reach the far end of the house! the $2 extra is for it to run all night, not quite 24/7 and works out to be $60 a month which is a lot to us. we've always heated our daughter's room and will continue to do so, one little luxury for this family.

mentalinc

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#338036 3-Jun-2010 20:25

Im not saying back your daughter suffer, sorry if this is how it seemed.
Yes its $60 a month for the heatpump to heat you but the other 2 heaters cost you $165 just to run at night...

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richms

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#338063 3-Jun-2010 21:28

beforenightfalls: its a wood burner yes. after doing a bit more of an investigation with powershop and working out my daily readings i'm pleased to say my power use HAS GONE DOWN over the last two days.

As an aside, why do you need powershop to be able to look at your daily usage?

Richard rich.ms

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#338074 3-Jun-2010 22:07

Buttonmash: What I read before purchasing our heat pump a year ago was:

If you have a well insulated house and an inverter heatpump it's better to leave it on 24/7. Maybe letting it drop to say 19 degrees while no one is in the house.

The reason is the heat pump is more efficient when it's not wringing it's guts out trying to get the house up from a cold temp. This also keeps your house more comfortable as the 'core temperature' of your house is kept at a nice temp. A nice warm couch, warm bench etc just makes the house more cosy.

If you have a poorly insulated house then it's going to waste power as the heat won't be retained, and you may as well only heat it when it's in use.

+1

I read that the number of houses that were suitable for 24/7 operation was actually quite a low amount.

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richms

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#338079 3-Jun-2010 22:21

Turn them on sooner and dont use the boost mode. I read somewhere that the COP when using boost would drop to the likes of 2:1 or worse just to get the extra couple of kW out of them.

Richard rich.ms

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Snowflake

#338083 3-Jun-2010 22:30

beforenightfalls: a home ventilation system would be awesome but there's no way we could afford it right now.

you could go the 'cheap' route and drop in a 'room to room heat transfer system'. this is simply some ducting and a motor that can suck heat from one room and spit it out in another room, or rooms. Check out the example on the plumbing world website - $309 for one room, $555 for two rooms, $769 for three rooms. Install yourself and get a sparky for 1 hour to wire up and provide certificate. Other cheaper options around too. you're probably paying $100 per month to run those oil filled heaters - wouldnt take long to make up the savings using one of these, i would expect.

http://www.plumbingworld.co.nz/Pages/ProductDetails.aspx?search=Weiss+One+Room+to+Two+Room+Heat+Transfer+System&pid=100286&page=true&cat=1&subcat=2&fpb=false

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#338087 3-Jun-2010 22:37

minimoke:

When I switched from on/off mode to "on all the time" mode there was no discernable difference in power bill.

But just to be clear the house has double glazing and extra layers of insulation and very well built for the sun - what works for me may not work for others.

you would certainly be in the minority. double glazing, minimum R-value insulation, ceiling/wall/underfloor is now required by the building code - higher requirements the further south you live - but that only addresses houses built very recently.

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