Heat Pump Thoughts

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#1342179 13-Jul-2015 13:49

well its been -1 to about 4degrees where we are in auckland recently which is the worst range for a heat pump to work in due to the dew point, and ours works fine, spends 5 minutes or so when it turns on to defrost then maybe 2 mins an hour to defrost, and when it does that it kills the internal fan so its just as though its off.

some older ones are not speced very good for temps around the freezing point and dont put out much heat and are not very efficient at those sort of temps. but they do still put out heat and should still warm a room reasonably quickly.

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#1342181 13-Jul-2015 13:51

north island isn't all warm nowadays (climate change??) ... didn't gisborne get snowed in literally?

but i presume all compressors have a lifespan. eventually the compressor won't compress anymore. (that's the limit of my knowledge of compressors!)

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#1342192 13-Jul-2015 13:53

This is a 2012 install - supposedly with an operating temp down to -5C - it's NEVER below zero at sea level in Wgtn

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#1342204 13-Jul-2015 14:04

lissie: This is a 2012 install - supposedly with an operating temp down to -5C - it's NEVER below zero at sea level in Wgtn

have you had a frost before?

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#1342222 13-Jul-2015 14:20

Jase2985:
lissie: This is a 2012 install - supposedly with an operating temp down to -5C - it's NEVER below zero at sea level in Wgtn

have you had a frost before?

Why would that matter? But no it just never gets that cold in Wgtn at sea level - it's been as cold as it ever gets here the last few weeks - and there wasn't actually frost on the ground

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#1342225 13-Jul-2015 14:22

frost only happens if there is an exposed area with no wind and clear sky.

exposed windy wellington would not get frost. i guess a cold wind would also make it colder (wind chill factor)

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#1342228 13-Jul-2015 14:24

seriously there is something wrong with
1) heat escaping somewhere -> heat pump really struggling here
2) heat pump issue

I had a Fujitsu Nocria 6kW in Dunedin once in a really cold house (servicing std height room of around 50sqm. It defrosts more often than it heats!

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#1342229 13-Jul-2015 14:24

joker97: frost only happens if there is an exposed area with no wind and clear sky.

exposed windy wellington would not get frost. i guess a cold wind would also make it colder (wind chill factor)

Actually it's been really, really still - sea like glass - never seen anything like it in Wgtn! Agreed - it's usually all about the wind chill!

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#1342231 13-Jul-2015 14:25

Wind chill is a perceived cold. Not the actual temperature. Wikipedia explains it.

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#1342232 13-Jul-2015 14:26

Lowest recorded temperature up on the hill at Kelburn is only -0.1C. Although there has been snow falling at sea level it doesn't last long.

I'm in Lower Hutt where we get a lot more frosts. We have our external unit sitting in the morning sun which helps a lot on frosty days. But we've never had any problem running it in the night or without sun. It takes 10 minutes at most to heat our dining room and kitchen.

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#1342233 13-Jul-2015 14:27

lxsw20: Wind chill is a perceived cold. Not the actual temperature. Wikipedia explains it.

Yup my physics class did too - it's utterly irrelevant to heat pumps

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#1342240 13-Jul-2015 14:44

if a house was uninsulated would it need more heating in still cold air compared to being blown by a strong cold wind? i guess i don't know ...depends?

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#1342245 13-Jul-2015 14:51

joker97: if a house was uninsulated would it need more heating in still cold air compared to being blown by a strong cold wind? i guess i don't know ...depends?

I would think it would depend on whether there are gaps - our windows are shot - and we get a strong draft thru them when it's windy - no condensation - but I assume it makes the room colder because cold air is being forced inside

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#1342248 13-Jul-2015 14:54

Hammerer: Lowest recorded temperature up on the hill at Kelburn is only -0.1C. Although there has been snow falling at sea level it doesn't last long.

I'm in Lower Hutt where we get a lot more frosts. We have our external unit sitting in the morning sun which helps a lot on frosty days. But we've never had any problem running it in the night or without sun. It takes 10 minutes at most to heat our dining room and kitchen.

Sounds like Tawa too - I'm by the west coast of Titahi Bay - definitely warmer than the Hutt, Tawa, or Whitby. The outdoor unit is on the east side but gets no sun in the winter - so that's probably not helping. Someone just said on FB that they are suposed to actually blow proprely hot air (her's was measured at 45C) - if that's the case this one has a problem - it's never been better than warm air out

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#1342500 13-Jul-2015 18:55

joker97: seriously there is something wrong with
1) heat escaping somewhere -> heat pump really struggling here
2) heat pump issue

I had a Fujitsu Nocria 6kW in Dunedin once in a really cold house (servicing std height room of around 50sqm. It defrosts more often than it heats!

A tad undersized so I am not surprised.

Without seeing the house in Dunedin and knowing its insulation my guess would be:

50m2 x 2.4 stud x 65 watts per m3 (guess) = 7.8KW

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