Heat pump queries

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xyeovillian

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#277173 30-Sep-2020 11:32

We have a Fujitsu inverter AST13PSA-W heat pump fitted July 2004.
It seems like its just blowing cold air at the moment with current weather conditions, as its been quite cold lately. Do the units need servicing to keep them up to date.
Or do we need to be looking at a replacement, as the same as everything technology is getting better all the time?

Blurtie

468 posts

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#2576414 30-Sep-2020 11:37

Have you checked it's actually on 'heat' mode rather than 'aircon' mode?

jnimmo

1097 posts

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#2576420 30-Sep-2020 11:45

if by blowing cold air you mean blowing room temperature air, it may have lost its refrigerant. Are the filters all clean?

I'm not sure how much a re-gas would cost, especially if it has a leak, but may be worth upgrading it rather than repairing (assuming a newer unit has a much higher COP than a 2004 model)

timmmay

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#2576422 30-Sep-2020 11:49

16 years old is a really good lifespan for a heat pump. I was told 10 - 12 years is about average. Replace it.

Eva888

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#2576504 30-Sep-2020 13:21

Our Toshiba in one room is about 6 years old and for reasons unknown decides to blow cold air usually on very cold days of course. It doesn’t happen often but it eventually rights itself within a half hour of freezing us. Aircon man said it knows what it’s doing and it’s just the way it cycles so I only check the controls to ensure it’s on heat. I have now put a red nail polish dot at the heat spot because with bad eyes the icon for cold and heat are very similar.

timmmay

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#2576514 30-Sep-2020 13:33

I wonder if some heat pumps use the cooling cycle to heat the outside unit to defrost it in really cold conditions? I think some made for really cold areas (Mitsubishi?) have dedicated heaters in the outdoor units.

bfginger

1271 posts

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#2576726 30-Sep-2020 20:00

xyeovillian:

We have a Fujitsu inverter AST13PSA-W heat pump fitted July 2004.
It seems like its just blowing cold air at the moment with current weather conditions, as its been quite cold lately. Do the units need servicing to keep them up to date.
Or do we need to be looking at a replacement, as the same as everything technology is getting better all the time?

Heat pumps don't like operating near 0 degrees outdoor temperatures but some models are better at it than others. It must defrost periodically which means heating will temporarily stop but the fan may not. If the model is really bad in cold weather it'll be defrosting more than heating.

Heat pumps do need some servicing. The indoors unit may have an internal filter and if you've not cleaned it it can clog and reduce efficiency. The outdoors unit may do with a clean after 16 years.

A professional can check to see if it still contains enough refrigerant. As your model's manual says it uses R22 it is unlikely you can have it topped up with more as it is an ozone depleting gas and would need professional decommissioning.

Kickinbac

430 posts

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#2577559 1-Oct-2020 23:12

bfginger:
xyeovillian:

We have a Fujitsu inverter AST13PSA-W heat pump fitted July 2004.
It seems like its just blowing cold air at the moment with current weather conditions, as its been quite cold lately. Do the units need servicing to keep them up to date.
Or do we need to be looking at a replacement, as the same as everything technology is getting better all the time?

Heat pumps don't like operating near 0 degrees outdoor temperatures but some models are better at it than others. It must defrost periodically which means heating will temporarily stop but the fan may not. If the model is really bad in cold weather it'll be defrosting more than heating.

Heat pumps do need some servicing. The indoors unit may have an internal filter and if you've not cleaned it it can clog and reduce efficiency. The outdoors unit may do with a clean after 16 years.

A professional can check to see if it still contains enough refrigerant. As your model's manual says it uses R22 it is unlikely you can have it topped up with more as it is an ozone depleting gas and would need professional decommissioning.

Thats how heat pumps defrost, they reverse from heating to cooling to put heat into the outdoor coil and melt the ice. The indoor fan motor stops to reduce cold air being blown around the house.

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Kickinbac

430 posts

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#2577650 1-Oct-2020 23:17

xyeovillian:
We have a Fujitsu inverter AST13PSA-W heat pump fitted July 2004.
It seems like its just blowing cold air at the moment with current weather conditions, as its been quite cold lately. Do the units need servicing to keep them up to date.
Or do we need to be looking at a replacement, as the same as everything technology is getting better all the time?

Recommend you look at replacing it.16 years is a good run for a heat pump. You may not get parts or may have lost the refrigerant. Any money spent on a technician would be better spent towards a new unit. A new unit will be more efficient and most likely quieter.

Jase2985

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#2577668 2-Oct-2020 07:06

Kickinbac:

Thats how heat pumps defrost, they reverse from heating to cooling to put heat into the outdoor coil and melt the ice. The indoor fan motor stops to reduce cold air being blown around the house.

thats how some heat pumps defrost, other have small resistance heaters in their outdoor coils

SomeoneSomewhere

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#2578302 2-Oct-2020 20:03

It's uncommon. The vast majority use the reversing valve that's already there for cooling mode.

Walk-in freezers generally use defrost elements though.

snnet

1410 posts

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#2578305 2-Oct-2020 20:11

The reversing valve might be stuck if you haven't used it on heating in a while.. try changing between cooling and heating a few times to see if this is the issue (it generally unsticks after a few goes)

Kickinbac

430 posts

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#2578322 2-Oct-2020 20:46

Jase2985:
Kickinbac:

Thats how heat pumps defrost, they reverse from heating to cooling to put heat into the outdoor coil and melt the ice. The indoor fan motor stops to reduce cold air being blown around the house.

thats how some heat pumps defrost, other have small resistance heaters in their outdoor coils

Thats how the majority of heat pumps defrost. I asked a couple of our techs today and they had not seen electric heaters in heat pumps.
There are all sorts of electric heaters in refrigeration such as crankcase heaters, heat trace and defrost elements but not in your usual domestic heat pumps.

bfginger

1271 posts

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#2578330 2-Oct-2020 21:22

From what I've read elsewhere, elements were more common in the past and worse some models may leave them running nearly all the time when in standby instead of only when needed.