Advice wanted re Heat Pumps

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#1995552 13-Apr-2018 15:00

^^^ This old chestnut... there are certainly those who push this ‘set and forget’ approach, but I’m not convinced by it. Hopefully pros in this area such as @Kickinbac will give their learned opinion.

I’d heard this was relevant in commercial settings, where the sheer amount of space to heat made it more economical to retain the space at a set temperature, given the length of time to bring it up to temperature each day - eg in a mall. I just can’t see this being the case in the home environment.

At this point of the year the additional cost may not be huge, given temperatures aren’t too low, but I’d imagine it will add up in the height of winter (though, of course,will depend on factors such as how well insulated the house is etc).

I acknowledge that one may need to provide a decent lead-in time to ensure a house is warm when people get up; my approach is to stick the heat pump on at 6, so by the time the family’s up at 7 the house is pretty toasty (it’s an all-house ducted system). I also supplement this with a radiator heater with fan for that one hour, as we’re with EK so don’t pay for power for that period, as some days in winter the heat pump struggles to get the house up to temperature. Personally, the noise is enough reason for me to not run the heater all night...

Glazza

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#1996127 14-Apr-2018 16:32

We recently replace a 10yr old Fujitsu unit with at Mitsubishi GE60 unit. Im not convinced that the Mitsubishi unit can match the performance of the Fujitsu unit at this stage... to the point i wander if we have a faulty unit

As an experiment today - outside temp is between 11 and 14 degrees, we set the unit to its max temp (31 degrees). At the time of doing this, the room was at 24 degrees. Upon returning 3 hours later I expected to return to a very hot house, however the room was at 26 degrees, and it hasnt managed to get any warmer.

For the test, mode was set to Heat, everything else to Auto.

Of interest, the Fan never really ramped up - its just running away quietly, at about a medium setting.

In our bedroom we still have a small Fujitsu unit - when we try to repeat this test on that unit, after setting the temperature the outdoor unit ramps up, then about a 90 seconds later the indoor unit fan starts ramping up, getting faster as the temperature of the air coming from the unit increases.

The temperature of the air from the Fujitsu is also hotter.... mmm maybe it is a fault... who knows

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#1996146 14-Apr-2018 16:56

I suggest calling installer to check for fault!

Handle9

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#1996152 14-Apr-2018 17:40

jonathan18: ^^^ This old chestnut... there are certainly those who push this ‘set and forget’ approach, but I’m not convinced by it. Hopefully pros in this area such as @Kickinbac will give their learned opinion.

I’d heard this was relevant in commercial settings, where the sheer amount of space to heat made it more economical to retain the space at a set temperature, given the length of time to bring it up to temperature each day - eg in a mall. I just can’t see this being the case in the home environment.

At this point of the year the additional cost may not be huge, given temperatures aren’t too low, but I’d imagine it will add up in the height of winter (though, of course,will depend on factors such as how well insulated the house is etc).

I acknowledge that one may need to provide a decent lead-in time to ensure a house is warm when people get up; my approach is to stick the heat pump on at 6, so by the time the family’s up at 7 the house is pretty toasty (it’s an all-house ducted system). I also supplement this with a radiator heater with fan for that one hour, as we’re with EK so don’t pay for power for that period, as some days in winter the heat pump struggles to get the house up to temperature. Personally, the noise is enough reason for me to not run the heater all night...

Basically the first thing you do when you do an energy saving project is switch the plant off, or at a minimum setback the setpoints. The only real exceptions are when you would short cycle the plant, which is only when the plant would be off for a short period of time then needs to be switched back on. If you can switch the units off for more than an hour then it's a no brainer.

If you are home for a couple of hours in the morning and then after work in the evening switch off the AC half an hour before you leave and switch it on half an hour before you occupy the space. Unless the unit is grossly undersized it'll get the space to setpoint in half an hour fairly comfortably.

If you are in and out of the house during the day it MAY make sense to leave the AC running but at a setpoint which is lower than than your occupied setpoint.

shk292

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#1996153 14-Apr-2018 17:42

madcarue:

Have given it a good try out over the last few days and it works a treat when set at 19-20 deg it heats the room adequately for this time of year.

I was using the timer to start a bit earlier as suggested by K so set at 5:30 for 6:30 start but I have been told by a couple of guys to leave it switched on all the time as it wont have to keep heating the room from cold, so I have knocked down to 16 when out or at night and that is much better but I still think it is a waste of power and more expensive.

It's definitely more efficient to turn it off when you don't need the rooms warm. You just need to think about heat going into the room/house and heat going out to work this out. The higher the temp difference between inside and out, the more heat escapes. Exactly the same for spa pools, hot water tanks etc

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#1996185 14-Apr-2018 20:34

shk292:

It's definitely more efficient to turn it off when you don't need the rooms warm. You just need to think about heat going into the room/house and heat going out to work this out. The higher the temp difference between inside and out, the more heat escapes. Exactly the same for spa pools, hot water tanks etc

It probably is more efficient, but leaving the heating on at a lower temperature setting when you're out means the house is warmed through. We had the heat pump on pretty much all last winter, the power bill was fine.

Kickinbac

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#1996191 14-Apr-2018 21:04

Glazza:
We recently replace a 10yr old Fujitsu unit with at Mitsubishi GE60 unit. Im not convinced that the Mitsubishi unit can match the performance of the Fujitsu unit at this stage... to the point i wander if we have a faulty unit

As an experiment today - outside temp is between 11 and 14 degrees, we set the unit to its max temp (31 degrees). At the time of doing this, the room was at 24 degrees. Upon returning 3 hours later I expected to return to a very hot house, however the room was at 26 degrees, and it hasnt managed to get any warmer.

For the test, mode was set to Heat, everything else to Auto.

Of interest, the Fan never really ramped up - its just running away quietly, at about a medium setting.

In our bedroom we still have a small Fujitsu unit - when we try to repeat this test on that unit, after setting the temperature the outdoor unit ramps up, then about a 90 seconds later the indoor unit fan starts ramping up, getting faster as the temperature of the air coming from the unit increases.

The temperature of the air from the Fujitsu is also hotter.... mmm maybe it is a fault... who knows

Call the installer back to look at it. You are testing it right. You should be getting well over 35 degrees supply air direct from the unit. Are there any flashing leds on the front of the indoor unit? I reckon that its most likely short on refrigerant so there may be a leak.

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Glazza

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#1996214 14-Apr-2018 22:08

Kickinbac:

Call the installer back to look at it. You are testing it right. You should be getting well over 35 degrees supply air direct from the unit. Are there any flashing leds on the front of the indoor unit? I reckon that its most likely short on refrigerant so there may be a leak.

Lights are all normal indication, etc. Ill give them a call next week... Cheers

Aredwood

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#1996240 15-Apr-2018 00:24

Glazza:
We recently replace a 10yr old Fujitsu unit with at Mitsubishi GE60 unit. Im not convinced that the Mitsubishi unit can match the performance of the Fujitsu unit at this stage... to the point i wander if we have a faulty unit

As an experiment today - outside temp is between 11 and 14 degrees, we set the unit to its max temp (31 degrees). At the time of doing this, the room was at 24 degrees. Upon returning 3 hours later I expected to return to a very hot house, however the room was at 26 degrees, and it hasnt managed to get any warmer.

For the test, mode was set to Heat, everything else to Auto.

Of interest, the Fan never really ramped up - its just running away quietly, at about a medium setting.

In our bedroom we still have a small Fujitsu unit - when we try to repeat this test on that unit, after setting the temperature the outdoor unit ramps up, then about a 90 seconds later the indoor unit fan starts ramping up, getting faster as the temperature of the air coming from the unit increases.

The temperature of the air from the Fujitsu is also hotter.... mmm maybe it is a fault... who knows

Read the manual and make sure that "hotel mode" isn't enabled. It is a mode to prevent guests running up large energy bills to the hotel owner due to setting the heatpump to a really high or low temp.

Also see if there is a mode where you can force it to operate on max output. Although that may be in a servicing menu.

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#1996278 15-Apr-2018 09:11

also make sure fan speed is on AUTO

Jase2985

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#1996448 15-Apr-2018 13:52

Batman:

also make sure fan speed is on AUTO

should make ZERO difference

Batman

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#1996451 15-Apr-2018 14:00

Not my Fujitsus

Jase2985

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#1996618 15-Apr-2018 21:00

Batman: Not my Fujitsus

not sure how?

Batman

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#1996629 15-Apr-2018 21:16

when i set it to low fan it doesn't heat the room. worse with quiet fan. it will heat if i set it to high fan, hence i suggest auto fan just in case it's on some eco / quiet fan mode or something.

Jase2985

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#1996658 15-Apr-2018 22:11

of course low isnt going to heat a room in some cases, but if its on high it should make no difference to auto

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