Fujitsu Heat pump problem

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Klausm

10 posts

Wannabe Geek

#288576 9-Jul-2021 14:32

Hi

We just got a Fujitsu Floor model Heat Pump - installed.

My question is, that in the evening I have it on 21-22 degrees inside, not on the remote it is only on around 18 degrees because the thermostat is inside the Heat pump and not in the remote!, which is REALLY BAD DESIGN!

Anyway I can get around that, but when I go to bed I turn it down to 16 Degrees on the remote (which is the lowest option), just so it is not freezing cold when I get up in the morning.

The mode on the Heat pump is set to Heat and and the Fan is on Auto.

So I would expect that as soon as I choose to change it to 16 degrees it should stop doing anything because it is 21 degree in the house. But no, it starts pumping out cold air???? Not really cold but luke warm.
I turn it down to save some electricity over night, but it seems like the heat pump want to get the temperature in the house down to 16 degrees and that even that the mode is set to Heat.

So what is going wrong here?

Hope that all makes sense, English is not my first language.

Sorry one more question, can't you get an external thermostat for Fujitsu heat pumps. Im thinking a wireless one which can send the correct temp. to the Heat pump? I think I have seen it somewhere.

RunningMan

8877 posts

Uber Geek

#2741892 9-Jul-2021 15:31

If set to heat mode, then it won't be cooling the air, but it needs to move enough air around that the room temperature is even (particularly with a floor model) and be able to sense the room temp.

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timmmay

20419 posts

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#2741893 9-Jul-2021 15:32

All thermostats / thermometers are different. Doesn't really matter what number is on the display of the remote, just set it to whatever makes it feel the temperature you want. I have different temp measuring devices that are out by three degrees. Thermostat in the heat pump is standard as well, just set the fan speed to auto / medium so it's pushing the air away from the heat pump and it'll be fine.

If a heat pump on heating mode starts pumping out cold air it's faulty. Make 100% sure you're using heat mode, ideally measure the temp of the heat pump output with an IR thermometer, then call the installer / repairer. Note that some heat pumps do run on a low speed when they're not heating, very low fan, but they push room temperature air around not cool air.

Not sure how many heat pumps can have remote temperature sensors, but not many I would think.

fe31nz

1199 posts

Uber Geek

#2741999 10-Jul-2021 01:25

timmmay:

All thermostats / thermometers are different. Doesn't really matter what number is on the display of the remote, just set it to whatever makes it feel the temperature you want. I have different temp measuring devices that are out by three degrees. Thermostat in the heat pump is standard as well, just set the fan speed to auto / medium so it's pushing the air away from the heat pump and it'll be fine.

If a heat pump on heating mode starts pumping out cold air it's faulty. Make 100% sure you're using heat mode, ideally measure the temp of the heat pump output with an IR thermometer, then call the installer / repairer. Note that some heat pumps do run on a low speed when they're not heating, very low fan, but they push room temperature air around not cool air.

Not sure how many heat pumps can have remote temperature sensors, but not many I would think.

Heat pumps set to Heat mode will push out cold air on days where the intake air temperature drops into the range where they ice up and need to defrost - typically around 2 C. They reverse their system for a short period and suck heat out of the room to use to defrost the outside unit. It normally does not take very long and usually has some indicator on the indoor unit to tell you it is happening, such as a LED blinking. Once the outside unit is defrosted, the system will normally attempt to make up for the heat that it has just sucked out of the room by putting some heat back into the room. Our Mistsubishi heat pumps have a bug at this point - if they are set to full fan speed, then when they finish defrosting they go into the mode where they think they have just been turned on in a room that is very cold and needs a lot of heat fast, so they blast out heat for a long time and the temperature climbs way above the setpoint. So on colder days we always need to remember to set them to auto fan before going to sleep, otherwise we get woken up by the fan noise and too much heat. You can get days where the temperature hovers around the icing temperature and defrost happens several times an hour, but that is rare. Normally the temperature will keep dropping and go below that point. Either way, most heat pumps will cope, but you do need to understand what is happening if you are there when it happens.

Apart from short periods of defrost mode, your heat pump should never pump out cold air. It may well run the fan (usually at very low speed) to run air over its thermostat so that it can read the temperature accurately. When it is doing that, it causes a slight breeze, which can feel a little colder, but it is not actually heating or cooling.

Most heat pumps come with on and off timers, so in unoccupied rooms using the timers is normally a better option than leaving them on all night at the lowest setting. It would be much cheaper to have them come on at say 07:30 than leave them on all night. Unless, of course, you have people getting up in the night at odd times (eg baby feeding).

Another option is WiFi remote control - we have that for our Panasonic unit in the kitchen, so if I wake early for some reason I can use my cellphone or tablet to turn it on remotely and then read in bed until the kitchen is a decent temperature. And we can turn it on when we are on the way home, so it will be hot when we get there.

There is a simple test to see if your heat pump is working properly. Turn it on (in heat mode) and set it to its maximum temperature setting and full fan speed. Let it get going properly so that the output air temperature has stabilised, then measure the temperature as close as possible to the unit directly in the airflow. It should be around 50 C or a little higher. If it is not, then there is a problem - possibly a gas leak. If it is way above 50 C then the unit is dangerous and needs urgent fixing as it could burn you.

Jase2985

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#2742022 10-Jul-2021 08:11

Klausm:

But no, it starts pumping out cold air???? Not really cold but luke warm.

people seem to have just read the first part, not the second part.

Being luke warm the inverter has probably ramped down to compensate for the change in temperature setting.

The unit might not have a no fan mode so just uses the inverter to alter the output heat.

Froglotion

208 posts

Master Geek

#2742300 10-Jul-2021 23:14

Unless you want to have the place warm during the night, you could just set a timer. I've always had a timer so that it comes on about half hour before we get up. At least that's what I did before we had a wee one, now I have to pay to keep the house warm at night $$$$$.

timmmay

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#2742324 11-Jul-2021 06:45

With a well insulated house we didn't find a leaving the heat pump on overnight cost all that much. We never bothered to work out exactly how much it cost because the power bill was still fine.

aucklander

477 posts

Ultimate Geek

#2743157 12-Jul-2021 14:26

I would not let the fan on Auto during the night (ever), as it would randomly ramp up and possibly become very noisy in the middle of the night. I always leave the fan during the night on "night" mode, which is even quieter than first fan speed. Any brand would have such "night" mode. Maybe changing the fan setting would change the overall behavior? NOTE: this is not the same with the "night" mode applicable to the outdoor unit sound level, that will limit the noise of the outdoor unit (not the indoor), it is a mode designed to help when outdoors are very close to a window (yours or the neighbor's...)

I never heard of any hand held remote control with temperature sensor incorporated and I do not see it as a good practice as you might leave the remote on the table, the Sun comes up and warms up only that spot and the unit will not start to heat the room, which might actually be fairly cold overall. If you want a temp sensor which is not in the indoor unit, then a wall mounted (wired) controller would be required, those are usually installed approx 1.5 - 1.6m above floor.

Jase2985

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#2743169 12-Jul-2021 15:05

my parents old place had the sensor in the remote as well as the unit, you could chose which sensor to use.

Technofreak

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#2743296 12-Jul-2021 18:46

We have a Fujitsu floor mounted heat pump.

We just set the timer each night when we go to bed for it to come on before we get up.

There is also a 10° mode that will ensure the room never drops below 10°.

So far as the thermostat settings go, just find a temperature that gives you the comfort you require and set that. Don't worry what the actual setting is. The heat pump is monitoring the temperature of the air it draws in near floor level which will be cooler than the temperature where you're sitting/standing.

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