Heat Pump Output Temperature Varies. What Might Cause This?

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Technofreak

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#285890 23-May-2021 17:06

Recently I noticed our heat didn't seem to be providing as much heat as usual at times.

I started recording the temperature at the outlet as well as the outside ambient conditions, i.e. Temp, Dew Point etc. I remember taking the outlet temperature for curiosity sake when we had it install and from memory it was around 48°C.

When I've measure the temperature during the past few days I've seen around 47°C at times but at others times the temperature is only about 35°C. The heat pump is running in the same mode on every occasion. There is no significant different in the outside ambient conditions between the 35°C and 47°C readings.

The heat pump is about 4 years old, we keep the filters on the indoor unit clean and the system was serviced about 2 years ago.

Any ideas on anything I can check?

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timmmay

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#2711812 23-May-2021 18:34

Is this causing a problem? The heat pump ramps its output up and down depending on the current and target temperatures.

Technofreak

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#2711860 23-May-2021 20:39

Yes, it is causing a problem. We're not getting the heat we used to get, the house is colder.

From what I can tell the target temperature and or ambient temperature aren't the problem. Usually the room will get to temp and then the heat pump will switch to effectively a "recirculation" mode where it is still pumping air at a very low rate without heating the air flow. When the temperature drops it switches back to a higher airflow and heating where the output will normally be at about 47 degrees. It's not doing that, at least not all the time.

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timmmay

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#2711873 23-May-2021 20:45

If it's not heating properly I'd get the people who supplied and installed it back. They should last a decade so you would have a chance of requesting service under consumer guarantees or maybe the warranty.

rphenix

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#2711879 23-May-2021 21:34

I'm guessing the aircon is reaching the desired temperature on its sensor where it is in the room close to the roof and the unit is now 'maintaining temp' this can mean cold air currents if the aircon is in a warm pocket but the room is cold.

Put the thermostat on the AC up higher than you really want it use max for a test and put the fan speed higher than normal so it moves more air. See if that helps.

Jase2985

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#2711880 23-May-2021 21:35

what temp is AC set to and in what mode? fan speed setting?

Technofreak

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#2711885 23-May-2021 22:00

rphenix:

I'm guessing the aircon is reaching the desired temperature on its sensor where it is in the room close to the roof and the unit is now 'maintaining temp' this can mean cold air currents if the aircon is in a warm pocket but the room is cold.

Put the thermostat on the AC up higher than you really want it use max for a test and put the fan speed higher than normal so it moves more air. See if that helps.

It's a floor mounted console, the sensor is close to floor level so is measuring the coolest air in the room.

Fan speed is on high. Increasing the required temperature seems to have no effect on the output temp, though I'd have to do more testing to make sure.

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Technofreak

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#2711886 23-May-2021 22:01

Jase2985:

what temp is AC set to and in what mode? fan speed setting?

The temperature the AC is set to is arbitrary. Usually 22 but because the sensor is close to floor level at that setting we will see 24 to 25 degrees on the thermometer which is about a metre above floor level.

The AC is in "Heat" mode and fan set to high. Both are the usual settings we run for heating.

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timmmay

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#2711888 23-May-2021 22:08

Try auto fan to see if it makes a difference. Also set it to 28 to see what it does.

But still, call the installer.

Kickinbac

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#2711897 23-May-2021 22:48

The supply air temperature varies based on several factors; Indoor temperature, outdoor temperature, setpoint (in relation to return air temp), compressor speed, indoor and outdoor unit fan speeds, what the electronic expansion valve is doing. Lots of tricky stuff happening in the refrigeration system for both heat output and efficiency.
Are there any blinking leds on the front? This usually indicates a fault code.

If you are concerned you will need to get a good technician to look at it. They will look for fault codes, signs of issues etc. but if there is nothing wrong you will probably have to pay for the callout.

MadEngineer

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#2711950 24-May-2021 00:03

What’s the model of the heat pump? What’s the difference in inlet vs outlet temperatures when you set it to run at both extremes of heating and cooling?

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#2711953 24-May-2021 07:01

1. set fan to auto

2. clean all filters

3. output indoors may depend on outside temp

Fred99

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#2711992 24-May-2021 09:41

We've got a high wall and floor mount Daikin heat pumps. Using the wifi app, they display temp setting, outside air temp using a probe on the intake side of the heat exchanger, and inside temp - presumably the probe is on the intake side of the indoor unit.

The remote control for the high wall unit also has a thermometer, there's two "comfort settings" - one uses the thermometer in the remote rather then the one in the unit, the other uses an IR motion detector and if set will shut the unit down to "economy mode" if it doesn't detect someone in the room for xxx? number of minutes.

Point of mentioning the above - RTFM before assuming there's an issue with the heat pump - it might be a "feature" not a fault - brands and features vary.

The high wall unit is useless to maintain set temperature with fan set to auto and the comfort setting set to use the sensor in the high wall unit. For example, it was set that way 10 minutes ago, I know from the app that it's 11 deg outside, the pump is set to 21 deg, the app is telling me it's 24 deg, but the heat pump has no way of knowing that it's not 24 degrees in the room - it's actually about 18, so it was more or less shut down. I set "comfort mode" so it uses the temp probe in the remote 5 minutes ago, and now it's "woken up", but you've got to leave the remote in a sensible position for this to work - if it's in the air flow from the pump then you created a feedback loop to sabotage correct operation, if you set it away from air flow but on a window sill, even if triple glazed you'll have cold air flowing down the inside face of the window, so it'll "think" the room is colder than it really is. Using that setting and ideal remote placement probably means leaving the remote on a side table or whatever, near where you're sitting. Then someone else will pick it up, press random buttons and stuff up all your best efforts. Ideally, I'd chuck the remotes away or hide them, but I'd be called a control freak or worse. Could turn the fan up to a higher fixed setting, but despite being quiet models of heat pumps, that's relative and too noisy for me. I tend to just set the high-wall unit a couple of degrees above what you really want, to compensate for the poor temperature measurement.

The floor mounted unit is much better at maintaining set temperature +/- 2 deg. It's pretty much set and forget as well as quieter on all settings we use.