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Air Source Heat Pumps (ASHPs)
Last Post by Derek M 4 years ago
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 adaml
(@adaml)
Trusted Member Member
Joined: 4 years ago
Posts: 42
Topic starter 02/01/2022 2:31 pm  

@derek-m 

 

Hi Derek, thanks so much again for sharing your expertise.

 

You are quite correct I was confusing the terminology. I have put equilibrium temp back to the default of -4°C.

 

That makes complete sense, so we should expect to the ASHP running more given the higher pricing for gas and electricity. I will leave the curve at 45°C at -10°C and 25°C @ 18°C and with the lot max modulation now set at 10°C and monitor the cycling and overall COP.

 

Thanks,

Adam


   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 4 years ago
Posts: 4427
02/01/2022 4:36 pm  

Hi @adaml 

When time allows, monitor how long the heat pump runs and then how long it is stopped before restarting. Also record the water flow and return temperatures, which may highlight any possible problems with your system. If your heat pump is running for short time periods then stopping for short time periods then it may be necessary to adjust some of the operating parameters.


   
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 adaml
(@adaml)
Trusted Member Member
Joined: 4 years ago
Posts: 42
Topic starter 02/01/2022 7:48 pm  

@derek-m 

Hi Derek,

I've been watching it run tonight and it is sometimes running for about 20 minutes and then stops and other times it is starting, running for only a couple of minutes and then stops. The required flow temp for tonight is showing as 31°C. The required was showing as 26°C and the lwt modulation seems to have increased this. The house is sitting at 21.7°C at the moment.

 

I think one potential problem could be that the Daikin thermostat/controller is situated in our downstairs hallway, with the kitchen door relatively close to it. This means that when we're cooking the temperature raises in the hall and trips the thermostat off, despite other parts of the house being cooler. I wonder if increasing the thermostat temp in the hall to say 22°C could be worth a shot?

 

Jan shows the compressor has been running for 4 hours with 42 starts at the moment. Other snapshots were 27 at 2 hours and 36 at 3 hours.

 

Stats from the controller tonight, couple of snapshots;

 

Outdoor temp. 9.0°C

Leaving water 26.8°C

Leaving water (PHE) 26.8°C

Inlet water temp. 25.3°C

Refrigerant temp. 26.0C

Flow rate 12.9l/min

 

Outdoor temp. 9.0°C

Leaving water 30.4°C

Leaving water (PHE) 30.0°C

Inlet water temp. 30.2°C

Refrigerant temp. 29.7C

Flow rate 12.6l/min

This post was modified 4 years ago by adaml

   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 4 years ago
Posts: 4427
02/01/2022 10:05 pm  

Hi @adaml 

First of all let's clarify what is meant by running, do you mean that the compressor is actually running, or that it is just the water pump that is running?

The water pump is often started before the compressor is started, and continuous to run for a short period after the compressor has stopped. The water pump is also run for short periods of time to check the water temperature, so that the controller knows when to start the compressor to provide more heat energy.

Looking at your snapshots, I would say that the upper one has the water pump running but the compressor is stopped, and in the lower one both compressor and water pump appear to be running.

I think that you may find that the data relating to running and starts should be interpreted in the following manner.

'Jan shows the compressor has been running for 4 hours with 42 starts at the moment'.

I think that this actually means that since the start of January, the compressor has run for a total of 4 hours, and since the start of January the compressor has started 42 times. So it would appear that what has actually happened is that the compressor has started 42 times in approximately 42 hours, so has started on average once per hour, and has run for an average 5.77 minutes each time.


   
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