The defrosts are every couple of hours.  I think it reverses the flow?  Anyway it causes the flow temp to drop so it ramps up the power to heat it up, overshoots a bit and settles back down. It's very consistent. 

Each of these peaks/troughs uses up about 130 Wh more energy than if the ASHP had kept going steadily. 

I'll have a look at these settings you mention. 

Kev 

@kev-m 

Thanks Kev,

The fact that the water flow temperature appears to be reasonably constant when the ASHP is running constantly, would indicate that the upper and lower limits are not being reached, so are not affecting the operation. The limits are probably why the heat pump stops for a short period after the defrost cycle has been completed.

Defrost operates in the same way as my A2A ASHP, in that it speeds up for a while during defrost and often stops the compressor for a short period before restarting.

Looking at the thermistor adjustment procedure, it would appear that it is just an offset similar to the weather compensation, rather than a full calibration. If you wish, you could adjust the water flow temperature indication (THW6) and the water return temperature indication (THW7) on the FTC controller to match the readings on your MMSP heat meter. You would then be able to see how the measurements vary as the required water flow temperature is varied by the weather compensation. A word of warning. Try making a 1C adjustment and note the affect, since a large adjustment may cause a change in the indoor temperature, before the controller readjusts. You will also need to adjust the weather compensation curve to match the new readings.

When time allows, I would suggest that you go through the FTC controller settings and note the values on a copy of the Engineers Form shown on pages 40 to 42. It may then be possible to see further ways in which your system could be optimised.

How's the performance been during the past few days being so cold? 

OK.  I'll do a summary at the end of the month but here's the last few days.  This is having most of the house 21-22C all day and night.  Tonight's going to be over 40 I think:

Kev

Posted by: @derek-m

@kev-m 

Thanks Kev,

The fact that the water flow temperature appears to be reasonably constant when the ASHP is running constantly, would indicate that the upper and lower limits are not being reached, so are not affecting the operation. The limits are probably why the heat pump stops for a short period after the defrost cycle has been completed.

Defrost operates in the same way as my A2A ASHP, in that it speeds up for a while during defrost and often stops the compressor for a short period before restarting.

Looking at the thermistor adjustment procedure, it would appear that it is just an offset similar to the weather compensation, rather than a full calibration. If you wish, you could adjust the water flow temperature indication (THW6) and the water return temperature indication (THW7) on the FTC controller to match the readings on your MMSP heat meter. You would then be able to see how the measurements vary as the required water flow temperature is varied by the weather compensation. A word of warning. Try making a 1C adjustment and note the affect, since a large adjustment may cause a change in the indoor temperature, before the controller readjusts. You will also need to adjust the weather compensation curve to match the new readings.

When time allows, I would suggest that you go through the FTC controller settings and note the values on a copy of the Engineers Form shown on pages 40 to 42. It may then be possible to see further ways in which your system could be optimised.

You're assuming the installers didn't leave me this with their comprehensive handover pack and commissioning notes?

And you'd be right. 😆 

Posted by: @kev-m

OK.  I'll do a summary at the end of the month but here's the last few days.  This is having most of the house 21-22C all day and night.  Tonight's going to be over 40 I think:

Date	kWh	Ambient
22/11/21	33.2	3.9
23/11/21	22.5	6
24/11/21	18.9	6.9
25/11/21	34.2	3.5
26/11/21	28.9	4.4
27/11/21	36.6	2.7

Kev

Thanks again Kev,

The above shows how a few degrees change in ambient air temperature can affect the operation and efficiency of an ASHP.

Will be very interested in the summary of November 

I'm awaiting an isg for mine so I can monitor and tweak remotely, currently out of stock so every time I want to adjust mine I need to go into the loft!

My system has weather compensation and a curve monitor, any guidance on which settings I should potentially use? 

My latest tweaks (can't resist 😆)

Weather compensation curve recalibrated so I can set my offset from -4 back to zero

DHW set to come on 12 noon-2pm only.  We still have electric showers and don't use much HW.  Better it comes on when it's a bit warmer out

And (most radically), heating is programmed to be off 12am-6am.  I know the 'slow and steady wins the race' theory for ASHPs and I know the ASHP will have to work hard when it wakes up.  But.... I have radiators, a relatively large ASHP and the house has a relatively low thermal mass.  Six hours doing nothing will take a big chunk out of the kWh.  It also just doesn't feel right heating the 12 other radiators when there's nobody there.  If it's too cold in the night or morning I'll revert back.  I also won't tell Mrs M and see if she notices or not. Risky, very risky ....    

Well that sort of worked.  The heating went off as planned.  But it warmed up overnight and while the heating came on as planned, the radiators weren't really warm enough to heat the house quickly.  Temperature was only down slightly though and a quick boost on the controller did the trick.  It's going to be a cheaper day today thankfully.  

Posted by: @kev-m

Well that sort of worked.  The heating went off as planned.  But it warmed up overnight and while the heating came on as planned, the radiators weren't really warm enough to heat the house quickly.  Temperature was only down slightly though and a quick boost on the controller did the trick.  It's going to be a cheaper day today thankfully.  

I have seen some users in the large government sponsored trials at the moment turn off their heat pumps overnight, but they have high temperature heat pumps and turn them back on a bit earlier than you did.

Whether they spend more over a year would very much depend on individual usage requirements as they are obviously giving up quite a bit of efficiency by having their heat pumps off perhaps several times a day. I can't imagine many users going down this route but it will be interesting to see what comes out of the trials if anything is published. 

Are you going to try it a few more times to get some more data points for your setup? 

Yes I'll try it for few days and see what happens.   

Posted by: @kev-m

My latest tweaks (can't resist 😆)

Weather compensation curve recalibrated so I can set my offset from -4 back to zero

DHW set to come on 12 noon-2pm only.  We still have electric showers and don't use much HW.  Better it comes on when it's a bit warmer out

And (most radically), heating is programmed to be off 12am-6am.  I know the 'slow and steady wins the race' theory for ASHPs and I know the ASHP will have to work hard when it wakes up.  But.... I have radiators, a relatively large ASHP and the house has a relatively low thermal mass.  Six hours doing nothing will take a big chunk out of the kWh.  It also just doesn't feel right heating the 12 other radiators when there's nobody there.  If it's too cold in the night or morning I'll revert back.  I also won't tell Mrs M and see if she notices or not. Risky, very risky ....    

@kev-m
Interested in the first sentence of your post.  I too wish to return my offset back to zero in order to reclaim the full range of adjustment available to me.   Currently I have set it to +4 and occasionally even +6 in this very cold snap.  However I don’t know how to do it.  I’m assuming it’s an adjustment to the compensation curve?  All I know is putting on + figures makes the house warmer.  Can you tell me please what I need to do in order for my current +4 can actually be my zero.  In other words I reset to zero but it’s operating at the current +4.  Hopefully that question makes sense.  SWMBO is giving me a bit of grief suggesting it isn’t warm enough and even wanted the log burner in the lounge lit last night.  I had a wisdom tooth extracted yesterday and feeling grumpy and under the weather (comp’ curve) so some peace would be good.