Defrost Cycles - Ho...
 
Notifications
Clear all

Defrost Cycles - How Common Are They?

51 Posts
13 Users
17 Reactions
3,193 Views
(@iancalderbank)
Noble Member Contributor
3640 kWhs
Joined: 2 years ago
Posts: 644
 

Posted by: @mikefl

The defrost temperature (light blue line) is fairly steady around -10C.

what do you mean by the "defrost temperature"? I don't quite follow.

 

My octopus signup link https://share.octopus.energy/ebony-deer-230
210m2 house, Samsung 16kw Gen6 ASHP Self installed: Single circulation loop , PWM modulating pump.
My public ASHP stats: https://heatpumpmonitor.org/system/view?id=45
11.9kWp of PV
41kWh of Battery storage (3x Powerwall 2)
2x BEVs


   
ReplyQuote
(@derek-m)
Illustrious Member Moderator
14399 kWhs
Veteran Expert
Joined: 3 years ago
Posts: 4273
 

Posted by: @cathoderay

A heat pump on the verge of a nervous breakdown:

image

 

Miraculously, the current actual IAT is only 1.4 degrees below the desired IAT. But just look at those defrosts, and the LWT when it does get up to temperature, not to mention the hourly energy use, and a COP that drops to 1.49. 

What is the actual temperature at the radiators and what is the temperature drop across the PHE?

 


   
ReplyQuote
Toodles
(@toodles)
Famed Member Contributor
6389 kWhs
Joined: 2 years ago
Posts: 1003
Topic starter  

@derek-m During the first 14 hours of today, (Tuesday 16th. Jan.) we have kept pretty well to target temperature of 22.5 C. throughout the 4 bedroomed semi detached house using 24 kW/h up until 14:00; I say pretty well, the lowest reading was 21.7 at about 07:00 in the living room but an hour or two later, this was back to 22.5 C. Allowing for perhaps 10% losses through charge and discharge of the battery, this means we have consumed approx. 27 kW/h during those 14 hours @ Cosy cheapest rate. I am quite pleased with that performance. Daikin 8kW EDL08 Monobloc - DHW is independent of this; it is space heating only. Regards, Toodles.

IMG 0536

 

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
ReplyQuote
(@derek-m)
Illustrious Member Moderator
14399 kWhs
Veteran Expert
Joined: 3 years ago
Posts: 4273
 

Posted by: @iancalderbank

Posted by: @mikefl

The defrost temperature (light blue line) is fairly steady around -10C.

what do you mean by the "defrost temperature"? I don't quite follow.

 

If my understanding is correct, it may be the temperature to which the refrigerant gas falls within the evaporator before the build-up of ice is sufficient to require a defrost to be performed. A lower defrost temperature should therefore indicate that there has been a slower build-up of ice due to there being less moisture in the ambient air.

 


   
ReplyQuote
cathodeRay
(@cathoderay)
Famed Member Moderator
6919 kWhs
Joined: 2 years ago
Posts: 1391
 

Posted by: @derek-m

What is the actual temperature at the radiators and what is the temperature drop across the PHE?

At the moment (just measured), rads ~47, primary in 53, secondary out 54 degrees (not a typo, either measurement error or some sort of lag effect perhaps? Both just about too hot to touch for any length of time). Here is the temp chart for the last hour and a half: 

image

 

Midea 14kW (for now...) ASHP heating both building and DHW


   
ReplyQuote
MikeFl
(@mikefl)
Reputable Member Member
1118 kWhs
Joined: 1 year ago
Posts: 114
 

@derek-m @iancalderbank In the Grant/Chofu docs it's referred to as 'defrost temperature', so that's what Ive labelled it. I'm guessing it's a temperature sensor somewhere close to the expelled air-flow from the HP i.e. when the HP is 'off' it tracks OAT fairly closely; when running, it's much lower than OAT, as shown. Initially I thought it would be a constant (i.e. "the temperature point below which a defrost cycle is required") but observation has disproved that.

Grant Aerona 3 10kW


   
ReplyQuote



Toodles
(@toodles)
Famed Member Contributor
6389 kWhs
Joined: 2 years ago
Posts: 1003
Topic starter  

@mikefl I think I’m getting the hang of interpreting the graphs now and it seems that the pump has gone through 6 defrost cycles so far today (just under 16 hours worth anyway).

 

IMG 0537

 

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
MikeFl reacted
ReplyQuote
Toodles
(@toodles)
Famed Member Contributor
6389 kWhs
Joined: 2 years ago
Posts: 1003
Topic starter  

@ghayne Thank you ghayne, i think I’ll ‘make do’ with an approximation as provided by the Govee units, the indoor humidity levels obviously do matter and we are fairly comfortable as we are so I don’t think we need to chase greater accuracy for this purpose. Now when it comes to what the heat pump is being exposed to, I suspect the measurement method used is probably equally ‘ish’, I note that my Homely graph for midnight to this afternoon shows 4 ‘defrost cycles’ though I think the air has been somewhat dryer today. I am not sure how to read the plot for the ‘defrost’ (top trace on this graph) if any reader is able to throw any light on how to read the scale, I would be very grateful; I think the layout is still a work in progress so maybe it is just a relative indication. Regards, Toodles.

IMG 0538

 

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
ghayne reacted
ReplyQuote
ghayne
(@ghayne)
Active Member Member
148 kWhs
Joined: 9 months ago
Posts: 7
 

Posted by: @toodles

I am not sure how to read the plot for the ‘defrost’ (top trace on this graph)

That seems very high! Did you see the screenshots I posted earlier? my defrost temperatures are much lower (except during defrosting.
Hang on I'll post one again!

Screenshot 2024 01 15 20 35 01

 

 


   
ReplyQuote
Toodles
(@toodles)
Famed Member Contributor
6389 kWhs
Joined: 2 years ago
Posts: 1003
Topic starter  

@ghayne As I say, I think the Homely graphs are ‘a work in progress’ and suspect that the humidity trace needs a line with its’ own parameters! Regards, Toodles.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
ReplyQuote
ghayne
(@ghayne)
Active Member Member
148 kWhs
Joined: 9 months ago
Posts: 7
 

@toodles 

Yes, need a bit of decluttering, those graph labels are quite imposing!


   
ReplyQuote
(@hughf)
Noble Member Member
2965 kWhs
Joined: 2 years ago
Posts: 485
 

I think the Carel platform just calls this ‘coil temperature’…. It’s always below ambient when in heating mode, unless it has just done a defrost.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
ghayne reacted
ReplyQuote



Page 3 / 5



Share:

Join Us!

Latest Posts

x  Powerful Protection for WordPress, from Shield Security
This Site Is Protected By
Shield Security