Forums

Forums
Renewable Heating
Air Source Heat Pum...
Replacing my 18 mon...
 
Notifications
Clear all

Replacing my 18 month old Hitachi Yutaki ASHP

 
Page 5 / 5
Air Source Heat Pumps (ASHPs)
Last Post by trebor12345 18 minutes ago
50 Posts
5 Users
5 Reactions
407 Views
RSS
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 3555
27/11/2025 1:13 pm  

Posted by: @trebor12345
↑

Regarding the last 3 cycles.  These are coming out of the defrost cycles, so the temperature rises. 

Yes but it reaches a higher temperature than the previous defrost cycles, for which there must be an explanation.  This might give a clue to why the rest of the defrost cycles don't get back to 31.  We saw this behaviour before and its a bit puzzling.  Lets see what this night tells us.  I feel we need to get to the bottom of this.  I will keep thinking about it in the mean time.

Do you by any chance know what the heat pump thinks the TWO and TWI are at the high point of a defrost cycle and at a high point of a non defrost part.  It could just possibly be a buffer effect.  I cant immediately see a mechanism for the specific symptom but it would be good to rule this out, and the heat pump knows!


This post was modified 36 minutes ago by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
ReplyQuote
trebor12345
 trebor12345
(@trebor12345)
Estimable Member Member
Joined: 2 years ago
Posts: 65
Topic starter 27/11/2025 1:59 pm  

Posted by: @jamespa
↑

Posted by: @trebor12345
↑

Regarding the last 3 cycles.  These are coming out of the defrost cycles, so the temperature rises. 

Do you by any chance know what the heat pump thinks the TWO and TWI are at the high point of a defrost cycle and at a high point of a non defrost part.  It could just possibly be a buffer effect.  I cant immediately see a mechanism for the specific symptom but it would be good to rule this out, and the heat pump knows!

I have been writing down the temperatures on the probes on top of the buffer.

High Point just prior to Defrost Cycle

Two - 28.8C (significant drop in temperature)

Twi - 26.3C

Water is a lot cooler because the HP is iced up and not producing the heat required.

High Point Normal Cycle

Two - 31.3C

Twi - 27.3C

Typically I see 31C into the top of the buffer.  4 or 5C across the floor manifold.  +0.7C differential across the lower ports of the buffer (so the mixing inside the buffer thats going on).

 


Hitachi Yutaki SCombi Heat Pump
(Indoor Unit ) RWD-3.0RW1E-220S-K
(Outdoor Unit) RAS-3WHVRP1

2024 build bungalow
Southern england
179 m2
High level of insulation
Underfloor heating
All 12 circuits are fully open all the time
1 thermostat in family room
7KW heat pump
50 litre buffer tank (4 port)
3.6KW solar panels
Energy used by heating 2527 KWh - 7527 KWh (SCOP 3.5 approx)


   
ReplyQuote
Page 5 / 5
Forum Jump:
  Previous Topic
Next Topic  

Currently viewing this topic 1 user ( trebor12345 ) and 5 guests.

Recently viewed by users: Toodles 16 minutes ago, Jancold 20 minutes ago, JamesPa 36 minutes ago.

Share:

Join Us!

Podcast Picks

Latest Posts

Click to access the login or register cheese
x Powerful Protection for WordPress, from Shield Security
This Site Is Protected By
ShieldPRO →