Renewable Heating Hub Heat Pump Forums

Search with Wattson
Forums
Renewable Heating
Air Source Heat Pum...
Four Heat Loss Surv...
 
Notifications
Clear all

Joining the Renewable Heating Hub forums is completely free and only takes a minute. By registering you’ll be able to ask questions, join discussions, follow topics you’re interested in, bookmark useful threads and receive notifications when someone replies. Non-registered members also do not have access to our AI features. When choosing your username, please note that it cannot be changed later, so we recommend avoiding brand or product names. Before registering, please take a moment to read the Forum Rules & Terms of Use so we can keep the community helpful, respectful and informative for everyone. Thanks for joining!

Four Heat Loss Surveys, Four Different Answers. How Do I Choose the Right Heat Pump Size?

 
Page 2 / 2
Air Source Heat Pumps (ASHPs)
Last Post by JamesPa 1 month ago
15 Posts
5 Users
2 Reactions
841 Views
RSS
JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 5242
23/06/2026 10:36 am  

Posted by: @bobflux
↑

When mixing occurs in an uncontrolled way, for example in a buffer or low loss header with mismatched flow on both sides, which is pretty much unavoidable

...And If the flow is the same both sides the buffer/llh is doing nothing in which case what value is it?

A buffer can of course be managed to have the same average flow with different instantaneous flow, not so an llh.


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
 AnnaB
(@annab)
New Member Member
Joined: 3 months ago
Posts: 6
Topic starter 24/06/2026 8:54 pm  
This is the response I have had to my request for them to explain why the low loss loader is required from the company who have suggested Ecodan with low loss loader...'a low-loss header creates mechanical separation between the heat pump pipework and your central heating pipework (the existing radiators and proposed underfloor heating). The benefit of this is that you can ensure flow rates (the amount of water flowing through the system) can be achieved. Your heat pump, your existing radiators, and your new underfloor heating could all have different flow rates, so a low-loss header can help optimise this. 
 
If you don't need one or there is no benefit, we'd recommend not having one. In that case, we would design out the low-loss header and recommend a volumiser instead. The volumiser isn't mechanically separated, so doesn't incur any losses - which is good! The volumiser increases the water volume in the system to ensure specific flow rates can be met.'
 
I have also now got the heat loss report from the company who calculated the lowest heat loss and are recommending Valiant Arotherm 7kW, so next I will be looking at this and trying to unpick where the difference comes from....


   
ReplyQuote
JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 5242
24/06/2026 11:15 pm  

Posted by: @annab
↑
..'a low-loss header creates mechanical separation between the heat pump pipework and your central heating pipework (the existing radiators and proposed underfloor heating). The benefit of this is that you can ensure flow rates (the amount of water flowing through the system) can be achieved. Your heat pump, your existing radiators, and your new underfloor heating could all have different flow rates, so a low-loss header can help optimise this. 
 
If you don't need one or there is no benefit, we'd recommend not having one. In that case, we would design out the low-loss header and recommend a volumiser instead. The volumiser isn't mechanically separated, so doesn't incur any losses - which is good! The volumiser increases the water volume in the system to ensure specific flow rates can be met.'

Well that could have been generated by AI and says absolutely nothing at all about your property  Thus it is almost (but not quite) content free, not quite because it does admit to the possibility of not having an LLH. 

TBH I don't necessarily blame installers for doing this, with perhaps a 10:1 hit ratio they have little choice if they wish to remain competitive and simultaneously preserve their sanity and personal relationships.

If you are leaning towards them then tell them so (without committing until you are ready) and seek a property-specific answer.  If you aren't leaning towards them then don't waste their time or yours, instead politely thank them and move on.


This post was modified 1 month ago 3 times 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
Page 2 / 2
Forum Jump:
  Previous Topic
Next Topic  
Share:

SPONSORS

Join Us!

Installer Finder

Degrees of Separation

Latest Posts

SPONSORS

Members Online

Click to access the login or register cheese
Protected By
Shield Security PRO