Renewable Heating Hub Heat Pump Forums

Search with Wattson
Forums
Renewable Heating
Air Source Heat Pum...
Need some help with...
 
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!

Need some help with choosing the right Rads

 
Air Source Heat Pumps (ASHPs)
Last Post by Toodles 8 months ago
3 Posts
3 Users
1 Reactions
1,221 Views
RSS
 Renewables345
(@renewables345)
Eminent Member Member
Joined: 1 year ago
Posts: 14
Topic starter 24/02/2026 11:36 am   [#2847]

Hi all,

 

I've got an installation coming up of a Warmflow Unit, and I am having some trouble with the radiators for the bathroom.

 

The heat loss is around 1.9kW. I plan to have one electric towel rad and a standard central heating rad. Does anyone have any recommendations?

 

Thanks in advance



   
Quote
JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 4 years ago
Posts: 5606
24/02/2026 11:53 am  

Posted by: @renewables345
↑

Hi all,

 

I've got an installation coming up of a Warmflow Unit, and I am having some trouble with the radiators for the bathroom.

 

The heat loss is around 1.9kW. I plan to have one electric towel rad and a standard central heating rad. Does anyone have any recommendations?

 

Thanks in advance

Wow, thats a big (or very poorly insulated) bathroom.  Are you sure its that much?

As I'm sure you know radiator output and thus selection depends on the design flow temperature so without that its impossible to say.  For example a radiator that is rated at 1kW at the standard 50C difference between rad and room (eg flow temp 75, return 65), will emit only 360W at a more typical heat pump flow temp of 45 and return temp 40.

Whats your design FT?  You may struggle to find a radiator, other than a large type 33, that will do 1.9kW at 45.  I had a similar requirement in my lounge area and ended up with a (very satisfactory) fancoil because a passive radiator with that capacity just wouldn't fit.

 


This post was modified 9 months ago 2 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.


   
🧐
1
ReplyQuote
Toodles
 Toodles
(@toodles)
Famed Member Contributor
Joined: 4 years ago
Posts: 3044
25/02/2026 4:53 pm  

@jamespa In case it may be of any interest (or help!), our bathroom is ~2m x~2m and 2m high with just one external wall with triple glazed window. The radiator is 600H X 700W K2 COMPACT and the dual fuel towel rail above is 760H X 600W. Our flow temperature was calculated at 50 C. but 40 - 45 is normal for most temperatures in the last three winters. We like an elevated temperature in our ablutting area of ~25 C. or so and this is achieved easily. The door is only shut over in the evenings ahead of shower time but does benefit from solar gain in the day as it faces SSW. Regards, Toodles.


Toodles, heats his home with cold draughts and cooks food with magnets.


   
ReplyQuote
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