Renewable Heating Hub Heat Pump Forums

Search with Wattson
Forums
Renewable Heating
Wood Burners, Bioma...
Hydronic plinth hea...
 
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!

Hydronic plinth heaters and ASHPs

 
Wood Burners, Biomass, Small Scale, Biofuels & Other Heating Alternatives
Last Post by benson 2 years ago
10 Posts
4 Users
7 Reactions
3,527 Views
RSS
 benson
(@benson)
Reputable Member Member
Joined: 3 years ago
Posts: 301
Topic starter 03/05/2025 3:44 pm   [#2292]

Hi all,

Wondering if anyone had experience of the above, combined with ASHPs? 

Redoing our kitchen at the moment. UFH is a no go. Looking at the plinth heaters some of the larger ones will just about meet the heat loss of my kitchen (pretty much dead on in fact), and will involve significantly less plumbing work than what I was looking at doing with having to move/change the radiator to accommodate the plans with the units. 

Thanks

 



   
Quote
 Judith
(@judith)
Prominent Member Member
Joined: 3 years ago
Posts: 554
03/05/2025 5:18 pm  

We have one and it’s a bit undersized since it was the original on the hotter water gas system. But nevertheless we only needed to flick it on for a few hours this last winter.

The only subtlety is it has to be on the summer setting (Myson 1kW) since on the winter setting the fan switches off when the flow temperature is below a (can’t remember) value.

It works very well because being fan driven the wattage reduction with flow temperature is not as steep as a radiator.


2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with SCOP >4) open system operating on WC


   
👍
2
ReplyQuote
 benson
(@benson)
Reputable Member Member
Joined: 3 years ago
Posts: 301
Topic starter 03/05/2025 6:10 pm  

@judith thanks. Good to know yours is working well. There do appear to be some that cater for lower flow temps, as in fan won't switch off on certain models, which is good. The only thing I can't quite get my head around is how they would be balanced as a normal radiator would, with lockshields, and whether this would lead to inefficiencies. I could get a radiator into the revised plans it would involve taking a fair few floorboards up, and I think extending the tees to the radiator around 3 metres as well to get it over the other side of the room.



   
ReplyQuote
JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 4 years ago
Posts: 5629
04/05/2025 12:31 am  

Posted by: @benson
↑

The only thing I can't quite get my head around is how they would be balanced as a normal radiator would, with lockshields, and whether this would lead to inefficiencies

I have a mitsubishi wall mounted fancoil which is I think essentially the same construction as a plinth heater.  No hydronic balancing needed, it modulates the fan speed to adjust the temperature.  Great piece of kit except that it turns off when the water temp goes below 30C and this figure is not adjustable, which could cause problems at the ends of the season.  For me it's just about ok but I can see it may be problematic in some cases.


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.


   
👍
2
ReplyQuote
 benson
(@benson)
Reputable Member Member
Joined: 3 years ago
Posts: 301
Topic starter 04/05/2025 10:11 am  

@jamespa we should be ok as the model I'm looking at has the same cut off (30) and our min flow temp is 35.

Would the reduced volume in the system be a problem do you think? Our current kitchen radiator is a fair size albeit we do have 17 radiators in total so it is a relatively small proportion of the total.



   
ReplyQuote
JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 4 years ago
Posts: 5629
04/05/2025 12:01 pm  

Posted by: @benson
↑

@jamespa we should be ok as the model I'm looking at has the same cut off (30) and our min flow temp is 35.

Would the reduced volume in the system be a problem do you think? Our current kitchen radiator is a fair size albeit we do have 17 radiators in total so it is a relatively small proportion of the total.

Unless your defrost is already marginal I can't see it making a material difference but of course you could, if you were concerned, do the calculation or add a volumiser when the system is drained.

 


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
 benson
(@benson)
Reputable Member Member
Joined: 3 years ago
Posts: 301
Topic starter 04/05/2025 12:50 pm  

Thanks. I suspected I was overthinking that part. 👍



   
👍
1
ReplyQuote
Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 6 years ago
Posts: 4973
05/05/2025 9:44 pm  

@judith off the topic, but just saw in your signature that you MVHR. Was that a retrofit install?


Dad’s Outside with the Heat Pump Again
He wanted to save the planet. His family just wanted him to come inside.
Get the book → · Free UK shipping
The Ultimate Guide to Heat Pumps · Britain’s Heat Pump Shitshow
Heat Pumps Explained · From Zero to Heat Pump Hero · Bodge Buster
From Zero to Heat Pump Hero and Bodge Buster are rewritten and updated for 2027.
New to heat pumps? Heat Pump Fundamentals course — 50% off with INTRO50.


   
ReplyQuote
Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 6 years ago
Posts: 4973
05/05/2025 9:50 pm  

@benson will you be proceeding with the plinth heaters and which brand(s) are you considering?


Dad’s Outside with the Heat Pump Again
He wanted to save the planet. His family just wanted him to come inside.
Get the book → · Free UK shipping
The Ultimate Guide to Heat Pumps · Britain’s Heat Pump Shitshow
Heat Pumps Explained · From Zero to Heat Pump Hero · Bodge Buster
From Zero to Heat Pump Hero and Bodge Buster are rewritten and updated for 2027.
New to heat pumps? Heat Pump Fundamentals course — 50% off with INTRO50.


   
ReplyQuote
 benson
(@benson)
Reputable Member Member
Joined: 3 years ago
Posts: 301
Topic starter 06/05/2025 6:59 am  

@editor yes I think so. It will be a while until I get around to fitting it but just need to plan for pipework etc hence researching early. It was the Thermix ones I was looking at which are specifically designed for ASHPs and lower flow temps.



   
👍
1
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