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. 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 10 months ago

10 Posts

4 Users

7 Reactions

1,771 Views

RSS

benson

(@benson)

Reputable Member Member

Joined: 2 years ago

Posts: 294

Topic starter 03/05/2025 3:44 pm

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

This topic was modified 11 months ago by benson

Quote

Judith

(@judith)

Honorable Member Member

Joined: 2 years ago

Posts: 493

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 4.7) open system operating on WC

👍

ReplyQuote

benson

(@benson)

Reputable Member Member

Joined: 2 years ago

Posts: 294

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)

Illustrious Member Moderator

Joined: 3 years ago

Posts: 4475

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.

👍

ReplyQuote

benson

(@benson)

Reputable Member Member

Joined: 2 years ago

Posts: 294

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)

Illustrious Member Moderator

Joined: 3 years ago

Posts: 4475

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.

This post was modified 11 months 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

benson

(@benson)

Reputable Member Member

Joined: 2 years ago

Posts: 294

Topic starter 04/05/2025 12:50 pm

Thanks. I suspected I was overthinking that part. 👍

👍

ReplyQuote

Mars

(@editor)

Illustrious Member Admin

Joined: 5 years ago

Posts: 4368

05/05/2025 9:44 pm

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

Get a copy of The Ultimate Guide to Heat Pumps

Subscribe and follow our YouTube channel!

ReplyQuote

Mars

(@editor)

Illustrious Member Admin

Joined: 5 years ago

Posts: 4368

05/05/2025 9:50 pm

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

Get a copy of The Ultimate Guide to Heat Pumps

Subscribe and follow our YouTube channel!

ReplyQuote

benson

(@benson)

Reputable Member Member

Joined: 2 years ago

Posts: 294

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.

👍

ReplyQuote