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How to choose Towel Rails for an ASHP

 
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Air Source Heat Pumps (ASHPs)
Last Post by GrahamF 7 months ago
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 Renewables345
(@renewables345)
Active Member Member
Joined: 7 months ago
Posts: 9
Topic starter 16/09/2025 10:28 am   [#2464]

Hi all,

 

I'm struggling a bit here. I am currently quoting up my first ASHP job. I have done the heat loss which comes out at 10.6kW. There is a bathroom which has a heat loss of 570 watts and a WC with a 400 watt heat loss. The bathroom currently has a 1m wide by 0.5m high towel rad, and can only go up to 0.6 high. In the WC it is 1m high and 0.6m wide. These don't match the outputs necessary but I can't find any which will even get close to fit in the space. What would you do in this scenario and is there anywhere you would recommend buying your towel rads from?

 

Thanks



   
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Heat Loss ASHP Towel rad
Mars
 Mars
(@editor)
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Joined: 5 years ago
Posts: 4513
16/09/2025 12:01 pm  

@rob-nezard is this one you can assist with in terms of sizing or guidance?

@renewables345, UK Radiators is a safe and reliable place to purchase rads from because of their transparent approach to emitters.


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JamesPa
 JamesPa
(@jamespa)
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16/09/2025 12:03 pm  

Posted by: @renewables345
↑

Hi all,

 

I'm struggling a bit here. I am currently quoting up my first ASHP job. I have done the heat loss which comes out at 10.6kW. There is a bathroom which has a heat loss of 570 watts and a WC with a 400 watt heat loss. The bathroom currently has a 1m wide by 0.5m high towel rad, and can only go up to 0.6 high. In the WC it is 1m high and 0.6m wide. These don't match the outputs necessary but I can't find any which will even get close to fit in the space. What would you do in this scenario and is there anywhere you would recommend buying your towel rads from?

 

Thanks

So far as I have been able to establish towel rails are essentially useless for low temperature heating, they simply dont emit sufficient energy.

In my bathroom I left the existing towel rail and relied on overspill from the adjacent hall, which works for me.  When I run a bath or have a shower steam heats the room anyway!  Other installers have suggested a normal radiator, a fan radiator or an electric insert to the towel rail for the short time its actually in use.  You can get add-on (sometimes magnetic) rails for normal rads so thats another option.

For my money this is an area where flexibility and customer preference takes over!

 


This post was modified 7 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.


   
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Mars
 Mars
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16/09/2025 12:19 pm  

Posted by: @jamespa
↑

So far as I have been able to establish towel rails are essentially useless for low temperature heating, they simply dont emit sufficient energy.

You've beaten me to the punch. I had this very conversation with Brendon yesterday relating to our towel rails and he said exactly that. They don't emit significant heat and they can affect the rest of your rad/emitter circuit. I will be covering this in our video of the retrospective work we're having done, but Brendon has highlighted to me that towel rails need to be throttled down almost fully.


This post was modified 7 months ago by Mars

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 Rob Nezard
(@rob-nezard)
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Joined: 2 years ago
Posts: 8
16/09/2025 12:23 pm  

@editor Hi Mars, sure I will do my best. The only way to increase heat output with any kind of emmitter (which is what is required when moving to lower temperatures) is to increase the surface area of the emitter.

If increasing height/width is not an option then your best bet would be to try and find something with more tubes.

 

We have one model that is particularly popular for lower temperature systems as there are 2 sets of tubes. https://ukradiators.com/products/crossmoor-white-towel-radiator-h1000mm-x-w500mm?variant=46742482256190 - this may work for the second room mentioned however the first does sound like it is going to be a struggle. 

 



   
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JamesPa
 JamesPa
(@jamespa)
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Posts: 4714
16/09/2025 12:26 pm  

Posted by: @editor
↑

Brendon has highlighted to me that towel rails need to be throttled down almost fully.

Why?  To stop them acting as a bypass?


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.


   
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Mars
 Mars
(@editor)
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Posts: 4513
16/09/2025 12:29 pm  

@jamespa yes, to essentially prevent them consuming unnecessary flow and to allow "more" for the remainder of the heating circuit.


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Morgan
 Morgan
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16/09/2025 2:42 pm  

The only viable solution for a radiator to be warm enough to dry towels and heat a bathroom sufficiently is an electric radiator.  There was no other way to achieve the required result in my view, and it's the route we went. Glad that we did.


Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.
14 x 500w Monocrystalline solar panels.

2 ESS Smile G3 10.1 batteries.
ESS Smile G3 5kw inverter.


   
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 Scalextrix
(@scalextrix)
Estimable Member Member
Joined: 2 years ago
Posts: 127
16/09/2025 2:50 pm  

Posted by: @jamespa
↑

a fan radiator

I've seen pictures of those fitted under a bath where the bath is boxed in.  Just make sure to get one that activates the fan at a low flow temperature.



   
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GrahamF
 GrahamF
(@grahamf)
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Joined: 12 months ago
Posts: 122
16/09/2025 3:12 pm  

We are going for Stelrad Vertical Ultra radiators in two of our bathrooms.  They are K2s with up to three rails attached to them.  This means that your towels hang in front of the radiator, so the radiator itself still gives off near to its maximum heat.  

They deliver 857 - 2,376 watts at delta T50, but obviously much less at heat pump flow temperatures.  Still, it should be plenty for all but the most enormous bathrooms.  The radiator won't get very hot, but hopefully if the bathroom is warm enough the towels will still dry.

You can buy them in lots of different colours, but be warned that any colour other than white has a 14 week lead time.  They are also eye wateringly expensive.  An 1840mm tall x 670mm wide Vertical Ultra costs £1,200 including VAT, but you may save the £200 VAT if it's a full heat pump system installation.


Grant Aerona 290 15.5kW, Grant Smart Controller, 2 x 200l cylinders, hot water plate heat exchanger, Single zone open loop system with TRVs for bedrooms & one sunny living room, Weather compensation with set back by room thermostat based load compensation


   
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 Rob Nezard
(@rob-nezard)
Active Member Contributor
Joined: 2 years ago
Posts: 8
16/09/2025 4:44 pm  

@morgan electric towel rails are a great option and definitely something I would recomend if viable.



   
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 Rob Nezard
(@rob-nezard)
Active Member Contributor
Joined: 2 years ago
Posts: 8
16/09/2025 4:46 pm  

@grahamf yeah great shout, we have something similar here https://ukradiators.com/products/alpha-black-vertical-towel-bar-column-radiator-h1800mm-x-w460mm-2-column-1 - I didnt recomend for the OP due to space constraints but if space is less of an issue then these types of options open up..

 



   
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