Retrofit UFH

[nwnw]

On 19/04/2024 at 15:33, SteamyTea said:

No, they are just fan assisted radiators that are small.

 

You can just plumb them in to the existing system.

 

https://www.plumbworld.co.uk/smiths-space-saver-ss55-hydronic-plinth-heater-with-brushed-steel-grille-1304-1261300

 

 

This got me thinking...does a product exist that simply adds fans to the top of standard radiators to perform this function.

Indeed, quite a few seem to exist, although they all seem to be cheapish and a bit of a hash-job.  E.g. https://radiatorfan.co.uk/radiator-fans/

 

 

I did find a very interesting report on experiments that were carried out on radiator fans...

https://www.sciencedirect.com/science/article/pii/S2214157X23007384?ssrnid=4513816&dgcid=SSRN_redirect_SD

They found that the 337W of a std convector radiator at 40degC was increased to 616W at normal fan speed and 1173W at higher fan speed.  Good empirical proof that they work as you would expect.

It states that the effect is greater at lower flow temperatures, so lends itself well to ASHP heating and I wonder if these are a good way around fitting bigger rads.

It would also be easily removed if it was found that the MCS heat demand estimates were overdone.

 

Anyone have any experience of these?

[Adsibob]

7 minutes ago, nwnw said:

Anyone have any experience of these?

No, but i imagine this will dry out the atmosphere in your house. Unless you have a damp house, I wouldn’t do this.

[SteamyTea]

6 hours ago, nwnw said:

Anyone have any experience of these

I have no experience but I think a couple of people on here have tried them.

 

6 hours ago, Adsibob said:

No, but i imagine this will dry out the atmosphere in your house

I don't see why it would be any different to increasing the radiator size, or the flow temperature.

The absolute humidity (the grams H₂O/kg_air) would stay the same, so the relative Humidity would just follow the normal Temperature/RH curve.

[nwnw]

18 months later and I'm revisiting the subject of UFH vs radiators.

I had my heat pump installed last August and it has been a revelation.  Warm house all year round.  Much much cheaper to run than my old oil boiler (I have solar and a battery also, which helps a lot).

I didn't rip up the floor and install UFH.  Basically my radiators work exactly as they were (one bedroom rad was upgraded, but that was it).

 

My extension is now going ahead next Spring/Summer.  This will add about 50m2 of living space, but will be very well insulated so should not add much wrt heat demand.

The extension work will remove a large section of wall (to make open plan with existing living space) which will also eliminate a large radiator.  There will not be much free wall space in the new space.

 

So, my quandary is, do I play it safe and cram in a couple of radiators as big as I can make them in the new space?  Or do I install a single loop of UFH in the new space (I'm having a 150mm slab floor so can easily attach to the reinforcing mesh)?  I still like the idea of UFH in the living space, to give an even, comfortable heat with less of the heat disappearing upstairs (open stairway in the living space).

 

Can I run a single UFH loop basically as I would a large radiator if I size it right? (I.e. fully open, without an extra pump, throttling, etc)  The ASHP is effectively on 24 hours a day so lends itself to this.

Are there any good calculators for UFH sizing?  (note that I will have 15mm engineered wood flooring on top).

Any pitfalls??  My only worry is that if oversized on the UFH, the flow temperature could lower to a point where the rest of the house doesn't get hot enough (which might take me back to fans on radiators!).

 

Edited October 5 by nwnw

[JohnMo]

Really depends on you current flow temp range. Is it a 50m² floor area extension? If it's that floor area, a single loop is unlikely, more likely 3 or 4 loops.

 

Really need more details on the specifics

[nwnw]

@JohnMo you're right, more detail required...below is a rough layout of existing and new.  Open plan area will be almost doubled.  Intention would be to have a small radiator in each of the new well insulated Entrance and Utility rooms.  It's the extended living area that I think would benefit from UFH.  As I say, there's also an open stairway so with radiators I practically need to heat upstairs before downstairs gets warm, although nowadays with the ASHP on all the time it's not such an issue.

 

My thinking is that I wouldn't need/want to fill the entire new floor with pipes.  In theory I just need to replace the heat from an existing 1200x600 K2 radiator that will be removed along with the wall and maybe a bit more to help reduce the flow temperatures from my ASHP (and hence improve efficiency).

 

"Power Output at Delta 50" for the K2 rad removed is about 2080W.  So if I assume that I want, say, 3500W Power Output at Delta 50 for the UFH then how do I go about detailing the pipe length, size, spacing?  How do I determine if a single loop is sufficient?  And how do I determine if the ASHP pump is up to the job?

 

Worth noting that I will still have another 1000mm K2 radiator in the existing living space, and if I find the ASHP flow temps are then too low for the rest of the house then I can always switch that off (until I upgrade some rads elsewhere in the house).

Hope that makes more sense now.

 

Edited October 6 by nwnw