Heated towel rail with UFH

[vala]

I will have UFH throughout the house off an oil fired combi boiler, is there anyway I can have a heated towel rail other than an electric one?

[PeterW]

Yes straight off the feed to the UFH manifolds but tbh it’s overkill … 

[vala]

23 minutes ago, PeterW said:

Yes straight off the feed to the UFH manifolds but tbh it’s overkill … 

I assume then this would be mean the towel rail temperature would be based on what the boiler is set to? Although not 100% confirmed with Wunda (drawings are being done at the moment), the technical staff noted flow temp will most likely be around 45-50deg as its a pug mix install.

If this is overkill, is there another option other then going for an electric towel rail?

 

 

[PeterW]

45-50°C is far too hot for UFH even with pug mix. What insulation have you got ..?

[vala]

Just now, PeterW said:

45-50°C is far too hot for UFH even with pug mix. What insulation have you got ..?

Hi Peter,

I'm just going off what the staff at Wunda said.

Insulation under the pug mix will be 70-80mm PIR boards.

[PeterW]

What’s the final floor surface going to be ..?

[vala]

5 minutes ago, PeterW said:

What’s the final floor surface going to be ..?

In the bathroom tiled, rest of the first floor will be carpet (which with underlay the tog will be 2.5 or less).

[PeterW]

You need to bring that temperature down. Ask them to redo the design with a 35°C flow temperature and see what it comes out at with pipe centres. Oil costs you the same at 3am or 3pm so tbh you can run it whenever. And you’ll need a buffer tank - oil can’t modulate down to a low flow temperature so you will get short cycling if you don’t fit a buffer tank. 

[vala]

1 hour ago, PeterW said:

You need to bring that temperature down. Ask them to redo the design with a 35°C flow temperature and see what it comes out at with pipe centres. Oil costs you the same at 3am or 3pm so tbh you can run it whenever. And you’ll need a buffer tank - oil can’t modulate down to a low flow temperature so you will get short cycling if you don’t fit a buffer tank. 

Would an option to not using a buffer be to down rate the boiler? Its a 12-18kw combi, but I've no idea what size it is. I assume 15kw as I'm led to believe they normally come set in the middle.

Edited July 9, 2021 by vala

[PeterW]

No because you won’t need 15kW of heat when the last zone closes down. You could be down to needing 1/2-1kW and you need to modulate to that point. 

[vala]

1 minute ago, PeterW said:

No because you won’t need 15kW of heat when the last zone closes down. You could be down to needing 1/2-1kW and you need to modulate to that point. 

Noted. Is there any other way without going for the buffer tank? Never planned on having one so not really got a location lined up for one.

And I assume the reason for the short cycling with UFH is, as you mentioned mainly due to the flow temp needing to be much lower than the boiler would put out? I'd have to look at the spec to see how low in temp I can run the oil boiler, its a Worcester external greenslave.

Maybe more insulation throughout the house? I can up the insulation between the joists to 100-120mm if I rest the insulation straight onto the batons, rather then stick a bit of ply in.

Loft space has 250mm of insulation throughout, all internal walls have been redone with rock wool and soundboard.

And all pipes will be lagged.

[vala]

18 hours ago, PeterW said:

You need to bring that temperature down. Ask them to redo the design with a 35°C flow temperature and see what it comes out at with pipe centres. Oil costs you the same at 3am or 3pm so tbh you can run it whenever. And you’ll need a buffer tank - oil can’t modulate down to a low flow temperature so you will get short cycling if you don’t fit a buffer tank. 

Peter,

What size buffer tank would you suggest? I'm thinking it could maybe go in the loft, however would need to check the weight when full up there. 

Thanks