Hot water 'tank'

[CC45]

Hi all,

 

Just looking for some views on what system we should put into our self build.

 

Some details. Timber frame - walls at 0.14, floor 0.1, ceiling 0.1.  Ufh downstairs with rads upstairs. Mains gas available. 4 bed, 3 bathrooms. May fit solar pv if we can get panels at the right price.

 

Was thinking of gas boiler feeding into thermal store. Immersion top & bottom ready for pv or as a backup.

 

Any thoughts?

 

CC

 

 

[Nickfromwales]

A TS will best deal with the rads / Ufh mix, and you may want to improve that with a separate coil in the TS to supply heat to the rads. That'll enable you to isolate the Ufh and therefore not allow any ferrous particulate ( rust / corrosion ) to contaminate the Ufh and associate components. That would create a separate circuit which would require its own filling loop / PRV / and exp vessel but would ensure the water stayed clean in the Ufh system, which it wouldn't do in a conventional 'mixed' setup. Contamination in a mixed system can be managed with inhibitors and a good maintenance schedule, but will not remove all of the problem like isolating it would. 

Consider slightly oversizing the rads and running them off an Ufh manifold to get the flow temp down so the rads run at a lower flow temp as you'll not want the rads running of the TS direct because then they'll be at the boiler flow temp which, with a TS, would be uncomfortably / unnecessarily hot in a well insulated house   Running off an Ufh manifold will easily allow integration of individual room stats in each bedroom / space served by rads for total comfort control and will prevent any unoccupied spaces from getting heated when not required. I've done these setups before, exactly like this, and they work really well, just depends on how much control you do / don't want. 

[CC45]

Hi Nick,

 

Thanks for that advice - sounds good to me.  I assume the rad circuit would need its own pump, the ufh manifold has its own pump - the pipes feeding it will be a reasonable distance and involve them rising around 2m in height so I assume they may also need an additional pump? Yet to work out heat loss upstairs but likely to be pretty low - how much would you oversize the rads to take account of the lower flow temps? 20%? Adapt the manifold to 15mm copper / plastic or use ufh pipe? and adapt at rad end? How big a TS?

 

CC

 

 

[Nickfromwales]

All manifolds and pipe work can be procured in standard 15mm format for ease of installation . The pump on the manifold for the rads will more than suffice, and the blending valve will allow you to fine tune the heat delivery for maximum comfort. The last one I did had two large convector rads downstairs on 10mm pipe runs and they worked perfectly well, with the manifolds some 15-18m away on the first floor. 

Sizing the rads is down to calculation. Tbh, in a low energy home, the 'standard' used for sizing rads would probably see you with rads much bigger than you actually need anyhoo so ask your local merchant to do the rad sizes per their rough as toast calculator and you'll be more than covered. Without any further specifics it's a bit of a "how long / piece of string" question but not rocket science by any means  

 

[CC45]

Cheers Nick.  I have a spreadsheet I've written that does a heat loss calc for me.  Its been accurate so far (this is my 5th heating system but first ufh).  Was going to use some 10mm pipe to selected rads and 15mm on others so that's good news about the manifold.  Where did you source them from?

 

Hwyl,

 

CC

[Nickfromwales]

I got all my stuff from Boulder Developments, but many on here have sourced via Wunda too. 

[CC45]

UFH was from Wanda so can give them a call.

 

Thanks

 

CC