Heat Loss - Pen & Paper Check

[endecotp]

It’s amazing how often radiators seem to come in a bazillion varieties but never exactly what you need. Stelrad tripples seem to come in 300, 500 and 600 high, but not 400.

Does anyone else make them?

Edit: how would 500 work out for you?

 

[Diggory]

Edit: how would 500 work out for you?

I think 450(h) is about my max -
that gives me 25mm (to cill) wiggle room to mount rad on brackets
and 125mm underneath for air convection (whereas Stelrad recommend 150mm)

D

 

[drives]

New boiler plumbed with two zones:
- Z1 17sqm UFH installed and running now.
- Z2 x9 rads; flow/return not yet connected - radiators being replaced.

By modern standards; house insulation isn’t great (parts are >200yrs).
Mix of solid walls and cavity (of sorts) walls, single glazing, sketchy loft insulation, gaps, drafts……….
I can make some improvements over time but fundamentally - I can’t see me ever looking at heat pumps.
Which is kinda why I was happy to work on T50 specs.

I wouldn’t write off running lower flow temps/ashp in the future, and overcompensating now with respect to radiator sizing is definitely a good strategy.

If it helps our house has very poor insulation in places. I remember experimenting with our old boiler where we would be running setbacks of 15/16 overnight and when we were out, and I couldn't get away with outlet flow temps less than mid sixties. The house just wouldn't heat back up to 19/20 when it was very cold outside.

Ashp is now constantly running mid 30s and I've had to dial my weather compensation curve down to run at outlet temps of 46 at -3, as the house was getting too warm when the outdoor temp was dropping. The difference is all in the weather comp approach and running 24/7 with no [or very limited] set backs.

 

[Mister Banks]

Thanks reply and pointer; I have been looking at these.

Eg….,window cill at 600mm.
The two outgoing rads were 300h
k3 at 300h x 1000 and 2000 are 1349W and 2698W respectively
I’d need one of each (2x 2000mm would block off the 13A mains socket)
That gives me 4,047W - I’m looking for 5,500W so I’d need a third rad.
Stelrad don’t do a K3 in a 450mm.
I’m also concerned about wall fixing K3s.
Walls are very old - I’m unable to add feet.
The practicalities in an old house are very real.

Set in context of ‘designed to operate at the lowest possible temperature while still meeting heating needs of the dwelling’.
Albeit not ideal, the DT40 sized rads are looking more viable.

D

5.5kW for one room is crazy, my whole 4 bed house is only a bit more than that! You could go with the DT40 radiators and run a suitable flow temp as required. Then fix the building insulation issues, especially the loft insulation as it’s a quick and cheap fix, then gradually lower the flow temp.

 

[Diggory]

5.5kW for one room is crazy,

I may have confused things there - I was meaning my DT50 equivalent figure is 5.5kW.
Ie I’ve taken my room heat loss of 2.8kW and used a DT30 correction factor (equiv 5.5kW in the ‘standard tables’).

That said, I’ve attached my workings out for that room - please let me know if you spot any clangers.

D