heating hot and quick or cool and slow?

[www.GymRatZ.co.uk]

Having finally insulated our loft from 0mm to 270mm of rockwool I am now having to re-tweak the boiler. It's automatically adjusted depending on outdoor temp. and does UFH in 4 zones in an upsidedown house (all heated air remains in upstairs living area so loses little heat) so I'm wondering whether it's more economical to set the boiler temp. curve to trickle along as low as can sustain a comfortable room temp (21 degrees) i.e. just keeping the room stats on the threshold of clicking off or.... getting a quick burn and rooms up to temp right away allowing prog. stats to regulate temp as expected.

The only downside of the quick/hot burn that I have noticed is the floor keeps radiating taking the room temp up to around 23+ degrees once stat has clicked off. (too warm for comfort) Setting the stat lower means room temp has to drop lower before it starts warming back up again.

Just wondering if one method was more economical than the other. The Boiler tries to modulate output (heat and pump) to maintain a 20 degree temp difference between Flow & return however the UFH only manages a 10 degree difference so that's not too clever.

Design temp for UFH is 60 degrees flow.

Cheers Pete

[Tabby]

Slow & cool is more efficient, because the return temp is lower thus more heat is extracted from the flue gases. This is why weather compensation is used, it turns down the flow temp when the weather is mild, and turns it up when more heat output is needed.

NT

[www.GymRatZ.co.uk]

Only thing that can be thrown into the pot I guess is that slow and cool means pump is now working for for significantly longer periods each day. But slow and cool is what I was working on more from a comfort level than anything else. Lots of monitoring and tweaking through the season to get it right now though.

When it was just a layer of platerboard for insulation everything was set flat-out.

8¬O

[Tanuki]

My approach is to run the heating at max-power to bring all the rooms to their desired temperatures - something I only need to do at the beginning of the heating-season.

Then I let the TRVs manage the individual room- temperatures; the boiler will modulate and cut-out on its own thermostat once all the TRVs are closed and the only circulation is through the bypass-valve.

Think of it like driving a car on a motorway: you accelerate rather briskly down the slip-road when you join, then when you hit your desired speed you engage the cruise-control.

Lots of thermal-inertia in the house helps: from a stable 20 degrees, mine typically loses 0.5 centigrade/hour with the heating off, and gains 1.5 centigrade/hour with the heating running full-bore and all the TRVs wide open.

I don't bother with time-switches.

I am now

depending on

(all heated

I'm

curve to

degrees)

off or....

prog.

the floor

once stat

means

again.

other.

a 20

only

[Tabby]

Pump 30w, energy cost 10-12p/unit. Boiler nearer 20kW, cost 3p/unit. Pump power use is trivial.

NT