Ufh vs replacing my radiators?

thevilla

If you're not using the boiler to heat water you could try to get through this winter with a lower flow temperature from your gas boiler and see if the radiators are adequate.  In this weird world it'll be cheaper to use Go cheap rate to heat water this winter.

Heat Geeks on YouTube have some interesting things to say.  They claim to be training heating engineers to more effectively install heat pumps without the one size fits all approach.

waqasahmed

Screwdriva said:

ABrass said:

That's a gross oversimplification. Radiators need to output the appropriate amount into the room given the heating needs of the room.

In a passivhaus then a tiny radiator will work. In a 1930s build with solid walls and draughts no realistic radiator is going to manage with sensible heat pump levels.

And since heat pumps are only ever suitable for very well insulated houses then radiators can be effective, if they're old enough.

Don't mean to disagree but there is a difference between "working" and maximizing SCOP. 

If you want to maximize SCOP (> 4) with a heat pump, the larger the emitter, the lower your flow temperature (think well below 45 degrees ideally).

Naturally, a heat pump won't save anyone money in a poorly insulated, drafty pre- 1970s house without serious insulation retrofitting. But a general rule of thumb really is maximizing the emitters surface area. 

FWIW, my house is a very well insulated timber frame 1979 house 

waqasahmed

thevilla said:

If you're not using the boiler to heat water you could try to get through this winter with a lower flow temperature from your gas boiler and see if the radiators are adequate.  In this weird world it'll be cheaper to use Go cheap rate to heat water this winter.

Heat Geeks on YouTube have some interesting things to say.  They claim to be training heating engineers to more effectively install heat pumps without the one size fits all approach.

Tbh so far I've been able to get away with a flow temp of say 45C. I guess not amazing for a heat pump however 

Reed_Richards

waqasahmed said:

Tbh so far I've been able to get away with a flow temp of say 45C. I guess not amazing for a heat pump however 

It's not good for a heat pump at this time of year.  My heat pump is set to target a flow of 45 C when it's 1 C outside.  When it's 11 C outside the target flow temperature would be about 36 C.

  

waqasahmed

Reed_Richards said:

waqasahmed said:

Tbh so far I've been able to get away with a flow temp of say 45C. I guess not amazing for a heat pump however 

It's not good for a heat pump at this time of year.  My heat pump is set to target a flow of 45 C when it's 1 C outside.  When it's 11 C outside the target flow temperature would be about 36 C.

  

I can only go as low as 40C on my boiler unfortunately tbf

I guess I'll sort the solar panels first, then batteries, then possibly MVHR as long as it doesn't mess with the aesthetics of the house, then upsizing radiators, and finally a heat pump

Reed_Richards

Screwdriva said:

Naturally, a heat pump won't save anyone money in a poorly insulated, drafty pre- 1970s house without serious insulation retrofitting. But a general rule of thumb really is maximizing the emitters surface area. 

A poorly insulated and draughty house of any vintage will be expensive to heat by whatever means you choose.  But it's a complete myth that a heat pump could not do the job or save you money over some other forms of heating.  You would just need a large output heat pump matched to really large area emitters.  This could preclude Underfloor Heating which, I think, is limited to about 100 W/m2  if you don't want the floor to become uncomfortably hot.  So the issue would be finding enough wall space for the large surface area radiators. 

waqasahmed

Reed_Richards said:

Screwdriva said:

Naturally, a heat pump won't save anyone money in a poorly insulated, drafty pre- 1970s house without serious insulation retrofitting. But a general rule of thumb really is maximizing the emitters surface area. 

A poorly insulated and draughty house of any vintage will be expensive to heat by whatever means you choose.  But it's a complete myth that a heat pump could not do the job or save you money over some other forms of heating.  You would just need a large output heat pump matched to really large area emitters.  This could preclude Underfloor Heating which, I think, is limited to about 100 W/m2  if you don't want the floor to become uncomfortably hot.  So the issue would be finding enough wall space for the large surface area radiators. 

FWIW, my house was built in 1979 and I guess part of why it doesn't cope with the low flow temps is because of suspected sludge in the radiators. That, and I might look into additional air tightness anyway 

ABrass

Rather than worrying about sludge in the radiators, why not isolate one by shutting the lockshield valve and the TRV, then removing the radiator and draining/rinsing the sludge out.

Then you can see how much there is.

Reed_Richards

ABrass said:

Rather than worrying about sludge in the radiators, why not isolate one by shutting the lockshield valve and the TRV, then removing the radiator and draining/rinsing the sludge out.

The difficult part of this it getting the radiator off without getting dirty water (and possibly sludge) all over the carpet.  Be prepared with drop sheets and buckets.  If you are dexterous you might be able to fit end caps to the radiator so you can take it outside then empty it - but that is a lot easier said than done.  

EricMears

Reed_Richards said:

ABrass said:

Rather than worrying about sludge in the radiators, why not isolate one by shutting the lockshield valve and the TRV, then removing the radiator and draining/rinsing the sludge out.

The difficult part of this it getting the radiator off without getting dirty water (and possibly sludge) all over the carpet.  Be prepared with drop sheets and buckets.  If you are dexterous you might be able to fit end caps to the radiator so you can take it outside then empty it - but that is a lot easier said than done.  

One way of minimising spillage is (if the fitment allows) to loosen connections then tip radiator forward so that 'top' lies on the floor.  There will still probably be some spillage - but nowhere near as much as if the full radiator was higher than the connections.