Interesting experiment

[Marvin]

18 minutes ago, Beelbeebub said:

I agree reducing demand should be a priority.

 

But my point is you can still run at low flow temps in a relatively unimproved dwelling as long as you have reasonable radiators.

Hi @Beelbeebub

 

Yes it works, but by 'reasonable', what is required are radiators with a larger surface area than for boiler heating so the lower temperature is dissipating over a larger surface area thereby giving off the same amount of heat.

 

Luckily I didn't believe that our renovated home would be as thermally efficient as it is and had installed larger radiators than calculated when fitting the boiler before converting to the ASHP.

 

Where we did have any cool spots i replaced a single panel radiator with a double. there are many upgrades you can do:

 

P1 also known as Type 10, is a type of radiator with 1 radiator panel and no convection fins.
K1 also known as Type 11, is a type of radiator with 1 radiator panel and 1 set of convection fins.
P+ also known as Type 21, is a type of radiator with 2 radiator panels and 1 set of convection fins.
K2 also known as Type 22, is a type of radiator with 2 radiator panels and 2 sets of convection fins.
K3 also known as Type 33, is a type of radiator with 3 radiator panels and 3 sets of convection fins.

 

As @ProDave says above be careful about cost efficiencies. Ours were achieved by the fact we were using expensive bottled gas to run the old boiler and we have PV that supplements the electricity used so the savings for us are good.

 

Good luck 

 

M

[Marvin]

On 10/01/2025 at 08:44, ProDave said:

That is most definitely not normal behaviour for an ASHP. If it is defrosting that often there is something wrong.

Sounds like the set temp for the defrost to kick in is high

[Beelbeebub]

13 minutes ago, Marvin said:

Hi @Beelbeebub

 

Yes it works, but by 'reasonable', what is required are radiators with a larger surface area than for boiler heating so the lower temperature is dissipating over a larger surface area thereby giving off the same amount of heat.

 

Luckily I didn't believe that our renovated home would be as thermally efficient as it is and had installed larger radiators than calculated when fitting the boiler before converting to the ASHP.

 

Where we did have any cool spots i replaced a single panel radiator with a double. there are many upgrades you can do:

 

P1 also known as Type 10, is a type of radiator with 1 radiator panel and no convection fins.
K1 also known as Type 11, is a type of radiator with 1 radiator panel and 1 set of convection fins.
P+ also known as Type 21, is a type of radiator with 2 radiator panels and 1 set of convection fins.
K2 also known as Type 22, is a type of radiator with 2 radiator panels and 2 sets of convection fins.
K3 also known as Type 33, is a type of radiator with 3 radiator panels and 3 sets of convection fins.

 

As @ProDave says above be careful about cost efficiencies. Ours were achieved by the fact we were using expensive bottled gas to run the old boiler and we have PV that supplements the electricity used so the savings for us are good.

 

Good luck 

 

M

Absolutely, the old single panel. Rads are only good for high temps - like 70C flows.

 

Thats too high anyway. There's a really safety issue with flow temps that high.

 

I use k22 by default and usually the largest one that can sensibly fit. I only drop down to K21 or p+ if there is a width consideration, eg narrowncorrodors or clearance for a door swing.

 

As a result almost all the properties I look after can function at moderate or low temps. Typically 50C or lower.

 

Tenants still tend to set the flow temps to 65C because that is what everyone thinks they should be. People expect their hearing system to be a scalding hot radiator for 15minutes followed by a cold radiator for 45 minutes whilst you mutter about the heating not being on.

 

Anyway, that policy has put me in a reasonable place for switching over to Heatpumps eventually.

 

I am being cautious though, as I am wary of making a change and the poor tenant's bills going up.

 

So my first switch is likely to be adding a HP to create hybrid system so the tenant has flexibility and isn't "trapped" on one system.