Heat pump radiators

[Dillsue]

52 minutes ago, Michael_S said:

How thick is your 'backbone/main loop' though - ours is rather long due to the house having bene extended and the whole upstairs is 15mm. 

28mm x 7metres from the HP to the centre of the house then 3 x 22mm x 6 metres down the centre of the house, 1 for upstairs and 2 running the length of the house for downstairs. Mainly 10mm drops off the 22mm for each rad typically 6 metre run with 4 drops of 8mm in the original part of the house around 4 metres each. Distance are one way so double for flow and return.

 

15mm for the whole of upstairs sounds a bit constraining!

[Michael_S]

1 hour ago, JohnMo said:

Why do you need rads doing that output with a heat pump system? If you room has that heat loss you must be living in an open shed. Flow rate just sets dT, it is the mean radiator flow temp that sets the output.

 

Why would you cycle the system on and off, or do you mean something else?

With the gas it is tempting to do a overnight setback and of course there is turning down to min heat during holidays and this is when the furthest rads take a while to warm up and then warm the room back up.  That being an issue with the gas it is likely to be even more so with a heat pump.  the issue not being total power output of the heat pump but how quickly that energy can be transferred to the the rads (whatever their size) due to the pipework constraint.  Obviously with an HP I wouldn't use such a big set back.

[JohnMo]

45 minutes ago, Michael_S said:

With the gas it is tempting to do a overnight setback and of course there is turning down to min heat during holidays and this is when the furthest rads take a while to warm up and then warm the room back up.  That being an issue with the gas it is likely to be even more so with a heat pump.  the issue not being total power output of the heat pump but how quickly that energy can be transferred to the the rads (whatever their size) due to the pipework constraint.  Obviously with an HP I wouldn't use such a big set back.

Set backs are generally a waste of time, you still need to replenish the heat back in to be building structure you lost during your setback.

 

If running suitably low temperature for weather compensation, the flow temperature should be equal to supplying only the heat lost no more. If you are running the correct temps you never really recover. So instead, you end up running hotter temps than you really need and bouncing of the thermostats.

 

Setbacks are a false energy saving sold by thermostat manufacturers to sell products.

 

There is a handy calculator here

https://protonsforbreakfast.wordpress.com/2022/12/19/setback-should-you-lower-heating-overnight/

 

So you can see for yourself.

[Michael_S]

11 minutes ago, JohnMo said:

Set backs are generally a waste of time, you still need to replenish the heat back in to be building structure you lost during your setback.

 

If running suitably low temperature for weather compensation, the flow temperature should be equal to supplying only the heat lost no more. If you are running the correct temps you never really recover. So instead, you end up running hotter temps than you really need and bouncing of the thermostats.

 

Setbacks are a false energy saving sold by thermostat manufacturers to sell products.

 

There is a handy calculator here

https://protonsforbreakfast.wordpress.com/2022/12/19/setback-should-you-lower-heating-overnight/

 

So you can see for yourself.

Agree with you re efficiency but it is more abut sleep comfort - I guess it doesn't take long to get used to warner nights as we do it every summer.

[JohnMo]

Just tune the heating to be cooler. Or design radiator to match the lower room design temp 

[marshian]

1 hour ago, JohnMo said:

Set backs are generally a waste of time, you still need to replenish the heat back in to be building structure you lost during your setback.

 

If running suitably low temperature for weather compensation, the flow temperature should be equal to supplying only the heat lost no more. If you are running the correct temps you never really recover. So instead, you end up running hotter temps than you really need and bouncing of the thermostats.

 

Setbacks are a false energy saving sold by thermostat manufacturers to sell products.

 

There is a handy calculator here

https://protonsforbreakfast.wordpress.com/2022/12/19/setback-should-you-lower-heating-overnight/

 

So you can see for yourself.

Absolutely what I found - need a higher temp to recover than what is needed to maintain the house at the desired temp