Power consumption heat pump

coffeehound

QrizB said:

Cardew said:

I went away for two weeks in the winter and set gas boiler to frost stat. Boiler was switched on a couple of hours before we arrived back and with a 30+ kW boiler circulating water at 80C the house was warm on our arrival.

Heating in my house goes off around 10pm and on around 6:30am and house is at required temperature by 7am. I suspect the majority of gas/oil CH properties adopt a similar practice - albeit with timings of their choice.

Your 30kW gas boiler took 2 hours to warm your house, so your house needed 60kWh to warm it. If you had a 12kW heat pump you would have had to turn it on 5 hours befofe you arrived home to get the same effect.

In the morning, your boiler takes 30 minutes so your house needs not more than 15kWh to warm from overnight. With a 12kW heat pump you'd need to turn it on at 0545 not 0630.

None of this is rocket science.

The gas boiler won't have run at full pelt for two hours, it'll heat the radiator circuit water to setpoint (80º in this case), then switched off until the water cooled back down to probably 65º, then rinse and repeat.

I would guess a HP does similar with lower output power and lower target temp, and probably a tighter temperature range

QrizB

wittynamegoeshere said:

What's the typical newbuild high density housing estate going to sound like when people start installing these?

I'm sure it will be fine. My neighbours have a heat pump (it might just be for air con, it might heat too - I honestly don't know) and when it runs you can hardly hear it. Even with our windows open. It's barely any louder than our other neighbour's boiler flue fan.

Reed_Richards

Cardew said:.

Also iirc you run your ASHP at considerably higher water temperatures  than the 'normal' 35-40C

That's the way the installer set it up.  @shinytop also had a heat pump installed recently and their system only operates at a few degrees lower than mine.  I hate to say this but are you sure you're not thinking of heat pumps running underfloor heating?

shinytop

Reed_Richards said:

Cardew said:.

Also iirc you run your ASHP at considerably higher water temperatures  than the 'normal' 35-40C

That's the way the installer set it up.  @shinytop also had a heat pump installed recently and their system only operates at a few degrees lower than mine.  I hate to say this but are you sure you're not thinking of heat pumps running underfloor heating?

35-40 C is for underfloor heating.  Any heating system using rads will have to be able to go hotter than that. Mine is low 40s at the moment but will go to 50 at 0 degrees. I can set it manually or tweak the compensation curve if I want but this is how it came from the installer.  The design flow temps are determined by the MCS calculations an accredited supplier has to do and depend on your location.  My system has to be able to heat the house to standard temperatures (e.g. 21 degrees for a living area) at outside temp of -3.4 C. If I lived in Cornwall it would be different.  It's not guesswork if you're MCS accredited.

Reed_Richards

It would not be impossible to have an ASHP system designed for radiators that operate at (say) 35 C average temperature but they would need to have around twice the surface area of mine, specified for 50 C flow and 45 C return.  The result might be something that does not have the visual appearance of a conventional central heating system?

My system was retrofit and there were one or two locations where it would have been difficult to fit a radiator that was wider or fatter or taller than the replacement I had.  Or to achieve a larger surface area I might have had to have two radiators side-by-side rather than a single radiator.  Actually, in the bedrooms we replaced double panel with double panel double convectors that occupy a smaller wall area then their predecessors.  

Cardew

Reed_Richards said:

Cardew said:.

Also iirc you run your ASHP at considerably higher water temperatures  than the 'normal' 35-40C

That's the way the installer set it up.  @shinytop also had a heat pump installed recently and their system only operates at a few degrees lower than mine.  I hate to say this but are you sure you're not thinking of heat pumps running underfloor heating?

No I am not thinking of UFH.

UFH is the ideal solution for heat pumps, but obviously not an option for almost all retrofit installations.

Both the old Energy Saving Trust trials of scores of ASHPs and GSHPs gave case studies of various installations. On the retrial(the first set of results were appaling) manufacturers were called it to redesign the installations and some used large triple panel convectors to enable the water temperature to be in the range 35 -40C.  iirc a couple used skirting radiators panels.

The COP difference between 35C and 50C is considerable; although in very cold ambient conditions it will be necessary to increase water temperature.

Manufacturers don't seem to give the full technical specification data sheets these days.

[Deleted User]

All of this extra electricity needed to power the heat pumps has to come from somewhere
Together with all of the extra power needed for EV's
Where exactly is the power coming from?
Remember that solar panels are not at their most efficient in winter
The grid is struggling as it is 

Verdigris

Deleted_User said:

All of this extra electricity needed to power the heat pumps has to come from somewhere
Together with all of the extra power needed for EV's
Where exactly is the power coming from?
Remember that solar panels are not at their most efficient in winter 

Do you not listen to the news? Wind generating capacity is going to be increased to 40GW. Guess which season the wind blows hardest in...

Swipe

Verdigris said:

Deleted_User said:

All of this extra electricity needed to power the heat pumps has to come from somewhere
Together with all of the extra power needed for EV's
Where exactly is the power coming from?
Remember that solar panels are not at their most efficient in winter 

Do you not listen to the news? Wind generating capacity is going to be increased to 40GW. Guess which season the wind blows hardest in...

Don't forget they have to be halted in strong winds

wittynamegoeshere

People are naturally resistant to change.  I don't hear any better suggestions though - Putin gas for ever?

Just in case anyone's not noticed, there's no gas left in the North Sea.  The easy days are over, we burnt it all.