Heat pump efficiency

[Brickforce69]

Been using an Ecodan 8.5 k for heating and hot water in my 180 m2 home,UFH on both floors.

Looking at the figures for 2021 just wondering if someone can tell me if it’s working efficiently 

Figures are: Consumed energy 4846 kWh of which 1397 kWh was DWH and 3449 kWh for heating

                     Delivered energy   9456 kWh of which 2780 kWh was DWH and 6676 kWh for heating

 

about to build the same house shortly so just wondering if another heat pump is the way to go 👍

[nod]

Whilst Heat pumps are supposedly cleaner than gas and oil 

They always seam to be more expensive to run 

We have no gas available on our next build 

and an oil boiler is no longer an option due to the sap constraints 

It doesn’t seam to matter how much gas goes up Electricity suppliers seam to find a reason to keep pace 

[Andehh]

I guess because a very large portion of electricity is generated from fossil fuel power stations which keeps the prices linked, bur electecitiy has the mark-up due to converting fossil fuels to electricity. 

 

Long term though, with new nuclear and more renewables should soften the link, and eventually the UK gov will load up gas prices more so then electricity to force people to convert.

 

It's all a good long term strategy, and the right one for the country....but I'm still going mains has boiler over ASHP because mid term it will still be cheaper. We will just design it so an ASHP can be installed at a later date.

[JohnMo]

Your getting a CoP of less than two.  I would be looking at flow temperature for UFH and hot water cylinder, you should be Getty a higher efficiency than you appear to be doing.

 

Other things that effect efficiency

Too many zones, cause short cycling

To many many on/off cycling of heating timers and thermostats

 

 

[ProDave]

12 minutes ago, JohnMo said:

Your getting a CoP of less than two.  I would be looking at flow temperature for UFH and hot water cylinder, you should be Getty a higher efficiency than you appear to be doing.

And being a Mitsubishi Ecodan, have a careful look at standby power consumption when it is not heating anything at all in the summer. There was a thread recently, some models have very high standby power due to a sump heater.

[Brickforce69]

Flow temp is 46 degs and we have about 14 zones over the two floors. Temps in all rooms in winter avg 19/20 degs with all heating turned off between May and September. COP on this heat pump shows 3.36 so getting nowhere near it atm.

House was completed in 2019,so not like it’s an old house 🤷‍♂️

[JohnMo]

Is that 14 zone (thermostat with time control) or 14 UFH loops? If it's zones I would reduce to one upstairs and one downstairs. Use the thermostat as a limit stop, tune flow temp and rates to get room temp where you need them.

 

I would say your flow temperature is set incorrectly.

 

For cylinder heating (45-46 cylinder temperature) you would need a slightly high flow temp 50ish, otherwise your heat pump will struggle to get the cylinder up to temp and use needless energy.  For UFH your flow temp should be no more than about 30.

[Brickforce69]

Try and get this right!

So the control valve on the UFH is set at 35 deg and the hot water is set at 46 deg on the panel.

With no heating on at all, consumed energy for July is 93 KWH  and delivered energy is 134 KWH,so this is poor for running the DWH and the weekly legionaries cycle,no?

[nod]

1 hour ago, Andehh said:

I guess because a very large portion of electricity is generated from fossil fuel power stations which keeps the prices linked, bur electecitiy has the mark-up due to converting fossil fuels to electricity. 

 

Long term though, with new nuclear and more renewables should soften the link, and eventually the UK gov will load up gas prices more so then electricity to force people to convert.

 

It's all a good long term strategy, and the right one for the country....but I'm still going mains has boiler over ASHP because mid term it will still be cheaper. We will just design it so an ASHP can be installed at a later date.

Nail on the head 

I think there lies the problem 

Until electricity generation eventually moves away from fossil fuel prices will be high 

 

I’ve a friend who runs a air con business Different but similar 

He said he would never have an ASHP

I told him we had no choice 

I think a  long way down the line All new builds will use Heat pumps or something newer and better 

But that is a long way off 

I’d hate to to see the bills for these homes that have been installed retrospectively with Heat pumps as part of government grant schemes 

 

[JohnMo]

Looked at Scotland's production profile, it has approx 10% of all production installed capacity as gas, the rest is renewables and nuclear.  General average of 97% of electrical generation comes from a none CO2 source.  Gas is pretty much only used as and when needed.

 

[nod]

46 minutes ago, JohnMo said:

Looked at Scotland's production profile, it has approx 10% of all production installed capacity as gas, the rest is renewables and nuclear.  General average of 97% of electrical generation comes from a none CO2 source.  Gas is pretty much only used as and when needed.

 

That’s probably why Scottish home energy bills are so much lower than the rest of the Uk 😁

[JohnMo]

38 minutes ago, nod said:

That’s probably why Scottish home energy bills are so much lower than the rest of the Uk 😁

That would be right!  We're being ripped off like everyone else

[ReedRichards]

I have no way of measuring my delivered energy but comparison with my previous oil consumption suggests I achieve a SCoP of around 3 with my ASHP.  And that is with all radiators, UFH should do better.

[Marvin]

12 hours ago, Brickforce69 said:

Try and get this right!

So the control valve on the UFH is set at 35 deg and the hot water is set at 46 deg on the panel.

With no heating on at all, consumed energy for July is 93 KWH  and delivered energy is 134 KWH,so this is poor for running the DWH and the weekly legionaries cycle,no?

My small ASHP runs on standby at 90Watts, so in 1 day 2kWh or 60 a month....

[dpmiller]

do you actually need the legionella cycle?

[SteamyTea]

1 minute ago, dpmiller said:

do you actually need the legionella cycle?

Only for legislation, and paranoid people.

[JohnMo]

https://www.hse.gov.uk/healthservices/legionella.htm