Mitsubishi Ecodan ASHP - Crippling Bills due to electricity usage.

LozT

Hi all

We have recently moved into a property which has an Ecodan air source hear pump. We have been in our home for 5 weeks and in that time have used 3500kwh (700kwh per week). I feel absolutely sick as at the current cost of electricity that's £1,500. 

Thinking this must be an problem with an appliance we have turned off all of them one at a time and the only thing chewing electricity is the ASHP. 

Having read some other threads I'm not sure we are using it correctly, but unfortunately the owner before us had passed and his family have no idea how it works. 

We really cant afford £1,500 a month in electricity costs it will financially cripple us - I'd rather rip the system out and go back to a gas boiler, so before I do anything drastic does 700kwh per week seem correct for the use of one of these things? And if anyone could help in the best way to set them up I'd be grateful for any pointers

Many Thanks

Laura

QrizB

700kWh/week - 100kWh/day - is probably 3x (or more) what I'd expect for an average home.

• How big is your house, when was it built and how well insulated/draughtproofed is it?
• Do you have radiators, underfloor heating, a combination of the two or something else entirely?
• Do you know what model of control system you have and do you have any of the relevant paperwork?
  

Gerry1

How are you obtaining those figures?

BTW, this would be better in the energy thread, which gets more views.

tacpot12

ASHPs need to run for long periods. They are very inefficient for the first 15-20 minutes or so, so you need to ensure that they are switched on most of the time, and they are not short-cycling (stopping and starting) due to the system being incorrectly designed. Does the family of the previous owner have access to his electricity bills, and would they be prepared to share these with so you so that you can see that the problem is is your use of the system, and not the design of it 

LozT

Hi all 

Thanks for coming back.

@QrizB - The house is a 4 bed detached house 2,200 square feet. It was built in the 30s / 40s so I would say badly insulated. We have radiators that look quite old. No underfloor heating. We know the model but have no other paperwork. However we have managed to contact Mitsubishi (hoping they would have a database of who installed it so we could contact them) & they have sent us a manual by email which we will read. 

@Gerry1 - We have been monitoring the electricity meter / looked at how EDF do their pricing. (I will look to add to the energy thread thank you!)

@tacpot12 - It definitely is now on a stopping and starting mode. When we moved in it was just on, but noticing that it was using a lot of electricity we changed the schedule to twice daily but for longer than we would have had a gas boiler on for. Most of the other threads says thats incorrect. The family of the previous owner may have access to his bills, but it was only installed 5 months before he passed, so it would probably have been off. Having said that EDF did say previously the house used a lot of electricity and they estimated £500 per month which we thought wasn't possible. But appears to be spot on. 

Rodders53

Read the sticky threadson ASHPs and GSHPs at the top of this sub-forum ...  and other threads with similar issues both here and in the parent energy forum.  The two are not that dissimilar in operation.

What does the building's  EPC give for heating and water kWh per annum.   That'll give a starting point for working out how much an ASHP with an assumed CoP of 2 or 3 might consume...  (i.e. 1/2 or 1/3 or even less if you're lucky).

Most common issue is too high a circulating water temperature or inadequate sized HP for the demand needing the backup / booster immersion heaters to run at CoP of 1 (where fan heaters would be equally, if not more, effective).

So we'll need the exact model of Ecodan along with the other information asked for to find the spec.

Gerry1 said:

How are you obtaining those figures?

BTW, this would be better in the energy thread, which gets more views.

Some (especially more recent) heat pumps have a meter that shows kWh of heat generated as well as the electricity consumed (and is why the question Gerry1 has asked "how "  as it may not be quite as bad as it seems at first sight).  Fingers crossed.

Nah... the experts on ASHPs are here as is the master ASHPs thread ^^^
The experts also frequent both so it'll be responded to by them shortly.

Gerry1

Try ruling out a meter problem first.  Do the Meter Sanity Test and post a photo of the meter (redact serial number, barcodes etc); some meters are notoriously difficult to read correctly.

QrizB

LozT said:

The house is a 4 bed detached house 2,200 square feet. It was built in the 30s / 40s so I would say badly insulated. We have radiators that look quite old. No underfloor heating.

OK. My 1000 sq.ft. 3-bed semi with partial DG, loft and cavity wall insulation and GCH is using 50kWh/day of heat at present. Your house could well need 100kWh/day of heat but that should need no more than 40kWh/day of electricity.

Rodders53 said:

Some (especially more recent) heat pumps have a meter that shows kWh of heat generated as well as the electricity consumed

If your Ecodan has a heat meter then it would be useful to know what it thinks it's producing. It might also have it's own electricity meter to measure how much it is drawing. If you have that info it would be useful too.

Reed_Richards

As the ASHP was installed in the last year it should have its own electricity meter that can tell you exactly how much it is using.  Will you get RHI payments now you own it?  You need to look into this if you don't know.

I have an ASHP that typically runs in 15 minute cycles with no detriment that I can see.  However @shinytop has an Ecodan and that does seem to like to run more continuously.

The radiators should not look old, most or all of them should have been replaced when the heat pump was installed.  My guess is that your radiators can only achieve sufficient output by running the ASHP to provide a higher than usual water temperature at a much less than normal efficiency and that is why your bills are so extreme.  Your controller should tell you what your Leaving Water Temperature is; what is it?

Several of us who own ASHPs post regularly; we should be able to help you.

shinytop

@LozT,

I have an Ecodan ASHP and it uses a lot less energy than yours.  My house is smaller though (1700 sq ft) and probably a bit better insulated being 1990. But my weekly usage is 2-300kWh in the winter so far. 

Others have asked the right questions but here are some specific Ecodan ones

Which Ecodan ASHP and controller do you have?  The controller will be something like FTC5 or FTC5.  Hopefully your manual from Mitsubishi will say.  Others have asked some good questions but here are some Ecodan specific ones.

How do you control the heating?  Do you have wireless thermostats and are they Mitsubishi branded or other?  Or maybe you use the wired in FTC controller?

How is the flow temperature being regulated (this is the water that ends up in the radiators)?  This is the single most important setting.  On an Ecodan it can be using weather compensation or fixed flow temperature or Auto Adaptation (which is a combination of the first two).  You can tell from the front screen on the controller.  

This is mine. The big zero and the small graph says it's using weather compensation.  A number of 40, 50 or so instead of the zero would indicate fixed flow.  A number around room temperature means it's using (or trying to use) auto adaptation. If you hold down the left button for a few seconds it will tell you the current target flow temperature.   
 

Cardew

QrizB said:

LozT said:

The house is a 4 bed detached house 2,200 square feet. It was built in the 30s / 40s so I would say badly insulated. We have radiators that look quite old. No underfloor heating.

OK. My 1000 sq.ft. 3-bed semi with partial DG, loft and cavity wall insulation and GCH is using 50kWh/day of heat at present. Your house could well need 100kWh/day of heat but that should need no more than 40kWh/day of electricity.

Depending on how many rooms are heated all the time( to what temperature) and how much domestic hot water is used(again at what temperature) -  I would have thought a badly insulated 1930's detached 4 bed 2,200 square feet house would use far moe than 100kWh a day in Dec/Jan.