Hi Alan

Do you have an EPC, does that agree with the 45MWh/year heating + DHW?  

Has your electricity consumption been similar after the units were installed in 2011?

I suggest that you have an electric meter fitted to each Ecodan, so you can be sure of the useage.  They're quite cheap now, and come in various forms (DIN rail mount or standalone).

Many heatpumps now have some sort of monitoring capability, does yours have?  I would expect somehow to get a thermal power output display.  I understand that the controller is unusual though, so perhaps not.  You can get aftermarket add-ons, such as below, which will do a good job:

https://guide.openenergymonitor.org/applications/heatpump/

On the face of it, (estimated) heat out doesn't seem much greater than electricity used, so the COP could be very low.  I think it is well worth investing in measurements though if you haven't got already, even a slight improvement to the situation will payback very quickly.

To answer your question:  I think the heatslope and offset are open-loop estimates as to what waterflow temperature will allow the house to be warm.  The 22.5C is I expect effectively an inbuilt hysteresis on/off control, that turns the heatpumps off at over 22.5C(+0.5C or so), and back on again at 22.5C(-0.5C or so).  If I'm right about that, then probably the optimum is when the heatslope curve is decreased so that the heatpump is on approximately 80% of the time, off 20%.  That gives you a little headroom, but will generally operate as cool as possible.  Slope 6 will I expect be fairly efficient though, at under 40C flow at 0C outside, so I don't think this is a smoking gun.  

It's to early to tell what is wrong.  Could be a lack of insulation, terrible COP, something else taking (loads) of power, faulty house elec meter.       

Hi AlanB,

The quickest and easiest way to lower your energy consumption would be to lower the indoor temperature from 22.5C to 21C or below. A 1C increase in indoor temperature can equate to up to a 10% increase in energy consumption.

A second fairly easy way to reduce energy consumption is to identify and eliminate any drafts. Then see if levels of insulation can be improved.

Check the temperatures around the buffer tank to see if this is causing any reduction in system performance.

Posted by: @alanb

Hello

Our system was specified by the now defunct Ice Energy back in 2011. We have 2x 14kw Ecodans, with a 300l hot water tank and a 120l Buffer Tank.

House is around 375m2 and mostly modernish with reasonable insulation.2 zones. One UFH for majority of ground floor and other rads for first floor and 2 rooms on GFlr. 

Ice Energy used a bespoke controller using 2 No FTC 2s because cascading controllers were not available in 2011.The controller only has 4 available settings as follows

Master room Temp

DHW temp

Return Flow Temp set by weather compensation

Fine tuning to raise or lower the heat curve in parallel.

Photos of relevant pages from the manual attached.

Current settings are 

DHW 47C

Heat Slope 6

Fine tuning -1

Room Temp 22.5C. ( not sure what this does to be honest )

Could anyone shed any light on whether these are the best I might get or am I missing something? Trying desperately to get out elec consumption down from around 40000 kWh /annum at present. The heat pumps appears to be the main culprit for this high usage.

Heating/water demand estimated at around 45000 kWh/annum

Any advice/help gratefully received.

Cheers

Alan

I think your flow temps look reasonable for ufh.  Unless there is a fault, it would be very unlikely for an Ecodan to return a SCOP of close to 1.  

What is your actual room temperature? Your estimated heat demand per sq metre is about the same as mine.  My house is about 1/2 the size of yours, also modernish with reasonable insulation, but my single 14kW Ecodan will consume less than 8000kWh per annum to keep the house at 21C.  Something doesn't add up.

Are you sure there is nothing else consuming electricity?  You really have to measure what the heat pumps are consuming. You did mention a swimming pool in another thread...  

@kev-m Thank you. Apologies for late reply but succumbed to Covid and have only just got my memory back !

I have altered the settings to 

Heat Slope 4

Fine tuning -2

Room temp 20C. ( sensor on landing next to airing cupboard in stair well ) 

DHW 47C

I also am trying switching off one pump until the heat demand needs it. Probably only need the two pumps in very cold weather.

Anyone know if this is sensible ?

Have also had smart meter installed and linked this to The Loop App. Trying not become obsessive with looking at the readings !!

Total energy usage since was follows

Last week April 523kWH

First week May 337 kWH

Second week May, switched off one pump..Usage after 2.5 days is 105 kWH

Cheers Alan

@derek-m Thanks Derek . Apologies for late reply but Covid got in the way.

I have always been suspicious of the buffer tank as we have quite large system and inverter driven ASHPs. So, will be disconnecting the buffer tank in two weeks, but leaving it in place in case this proves to be the wrong move. Will keep all the other gubbins attached to the tank in place, just by pass the tank itself.

Drafts under control. Additional roof insulation in hand. Currently have 200 mm so adding another 100mm and placing loft lids over the downlighters, which are all LEDs.

Current settings now 

Heat Slope 4

Fine tuning -2

DHW 47c

Room temp 20C

One pump switched off a week ago.

Running on one 14kW Ecodan at the moment.

Cheers

Alan

@robl Thanks Rob. Apologies for late reply as Covid finally got me!

EPC rating is 27000 kWH/yr for heating and 2700 kWH/yr for hot water.  Its 400 m2, reasonably well insulated.

The 45000 kWH is total elec usage estimate for the entire property as we are an all elec house. This includes charging our PHEV, which could use up to 10.5 kWH.day.

The Swimming pool is mostly solar heated with a separate 12kW Calorex heat pump as a top up. The pool is only open from June until end August.

Am bypassing the buffer tank and am running only one pump at present. Have played with settings and turned them all down, 

Heat Slope 4

Fine Tuning -2

DHW 47C

Room Temp 20C

Will definitely add in elec usage meters to each pump.

No idea if my 2 Ecodans have any monitoring capability. The controller certainly doesn't.

Now have smart meter and linked to Loop App to monitor overall elec usage.

Cheers

Alan

@alanb Hope you’re getting over the lurgie, there’s a lot of it about!  I can understand you wanting to reduce your electricity use, it is high.  Can I double check it’s right?  Electricity use of 40MWh/year, at a tariff of 30p/kWh, will now cost £12000 a year, or a monthly bill of £1000.  Did I guess about right for your tariff, and is the bill similar?

I think you should have elec meters fitted to all major appliances so they can be monitored, certainly the 3 heatpumps you have mentioned, and also the car charger.  It would be money well spent!  If as you suspect it turns out to be the heatpumps taking the majority of the energy, then they can be investigated - there are a number of possibilities, but I think it is unclear they are the culprit so far.  I think we should be expecting a more significant change than adjusting the weather compensation, if it is the heatpumps.  Eg. They have internal resistance heaters, that are left on.  Or the elec meter is faulty.  Or the Heatload number is very wrong.

I believe that you can get clip on power monitors which are convenient, I haven’t got one myself.  The better clip on units also plug in or attach to live to measure Volts and Amps, so can accurately measure ‘Real Power’ in kW, and not just guess the voltage and assume it is in phase with the current, which most cheap clip on units do.  It should be able to remain in place long term, and show total energy in kWh also.

We have an accurate din rail mount kWh electricity meter giving a running total of the consumption of our heatpump.  It’s small, and could maybe go in a slot of a consumer unit, fitted by a sparky.
Cheers, Rob

@robl Hi Rob

Have just received my Shelley EM with 2 clips to go around each of the 2 house heat pumps. I'll fit shortly and see what happens.

But, yes you're correct, annual estimated elec bill circa £12k ! Ouch

Cheers

Alan