ECODAN , can I run just the heating without DHW?

berrybug

Hi, I’ve recently had an ecodan heat pump installed and new radiators throughout also solar panels fitted to my roof no battery storage though. All this has replaced fisher type radiators which ran on economy 10 tariff what I’d like to know is do I need to inform my electricity supplier as to these changes ? Should I still be on an economy 10 tariff ? Or would the system work better on a different tariff ? I’m just a bit lost as what would be best ,electricity supplier not the easiest to call and speak to a person with knowledge on the subject 

QrizB

berrybug said:

Hi, I’ve recently had an ecodan heat pump installed and new radiators throughout also solar panels fitted to my roof no battery storage though. All this has replaced fisher type radiators which ran on economy 10 tariff what I’d like to know is do I need to inform my electricity supplier as to these changes ? Should I still be on an economy 10 tariff ? Or would the system work better on a different tariff ? I’m just a bit lost as what would be best ,electricity supplier not the easiest to call and speak to a person with knowledge on the subject 

You don't need to inform your supplier.

Whether you're better with E10, or on a single-rate triff, or on one of the more innovative smart tariffs, will depend on exactly how you manage your electricity use.

When are your cheap-rte periods? I guess there's an overnight one, and afternoon one and an evening one?

Cosy Octopus (Octopus's tariff intended for heat pump owners) has two cheap-rate periods, a little bit like the cheap rate periods on E10. Can you manage your heat pump to run harder in your cheap periods and just idle inbetween them?

Reed_Richards

@matt_drummer hates me to comment on his posts but he asserts some things I find impossible to let pass unchallenged.  Heat does not vanish.  

If your radiators emit 3000W when your heat pump heats water to 35 C, your heat pump achieves a COP of 5 under these conditions but has a minimum power of 920 W then it will output 4600 W.  So it will heat the water up to 35 C, but then the water will continue rising in temperature and so the heat pump will switch itself off for a while.  On average it will be on for 3000/4600 of the time and off for 1600/4600 of the time so its time-averaged output power matches the output of the radiators. 

It's really a little bit more complicated than that because the water will cool when the heat pump is off, then warm up until it exceeds 35 C (by whatever margin the controller allows) so the COP of the heat pump will vary during a cycle, as will the output of the radiators, but the principle is the same.  The heat pump cycles on and off because it cannot modulate its power down enough to match the requirements of the radiators.  Boilers do the same.

Most oil boilers will not modulate at all so are either full on (at 9000 W say) or off.  So a 9000W oil boiler paired with radiators needing only 3000 W will be on 3000/9000 of the time and off for 6000/9000 of the time.

Gas boilers can modulate and generally have a greater modulation range than heat pumps but still if you reach the bottom end of their modulation range they will cycle.    

matt_drummer

You're on your own now that RR is on the case.

This will be the last post I ever make on this forum.

I asked him nicely but he can't resist.

Reed_Richards

I'm sorry to lose @matt_drummer but this is a forum where different people will have different opinions, possibly even different interpretations of the same facts.  You have to be able to cope with other posters who see things differently.  I've had a heat pump for almost three years; Matt, I think, got his earlier this year but invested in equipment to measure the actual heat output, something I cannot do.  We're bound to see things a bit differently.

If I see a response which I believe may be incorrect then it seems unfair to the OP who asked the question not to offer my alternative answer.  The best answers often emerge after a bit of healthy debate (and it may turn out that I was wrong in my original opinion).  I'm sorry Matt was unwilling to engage.  

MultiFuelBurner

Reed_Richards said:

I'm sorry to lose @matt_drummer but this is a forum where different people will have different opinions, possibly even different interpretations of the same facts.  You have to be able to cope with other posters who see things differently.  I've had a heat pump for almost three years; Matt, I think, got his earlier this year but invested in equipment to measure the actual heat output, something I cannot do.  We're bound to see things a bit differently.

If I see a response which I believe may be incorrect then it seems unfair to the OP who asked the question not to offer my alternative answer.  The best answers often emerge after a bit of healthy debate (and it may turn out that I was wrong in my original opinion).  I'm sorry Matt was unwilling to engage.  

Agreed I am 8 years in and still tinkering for best performance. The drop to -1oC last night has blown my WC curve out the window with me putting a +2oC on top of the WC for today. Sadly I can't measure COP but just know heating of the house is cheap overall for the year compared to previous similar age or newer houses with gas and electricity.

So that keeps me happy.

We cut our usage of electricity by a third on heating by messaging extensively with an Ecodan owner here that one month of back and forth saved me £300-£500 a year

Swizz

I'm so confused ....
Last night I increased the curve by +3, as an experiment. It used 25kwh which I feel is too much, and we were too hot overnight.
When the WC is at -1 or 0, it is using about 15-19kwh
But the cop is rubbish.
I am at a bit of a loss. 

Reed_Richards

There are two Coefficients of Performance, there's what you get minute-by-minute or there's an average value over a period of time.  If the average is taken over a full year it's called the Seasonal Coefficient of Performance, SCOP.  A modern heat pump, properly installed, should have an SCOP of 3 or better.  Day to day the SCOP will be greater than 3 when it's milder out and less than 3 when it's cold.  2 is a poor figure for the SCOP but might be all you get on a cold day.  

If it's at least quite cold out and your house has enough radiators then there will be a leaving water temperature setting where the heat output from the heat pump matches the heat output from the radiators and the heat pump is on all the time.  Conventional wisdom, which I agree with, is that this is the most energy-efficient way you can operate your heat pump.  The ideal Weather Compensation curve matches the leaving water temperature to the outside temperature so the radiator output is just enough to keep your house at the temperature you want.

Things get a bit more complicated if you switch your heat pump off at night, or reduce the set temperature, but the principle is still basically the same, you should use the lowest leaving water temperature that you can which will make your house as warm as you want it.  Trial and error can tell you what output water temperatures you need for different outside temperatures.  Or you can estimate what values to use by calculation.  You use these values to set your WC curve.

Now @matt_drummer seemed to think that if it was mild enough outside this conventional wisdom did not apply. I   could not follow his reasoning for this, to me it seemed wrong.  Anyway, at the moment it's cold out (where I am) so we're in the "cold" regime where the heat pump is capable of running continuously and Matt's idea doesn't apply.
       

Swizz

Hello, obvs it's pretty cold now, and I've noticed it's running all day and night...outside temp between 0 and 2/3
Horrified that for last 3 days it's using 52kw per day...
We were told the anti freeze needed topping up a year ago, and quoted £500 for it...is this relevant to the consumption? At this rate, about £15 a day is alarming

MultiFuelBurner

Swizz said:

Hello, obvs it's pretty cold now, and I've noticed it's running all day and night...outside temp between 0 and 2/3
Horrified that for last 3 days it's using 52kw per day...
We were told the anti freeze needed topping up a year ago, and quoted £500 for it...is this relevant to the consumption? At this rate, about £15 a day is alarming

To confirm that's just your heating or heating and hot water or the total of 52kWh a day?

Are you still on the WC curve?

Not that you can compare but we are in a test phase at the moment with our ASHP having used WC last year we learnt a lot and have move now to a fixed temp flow rate 24/7 and thermostats set high all over the house so it just keeps pumping 35oC into every room. Last night we hit -2oC and our flow rate is set to 35oC 24/7 upstairs and down. Usage at 0oC to -2oC overnight and max of 4oC during the day is averaging out at 20-24kwh including hot water set to eat to 50oC during this cold spell. Ours is 9kWh unit. That's enough to make most areas 20-22oC depending on where they are in the house with the exception of vaulted tall ceiling areas they start off like this morning at 5am at 18-19oC and warm up more gradually during the day. On Octopus Tracker taking the last few days average price that works out at £4.93 a day for heating and hot water.

As for glycol (anti freeze) replacement of the whole lot may cost £500 as up to 25% of your wet system will need to be glycol. A top up maybe £100-£150 or cheaper if you have a local handy plumber.

We just had ours serviced and they said glycol was a little low but as we run it 24/7 it won't matter and it's got enough for down to -10oC as a rough estimate should we lose all power during a prolonged cold spell. 

With less glycol you actually produce more heat but that's a debate for another day and one that others on other sites have gone back and forth running 24/7 with no anti freeze and better efficiency versus the power cut protagonists and those that don't run their systems 24/7.

I suspect you need to delve into your usage figures and see the temperature drops and the power spikes in your electrical usage. It could be you have the backup 3/4kwh heaters kicking in to give your system a boost. In which case you can look to turn those off if you want to in the service maintenance menu options. They should not be needed unless we hit -5oC and below so they may be set a little cautiously.