How do I set Ecodan Heating

Reed_Richards

Mstty said:

Crazy that's 20p more a day just to pump your hot water round than for us to heat all the hot water we need for the day. You never did back with your daily figure to heat your hot water all day after saying I was fixated with the way we do it. I am interested if you can beat it with your way?

Well on a sunny day I heat my water via the immersion heater and spare electricity from my solar panels so it costs me nothing at all.  On a cloudy day I really don't know because the average outside temperature here is well below 15 C and that's not warm enough to go without a small amount of heating.  And the average cost per year is difficult to estimate because most of the power consumed by my heat pump goes on heating.

As I said before, all heating, space heating and water heating, is a trade-off between cost and comfort.  I like the comfort of having hot or warm water out of my hot taps all day.  If I only wanted hot water for a few hours each morning, as I presume you do, @Mstty , I'm sure I could save money.  I could save even more money if I took a hot shower once a week and used cold water the rest of the time.  Where you draw the line is down to individual choice.       

Mstty

Great dodge. It doesn't matter where the power comes from at this point it is energy user and as you advocate heating the hot water all day for those with heat pumps you must have an idea?

In this instance and thread the person uses their heat pump only for hot water so your way won't work for them. I would suggest stop advocating people leave their hot water on all day unless you have the heated by heat pump figures?

Reed_Richards

I woke up early this morning, before my hot water heating comes on at 6:30.  The cylinder temperature had fallen to 39 C.  It took the heat pump 29 minutes to bring the cylinder back up to the target temperature of 50 C and the electricity consumed was 1.74 kWh.  During this heating cycle the power drawn by the heat pump ramped up gradually, reaching a maximum of about 6.5 kW  

The recirculation pump then came on for the first time of the day and this dropped the cylinder temperature to 48 C.  This is the worst case because the water in the pipes will have cooled to loft temperature overnight.  I then washed dishes in a bowl of water, near instant hot water out the tap.  Afterwards the cylinder temperature still reads 48 C.

I still have hot water set to on but the cylinder won't actually get heated again unless it drops below 45 C.  I could potentially save money by reducing the target temperature to less than 50 C and/or increasing the hysteresis temperature drop to more than 5 C.       

Mstty

That's got me thinking (this generally goes wrong but here goes)

So do you lose about 1oC per hour overnight?

Then you run a hot water circulation at the cost of 50p a day. Would you agree that every hour this then takes of 0.5oC as it lost 2oC on the first circulation of the day?

So if you run your hot water for 12 hours a day constantly topping up :-

First heat of the day 1.75 kWh

Presume heat loss of 1.5oC per hour every 3 hours 30 a heat up as the temperature drops below 45oC

3 heat ups per day from 45oC-50oC roughly 0.75 kWh each call is 2.25kWh

Total approx 4kWh and I think this is conservative probably more than this and only you can really confirm.

That's an estimated £409 a year (using 28p kWh electricity) for hot water that way plus £182.50 for your water circulation pump.

Cost of heating once a day even for a large family is going to come out at 2.5kWh max with a heat pump and ours averages 1.2kWh but I will air on the generous.

Saving of heat once a day rather than 12 hours a day (excluding the water recirculation you use) £153.50 a year saving.

All very non scientific but adds up in my mind.

I appreciate you have other cheaper ways with solar and this is a very specific way you run your hot water and you have stated you want that hot water all day long and don't want it to drop during the day.

I reckon try 45oC and save yourself some money👍

Reed_Richards

Mstty said:

So do you lose about 1oC per hour overnight?

That's probably about right but I set the target temperature to 45 C for the final 90 minutes of the day (i.e. at 21:00) so it's unlikely the water will be heated after then.  So at 21:00 yesterday the water temperature was somewhere between 45 C and 50 C and at 6:30 it was 39 C.  So in 9.5 hours the water temperature dropped somewhere between 6 C and 11 C

Would you agree that [recirculation] every hour this then takes of 0.5oC as it lost 2oC on the first circulation of the day?

Yes, that would seem to be about right.

Presume heat loss of 1.5oC per hour every 3 hours 30 a heat up as the temperature drops below 45oC

It's more complicated than that because the target temperature drops to 40 C at 10:00.  This normally stops the heat pump coming on again before then so I can use my solar-powered immersion heater to heat my water for free.  Since 7:00 to 10:00 is normally the peak time for hot water usage this might imply that the 1.5 C temperature drop with no hot water usage is an overestimate.

Total approx 4kWh and I think this is conservative probably more than this and only you can really confirm.

That's an estimated £409 a year (using 28p kWh electricity) for hot water that way

I would estimate maybe 2 x 1.75 kW heats on a cloudy day, possibly with another 0.75 kW so total daily use 3.5 to 4.25 kW.  Bit that includes the cost of running the recirculation pump.  Anyway that means your 4 kW estimate won't be far wrong.  But that would be £409 per year total if the sun never shines.

I reckon try 45oC and save yourself some money👍

You could well be right.
    

Swizz

Hello everyone, I hope I don't annoy you with my asking for advice..I wasn't sure if I should start a new thread..apologies if I've got this wrong
We've had our ecodan for 5 years and I don't think I understood fully how they optimally run as installer didn't tell us. We have Woodburner for evening heat, only 2 in the house, very mild here in south Devon. I was using the thermostat rather as if it was gas boiler, and looking back over the stats, wild variations over the years.
We have solar, and iboost for surplus. 
My question is related to COP and flow settings. I just looked and these are the settings. I've no idea if they are optimal...any help appreciated 

Reed_Richards

There is no visual presentation of my settings but at outside temperatures below -4 C the Leaving Water Temperature would be 50 C, at temperatures above 18 C it would be 29 C and a straight line connects those two points.

The lower point is derived from my MCS heat loss calculation which assumes an outside temperature of -3.8 and a LWT of 50 C.  The slope of the line I calculated to balance radiator outputs at lower temperatures.  Above 18 C outside I surely would not be running the heating so the upper point is just one that gives me the right slope.

If your winters are mild it makes sense to set your starting point for weather compensation at a lower temperature, in your case it looks to be around -8 C.  But your upper limit at around 13 C outside is about 5 degrees higher than I would be using at that temperature, So maybe that is a bit conservative.

The real test is if you ever find yourself too cold and if you do, at what sort of outside temperatures.  If that never happens then there may be scope to make your weather compensation at bit more stringent, which should save you money on running costs.      

Swizz

I'm really sorry, but I just can't get my head round this..should I change these parameters..?

Reed_Richards

If it was me, I would change the 40 C on the first screen to 35 C or a bit less.  But if that's wrong your house will be too cold when it's more mild outside.  You won't know for sure until you try.  If your house is not too cold it will be saving you money.   

Scoobnut

My test revealed that the cost of heating hot water was the same ( as far as can tell ) whether its on 12 hours 6 till 6 or three hours, morning, afternoon and evening. It's not a proper test but it gave me an idea of cost to run. The thermostat is still in the living room and with the good weather it's not coming on. I've got it running at 18 degrees which it will stay at over the winter. I have turned the radiator thermostats down too but that doesn't do anything, the radiators still get very hot. I thought of dropping the temperature of the water as that's scolding but as yet I'm undecided. I worked it out in the winter it was cheaper for use to run a boiler stove on peat, logs and coal than it is to run this thing. I looked into a fixed rate electric but that was nearly 400 a month. One thing I did do was put a tick on the legionella box. All the videos I've seen showed a tick where mine didn't have it, was this right.