Air Source Heat Pumps

Edale

Cardew wrote: »

You look like running up a bill of £250 for the mildest November for many years in a highly insulated new build house! That frankly is a cause for concern.

How big is your house?

That seems massive, I used a total of 564 kwh in the first 17 days of November, we have a 14kw ecodan running radiators in a well insulated late 1960s 4 bed house c1800 sq ft. Total bill should be well under £100 for November.

Edited to add usage to today (25 days) is 862 kwh, currently paying 8p per kwh with edf so cost to date in November is less than £70 plus standing charge. Last year our old oil boiler used 100 litres per week on average in the 7 weeks from end of October, granted it was much colder but at current prices this would cost over£60 per week plus our electricity usage before the ashp was fitted averaged 16kwh per day or another £9 per week.

Still waiting to see how the ashp copes with much colder weather!

[Deleted User]

It's my understanding that the DHW is timed say twice a day and the heating is on constant with only the temp set to vary e.g. 20c during the day with 17 at night and perhaps different temps at weekends but NEVER let the house get cold.

With this approach the ASHP costs around £45 per month with lights, cooking etc £25 per month. We are on a standard electricity tariff.

This is in a large 1906 victorian detached bungalow with only CWI, some insulation under the floors, 50% carpets and 3 meter ceilings. EDF are going to be doing the loft soon for free so bills will come down further.

I would say your bills are far to high and it may just be a case of getting it adjusted...

Again a 14kw Ecodan. Have 4kw PV but that makes no impact on the costs of the ASHP at the time of year.

Ally74

Edale wrote: »

That seems massive, I used a total of 564 kwh in the first 17 days of November, we have a 14kw ecodan running radiators in a well insulated late 1960s 4 bed house c1800 sq ft. Total bill should be well under £100 for November.

Edited to add usage to today (25 days) is 862 kwh, currently paying 8p per kwh with edf so cost to date in November is less than £70 plus standing charge.

You pay 8p per kwh? Is this a single rate tariff?

jeepjunkie wrote: »

It's my understanding that the DHW is timed say twice a day and the heating is on constant with only the temp set to vary e.g. 20c during the day with 17 at night and perhaps different temps at weekends but NEVER let the house get cold.

With this approach the ASHP costs around £45 per month with lights, cooking etc £25 per month. We are on a standard electricity tariff.

This is in a large 1906 victorian detached bungalow with only CWI, some insulation under the floors, 50% carpets and 3 meter ceilings. EDF are going to be doing the loft soon for free so bills will come down further.

I would say your bills are far to high and it may just be a case of getting it adjusted...

Again a 14kw Ecodan. Have 4kw PV but that makes no impact on the costs of the ASHP at the time of year.

My bill for November will work out at roughly £60.. that's for heating and everything else. I'm in a 1950's 3 bedroom bottom floor flat of four. The exterior walls are made of steel(?) with roughcasting (I hope that makes sense). I have the 8.5kw ecodan which heats 7 rads.

I found the installers set the heat curve settings far too high so set mines to run at temps so as the thermostat (22C) in the hall doesn't have to kick in. If the thermostat is kicking in the HP is using more electricity to heat the water from cold so a nice steady flow is more efficient in my view.

EDIT: I should add that i only need the heating on in the evening so far.

[Deleted User]

Our heat curve has been adjusted once, upped by 5c. I thought this might impact running costs but can’t say I noticed any change. In my mind this was unnecessary but kept the wife happy with ufh in the bathroom which makes the floor feel warmer now even though the room was warm already... I may change it back since running cost are low there's no rush.

With the house occupied during the day we can't make savings by dropping the temp during the day by a couple of degrees. On the plus side as the house as warm so the fabric of the building is warm the ASHP does very little late evening when the WBS is on and the house rarely drops below 19c overnight.

Far cry from this time last year when on LPG... LPG £200pm vs ASHP £45pm. From readings the ASHP used less than £20pm [house heated to 20c & DHW] during the summer months when LPG used approx £90pm for DHW and occasional heating.

lovesgshp

gterr wrote: »

Another question if I may (especially for Geotherm if he's reading).

We are on Economy 10 tariff but at the moment we are using more peak rate units than off-peak units. I'm sure this is the pump, because for washer, dryer, dishwaher etc. we are dilligent about using off-peak hours.

I've discovered that it is possible to programme the domestic hot water function of the pump so that it uses off-peak hours rather than just on demand 24/7. Might this be a way to save money? Could I do this without adversely affecting the efficiency of room heating function of the pump, provided I left the room heating function on 24/7?

The user manual warns not to control heating by time control, since this can "affect consumption negatively", but for hot water time control it just says "time control hot water can impair hot water production".

Oh yes, and talking about economy, over August, September and October our electric bill (total) worked out about £80 per month. For November to date - including the 21 days we had raised the heat curve to get warm water to the radiators - we have used about £190 worth! OK, some of this will be because of cooler weather, and some because of a modest rise in tariff, but even so!!!

I am now taking daily meter readings.

Any comments?

Yes, you can time the hot water as you wish. Please remember though that DHW production is usualy only about 20% of the pump usage.
The reset to factory settings possibly caused the usage spike as the external control took over. I do not know what the internal sensor influence was, but that could have been too high.
I have both user and installer manuals for the WB now, so I can see better the info.

grahamc2003

GT, Surely you want the HP to be working hard in cheap rates, and do next to nothing in expensive rates. To try to do that, not only would I want to heat the dhw tank in cheap hours, but also the whole house, even though it wouldn't be ideal for the hp, which probably prefers to supply heat at a constant rate.

Firstly, I'd make sure I knew the cheap/expensive hours. I have e7, and have a plug with a led which lights when the circuit is live, so I know exactly. If you have the printed hours, make sure they are not gmt, or adjust ifd they are.

Then, during the daytime, I'd set the thermostat up, probably a couple of degrees higher than ideal (say 22C) when the cheap rate starts, then down a couple of degrees lower than ideal (or as cold as you can stand it) when the expensive rate starts (say 18C). With the thermal mass of the house, and the general variation in temperature anyhow from domestic thermostats, you may not notice a great deal of difference comfort wise. Obviously, I'd just try it for a few days, and make small adjustements so it's comfortable enough all the time. One thing to watch out for, imv, is that the harder the hp works, the greater the chance of icing (and therefore defrost cycles) at recent ambient temps. Have you had any defrost cycles? Are you told when they happen?

I'm a bit surprised how much others are reporting for the running costs this month. At the warm temperatures we've had so far, these things should be operating on a cop approaching 6 or 7 imv, so I'd expect them to be about 1/2 the cost of gas ch at the moment.

[Deleted User]

Unless you are running a huge thermal store heated by more means that just an ASHP I just don't see how it is worthwhile running an ASHP during the night. It may be a cheaper rate but it's a lot of water to heat. Sounds like a system with all the disadvantages of storage heaters... A small store would be depleted very quickly resulting the ASHP coming on during the day.

Vs

ASHP doing 99% of the heating during the day but heating a fraction of the water at a dearer rate. Depending on the heat emitters the big advantage is the system has much faster reponse times... It is also working less hard and as it's during the day there is less chance of icing.

I suppose it's a bit like running your lightbulbs during the night to take advantage of cheap rate electricity

From past experience I would say our system is running less at than half the cost of mains gas. Considering the age and type of property we have I consider our bills stupidly cheap. Remember the £200pm when we were on LPG was with minimal use so could have been double that easily...

I digress... as this is a brand new system with the way it is setup a normal electricity tariff is the way to go... Going back to basics for an min an ASHP is supposed to be a very cheap way of heating/DHW... If it's not then there is an issue to be resolved somewhere...

Without sounding rude running appliances like dishwashers etc during the night is absolute madness from a safety point of view and simply not worth the risk - ask a Fireman. With PV we run these appliances and heat DHW during the day.

Summing up... this is just my POV and may not suit everyone, different lifestyle etc

zeupater

jeepjunkie wrote: »

Unless you are running a huge thermal store heated by more means that just an ASHP I just don't see how it is worthwhile running an ASHP during the night. It may be a cheaper rate but it's a lot of water to heat. Sounds like a system with all the disadvantages of storage heaters... A small store would be depleted very quickly resulting the ASHP coming on during the day ....

Hi

Isn't this really a view of thermal store v thermal mass ? .... If you've got ample thermal mass then you have a ready-made thermal store ....

Roughly speaking if you consider that 1kW raises 1Tonne by 1 degreeC in 1 Hour then the only advantage of a thermal store would be to deliver the heat (energy) to where it's wanted, when it's wanted because the thermal mass has lost some of it's stored energy, probably because there wasn't enough mass in the first place to hold a decent temperature ....

If we had a heatpump I'd certainly be running it on cheap rate, sacrificing a couple of percent on the efficiency and not paying a couple of hundred percent more for the fuel ... if it got colder I'd see how it went and possibly change to running during the day when the ambient temperature is higher ...

We have a pretty modern house with quite high levels of perimeter insulation and literally tens of tonnes of internal solid mass. Every internal wall is solid construction and there is a wall which was built extra thick just to provide more mass in a living area ... we've only had a handfull of fires (log burner) this season and the last two were Mo&Tu this week when the temperature was topped back up to ~20C .... it's Friday afternoon now and the where I'm sitting is less than 3C cooler than Wednesday morning ... no heating and little solar gain, but no thermal store either, so there would be no need to run a HP 24/7 at the moment, an overnight E7 topup would be ideal if it was our heating source ....

.... Having said all that, the downside is that it takes an age to warm the building up from cold

HTH
Z

gterr

Geotherm wrote: »

Yes, you can time the hot water as you wish. Please remember though that DHW production is usualy only about 20% of the pump usage.
The reset to factory settings possibly caused the usage spike as the external control took over. I do not know what the internal sensor influence was, but that could have been too high.
I have both user and installer manuals for the WB now, so I can see better the info.

Thanks, Geotherm, and others,

Just a quick summary of how we are running now:

Room sensor influence set to 0, so effectively off, so we're relying on external temp sensor plus individual room thermostats/timers. Pump on 24/7. Room stats set between 18 C and 21 C (18 for hallways, kitchen, 21 for lounge, dining room), set-back to 18 or 19 C for a few hours in middle of day and between 10.30pm and 6.00 am. Hot water presently on 24/7 (but I may experiment with this later).
Heat curve: V=22, H=55. We are usually seeing a DHW temp of around 53, flow temp around 35
External sensor shows between 5 C and 8 C today (but must have dropped close to zero overnight since we have storm + sleet and hail just now).
Yesterday evening and this morning U/F heating failed to reach target temps in lounge and dining room. They were about 1 degree under.
Upstairs rads did get warm - just.
We used 16 units peak rate electricity plus 11 units off-peak electricity (total 27 units) in the 24 hours ending 10.30pm last night. Didn't use washing machine or dryer during this time.

Our house is a new build, 3-bed detached 1.5 storey. The lounge has external walls on 3 sides and big windows, often bears the brunt of the gales. It's the room furthest away from the pump and the manifold, which probably doesn't help. We have a wood stove in the lounge which we haven't started using in earnest yet (waiting for delivery of logs) but I have enough scrap to light it tonight, in the hope of a little cheer! Right now the warmest place in the house is always the hallway - a closed corridor. The indoor temp sensor is there and currently shows this to be at 22 C. I'm thinking of moving an chair out there!

More big storms coming!

Grateful for any comments.

[Deleted User]

zeupater wrote: »

Hi

Isn't this really a view of thermal store v thermal mass ? .... If you've got ample thermal mass then you have a ready-made thermal store ....

Roughly speaking if you consider that 1kW raises 1Tonne by 1 degreeC in 1 Hour then the only advantage of a thermal store would be to deliver the heat (energy) to where it's wanted, when it's wanted because the thermal mass has lost some of it's stored energy, probably because there wasn't enough mass in the first place to hold a decent temperature ....

If we had a heatpump I'd certainly be running it on cheap rate, sacrificing a couple of percent on the efficiency and not paying a couple of hundred percent more for the fuel ... if it got colder I'd see how it went and possibly change to running during the day when the ambient temperature is higher ...

We have a pretty modern house with quite high levels of perimeter insulation and literally tens of tonnes of internal solid mass. Every internal wall is solid construction and there is a wall which was built extra thick just to provide more mass in a living area ... we've only had a handfull of fires (log burner) this season and the last two were Mo&Tu this week when the temperature was topped back up to ~20C .... it's Friday afternoon now and the where I'm sitting is less than 3C cooler than Wednesday morning ... no heating and little solar gain, but no thermal store either, so there would be no need to run a HP 24/7 at the moment, an overnight E7 topup would be ideal if it was our heating source ....

.... Having said all that, the downside is that it takes an age to warm the building up from cold

HTH
Z

Very interesting, sounds a bit like the way my house works. My house was not really a house originally...

That's what I like about the ASHP/PV combination... totally hands off and bills are low.

I'm hoping that with summer PV production offset against ASHP winter usege the offset will mean nPower make very little [ok I know that's not how it really works but in my little head...]

Have a great evening all, off with mates for curry and beer now