Air Source Heat Pumps

zeupater

AH9999 wrote: »

@zeupater

Thank you and well spotted - monthly £ value is correct, I'm doing some double checking but I think the usage is actually more like 4,137kWh per year

Hi

If the electricity DD is £110/month then the annual consumption would probably be more like 11000kWh/year ((110x12)/0.12) .... are you sure that your figures aren't quarterly which would reflect around 3600kWh/year ((110x4))/0.12), which is much closer to the accepted UK annual average of 3300kWh.

HTH
Z

AH9999

Cardew wrote: »

Just a further note on 'money saving'.

You have a working CH system.

I suspect an ASHP system for a 1940's 5/6 bed will cost nearer to double the £7k you estimate.

However let us take £10,000 as a cost. That invested in a long term Account will earn 4% - taxable unless in ISA. So 3.2% after 20% tax.

That is £320 a year in lost interest you need to save on heating bills before you start paying of the £10,000.

If you have to borrow £10,000 the position is a lot worse.

@Cardew

Thank you, I absolutely understand the points you're making.

I wish I was paying 20% tax - I'm having to pay a significantly higher rate than that which effectively means I'm losing money whilst it is in my bank account once inflation is taken into account........I assume a 5% compund increase in fuel costs whenever modelling which I think is conservative.

When the £850 grant is taken into account plus the future FIT for ASHP there's definate financial upside in this.

Notwithstanding this, I agree - I have a perfectly good/working CH system, why not stick with that and sweat that asset PLUS I agree there's good and bad points regarding ASHP......if it is not sized correctly it looks like a disaster waiting to happen

......all useful points for my thought process

AH9999

Cardew wrote: »

I will just comment on the above.

It is not easy to combine two heating systems - and in fact can be downright dangerous. How will you stop the Heat pump water flowing back through the AGA, and vice versa. You should not fit a stop valve on the output side of a boiler, and I doubt if a plumber will do so.


You need something like a Dunsley Neutraliser

[Link Removed - New User, Not Allowed]

I am not a fan of Heat pumps, but if you get one, then I would use straight electric heaters for the days when you feel the ASHP won't cope.(you state 1%)

Just take advice on the combining of two systems.

@Cardew

This makes absolute sense to me - you can tell I'm approaching this from a theoretical/logical point of view rather than one of real world experience

So that would mean all or nothing in terms of CH - ASHP (plus immersion backup) or AGA Rayburn

.....and that's where I start to get concerned.

Sizing seems to be key to this - get it wrong and you're in trouble, I'm going to have to build some contingency into the sizing which in turn will increase pricing

Cardew

AH9999 wrote: »

@Cardew

Thank you, I absolutely understand the points you're making.



When the £850 grant is taken into account plus the future FIT for ASHP there's definate financial upside in this.

Notwithstanding this, I agree - I have a perfectly good/working CH system, why not stick with that and sweat that asset PLUS I agree there's good and bad points regarding ASHP......if it is not sized correctly it looks like a disaster waiting to happen

......all useful points for my thought process

I assume you mean RHI payments not FIT?

The 'Jury is still out' on those payments. How(or if) those payments will be made is still up for discussion.

http://www.decc.gov.uk/en/content/cms/meeting_energy/renewable_ener/incentive/incentive.aspx

TiredGeek

It sounds to me like a pretty large house with 5/6 bedrooms and with limited insulation being 1940's then I think you'll be looking at at least a 14kw Mitsubishi, if not a dual system using two smaller ones to give you 18kw or a tad more.

Bearing that in mind, the price will more than likely be north of £12k fitted, and then you'll need to do some modifications to the heat distribution side of things as well, your best bet would be fan coils which are very efficient at kicking the heat out while still leaving you some wall space. All in, for that size house, you're probably looking at £20k.

If it's done by the right people (see my PM) then it'll more than likely reduce your bills a lot, whether it makes financial sense in the long run is up to you as it will take years to break even unless the RHI is brought in at some time, in which case the financials look much healthier. I fall towards Cardews way of thinking if money is being borrowed to finance the system, less so if you have ready funds available.

Linking with the Rayburn, it is possible, but the complexity of doing so for the limited amount of time it's needed sort of kills it dead.
Your existing pipework would be OK to re-use so long as there's either a buffer tank or my preference, a low loss header in there. The heat pump gets the high flow it needs through the header while you can take off to the heating side which will flow slower because of the restriction of the smaller pipes.
Ideally, a 14kw Ecodan would like 40litres / min through it. My house has got 28mm pipe through most of it and with four pumps on the circuits and all rads fully open we do not achieve that. Even the bit from my low loss header through the ASHP and back to the header only gets 35L/min and thats all in 28mm and short.

Don't be put off, these things do work well for some people, Jeepjunkie I'm looking at you, you just need to go in with your eyes wide open and know what you're buying.

[Deleted User]

As TiredGeek says it's all in the planning and detail or it will fail.

There are other types of renewable heating and good old oil is not that bad. Just avoid LPG.

Cheers

PS Pipework under vented suspended floors needs to be insulated. If within the house then not so bad but in an ideal world you don't want to loose valuable heat before fancoils/ufh can make the most from the low grade heat.

Baz@rr

Sorry to drag this thread up from the depths, but I'm hoping someone might be able to help me out.

I'm due to start renting a new build house this week and have been allowed in for the past few days so we can move our stuff in. It's a four bedroom detached house with an air source heat pump system, which I have absolutely no prior knowledge of whatsoever. There's also solar for the hot water, although I don't think that's working properly, but that's another issue.

Over a 24 hour period between 8am yesterday and 8am today, with nothing on but the heating (which had been set to stay on all day) the house used 75 units of electricity. The wee red light on the meter was going crazy. Both the heating and hot water controls were set to "on" throughout that entire period, as I say.

Today I did an experiment and put the controls onto timed, setting them both to go off at 8:30 and stay off until 5pm today. I checked the meter and the light was blinking once every 30 seconds after 8:30am, as opposed to 2 times a second as it was with the pump going.

I swung back at 1:30 to see what was happening and the light was blinking like mad again. I checked the usage and the meter had gone through 13 units - which averages out at pretty much exactly what it was using yesterday when the heating was on.

I checked the pump unit out the back and sure enough it was humming away, yet both heating and hot water were set to be off.

So my question is - does the pump keep pumping regardless of what heat the controls are set to output, or should the pump only kick in when the timer does? I checked the control panel in the garage and the pump wasn't in defrost mode, so I have no clue as to why it was running when the heating and hot water aren't set to come on until 5:30pm.

Anyone have any ideas? I really can't afford to pay for 75 units of electricity a day before even switching on a single light, and it would seem to make a mockery of the "green credentials" these ASHPs are supposed to have.

lovesgshp

Baz@rr wrote: »

Sorry to drag this thread up from the depths, but I'm hoping someone might be able to help me out.

I'm due to start renting a new build house this week and have been allowed in for the past few days so we can move our stuff in. It's a four bedroom detached house with an air source heat pump system, which I have absolutely no prior knowledge of whatsoever. There's also solar for the hot water, although I don't think that's working properly, but that's another issue.

Over a 24 hour period between 8am yesterday and 8am today, with nothing on but the heating (which had been set to stay on all day) the house used 75 units of electricity. The wee red light on the meter was going crazy. Both the heating and hot water controls were set to "on" throughout that entire period, as I say.

Today I did an experiment and put the controls onto timed, setting them both to go off at 8:30 and stay off until 5pm today. I checked the meter and the light was blinking once every 30 seconds after 8:30am, as opposed to 2 times a second as it was with the pump going.

I swung back at 1:30 to see what was happening and the light was blinking like mad again. I checked the usage and the meter had gone through 13 units - which averages out at pretty much exactly what it was using yesterday when the heating was on.

I checked the pump unit out the back and sure enough it was humming away, yet both heating and hot water were set to be off.

So my question is - does the pump keep pumping regardless of what heat the controls are set to output, or should the pump only kick in when the timer does? I checked the control panel in the garage and the pump wasn't in defrost mode, so I have no clue as to why it was running when the heating and hot water aren't set to come on until 5:30pm.

Anyone have any ideas? I really can't afford to pay for 75 units of electricity a day before even switching on a single light, and it would seem to make a mockery of the "green credentials" these ASHPs are supposed to have.

Is it underfloor heating, or rads. If underfloor, it could take up to 48 hrs to reach the room thermostat setting, after first switch on.
Your high leccy use could be due to the built in immersion heater cutting in to help the ASHP cope in the initial start up.
What pump is it??

dullnote

Hi I have just installed a ASHP and GEOthrem is right house took a full day to heat up and for the pump to calm down, however never had anything like the 75 units used, first day cost me £3 approx 30 units, house was too hot, now we have the pump running 24 hours a day and heating cost under £2 a day,and the whole house is very pleasant, compare this with LPG at £5 a day last year and house cold.

My pump is Danfoss AQ 13kw, uses 3kw per hour, the pump would have to be running 24 hours to get to the figures you are looking at. Does your pump kick on and off. What temp are you asking the pump to produce, I have UFH throughout and the water temp for the pump is only30 degrees.

I suspect there is a immersion heater working alongside ASHP as GEOthrem has said. Please give more details of system it may shed some light on the subject

Dullnote

lovesgshp

dullnote wrote: »

Hi I have just installed a ASHP and GEOthrem is right house took a full day to heat up and for the pump to calm down, however never had anything like the 75 units used, first day cost me £3 approx 30 units, house was too hot, now we have the pump running 24 hours a day and heating cost under £2 a day,and the whole house is very pleasant, compare this with LPG at £5 a day last year and house cold.

My pump is Danfoss AQ 13kw, uses 3kw per hour, the pump would have to be running 24 hours to get to the figures you are looking at. Does your pump kick on and off. What temp are you asking the pump to produce, I have UFH throughout and the water temp for the pump is only30 degrees.

I suspect there is a immersion heater working alongside ASHP as GEOthrem has said. Please give more details of system it may shed some light on the subject

Dullnote

Admit, I forgot to ask what temp the pump was trying to produce!