Which system to go for ... AGRRRGGGHHH

Cardew

albyota wrote: »

e.g. 24,000kWh of heating with oil...roughly 2,400 litres @ 60p/L is £1,440.........heat pump @ COP 2.8 is 7,142kWh @ electric 12/kWh is £857

I think your arithmetic is wrong!

24,000kWh with a heat pump giving a COP of 2.8 is 8,571kWh so @12p is £1028.

The big 'IF' is to get an overall COP of 2.8 - what if you get a COP of 1.8? - or the average of the EST trial of about 2.0.

Then factor in the additional cost of lost interest of, say £300pa; and the 'lost' heat when running the ASHP when occupants are out/asleep.

Cardew

albyota wrote: »

Go for the heat pump......if less, wack in a oil boiler, running costs for a heat pump are typically 30 to 40% of what you would spend on oil for the same heat.

I don't think this is what you meant to say!

I think you are suggesting that running costs are 30% to 40% less than oil???

Not that I would agree even with the latter!

albyota

Thanks Cardew,

Granted....I didn't correct my previous calcs, 8,571kWh
and yes I did mean in general 30 to 40% less than oil costs, typically someone who spends £1,500 / yr buying oil compared with someone spending £750 running a heat pump would be a saving of 50% so spending between £900 & £1,080 then is between 30 and 40% saving, is it not? I agree, re reading made it seem the other way, apologies.

And I wouldn't expect you to agree with the latter.

The COP is not a fixed thing.....no manufacturer has ever said so. the COP adjusts with the external temperature / the seasons. it is just how the BRE british research establishment wanted to test to... they have had to document under BS EN 14511 at ambient minus 5 & 35 degree water temp.

So you don't want to comment on the 80 degree high temperature kit then?

albyota

Also.....With 3.5kWp of solar PV......what better way of heating your hot water, and a good percentage of the heating using the free excess power from the panels, which would bring the annual running cost down even further.

And


At minus 7 A brand new high efficiency Warmflow 80,000 btu / 24kW oil boiler including cycling on/off will use 2.7 litres per hour @ 60p/L ......thats £1.62 / hr....

At minus 7 a 14 kW Heat pump.......continually running would draw 6.7kW/hr @ 12p/kWh would cost 81p/hr

albyota

Hurry up cardew....... I've got to get up for work:D

Cardew

albyota wrote: »

Thanks Cardew,

Granted....I didn't correct my previous calcs, 8,571kWh
and yes I did mean in general 30 to 40% less than oil costs, typically someone who spends £1,500 / yr buying oil compared with someone spending £750 running a heat pump would be a saving of 50% so spending between £900 & £1,080 then is between 30 and 40% saving, is it not? I agree, re reading made it seem the other way, apologies.

And I wouldn't expect you to agree with the latter.

The COP is not a fixed thing.....no manufacturer has ever said so. the COP adjusts with the external temperature / the seasons. it is just how the BRE british research establishment wanted to test to... they have had to document under BS EN 14511 at ambient minus 5 & 35 degree water temp.

So you don't want to comment on the 80 degree high temperature kit then?

As has been said many times, claimed COP figures of the Heat Pump itself are not the same as the figures for a Heat Pump system installation. There are a variety of factors that contribute to a lower overall COP - not least the defrost cycles.

However unpalatable to those of you installing systems, the EST trial gives 'Real World' results.

With regard to the 80C Daikin pump, I haven't found the specification sheet for the latest model; but the cascade type have been mentioned before, and under closer examination the claims don't hold up.

They achieve a good COP, say 3.0, at lower water temperatures but at 80C they are ??? and at what ambient temperature???

Even then the overall system COP cannot be given with any certainty.

However even if they did save £300 or £400 a year over oil CH, at a capital cost of £7,000 more than Oil CH, no economic case can be made for having them fitted.

Taking into account you lose £300 a year in lost interest(more if you borrow) on the additional £7k paid out, you are breaking even on running costs at £300 pa fuel saving, or at £400 fuel saving pay back the £7,000 in 70 years!!

albyota

Cardew wrote: »

As has been said many times, claimed COP figures of the Heat Pump itself are not the same as the figures for a Heat Pump system installation. There are a variety of factors that contribute to a lower overall COP - not least the defrost cycles.

However unpalatable to those of you installing systems, the EST trial gives 'Real World' results.

I think we see many many more... 'Real World' results than the 29 EST Tested

With regard to the 80C Daikin pump, I haven't found the specification sheet for the latest model; but the cascade type have been mentioned before, and under closer examination the claims don't hold up.

Cardew wrote: »

They achieve a good COP, say 3.0, at lower water temperatures but at 80C they are ??? and at what ambient temperature???

about 2 @ minus 7

Even then the overall system COP cannot be given with any certainty.

Can you tell me how efficient your gas boiler / house is going to be this year...and how much its going to cost to run.......??

However even if they did save £300 or £400 a year over oil CH, at a capital cost of £7,000 more than Oil CH, no economic case can be made for having them fitted.

Taking into account you lose £300 a year in lost interest(more if you borrow) on the additional £7k paid out, you are breaking even on running costs at £300 pa fuel saving, or at £400 fuel saving pay back the £7,000 in 70 years!!

people fitting heat pumps are usually replacing their existing boiler...and with that, they now find out that the oil tank has to be replaced and re-sited....OFTEC regulations.....and those with PV cannot use the excess to fuel the boiler.....

albyota

Take a look at the MCS 3005 v3 to see how strictly we are scrutinized, U values of every wall, floor, ceiling, window, ventilation rates, levels of insulation, no stone unturned......and we have to calculate the running cost of the space heating separately from the domestic hot water and show cost for running the central heating pump including defrost cycles.

I have always agreed with you that this is the way to go to get rid of the cowboys but you keep referencing old material.......from 4 years ago, The RHPP requires that all installation be fitted with heat meters for monitoring, when the results from year 2 field trials is over in Oct, hopefully it will put the past to rest.

[Deleted User]

I was going to stick in some comments but then I thought... why bother

Cardew

albyota wrote: »

I have always agreed with you that this is the way to go to get rid of the cowboys but you keep referencing old material.......from 4 years ago, The RHPP requires that all installation be fitted with heat meters for monitoring, when the results from year 2 field trials is over in Oct, hopefully it will put the past to rest.

The trial started in Nov 2008 and because of the poor results was extended to June 2011 and the results of the trial are on the EST website.

They published this in February 2012:

http://www.energysavingtrust.org.uk/Media/Generate-your-own-energy/PDFs/Heat-Pump-Monitoring-FAQs

They are monitoring selected heat pumps until the end of April 2013 and then will publish results in ???(probably end of 2013?)

Any steps to get rid of the cowboys is welcomed and also of the claims in the some brochures.

The position at the moment is still that you take 'pot luck'(in UK) if you get a system producing good results.

In the future I hope that with RHI and manufacturers taking some more responsibility for installation, heat pumps will become a better proposition.

However they are IMO still far too expensive and £10,000 to £12,000(which seems to be normal) will never IMO make economic sense. As said above, with loss of interest taken into account, even savings of £500 a year over oil will mean that paybck of the extra will never be achieved in the life of the equipment.