Still trying to make the numbers work for a heat pump

Reed_Richards

michaels said:

For us a big issue was our energy demand is way over our EPC with the biggest difference being on how water (I seem to remember we use about 5x the EPC level) ....

You might consider a hybrid system where an ASHP operates in tandem with an oil boiler.  Grant tried to sell me one of their hybrids but it turned out to be unnecessary for my energy usage.

michaels said:

We also potentially have an issue that some of our pipework may be too small so it wouldn't just be a matter of upgrading rads. 

It's never just a matter of upgrading the rads, you also have to upgrade your hot water cylinder.  My completely-replumbed system uses 28 mm pipe from the heat pump to the cylinder and back.  The cylinder also incorporates a buffer tank.  The central heating pipes are plumbed from the cylinder and are 22 mm with 15 mm branches to individual radiators.    

Cardew

I posted this in Reed_Richard's thread but it may be more suited to this thread

'A very comprehensive report here:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/606818/DECC_RHPP_161214_Final_Report_v1-13.pdf

You can take what you like from the various tables; but the bottom line is you will be lucky to get a SPF of 3.0 and with Michael's usage you have no chance'

shinytop

Cardew said:

I posted this in Reed_Richard's thread but it may be more suited to this thread

'A very comprehensive report here:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/606818/DECC_RHPP_161214_Final_Report_v1-13.pdf

You can take what you like from the various tables; but the bottom line is you will be lucky to get a SPF of 3.0 and with Michael's usage you have no chance'

Same for my response.
Very interesting. The median numbers are spookily close to what I worked out/assumed would be the case for my house. I just need to see what the install costs are to see whether it's viable. Got someone coming tomorrow. 

ASavvyBuyer

Also worth taking a look at this very detailed account from someone that is using an ASHP in the sort of property most would not think suitable.

Heat pump performance and home energy 2020

A lot seems to depend on how well the system is designed for the property.

ASavvyBuyer

Cardew said:

I posted this in Reed_Richard's thread but it may be more suited to this thread

'A very comprehensive report here:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/606818/DECC_RHPP_161214_Final_Report_v1-13.pdf

You can take what you like from the various tables; but the bottom line is you will be lucky to get a SPF of 3.0 and with Michael's usage you have no chance'

I posted this in the "I bought a Heat Pump" thread, but thought is was also worth adding here.

Agree, that is a very interesting report. However, there are a few things I was not able to find in it; like which models of heat pumps were they assessing and what were the claimed COP's from the manufacturers. That detail may be in the references, but I could not find it. The image on the front appears to be quite an old model of heat pump.

Also, could not see any details of whether some of the heat pumps had rotary inverter compressors or more basic compressors (which can make quite a difference to their efficiency). Interesting to note that quite a few also had additional “cassette” heaters, using resistive heating elements.

However, very useful to see the difference between the worst & best performing systems, as shown in Figure 6.2 and Paragraph 6.7 Factors influencing performance.

One main observation gleaned from the report and from comments elsewhere, is that the most important aspect is to ensure the whole system is correctly designed and set up, as it appears that quite a few assessed in the report were not, or were not being used in the most efficient way.

Thanks for posting the link.

ASavvyBuyer

Found another useful source of information here.

matelodave

ASavvyBuyer said:

Found another useful source of information here.

Yes, that's who I've been following ever since I got my heatpump ten years ago, lots of useful info

Coastalwatch

Oh my Chaps! I've been trying to keep abreast of all that's involved with either GSHP or ASHP installations with the resulting complications of RHI, increased radiator sizes and flow rates etc, etc. From the outside what a complex and costly affair it all appears to be?

Can't tell you how relieved I am that we got away with simply installing two air to air heat pumps. It did mean removing all the radiators and what joy to learn that I'm relieved of having to paint all the accompanying pipework any more. Glad to see the back of it all, not to mention a nice little bonus from the scrap dealer. Phew!

Oh, DHW handled by thermal store powered either by the Solar panels or cheap overnight tariff.

Total cost around £4.5k.

ASavvyBuyer

Coastalwatch said:

Oh my Chaps! I've been trying to keep abreast of all that's involved with either GSHP or ASHP installations with the resulting complications of RHI, increased radiator sizes and flow rates etc, etc. From the outside what a complex and costly affair it all appears to be?

Can't tell you how relieved I am that we got away with simply installing two air to air heat pumps. It did mean removing all the radiators and what joy to learn that I'm relieved of having to paint all the accompanying pipework any more. Glad to see the back of it all, not to mention a nice little bonus from the scrap dealer. Phew!

Oh, DHW handled by thermal store powered either by the Solar panels or cheap overnight tariff.

Total cost around £4.5k.

Similar here, with two ASHP's, each at either end of the bungalow and DHW heated by cheap overnight tariff or excess Solar generation. Still have the gas central heating as a backup, but on target to reduce gas consumption by over 90% this winter, with no increase in overall cost of energy (in fact it is working out cheaper) and the rooms feel warmer, even during the recent cold snap.

It was useful to note that the report, done in 2017, identified that a number of the systems they assessed were poorly designed or not being used in the most efficient way; lowering the overall efficiency of the systems.

shinytop

ASavvyBuyer said:

Coastalwatch said:

Oh my Chaps! I've been trying to keep abreast of all that's involved with either GSHP or ASHP installations with the resulting complications of RHI, increased radiator sizes and flow rates etc, etc. From the outside what a complex and costly affair it all appears to be?

Can't tell you how relieved I am that we got away with simply installing two air to air heat pumps. It did mean removing all the radiators and what joy to learn that I'm relieved of having to paint all the accompanying pipework any more. Glad to see the back of it all, not to mention a nice little bonus from the scrap dealer. Phew!

Oh, DHW handled by thermal store powered either by the Solar panels or cheap overnight tariff.

Total cost around £4.5k.

Similar here, with two ASHP's, each at either end of the bungalow and DHW heated by cheap overnight tariff or excess Solar generation. Still have the gas central heating as a backup, but on target to reduce gas consumption by over 90% this winter, with no increase in overall cost of energy (in fact it is working out cheaper) and the rooms feel warmer, even during the recent cold snap.

It was useful to note that the report, done in 2017, identified that a number of the systems they assessed were poorly designed or not being used in the most efficient way; lowering the overall efficiency of the systems.

A bit like buying a PHEV rather than an EV then ?