Planned ASHP 1930s semi retrofit - experiences please?

[Greenbot]

16 hours ago, Iceverge said:

Is it an option to install an air to air heat pump in a central area and an immersion in the tank. 

 

You could use these to avail of low carbon electricity when available.  While leaving your boiler to top up when needed? 

 

Gas boilers are a still a very efficient method of using fossil fuels. In terms of your global carbon usage have you compared the benefit of house modifications Vs changing to an electric car for instance?

 

Excellent question; yes I did.  We currently run an Audi A2 that owes us nothing (had one for 10 years, then replaced it with another for well under £3k) and because we cycle to work sometimes, it's not going to make much of a dent to go electric - 2 of us do about 8,000 miles a year together, max.  But we will go electric in a couple of years because I am sick of maintaining older cars (18 years and counting).

 

20 hours ago, TonyT said:

ps thanks for the link above, some good reading!

 

No problem, glad it's interesting!

 

20 hours ago, Ferdinand said:

Absolutely. We are not at all confrontational.

I'm sharpening my pitchfork as we speak ?.

If you drop a note to the mods, a blog can be created for you. 

Renovation blogs will be good alongside the new build blogs.

Remember that it is important to PROVE what you have done to the EPC surveyor, otherswise they have to make all sorts of pessimistic assumptions.

F

 

Thanks, I'll look into that at some point hopefully - I wish I'd blogged about the last 4 years but I wasn't doing anything unusual then!

[designerC]

Do you have any updates on this? How did it go? I've just been researching ASHP as a retrofit (until now I've only used on new-build). Thank you!

 

[J1mbo]

The main thing @designerC with retrofit is that the way the system is used likely needs to change - if replacing a oil or gas boiler say 20kW with a 10kW ASHP, it will need to run twice as many hours to produce the same amount of energy.

 

When designing the system, focus relentlessly on reducing the design flow temperature and sizing pipes enough to provide 5K drop across radiators.

[SteamyTea]

1 hour ago, J1mbo said:

The main thing @designerC with retrofit is that the way the system is used likely needs to change - if replacing a oil or gas boiler say 20kW with a 10kW ASHP, it will need to run twice as many hours to produce the same amount of energy.

While that is true, arithmetically, traditional boilers are often sized for the DHW, especially if they are combination boilers.

So a proper heat loss calculation needs to be done all the same.

You can, if you have monthly bills (or your own data), work out the non space heating loads by subtraction the usage in the non heating season usage from the heating season usage.

[J Pearse]

Hi Greenbot.  I would be very interested in hearing what you did in the end and how it worked out for you.  Love your ethos and we may be finding ourselves in a similar conundrum shortly.

[Greenbot]

PM sent (J Pearse).

I'm planning to document my experieces and my system on some sort of blog as I've had a lot of questions in the real world.  For any interested that read this, I'll post a link when I do.  The headlines:

- Poor installation by an experiences company, mainly wiring and setup errors.

- I added radiators to keep our existing pretty column radiators, all pipework is 22 or 28mm to all radiators.

- One winter with the original radiators ran fine.

- With increased radiators and improved pipe diameters, installation mistakes rectified and settings all taken care of, I'm now fine tuning tun times and temperatures.  I've ran during October at 28-32C, in a very normal 1930s semi (basic insulation measures only), and COP has been 5 +/- 0.3 (!).

- We'll see what happens in colder weather, but I am very happy with the system, if not the company that installed it and the amount of time I put into finding their mistakes!

[PhilT]

On 04/11/2022 at 14:55, Greenbot said:

I'm planning to document my experieces and my system on some sort of blog as I've had a lot of questions in the real world.  For any interested that read this, I'll post a link when I do.!

Please do. My experience has been similar to yours, house spec, floor area etc. 11kW ASHP using electricity at 3k kWh pa on an MCS/EPS of 16k kWh pa (two different surveyors came to the same result) implying COP of at least 5. The installer estimated annual electricity usage of 5k kWh. In retrospect the ASHP is well over capacity but that musty be giving it the ability to work in an efficiency sweet spot most of the time.