Best setup for ASHP and solar

[d438a1]

Hi there, 

 

After some guidance as to how best to configure and use new system that is just starting to get installed. Setup: -

 

1. 22KW Three phase ASHP
2. 400 lire HW cylinder (wth dual immersion)
3. 400 litre buffer tank
4. 16kw solar panels
5. 16kw sigenergy batteries
6. 15kw three phase sigenergy inverter
7. Sigenergy gateway
8. DNO permission to export 15kw
9. myenergy eddi

 

Context for larger setup is this system is powering the main house, as well as a separate dwelling which will be used as an air bnb and also a large separate workshop dwelling.

 

 

My initial questions is around the best way to configure and use the surplus PV in relation to ASHP and HWC. I also understand you can potentially use the sig gateway as an alternative for the eddi, but not sure if it can handle the dual immersion?

 

Any advice would be great

 

Thanks

 

[JohnMo]

Export excess and run pure WC on ASHP. Time cylinder heating early afternoon and other off peak period if needed  Don't bother using immersion, you get better value exporting.

 

Go on something like Octopus Cosy to give you three chances to charge battery in mid winter.

[JohnMo]

1 hour ago, d438a1 said:

400 litre buffer tank

Why? If so how are you configuring it.

[d438a1]

Thanks for replies. When you say configuring the buffer tank, what are the options for that?

 

So I believe they specified a higher buffer tank to deal with not all 3 dwellings being ready yet and to avoid short cycling on HP itself. Right now only the house will be operational, and mid next year workshop and air bnb  dwelling will also come online.

 

There's also a possibility we may rebuild house in coming years so for a period of time only workshop and air bnb dwelling will be online. 

[JohnMo]

So buffer makes sense big ASHP not doing it's full duty.

 

A decent write up here

https://blog.heatspring.com/2-pipe-versus-4-pipe-buffer-tank-configurations/

 

And here

https://kensa.co.uk/installer/resources/buffer-tank-sizing-heat-pump

Edited September 4 by JohnMo
Added link to kensa

[d438a1]

Ok thank you, will try find out from installers how they're planning on doing it. 

 

Back to your other point, that's interesting. Seems to be a heavy divide on people prioritising immersion vs exporting 

 

 

[JohnMo]

35 minutes ago, d438a1 said:

Back to your other point, that's interesting. Seems to be a heavy divide on people prioritising immersion vs exporting

I pumped everything excess until I got export into my immersion. But I now get 15p for export so why bother. ASHP can heat DHW at a CoP of 3 all year round. So as I pay 12.79p for import that's about 4p per kWh so makes perfect sense to export.

 

You just need to own maths based on your own circumstances and tariff. What's right me, may not be you.

[d438a1]

Yeah, thanks. See attached for current progress of works. 

 

One thing I haven't finalised yet is how to control it all. Any recommendations? Obviously I want full smart control. And is it worth making use of controlling the lower and upper immersion for occasions I do need to use?

 

Thanks

[JohnMo]

41 minutes ago, d438a1 said:

Obviously I want full smart control

Not really that obvious, nor the best. My view is a simple one, run weather compensation, you then need no control.  Looking at your schematic, there are no mixers, which is good, so means the radiators and the UFH have the same flow temp, so should be easy to do just straight WC. Gives the best CoP generally, so lowest running costs. your other option is to do WC with set forwards in cheap tariff periods, here you would use a timer to up the WC curve to second set point 1 or 2 degs warmer, this then means when outside the cheap period the heat pump works less hard, so a little less likely to run down the battery too quickly. Fully open system (nearly) gain good.

 

Your buffer is a 3 port, so a good compromise. Do a search on 3 port buffers to see the advantages and disadvantages.

[d438a1]

So it's all up and running and on weather comp. Starting to understand the comments now. Just had it running with room/house sat at 20 degrees and it's just a nice comfortable temperature all day long.

 

Did have a few questions..

 

1. Was disappointed as I should have done more reading, but the worcestor compress 2000 I have does not have any smart app capability. https://www.worcester-bosch.co.uk/professional/compress-2000-awf. It's not a big deal, but certainly would have been nice to see some of the data and info, especially given the unit is not in same building as house. Certainly I did want to be able to control the hot water at times, e.g when going on holiday. Does anyone know anyway to delegate the hot water control from the unit? It does allow for the stat to be delegated, and the installers set me up with the EPH stat and gateway for that. As FYI my understanding is this unit is a rebadged Midea who themselves do have smart capability. 

2. There isn't any sensor attached to the buffer. Is that normal? I would have thought the heat pump would need to know the temp of buffer tank else it's just continously running potentially unncessarily?

3. When the MCS guy came on Friday to sign off he commented that it's better practise to ensure the controls are wired so that if all zone stats are off, it also shuts down the heat pump itself. But my installers said "It's wired correctly. It's to always heat the buffer, it's far more efficient, stops short cycling, and gives you quick heat up times in the cold months". Any thoughts on this one?

 

Thanks as always.