ASHP with two cylinders?

[Omi]

Might something like this work?

 

 

 

No idea whether the ASHP can be connected to two UVC coils in parallel though ...

[SteamyTea]

4 minutes ago, Omi said:

It's a dual-zone (DHW/Heating) cylinder so I imagine it is able to maintain them at different temperatures

I have never been sold on this type of design.  I think there has to be compromises along the way.  I suspect they were originally designed for sub 40 m² flats in Tokyo, rather than larger detached houses in Scotland.

 

Below is the heat profile of my very basic cylinder.  The heating element is at the base, the heating window is limited to 1AM to 7AM.  Generally I have finished using lost of hot by 9AM, then it is minor stuff and a shower in the evening (I work the later shifts).

You can see that the cylinder 'settles out' by 10AM and then gradually cools during the rest of the day (there is usage in this time)

So short of 'churning up' the water, there is little headroom to draw of a constant low temperature for space heating, without reducing the DHW temperature.  Note that the bottom of the cylinder is about 18°C by 10AM.  But while it is being heated it get to about 42°C (probably higher as all the probes are just taped to the exterior pipework/copper cylinder, except the cold supply with is in the loft tank water itself, why it rises a bit during the day, ~1.4°C, since the mid Feb, so will rise more as the year gets on).

So if you look at the mean temperature line, most of the day it is only 30°C, which gives you about 100 litres of water holding about 2 kWh of energy.

Now the temperature of the whole cylinder can be raised until the top is sitting at around 65°C, but the bottom will still be at around 18°C or so, that would be a mean of 42°C, so the bottom half is only 12°C higher, not enough to make much difference (shade under 4 kWh).

These calculation do assume perfect stratification, which does not happen.  It is also late, so my sums may be wobble, and I have broken my glasses, so even @Onoff is starting to look good.

[Omi]

50 minutes ago, Omi said:

No idea whether the ASHP can be connected to two UVC coils in parallel though ...

 

Nevermind - getting late in the evening ... I guess the coils can be in series as well?

 

[PeterW]

That Mitsubishi cylinder only has zone valves - it’s also the one with the Plate Heat exchanger so has additional pumps. The only “clever” bit is the FTC6 mounted on the tank itself - that’s just a big wiring controller. 

[Scoobyrex]

The ASHP in my quote was a 3 phase 16kw panasonic bi-bloc T-Cap.

We have 10kw of solar, and I believe both water tanks had immersion heaters.