Solar PV system.

[Dazza101]

Hello. 
 

I am due to get a 5KW system spreed between my SW roof and S facing garden in Feb. Along side this will be 10Kw ‘9kw usable’ of batteries. I’m looking at possibly trying to figure out a way to either preheat cold feed going into combi boiler ‘might need a different boiler but it’s 15 years old’ or preheat cold mains feed going into 10.5 Kw shower. Anybody recommend  a way to preheat water to set temp in either from excess power from PV’s?
 

 A question on solar array. If on a bright sunny day I’m producing 4.5KW and fire up 10.5KW shower, do I just draw 6kw from the grid? That might be a daft question? 
 

lastly has anybody have any experience with PureDrive batteries? Dc 5kw x2. 
 

Many thanks 

[ProDave]

Well you would need a buffer tank feeding whichever you are pre heating, with an immersion heater in it, and a solar PV diverter to send excess power to the immersion.

 

You would also have to determine of the shower or combi will be happy with a warm, or possibly very hot feed into them.

 

[joth]

2 hours ago, Dazza101 said:

Along side this will be 10Kw ‘9kw usable’ of batteries.

You probably mean 10 or 9 kWh - that is a measure of energy storage, not power delivery?

 

2 hours ago, Dazza101 said:

Anybody recommend  a way to preheat water to set temp in either from excess power from PV’s?

You need a large invented cylinder and PV redirect to immersion heater. If the combi can't accept 60°C+  hot water as input (and I don't believe many can?) you need a complex 2 position valve to switch over to the combi as the UVC empties which will very likely give a slug of cold water during the transition

 

2 hours ago, Dazza101 said:

 A question on solar array. If on a bright sunny day I’m producing 4.5KW and fire up 10.5KW shower, do I just draw 6kw from the grid?

No, you draw 4.5 kW from PV and 6 kW from the battery (or whatever their power limit is, often 5kW) and the remainder from the grid, unless the battery is empty...

 

[JohnMo]

Photo of my combi set up.

 

Thermal store upstream of combi.  Cold water is connected to DHW coil, and is preheated prior to going into Atag combi.

 

Winter, combi central heating circuit connected to closed loop heating coil, acting a UFH buffer, UFH connected to thermal store.  Thermostat limits boiler heating of thermal store to 40 degs half way up cylinder.  If there is excess solar PV, this heats boiler immersion.

 

Summer, heating side of boiler off.  PV excess to immersion.  Immersion set to 75 deg.

 

Temperature of cold Water feed to boiler limited to 55 degs by thermal store mixing valve.

 

Atag boilers can take preheated water.