ASHP and UFH wiring questions

[BMcN]

Hi guys, 

 

I finally got my ASHP. fired up after a few issues.  The heat pump is a Grant UK 10kw.  My system has a 300 litre for DHW and then a motorised valve for a radiator circuit and one for UFH )with DHW having priority via a relay).

 

These 3 'circuits' are run off a 3 channel timer.

 

I was told to leave the DHW running all the time and to leave the UFH running all the time, then allow the UFH manifold and stats to control everything.  

 

Now to my issue - since turning on it has consumed between 30 and 50kw of electricity a day.  This is with no DHW on and no radiators yet fitted, so purely UFH and all stats set to around 16 degrees.  Most of the time no stats are calling for heat so the UFH pump shuts down however the ASHP still runs to keep the supply at UFH manifold at temp.  Should I use the 'Heat Enable' contact on the UFH manifold, so that when no heat is called for the ASHP shuts down completely?

 

The loft isnt fully insulated and there are no doors internally yet but this is still higher than I was expecting to keep the chill off the house.

[PeterW]

No buffer tank ..??

 

Who’s manifold controller is it...? I would be using the heat enable to open the zone valve and use the micro switch to trigger the ASHP. 
 

Does the ASHP only have one temperature setting ..?

[ProDave]

Controls vary a lot between 1 make of ASHP and another, but there should be some kind of "call for heat" input to the ASHP which as @PeterW says should be connected and the ASHP will stop when all the rooms are up to temperature.

 

But even so, just left running, the ASHP would run at a very low duty cycle just circulating the heating loop with little loss from it so I am at a loss to know where 50kWh of electricity is going per day. 

 

Look at the manual for the ASHP and find what sort of demand input it has and connect that to the call for heat from the manifold for now.  But later when you comission the radiators you will also need a call for heat for those as well.

[BMcN]

Yes there is a buffer too.  

 

@PeterW  not 100% to be honest -  it heats the DHW till the cylinder stat is happy.  The rads and UFH are then run straight through the ASHP and plumbed in parallel, with the 3 channel programmer controlling the motorised valves.

 

Manifold controller is a Heatmiser so does have a 'heat enable' that is closed when a stat asks for heat.

 

Attached is pretty much how mine is wired except there is no 'room stat'  for the UFH circuit.  I am proposing adding the heat enable from the manifold in here.

grant-aerona-r32-installer-uk-doc-0136-rev-2-0-september-2020.pdf

[ProDave]

3 minutes ago, BMcN said:

Yes there is a buffer too.  

 

@PeterW  not 100% to be honest -  it heats the DHW till the cylinder stat is happy.  The rads and UFH are then run straight through the ASHP and plumbed in parallel, with the 3 channel programmer controlling the motorised valves.

 

Manifold controller is a Heatmiser so does have a 'heat enable' that is closed when a stat asks for heat.

 

Attached is pretty much how mine is wired except there is no 'room stat'  for the UFH circuit.  I am proposing adding the heat enable from the manifold in here.

grant-aerona-r32-installer-uk-doc-0136-rev-2-0-september-2020.pdf 168.24 kB · 0 downloads

Yes the heat enable from the UFH controller is effectively the logical OR of all the room thermostats for the whole UFH system, so connect the heat enable from the UFH controller as a "room thermostat" in that diagram.

[PeterW]

I would ignore that - where you have the second room stat I would make that a tank stat on the buffer so it calls for heat when the buffer is cold. Let the UFH do it’s own thing and simplify it. 

[joe90]

1 hour ago, PeterW said:

I would ignore that - where you have the second room stat I would make that a tank stat on the buffer so it calls for heat when the buffer is cold. Let the UFH do it’s own thing and simplify it. 

This is what I have done, heating is only on fir a few winter months and in that time the buffer is always topped up and controlled by a tank stat. When the room stat calls for heat the manifold pump has instant heat from the buffer. 

[BMcN]

I've just checked mine and it's not a buffer, it's a 30L volumiser.  No stat on this. 

 

 

I have installation pack 2 from the pdf attached. 

 

grant-aerona3-installation-packs-january-2020.pdf