Switching a Cool Energy ASHP between heating and cooling - on the actual unit as opposed to with the app or the internal control/display

[Bramco]

Hi,

 

We have a Cool Energy ASHP - it's doing sterling work during the heat waves at cooling our insulated slab, however....

 

To make this work, we have to set the unit to cooling on the internal display/control unit, then whack the thermostats up to their maximum to trick the system into actually running. So the call for heat gets the unit running and opens the manifold valves. There are a couple of issues with this. Firstly our thermostats highest setting is 25C, so if it's hotter than that, then the trick doesn't work (we can live with this by making sure we get the cooling running before things get too hot.

 

The second, is that in an ideal world we would use thermostats that could generate a heating or cooling signal depending on the temperature and use this to switch the ASHP between heating and cooling. We could do this if there was a connection on the outside unit that controlled heating/cooling mode. Does anyone know if there is such a conncetion, we can't see one from the schematics in the manual.  Or has anyone managed to sort this out in some other way?

 

@dpmiller any thoughts?

 

Simon

[JohnMo]

6 minutes ago, Bramco said:

The second, is that in an ideal world we would use thermostats that could generate a heating or cooling signal depending on the temperature and use this to switch the ASHP between heating and cooling

The other option is to do away with thermostats altogether? Just let the ASHP look after itself.

 

No idea of the connection sorry

[Bramco]

5 minutes ago, JohnMo said:

The other option is to do away with thermostats altogether? Just let the ASHP look after itself.

 

Agree and it's an option but the thermostats do manage when the ASHP is running - we only heat the slab at night on cheap rate. And there's a downstairs bedroom which needs less heat than the rest of the house, so we do need some zoning....

[JohnMo]

8 minutes ago, Bramco said:

 

Agree and it's an option but the thermostats do manage when the ASHP is running - we only heat the slab at night on cheap rate. And there's a downstairs bedroom which needs less heat than the rest of the house, so we do need some zoning....

Fair point

 

Computherm Q20RF is selectable between heat and cool. Adjustable hysterisis down to 0.1 degs. I used when I was batch charging, very good with very little overshoot.

[Bramco]

Thanks @JohnMo - I'd had a look at these a while ago. Looks though as if you have to switch modes manually as opposed to based on the temperature?

 

If I can find a way to automatically switch the Cool Energy unit from heating to cooling, then I think I'll end up using some Open Energy Monitor emonTH units as thermostats, sending data to a Pi with the eMon software and then sending signals to something like a Sonoff 4 switch gizmo, to control the call for heat on the 3 zones and to manage the ASHP.

But if I can't find a connector on the ASHP unit, then I'll have to start writing down how to make cooling happen so that when I'm gone someone else can program it.

 

Simon

[Dillsue]

No idea if cool energy provide this but on post 2020 LG Therma VS there's two inputs for thermostat control, one to call for heat and the other to call for cooling. Might be worth having a trawl through the cool energy manual to see if they provide similar

[dpmiller]

didn't we have a discussion on this in the past week?

[HughF]

We did…

 

The carel controller inside the outdoor unit has three digital inputs, call for heat, call for cool and call for a/c.

 

The a/c input is the one brought out to the terminal strip as ‘volt free call’.

 

There is nothing to stop you bridging DI-common to DI-4 for cooling 

 

I’m about to build a small din rail box with the required spdt relay so that when my fan coils are switched to ‘cool’ mode and their fans spin up, it disconnects the room that from ‘a/c linkage’ and connects di-4 to di-common.

Edited yesterday at 05:26 by HughF

[HughF]

Page 17, the 3-phase section of the manual, shows the digital inputs for heating and cooling and their corresponding terminals on the green plug.inverTec_Range_Manual_Version_6.6_Final.pdf

[MikeSharp01]

35 minutes ago, HughF said:

Page 17, the 3-phase section of the manual, shows the digital inputs for heating and cooling and their corresponding terminals on the green plug.

Interestingly not shown on the single phase diagram - we are going for an invertec model and it clearly says it can do cooling so I would expect a way to switch this over on the board.

[HughF]

Just now, MikeSharp01 said:

Interestingly not shown on the single phase diagram - we are going for an invertec model and it clearly says it can do cooling so I would expect a way to switch this over on the board.

I suspect it’s a manual error rather than a definite difference between the single and three phase models. They use the same p.CO controller in both units.

 

I know for a fact that the single phase ones can do cooling, the CE display/demo trailer has a unit there running a fan coil in either heating or cooling mode.

[dpmiller]

Yep, ours is running in cooling mode currently

[Bramco]

17 hours ago, dpmiller said:

didn't we have a discussion on this in the past week?

Apologies if so - I did a search before posting but didn't see anything

[Bramco]

1 hour ago, HughF said:

Page 17, the 3-phase section of the manual, shows the digital inputs for heating and cooling and their corresponding terminals on the green plug.inverTec_Range_Manual_Version_6.6_Final.pdf

Thanks @HughF 

 

Like Mike, I'd ignored that page because it was headed 3-phase unit and we've a single phase unit - next time I speak to them, I'll point this out.

 

Simon

[Bramco]

7 hours ago, HughF said:

We did…

 

The carel controller inside the outdoor unit has three digital inputs, call for heat, call for cool and call for a/c.

 

The a/c input is the one brought out to the terminal strip as ‘volt free call’.

 

There is nothing to stop you bridging DI-common to DI-4 for cooling 

 

I’m about to build a small din rail box with the required spdt relay so that when my fan coils are switched to ‘cool’ mode and their fans spin up, it disconnects the room that from ‘a/c linkage’ and connects di-4 to di-common.

 

@HughF I'm assuming that these connections override whatever may be programmed on the internal Carel controller (and the app)?

 

So you could leave the controller/app on Heating but have a relay make the connection between DI-common and DI-4 and the unit would switch to Cooling mode. Obvs, I'd need to also provide switched live to the 4 zones on our Heatmiser UH4 wiring centre to open the valves on the manifold and give the ASHP the  boiler enable signal.   In our case, we'd have to replicate the programming for when the cooling comes on which is currently in the thermostats but that's pretty easy to sort out. We normally run the ASHP at night on off peak.

[Dave Jones]

On 11/07/2025 at 14:06, Bramco said:

 

Agree and it's an option but the thermostats do manage when the ASHP is running - we only heat the slab at night on cheap rate. And there's a downstairs bedroom which needs less heat than the rest of the house, so we do need some zoning....

 

zoning.....

 

This should be re-worded to 'waste more energy for no reason at all'.

 

Try just heating the bottom right corner of a radiator. same thing.

 

 

[HughF]

23 hours ago, Bramco said:

 

@HughF I'm assuming that these connections override whatever may be programmed on the internal Carel controller (and the app)?

 

So you could leave the controller/app on Heating but have a relay make the connection between DI-common and DI-4 and the unit would switch to Cooling mode. Obvs, I'd need to also provide switched live to the 4 zones on our Heatmiser UH4 wiring centre to open the valves on the manifold and give the ASHP the  boiler enable signal.   In our case, we'd have to replicate the programming for when the cooling comes on which is currently in the thermostats but that's pretty easy to sort out. We normally run the ASHP at night on off peak.

I need to check that, but I’m pretty sure the time clock will override any external calls and you’ll see ‘off by time’ on the display - other options being ‘off by change’ and ‘off by a/c linkage’….

[Bramco]

@HughF thanks - there's a spare pair on the cat 5 into the house, so I'll rig that up with a switch in the house to see what it does.

 

Simon

[Bramco]

@HughF

 

Interesting - it works as a latch. (Probably should have expected this thinking about it).

 

So when you connect DI-4 to GND, the unit switches from heating to cooling. But when you disconnect it, it stays on cooling, so you'd have to connect DI-3 to GND to get it to switch back to heating, or do that on the controller or app.  With a suitable relay, you could switch to cooling and then drop back to heating but you'd need 3 wires.

 

Simon

Edited 7 hours ago by Bramco

[HughF]

4 hours ago, Bramco said:

@HughF

 

Interesting - it works as a latch. (Probably should have expected this thinking about it).

 

So when you connect DI-4 to GND, the unit switches from heating to cooling. But when you disconnect it, it stays on cooling, so you'd have to connect DI-3 to GND to get it to switch back to heating, or do that on the controller or app.  With a suitable relay, you could switch to cooling and then drop back to heating but you'd need 3 wires.

 

Simon

Interesting, thanks for taking the time to experiment, I didn’t have a chance to do so today.

 

My plan is to come out of my room stat (unfortunately a heat only one, used as a hi-limit stat) and go through the NC contact of my din-rail relay and back to di-3. Switching any of my downstairs fan coils from heating (fan won’t run till the thermal switch is closed by the water flow) to ventilation (fun runs irrespective of water temp) will energise the relay and connect di-4 to di-common, through the NO contact. As soon as the fan coil is switched off, unit returns to heating mode under thermostat and weather comp control.

 

I have a good few spares cores in my comms cable so can bring di-3 back into the house.

Edited 3 hours ago by HughF