HughF

Nest + weather comp for us. Nest gives the wife an easy to use hi-limit (which is only rarely met in shoulder months). I consider myself a good designer/installer. heck, even the Samsung controller when used as a room stat is just that, an on/off stat. It doesn’t do load compensation, despite what people have been led to believe.

When I was using mine for cooling yesterday, using ambient temp switching, it just said ‘cooling + dhw’ on the display. So I assume that dhw always takes priority. Fine for us as we use a moderate amount of dhw all year round

The plan was that when the fan coil is switched away from ‘ventilate’ to either ‘off’ or ‘heat’, the cooling relay is de-energised and the NC connection remakes the di-6 to di-common connection. My fan coils are smiths ecovector units, very simple on/off controls.

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.

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’….

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.

Coil is right at the bottom, I’ve yet to see it ramp either the pump or the compressor down during a dhw charge.

OSO (Vaillant) slimline for me, it was £500 on eBay 😂 1m2 coil, 9kW pump - reheat times are perfectly acceptable and the coil can take all the heat pump can throw at it.

It appears that appliances direct have stopped selling these - as of last night I couldn’t find one on their website.

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

Fan mode - eco, enables weather compensation. On any other fan mode it runs at a fixed flow temperature and/or a fixed dhw temperature. you will 100% want to re plumb this to direct weather compensated heating and use the TS just for dhw, otherwise come winter time you’ll have radiators that are too hot and a terrible COP.

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.

Or just buy it and fit it without the grant or any mcs rubbish? 7kW monobloc is sub £2k if you know where to look.

I’ll give it a try and report back. Currently drawing up a simple relay based circuit to enable to cooling call when any of the fan coils are switched to ‘fan only’ mode.

Do you know if dhw still has priority if I use the separate heating and cooling call inputs, instead of the a/c linkage input?

The midea are nearly always installed with either a plate or a llh for separation.

Perfecto…. He’s at installer show this week so I’m not bothering him with questions. So a/c linkage is a simple call for heat/cool with the ambient switching taking care of changing from heat to cool. The dedicated cooling call is just that and the same for heating call?

Hmm…. A dedicated call for cooling you say?

I’d like mine to have a little more options for cooling (dedicated cooling zone valve output for example, dedicated cooling call instead of a combined heat/cool call), but it does what we need

A good unit if I recall (I remember reading the manual from cover to cover)

Interesting thermostat, cheers. Shame my wife wouldn’t be able to use that - we run a nest for that very reason (peak ergonomics imho) Remind me again if you could be so kind what heat pump you’re using?

If we get another hot spell I’ll try setting the heat pump to 12 degrees and jumper out the call for heat (why oh why can’t we get heat/cool thermostats in the UK)… see how the fan coils work.

That’s an option for sure. Replace the bedroom rads with wall mount fan coils. I was thinking a separate unit and ducting would make pipe work easier as when I replumbed I didn’t consider cooling so made a few mistakes with pipe runs and lack of zoning. Not an issue with heating but certainly an issue if I want to cool, I’d need to valve off the existing fan coils which don’t have a condensate pan, and the rads. They’re all on the same zone.

This…. I raised the issue at installer show last year at the heat geek theatre talks. Because of the fact that we have the most expensive electricity in Europe (pretty much) , we’re scop chasing. If we could settle for an easy 2.8 and chuck em in like a boiler, it would make things much easier.

If only electricity was 5p/unit all the time - then we could actually get on with this decarbonisation without needing any complicated additional work. 50deg fixed flow temp, separation, on/off stats. Easy.