My Danfoss TP9000 with wired Stat is playing up.

I use it to control the hot water and heating of zone 1. Zone 2 is controlled by underfloor heating thermostat.

Can anyone recommend a wireless version without breaking the bank? It is to be used with Mitsubishi Ecodan FTC2

Just realised that's just a room stat, not one for hot water too...

Id assumed the "wired stat" was a tank stat and the DHW function was only a timer??

VE has a setup with a base unit with two time programmer channels (usually for CH and DHW), one channel is also switched by a wireless/wired room stat. The DHW stat is usually provided separately, built into the cylinder, and is wired in series with the DHW channel output.

We previously had a wireless room stat which we carried into whichever room we were using, eg the kitchen/dining in the morning and lounge in the evening, so it turned off the whole house heating once the occupied room was warm enough. It was always 'to hand' to tweak the temperature, say if we were sitting inactive. But needed to adjust TRVs so they didn't close off rads while the RF room stat was still calling for heating. If doing that again I'd use wi-fi radiator thermostats.

Better ones have the timers built into the RF unit, so you can program time/temperature profiles eg 17degC overnight, 18deg during the day and 20deg in the evening.

VE, is there a programmer built into the heatpump controller? Then you just need whatever room temperature sensor is compatible, the HP can then tweak its operation for max efficiency with load compensation. Does the HP also do the hot water cylinder?

Edit to add: the heatpump will be happier with long run times, eg 15-20minutes at a time. Some thermostat programmers might let you specify the minimum run time value, which might be set to only a few minutes by default, especially if it does TPI control (IE it fires the boiler in very short bursts when the room is nearly warm enough and longer bursts when the room is cold).

If you Google up the installer manual for the FTC2 heatpump controller, or call Mitsubishi, it will show how to link sensors on the cylinder and in the room back to the heatpump. Once the heatpump knows how warm they are in degrees C, it does clever stuff to adjust its operation for best CoP. Eg it looks at how long it is taking to heat the cylinder, in minutes per each 1degC rise.

If it's just getting an on/off signal from a stat then it can't work as well, especially if the signal is flicking on and then off every couple of minutes, which gas boiler stats tend to do.

Think it can do, if you want it? All singing/dancing mitsu controller.

You are correct, it does have WC, I've even set the temperatures and parameters 😂

I'm not an electrician. I'm not familiar with these products. Assume all of the following sentences are prefixed by “I guess”. Work out for yourself if that's good enough for you to make any connections.

Posted By: VictorianecoThe orange goes to earth on the old stat. Would this be deemed COM on the new one?

No, connecting that would cause a quite load bang and (hopefully only) trip the circuit breaker or RCD. COM will be the common connection on the output relay of the thermostat. The two other connections to the relay will be NO (normally open) and NC (normally closed). When the thermostat is not calling for heat it'll connect the COM connection to the NC connection. When it's calling for heat it'll disconnect that and connect the COM connection to the NO connection.

Going on what you say it looks like the new thermostat doesn't need an earth connection (double insulated, presumably). The N and L connections are, of course, neutral and line (“live” as it was called decades ago [¹]).

S/L on the FTC2 will be the switched line input which should be connected to line when the thermostat calls for heat.

So, what I think you need is the following connections:

FTC2             RX1-S
L -----------+--- L
             |
             +--- COM

N --------------- N

E --/

S/L ------------- NO

[¹] If you flip the circuit breaker or RCD protecting the circuit to the off position that wire will no longer be live but it'll still be line. When you turn the breaker back on the line wire will become live. So will the neutral wire. I.e., “live” is the opposite of “dead”, not the opposite of “neutral”.

FWIW, I think Ed is right. I am not an electrician either, but what he says seems to match the manual.

Posted By: Ed DaviesWhen you turn the breaker back on the line wire will become live. So will the neutral wire.

But I do take exception to the above. I agree that there will be current in the neutral if there is any in the live. But 'live' normally refers to the voltage and hopefully that stays close to zero (i.e. earth potential) in the neutral.

Posted By: djhBut I do take exception to the above. I agree that there will be current in the neutral if there is any in the live. But 'live' normally refers to the voltage and hopefully that stays close to zero (i.e. earth potential) in the neutral.

The IET seems to think otherwise, namely that 'live' refers to being a current carrier. I originally got this from a John Ward video but can't be bothered to wade through hours of those to find the particular point so a web search for “BS7671 live line neutral terminology” will have to do:

https://electrical.theiet.org/media/1482/rcd.pdf

Note that the term ‘live’ conductor includes both the line and neutral conductors.

Also: https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=102849