Programmable Room Stat to replace Myson MRTE

We have a number of Myson MRTE rooms stats controlling our Daikin ASHP via the Myson wiring unit.

I believe that these are volt-free 2 wire stats, I asked Myson if they have an alternative programmable stat (different temps at different times) and they said their only compatible stat is the MPRT, however, this is a hideously ugly unit that the wife would never allow in our house.

Are there any other manufacturers' stats that I could use and if any recommendations?

Thanks

The Flomasta 22199SX wired digital programmable thermostat screwfix 6259G says it is SPST (single pole single throw) but it is a change over switch with as you would expect 3 contacts, it also says three wire installation, but it's what most of us would call two wire. It had a dip switch to change the default N/O (normal open) from being used with heating or cooling, so if batteries go flat it will as default not power up the boiler or air conditioner.

However when I was brewing beer, I found you needed two sets of contacts to control heating and cooling with a dead point between the two where nothing runs, and also a delay for cooling so the compressor can't be restarted without there being time for the pressure to drop, I used a STC-1000 which is not really the sort of thing that can mount on a wall.

I know the Myson iVector radiator can have two radiators built into the one unit, one for cooling and one for heating, and has a 5 speed fan so adjusts the heating or cooling output by adjusting the fan speed, but when I looked further into them, the building management system used to control them cost an arm and a leg, so was not really an option.

So the only way I can see for auto changing the temperature between to set points is a timer that swaps between two units set to different temperatures, my simple TRV has that built in, press one button to swap from comfort to eco mode.

I can't see anything special about the MRTE room stat but it seems a massive unit if only a simple thermostat, maybe the Flomasta 22199SX would work, may be the delay is built into the heat pump? May be @stem can advise further?

I had a look at the MTRE and you are right. It just has a single voltage free changeover contact rated at 8 amps restive load, 3 amps inductive load. Pretty standard really.



So, in theory any thermostat with an NO and NC contact could replace it. Except that the OP is using it with a ASHP. In which case, if it's used for heating and cooling, the heating would utilise the NO contact and the cooling the NC. But as you mention, the thermostat would continually toggle between heating and cooling, so not an ideal way of working, unless there was a method of selecting either 'heating' or 'cooling elsewhere'. Of course the ASHP could be being used with UFH (no cooling) in which case any battery operated thermostat with a single contact would be fine.

stem said:

I had a look at the MTRE and you are right. It just has a single voltage free changeover contact rated at 8 amps restive load, 3 amps inductive load. Pretty standard really.

View attachment 175233

So, in theory any thermostat with an NO and NC contact could replace it. Except that the OP is using it with a ASHP. In which case, if it's used for heating and cooling, the heating would utilise the NO contact and the cooling the NC. But as you mention, the thermostat would continually toggle between heating and cooling, so not an ideal way of working, unless there was a method of selecting either 'heating' or 'cooling elsewhere'. Of course the ASHP could be being used with UFH (no cooling) in which case any battery operated thermostat with a single contact would be fine.

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Although we have an ASHP it is only used for heating and not for cooling, I have still not been able to find a room stat that will do what I want and I wonder if I am complicating things, can you suggest any specific models that might work? Thanks

If only used for heating then the Flomasta 22199SX would work as I have said.

The STC 1000 would do heating and cooling however it needs mounting in some way.

ericmark said:

If only used for heating then the Flomasta 22199SX would work as I have said.

The STC 1000 would do heating and cooling however it needs mounting in some way.

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Thanks but the reason why I am confused is that this one like most others I have seen states that "Power Voltage Supply 230 V" mine does not have a 230V supply and the wires at both ends never see 230V, I have checked they are low voltage.

The Flomasta 22199SX is volt free, that means there is no connection to mains or any other supply, power comes from a battery, it is rated 230 volt as it can switch low voltage if needed, but it will work just as well with extra low voltage, I have one in my other house it switches 24 volt.

Sorry to drag up an old thread but it was a threat I started and I need to revisit the topic.

I never got round to sorting out this thermostat issue but now with the price of electricity, I am looking to change some of our Myson MTRE thermostats to alternatives that allow different temperatures at different times.

I have looked at the Flomasta 22199SX that was recommended but my wife doesn't like the look of it! so I am looking for other 2 wire, volt free thermostat recommendations. A simple plain thermostat with a clear display would be great.

Any ideas?

TIA

If it’s just 2 wire thermostat you’re after, plenty on the market. Large display - Siemens RDH100 are cheap enough.

CBW said:

If it’s just 2 wire thermostat you’re after, plenty on the market. Large display - Siemens RDH100 are cheap enough.

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That looks nice and the price is good but as far as I can see it does not allow different temps at different times? we want to be able to set the temperature lower during the night and increase slightly during the day, eg 18c at night 21c during the day.

Apologies, wasn’t sure you wanted programmable (even though the tread title says so ). Try the RDJ100 then.