Does anyone have a Myson MPRT wall thermostat, need some help. 12 January 2021 at 8:40PM edited 12 January 2021 at 11:04PM in LPG, heating oil, solid & other fuels 17 replies 1.1K views

_Jem_

I haven't got anything to measure the room temperature just the wall thermostat, I know they aren't totally accurate, So I'm not too worried when it turns the heating off, but it's no good if it turns the heating off then back on every two or 3 minutes. 
I have been in touch with Myson to put it plainly if I set it to 21c then it should go off at 21.5c and then will turn back on when it's 20.5c. That's definitely not doing that. 

matelodave

with a one degree differential then it will keep doing it every few minutes unless the place is well insulated and has a high thermal mass. If it seems as though the room takes a very long time to get up to temperature you might find that the radiators only just emitting sufficient heat to counteract the building heat loss so they are working at full capacity and the fabric isn't getting warmed sufficiently. What happens when you leave it set for several hours

Do you know what differential has been set in the thermostat - I understand that it can be adjusted using the engineers setting if you can find out how to do it.

What temperature does the room actually get to - you probably need to get a thermometer to check it. Where is your thermostat situated, in a draught, near a rad, in the hall or even on an outside wall. Location of the unit can make a difference to it's responsiveness. How long does it take to get up to temperature (how long do you allow it to get up to temperature)


What have Myson said about it

_Jem_

matelodave said:

with a one degree differential then it will keep doing it every few minutes unless the place is well insulated and has a high thermal mass. If it seems as though the room takes a very long time to get up to temperature you might find that the radiators only just emitting sufficient heat to counteract the building heat loss so they are working at full capacity and the fabric isn't getting warmed sufficiently. What happens when you leave it set for several hours

Do you know what differential has been set in the thermostat - I understand that it can be adjusted using the engineers setting if you can find out how to do it.

What temperature does the room actually get to - you probably need to get a thermometer to check it. Where is your thermostat situated, in a draught, near a rad, in the hall or even on an outside wall. Location of the unit can make a difference to it's responsiveness. How long does it take to get up to temperature (how long do you allow it to get up to temperature)


What have Myson said about it

The thermostat is placed in the hallway it is near a radiator no draughts, silly place to put it. The hallway gets very warm and stays warm, the differential is set to 0.5+- out of the box, I have also seen that it can be adjusted but can't find any information on how it could be changed.
To be honest I haven't left it for hours to see what happens as it's just wasting heat because it goes on and off to quickly that means all the radiators dont get warm enough to heat the rooms.
I'm still waiting from Myson to see if it's supposed to work this way. It can't be right though if the temperature on the stat reads 24c if I then  turn it down to 20c in theory it shouldn't come back on if I turn it off and then turn it back on.
I have sent the information on to the housing association but how things are going with the developers the cold weather will be over by the time they sort it out.

Edit: I have set it lower to 21.5 so this time I will see how it behaves when I leave it on for longer. 

matelodave

Sounds as though the hall is getting too hot too quickly and shutting the heating down before the rest of the place has a chance to warm up, especially if the stat is located fairly close to the radiator. Try adjusting flow rate through the radiator by closing the valve down at one end - even turn it off altogether and then ease it open by say half a turn. 
By slowing down the rate rate at which the hall gets heated you should give the rest of the place time to warm up - thermostats should not be located anywhere near radiators as they'll be affected by the rapid heat rise

_Jem_

matelodave said:

Sounds as though the hall is getting too hot too quickly and shutting the heating down before the rest of the place has a chance to warm up, especially if the stat is located fairly close to the radiator. Try adjusting flow rate through the radiator by closing the valve down at one end - even turn it off altogether and then ease it open by say half a turn. 
By slowing down the rate rate at which the hall gets heated you should give the rest of the place time to warm up - thermostats should not be located anywhere near radiators as they'll be affected by the rapid heat rise

That's not what the issue is, you are totally right in what you are saying here. 
My issue is the wall thermostat not behaving how it should, setting the wall thermostat to 21c the wall thermostat should turn off the heating when its 21.5c and not come back on until the wall thermostat reads 20.5c, it goes beyond 21.5c up to 22.3c  and then cycles on and off when it's 22.3c.

I just read back my first post it may sound like I'm talking about the rooms not reaching 21c, no what I'm meaning is the wall thermostat turns off before the Myson reads 21c. and when it does reach the target temperature it will then keep on going on and off when the Myson reads 21c.

matelodave

I still cant really understand what your problem is - if the stat turns on and off at approximately the temperature your require then what is wrong with it. If the room temperature overshoots the set point then that's probably because the radiator is still red hot when the stat turns off.

Hopefully you can explain it better either to Myson or your building engineer because I'm really confused.

I set my stats to the temperature where the room is comfortable without bothering too much about the actual number although once I've established what that number is then that's where it sits (in my case it's 19 degrees) and then let it get on with it. The actual room temperature then sits at around 18-19 degrees (measured by a separate thermometer in another part of the room). However my system, having low temperature underfloor heating is extremely slow at responding (it can take several hours to increase the room temp by just one or two degrees). A system using hot water radiators will respond much more rapidly and over/undershoot a lot more.

As I can't hear them click on and off I don't  know (or even care) at what temperature they actually switch providing the room temp stays fairly even .

If you ever get it sorted to your satisfaction  please let us know the outcome as it may help others with a similar problem

_Jem_

That's the problem Yes it now shuts off around the temperature I have set it at, Changing it to Oil mode seems to have fixed the problem. But it will then keep coming on and off without any temperature drop, it keeps on doing this on for 3 minutes off so no heat is coming from the radiators. Like I said if setting it to 21c then it should come back on around 20c.
I have now had a phonecall from the housing association, they are going to send a replacement out.
I definitely will update on this to see how it should work.