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'm renting but I dont want to get in contact with the Landlord just yet, untill I know for sure. 
I have the MPRT set to 21c and what happens is it will go off before it reaches 21c then 3 minutes later it will come back on, I know some wall thermostats do this to save on fuel, but it doesn't seem right doing this because when it reaches 21c it will go off but then come back on again and off again.

Thanks 

greatcrested

Oil? Or LPG?

_Jem_

Good question im living in a district heating town. The thermostat is set for gas. 

matelodave

 That's what thermostats are supposed to do.
  
When they initially turn on (which usually starts up the pump/boiler) they then allow the room to get up to temperature. Once they've reached the desired temperature when they turn it off & on to maintain the temperature.

If they didn't turn off then the room would get hotter and hotter. Conversely if they didn't turn back on again the room would get cold again. So they turn on & off to maintain the set temperature.

Some thermostats work in quite a narrow band and control the temperature quite closely, others may not be quite so responsive and you may feel the temperature variations between cycles. However, if the stat just switches off at say 21 degrees, the radiators will still be red hot and so will still keep heating therefore the room temperature will over shoot.
Some programmers have the ability to anticipate the overshoot and turn the pump off before the room reaches the set temperature to minimise the overshoot. Its called PID control and is a feature of more sophisticated programmable thermostats.

Here are the instructions - https://www.myson.co.uk/static_files/my/media/downloads/MPRT_Hard_Wired_User_Instructions.pdf.
You may have  "Smart Start" enabled, which might switch the stat on earlier than the time you've set, to ensure that the room is getting up to temperature by the set time.

The thermostat doesn't know nor care what sort of heating you've got, its just a simple switch which turns something on or off according to temperature - if you've got district heating then its probably just opening and closing a valve to control the hot water supply to your radiators.

_Jem_

Hi
Thank for your detailed information, Yes I know that's how they are supposed to work but this one turns off before the target temperature then turns back on it keeps doing this on and off so quickly that the radiators don't get warm enough again so it never reaches what ever temperature you set. So say I set it to 21c it may only reach 20c and the temperature doesn't rise. 
I have sent a email to Myson to see what they say. 

matelodave

_Jem_ said:

Hi
Thank for your detailed information, Yes I know that's how they are supposed to work but this one turns off before the target temperature then turns back on it keeps doing this on and off so quickly that the radiators don't get warm enough again so it never reaches what ever temperature you set. So say I set it to 21c it may only reach 20c and the temperature doesn't rise. 
I have sent a email to Myson to see what they say. 

That's a bit different to what you said in your first post

_Jem_

matelodave said:

_Jem_ said:

Hi
Thank for your detailed information, Yes I know that's how they are supposed to work but this one turns off before the target temperature then turns back on it keeps doing this on and off so quickly that the radiators don't get warm enough again so it never reaches what ever temperature you set. So say I set it to 21c it may only reach 20c and the temperature doesn't rise. 
I have sent a email to Myson to see what they say. 

That's a bit different to what you said in your first post

I can't see how that's a bit different but now you know what I mean. 

Rodders53

I'd try setting the thermostat to OIL rather than GAS  
https://www.myson.co.uk/static_files/my/media/downloads/MPRT_Hard_Wired_Instalation_Instructions.pdf

Reason:  My Honeywell T-stat explains (in the installer manual) that:
Oil Boiler setting = 4 cycles per hour with minimum on time of 4 (units?)
Gas Boiler/Zone valve = 6 cycles per hour with minimum on time of 1
I'm guessing that oil may work better for you (mainly with the longer on periods?).  If not nothing really lost is there, and you can revert to the original gas setting?

Note that if 'Smart Time' is on you set the time(s) to be when you want the set temperature(s) to be by/at that time and the timer stat will start (or stop) heating to try to achieve that goal at a time it 'learns' with use of the system over many days...  so they claim

_Jem_

Cheers I will see how it behaves on oil, I haven't got it set up on smart mode never bothered about that. 

_Jem_

Just a bit of update. 
Set it to oil instead of gas seems to be better it now doesn't go off before the target temperature, I set it to 22c and it went of at 22.2c but it came back on and off until it reached 23.2c.

Edit Again: It's got to be faulty as it came back on @23.1c and then turned off at 23.2c

matelodave

How are you measuring the temperature in the room and comparing it with the temperature on the programmer/thermostat. They aren't actually precision calibrated devices

There will always be a differential between turn on and turn off temperatures so the room temp will always fluctuate a bit. The smaller the differential then hopefully the less the temp will fluctuate but the stat will just switch on and off a lot more rapidly