TR2 reading wrong temperature - any fixes

NigelCollins · 12 Mar 2018

I have a Worcester Bosch HE Plus 35 working with a TR2 thermostat. We have noticed that the heating never seems to fire up when we 'feel' it should. So I thought I would check out whats happening. I set the TR2 to 20 degrees and then looked at the Info display on the boiler which says that the required room temperature is 17.5 degrees. Tried upping the TR2 to 25 degrees and the Required room temperature says 22.5 degrees - so it appears that the TR2 is out by 2.5 degrees.

so 2 questions: 1) am I missing something in my simple analysis and 2) if I'm not is there any way of adjusting / calibrating the TR2.

Thanks in advance

stem · 12 Mar 2018

Sounds like it has a 'night set back' setting? If so, that automatically lowers the actual set temperature by 2 degrees or so from the figure shown. If so, changing the settings to deselect the night set back will fix it.

NigelCollins · 12 Mar 2018

Hi stem - pretty sure it doesnt have 'night set back' - have checked the Greenstar 35 HE manual and the TR2 manual and not mentioned. thanks Nigel

stem · 12 Mar 2018

Are you sure it's a TR2? The moon symbol is the 'night set back'.

It might be known as 'economy mode' in the boiler settings.

NigelCollins · 12 Mar 2018

Hi - stem yes its a TR2, I am using it on timed or 'day' setting. As I understand it the 'moon' setting is Constant “Off (Economy)” mode and uses an economy temperature which I have set to 10 degrees and only use when I am away from house.

stem · 12 Mar 2018

That sounds about right. TR2 settings are:

'Constant' (Sun Symbol)= Heating 'on' permanently and to the temperature indicated.
'Economy' aka Night Setback (Moon Symbol) = Heating 'on' permanently but set lower than the indicated temperature value.
'Automatic' (Clock symbol) = Switches automatically between 'Constant' & 'Economy' according to programmer settings.

However if the 'Economy' setting is set to be 10 degrees lower than the 'constant' setting, which I'm guessing is so that it doesn't normally ever come on, it doesn't explain the 2.5 degrees difference you are seeing. So sorry "I'm out" (of ideas)

D_Hailsham · 12 Mar 2018

NigelCollins said:
I set the TR2 to 20 degrees and then looked at the Info display on the boiler which says that the required room temperature is 17.5 degrees. Tried upping the TR2 to 25 degrees and the Required room temperature says 22.5 degrees - so it appears that the TR2 is out by 2.5 degrees.

The temperature displayed on the boiler comes from the TR2 when heating is On (Comfort mode) and from the boiler when heating is Off (Economy mode). If the actual room temperature is lower than that set on the TR2, I would check that the clock is set and programmed correctly.

This is what the manual says:

6.5.1 Heating programme

Comfort Mode:
• With TR2 Room thermostat fitted: Central heating is on. House will be heated to temperature set on TR2.

Economy Mode:
• With TR2 Room thermostat fitted: Central heating is on. House will be heated to temperature set on ‘’Economy mode’’ of Text Display.

Can you post two pics: one of the TR2, the other of the boiler display. Don't make any changes to settings between pics.

NigelCollins · 12 Mar 2018

Hi - well strange I went to take the photo's and now the difference between the TR2 temp and Required room temperature is only about 0.5 degrees - so irrelevant. I cant figure out why this has changed. I checked about 3 or 4 times this morning - whatever temp I adjusted the TR2 to, the Required room temp was always about 2.5 degrees lower. Presumably its nothing to do with Optimum Start (which is enabled but which I cannot

find any good description about what it actually does.)

D_Hailsham · 12 Mar 2018

So there is a discrepancy between what the TR2 shows as the required temperature (approx 20C) and what the boiler shows (19C). The only solution I can see is to turn the stat up very slightly until the boiler shows the temperature you require. You can always mark the setting.

As for 'Optimum Start', that automatically adjusts the time the boiler comes on, depending on how cold it is. Let's say you want the house to be up to temperature by 0700. Without OS you have to guess how far the temperature will drop overnight and set the boiler turn on time appropriately. With OS you set the start time to 0600 and the boiler/TR2 turns the boiler on sometime between 0600 and 0700, depending how much the temperature has dropped overnight. I must say that one hour seems a rather short time to bring the house up to temperature, though it will depend on what Economy temperature has been set as this determines how far the temperature falls overnight.

NigelCollins · 13 Mar 2018

Thanks for the suggestions and the very clear explanation of 'Optimum Start' - very useful!!

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TR2 reading wrong temperature - any fixes

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