What an idiot!
I've bought a starter kit with smart room thermostat and bridge (successfully fitted) and some radiator thermostats. Being an idiot I didn't check that my existing thermostatic radiator valves were compatible with the tado ones and they're not - they're Pegler Mistral II. Will I need to have these replaced before I can install the tado smart valves? If so any suggestions as to what I should replace them with? Thanks
Best Answer
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Yes, a heating system will need a bypass that prevents the water circuit from being fully closed. Historically this was done with a single radiator, but today it is done with an auto bypass valve. The valve is normally closed but opens when the TRVs close, due to the difference in water pressure. The auto bypass valve can be fitted on the pipework outside the boiler, or some boilers have an internal bypass.
You may still need your bypass radiator. It depends how your heating system has been updated in recent years. Probably need a plumber to determine where your bypass is and whether you can have TRVs on all radiators.
If you do fit a TRV in the same room as the wall thermostat then group the two together in the App. The TRV will be controlled by the wall thermostat to accurately regulate the temperature in the room.
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Answers
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Replace them with a TRV that has a M30 x 1.5mm thread. Personally I’d use Honeywell or Drayton, but it depends what is available in your region.
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Thanks for the reply - looks like I'll need to spend some more money and get the TRVs changed to get the tado system fully up and running.
Another question if you don't mind. The room where the wall thermostat is fitted has a radiator with no thermostatic valve so is permanently on when the heating is switched on. I assume this is some sort of by-pass system. Do I need to leave this as it is or can this be fitted with a TRV as well?
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Looks like I’ve done same 🥲0
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Tim_F did you find a solution for the Pegler Mistral II TRVs? I’ve done the same, although I have realised my error before trying to fit them. What was the additional cost to get the plumbing works done? I’m trying to work out whether it’s feasible to get the works done now or return the TRVs to Tado and re-buy at a later date when I can afford the plumbing works. I’m kicking myself.0
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May be worth trying to fit them?
I have Pegler Terrier TRVs which are listed as not working, but have actually worked fine in my house for over two years now. They're listed in the same box as the Mistrals on the compatibility chart: https://cdn.brandfolder.io/607DGEMS/at/wngg83j9q93x6s7qn93hzs7/0130_B_SRT_Compatibility_Guide_EN.pdf
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Hi NicB. In the end I bit the bullet and bought replacement valves and got my plumber to change them. Cost a couple of hundred quid but I'm glad I did it now (although it hurt at the time!). The tado valves are great and heating the house so flexible and much easier to manage using the app.
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Actually, I recall some discussion on here about the Tado heads not physically fitting due to the shape of the Pegler valve. Doing some Google searching, I think the Terriers have an octagonal base (between the brass valve and the thread), but the Mistrals have a square base. I wonder if it's the square base that causes the issue, but worth checking what shape yours are...
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Thanks everyone. I will double check the shape of the connection on the Mitral II, but suspect it won’t be compatible. I’ve watched a few YT videos on how to replace radiator valves and the process looks fairly straightforward (famous last words), so I shall have a go at doing it.
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