Ideal Logic ESP1 35: Do I need a harness to get OT to work?

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NicB
NicB
edited December 2023 in General Questions & Topics

Hello

I have an Ideal Logic ESP1 35 combi boiler which is currently connected to two wired ESI thermostats, which control the heating only (no hot water tank). This week I purchased 1 x Tado wired starter kit (v3), 1 x Tado wired extension kit and 4 x smart TRVs. Reading through a lot of websites and posts on here, I understand that the Tado thermostats work best with OT and the boiler is modulating the call for heat (apologies if that is the incorrect terminology - I'm on a huge learning curve!).

Before I get stuck into installing the thermostats, etc. I wonder if someone could double-check that I'm on the right path.

Photo 1 - Existing wiring to ESi thermostats (second thermostat is wired the same). Remove the Brown and black wires and connect them to the OT terminals on the Tado thermostat. Do this for both thermostats.

Photo 2 - Remove the block.

Photo 3 - Connect the two blocks labelled 1 & 2 together and push black bung into hole in front plate (where 1 was disconnected from). Top right - disconnect the purple wire from the block which was removed from behind the front plate and connect each end to the OT terminals (I think).

Photo 4 - Do I need to remove any wiring from the Room Stat blocks on the top left?

Should this setup work? I know a lot of people have mentioned that some Logic boilers need an additional harness.

Forgive me for speaking in layman's terms. I hope i've explained the steps correctly (fingers crossed).



Comments

  • NicB
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    Thanks rafm5. I've studied that post in detail today, as well as every other post which mentions logic boilers. I was hoping that someone would be able to give me the answer in more layman's terms and confirm that my understanding was right or wrong (as per my photos). If I do need the harness which is photographed in the post you mentioned, then how is it connected? I was hoping to do this myself, but perhaps I need to admit defeat and say it's above my capabilities.

  • johnnyp78
    johnnyp78 ✭✭✭
    edited December 2023
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    If you have zoned heating, which is implied from having two thermostats, you won’t be able to use Opentherm -zone valves are either open or closed so connect via relay. You would need to have the zone valves removed first or taken out of circuit so they’re always open. In principle what you’re saying about connecting the boiler with Opentherm would work but not with your current system.
  • NicB
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    Thank you. Your explanation makes perfect sense.
  • physicsboy
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    @johnnyp78 am I correct in assuming that if wanting to use OpenTherm on a dual zone system means removing/disabling the valves to be permanently open... To get a similar functionality, one would have to fit TRVs? Or is fitting TVRs almost mandatory when going the OpenTherm route?