Wiring open therm stat

[Matt0029]

When wiring in an open therm stat. Swapping a boiler and swapping the wired stat on the wall, Honeywell one. For an open therm one. I know you take two wires I believe from the supply to the boiler to the open therm connections in the boiler. Ideal instinct. Am I right in saying open therm is low voltage? I need to get the instructions for the stat and read up. Thanks for any insight.

 

[ShaunCorbs]

Yes around 5v I think

 

[Matt0029]

Thanks any idea what gets wired across to the boiler open therm connections, is it switch live?

 

[ShaunCorbs]

No think of it like data connections normally a 2 core

 

[IND_Nick]

There is normally a dedicated Bus or 'open therm' terminal block for the two wires. Some manufacturers use different terminology and they aren't all compatible.
I may be wrong but I don't think the Ideal Instinct has an eBus system, I'm happy to be corrected on that though.

 

[Matt0029]

It does have a separate terminal on the right of the boiler for open therm. Just 2 connections

 

[IND_Nick]

It does have a separate terminal on the right of the boiler for open therm. Just 2 connections

I thought it was odd as most have this type of system available, I only flicked through the manual on the wiring page, but it may have been updated from the version I have.

 

[Deleted member 120897]

I don’t believe it matters on OT, as it’s not polarity sensitive, so no switched live. You’ll need L-N-E for the power supply if wireless, and 2 wires for OT. Otherwise it’s just the 2 wires.

 

[Matt0029]

It does have a separate terminal on the right of the boiler for open therm. Just 2 connections

Was thinking of using the old stats wires from the wall stat for open therm. The boiler is wired in 5 core. And swapping the hard wired stat for the open therm stat.

 

[ShaunCorbs]

Can’t run high and low voltage together in the same cable

 

[Matt0029]

The live neutral and earth coming to the boiler would be in the same cable as the stat wires. So I couldnt use this 2 wires to take a feed to the open therm connections? Putting wagos on the 2 stat wires and running heat resistant 2 core to the open therm?

 

[Matt0029]

If not acceptable with the current wiring set up I'll look at just putting a hard wired stat on. Boiler plus compliant

 

[Deleted member 120897]

Can’t run high and low voltage together in the same cable

Is this to do with ghost voltages, inductance or something? Is it a BS?

 

[ShaunCorbs]

Is this to do with ghost voltages, inductance or something? Is it a BS?

Correct your spot on

 

[Matt0029]

Can you explain more please. Thanks

 

[Deleted member 120897]

Can you explain more please. Thanks

I’m thinking the thermostat might start misbehaving.

 

[IND_Nick]

I’m thinking the thermostat might start misbehaving.

Yeah I believe the 240V could cause an induced voltage in the Low Volt open therm, causing mixed signals etc. The sparkies I work with won't run anything low voltage, Cat 6/ alarm etc in same runs as socket/lighting cable as it can cause the same problems apparently.

 

[ShaunCorbs]

Yep you will get it famtonly turning on / mind of its own

 

[Timmy D]

Need a minimum of 10mm spacing between low voltage and extra low voltage.

If you can find another source close by for your low voltage power, you could use existing wires for the extra low voltage back to boiler.

 

[Brian D]

Recently wired two open therm stats using 5 core. Not had any communication issues at all.

 

[Lou]

(Just bumping a few older threads, they will drop off what is new soon)

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