Connecting Salus rt500rf thermostat to Atag iC24 Boiler

2 Aug 2016
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United Kingdom
Now it has got around to winter I'm finally getting around to fixing the thermostat on our heating.

The existing Honeywell T40 Thermostat is faulty (we're just using it like an on/off switch at the moment); as its also been installed above a radiator, and on a half landing leading into the flat I'd like to better locate a replacement.

The easiest thing seemed to be to connect a new wireless thermostat and install the receiver near the boiler. I've picked up a Salus rt500rf as this was the cheapest option I could find (and just want a solution for this winter as we plan to extensively renovate next year).

Seems like its not a straightforward swap as I hoped though. Seems like I need to change the connection to the boiler as well as the cable.

Here are the extracts from the manuals for the boiler and thermostat:

Atag Boiler (p30-31)
Atag iC_Page_30.jpgAtag iC_Page_31.jpg iC.pdf

Salus Thermostat (p6-7)
Salus-RT500RF-_Page_06.jpg Salus-RT500RF-_Page_07.jpg

The existing T40 has 3 wires but assume this is now irrelevant as will need to replace the wiring from the boiler (for information the existing cables for info are Green/Yellow to what I assume is the earth, Blue to "3" and Black to "1".)

Based on the manuals for the Boiler and Thermostat, and some on-line videos I believe that I will need a 3 core cable (no earth required) and the following connections:

Atag SwL connects to Salus NO
Atag L connects to Salus L & Salus COM
Atag N connects to Salus N

Is this correct?

If so the Boiler Manual also notes "230V out" for L/N/E and "230V Control" for SwL/L/N/E - which connections should I be using for L/N/SwL?

All help much appreciated.
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Thanks D_Hailsham

What about the label for "230V out" for L/N/E and "230V Control" for SwL/L/N/E on the boiler? - I've not opened the boiler up yet but assumed these were two connection options? or is this just a labelling term and its the same thing?
You've got a boiler with OpenTherm capability and you're putting a cheap nasty on/off stat on it? Your boiler would be sooooo much more efficient if you bought an OpenTherm stat, the additional cost would pay for itself in gas savings
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Hi Muggles, yes we looked into OpenTherm and part of the reason we went for the boiler we did when we moved in (we only bought new boiler as the old boiler was bust) - we're just going cheap with the thermostat to get us through this winter as come spring we are completely stripping the entire flat and extending upwards so will be changing everything then (apart from the boiler although that will move), and we will most likely be zoning too so will put in a better control system then.

Fortunately we don't seem to use much gas at the minute anyway as we are in a terrace with other flats either side and below - last month once we took off daily standing charges etc. we used less than £2 in actual gas.
What about the label for "230V out" for L/N/E and "230V Control" for SwL/L/N/E on the boiler?
Just confusing labelling!

"230V out" L/N/E just tells you that these three terminals supply 230V, i.e they are not the mains input to the boiler. So they can be used to supply power to, e.g. a programmer.
"230V Control" is telling you to use these terminals if you are using 230V to control the boiler, not the Volt free or Opentherm terminals. L/N/E feed the programmer and thermostat; SwL (switched Live) is the return signal form thermostat which turns the boiler on and off.

Hope that clears up the confusion.
Great thanks D_Hailsham.

This might be a daft question but can I use a 3 core flex cable to connect this utilising the earth for the SwL and just labelling/sleeving the wire accordingly? - I assume this will be frowned upon as wrong coloured, but is it acceptable? I don't have any other cable and would like to avoid buying several meters for a mere 20cm needed.

I'll do check our my local electrical store and see if I can buy 1m or less of 4 core but last time I needed cable seemed like everywhere wanted to sell at least 10m.

Edit: I'll get some from Amazon/Ebay if not in my local sotre - seems like I might as well wait a couple of days and do it properly.
That's OK if the earth has green/yellow insulation.

The cable does need to be heat resisting as it will be going inside the boiler.

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