New Boiler Thermostat help

20 Jul 2012
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United Kingdom
hello I have a ariston e-combi evo boiler and currently have a crappy thermostat. I wanted to install a better one. currently I only have two wires going to the thermostat from the boilers ta1 connector. manual for boiler found here
I was looking at geeting a salus st620 thermostat and it says I need a live feed and a switched live feed. I figured the switched live was from ta1 on the boiler. does it matter what wire from ta1 as not sure witch one to use. thanks
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I figured the switched live was from ta1 on the boiler.

You figured wrong, all that can be connected to the TA connections is a contact that closes when heating is required.

Please get a qualified person to connect the new thermostat

From page 26 of the manual you refered to

Room Thermostat / Remote Clock Connection
To connect a room thermostat, it is necessary to:
1. Open the control panel
2. Loosen the cable clamp using a screwdriver and insert the wires
leading from the room thermostat
3. Connect the wires to the terminals as indicated in the fi gure
below, removing the link
4. If a remote time clock is to be fi tted, using a volt free switching
time clock connect the switching wires from the time clock
following points 1 - 3 above
5. If using an external time clock and room thermostat, these must
be connected in series as shown in diagram C,
6. Ensure that they are well connected and not subject to stress
when the control panel is closed
If you already have a thermostat, show us a picture, and of the connections inside it.

I think there will be two (plus an earth) and I think I know what they will be.

A room stat is just an on-off switch. If your existing one works, you have no need to touch anything at the boiler end of the cable.

BTW Salus is a brand renowned for its cheapness, but not for its quality.
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Sorry I know it is a sales rt100 and only has two wires going into it from the boiler but I'm out at the moment
The ST620 is a 2 wire stat,Easy job.

Your existing boiler -- roomstat wire may have more than 2 wires so it could be adapted for an alternative stat.Harder job

Although 2 wire connections,all wires need to be checked on site to ensure correct/safe wiring.

Good luck.
Last edited by a moderator:
your old RT100 stat also uses two wires, COM (live) and NO (switched live)

so you already have the two wires you need at the thermostat.

No need to touch anything at the boiler end.

Honeywell stats are much better than Salus. You can get a CM907, reduced price, at Plumbworld (and maybe others. Reduced because it is last year's model)
Thanks guys for your help it much appreciated I'll have a look at the Honeywell one too thanks once again guys

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