Replace wireless thermostat myself

DocQuincy

I have a Logic+ 30 boiler managed by a wireless thermostat (Salus RT300RF). Although obviously a cheap one the thermostat has been fine for a while but is now sometimes struggling to communicate with the boiler (even with fresh batteries). Also, I don't like the way you can't turn the heating on without the wireless control working.

I am wondering if I get a new wireless thermostat if I can replace it myself? I took the front of the boiler off last night and it looks like it would be fairly easy to take the old one out and put a new one in. It seems to be two wires that each split into two.

My question is: are they fairly standard? I.e. can I buy one and disconnect the old one and connect the new one. I am looking at this one as a replacement:

https://plumbbox.co.uk/product/salus-wireless-thermostat-rt510rf/

Is it a simple replacement or should I get a boiler engineer to do it? Is there anything I could get wrong that could damage the boiler, cause an electrical fire, etc?

Thanks.

Jeepers_Creepers

To answer your last Q - is there anything that could go wrong? Yes, of course there is.

Boiler controls work on two basic systems - 'zero'-volt (actually, usually around 5V), and 'mains' - ie 240V. Wire up the wrong type and you will fry your boiler's PCB.

This is a 'competent DIYer' type job, but is potentially a lot more tricky than, say, adding an extra wall socket or light fitting. The thing about sockets and lights is, you know what you are dealing with - a Live, Neutral and an Earth. With boiler controls, you are talking about a power supply to the control receiver (could be 5VDC or could be 240VAC), and you are talking about the boiler 'switching' wires.

If your boiler currently has its wireless receiver built-in to its casing, then it'll almost certainly be 5VDC operated. The receiver you are now considering will be externally mounted near the boiler, and will be mains powered, and then additional control wires going to the boiler (or a nearby wiring centre).

Can you do this? Yes. As long as you completely understand what you are doing.

Look up the installation instructions for the Logic+ and read the section on 'wiring controls/thermostat' and stuff. If it doesn't make total sense, then don't do it.

But a sparky (not a plumber) will have this done in a half-hour or so.

Jeepers_Creepers

You can often pick up a new or near-new Hive SLT3 (if you have a combi) on t'Bay for around £40 or so. They are really nice to use.

The receiver has an override button should the thermostat fail or the batteries go flat, and the actual control of the temps and times are super-intuitive to use. A far better option, imo.

Your chosen Salus also has this override control - see the auto/manual switch?

DocQuincy

Many thanks for your detailed reply!

You have answered my question: I am not going to attempt it myself. I thought it might be like changing a light or plug but the fact it isn't means I think I'll get someone to do it.

Our current thermostat is external to the boiler, by the way. As is what I would replace it with.

The current Salus I have has no override but the one I was going to get does. I picked that one because I thought it was similar to the current one so would be more suitable for a like-for-like swap.

If I went for something more fancy, like your Hive example, and then got an electrician round, how do I know whether a particular thermostat would work with my boiler‚ or will an electrician be able to sort it regardless?

Thanks!

Jeepers_Creepers

Could you post a pic of your current receiver, please - I'd assumed it was internal to the boiler casing.

As for the Hive model - what type of boiler do you have, combi or system?

If your current Salus is external, then there's a good chance no wiring is required! It's pop old one off - pop new one on!

Photo, please, and/or exact model.

DocQuincy

Thanks, the boiler is Logic+ 30 boiler, combi condensing.

Wireless controller is Salus RT300RF and the receiver is the same as the one in this picture. It is external to the boiler and has two connecting wires going into the underneath of the boiler (not at home at the moment so can't post a photo). Each of those wires splits into two once inside the boiler.

Jeepers_Creepers

Ok, when you said you removed the boiler front panel, I assumed...

This is good news! The wiring of the 510 is exactly the same as the old 300.

OLD RT300:  Page 7 https://salus-controls.com/files/RT300RF-Manual-005-cr.pdf

NEW RT510: Page 5 https://salus-controls.com/files/RT510RF_full_manual_UK_V005.pdf

The new 510 has a removable backplate, and this is fitted to the wall and wired up first, and then the receiver is clipped on to it - jobbie jobbed.

The old 300 receiver doesn't have this separate plate, I don't think? In which case you'll need to remove it from the wall (not sure how to do this - the instructions aren't clear) in order to access the wiring.

FIRST, of course, you turn off the isolating switch for the boiler. You may wish to also turn off your whole consumer unit, or at least the circuit which supplies your boiler - is it labelled?

Then you remove the cover of the 300 receiver - the one near your boiler. I don't know how to do this, and the instructions don't explain it either - lawdie. Anyhoo, once the cover is off/the unit removed, you will find that the wiring is exactly the same as the new unit's.

This is where you take 100% care that you do NOT mix up these wires in any way whatsoever. You mark the cable with pen, you apply taped labels to each wire, and you take photos. There will (likely) be two 'cables', and each will have two wires. One is the power supply - 240v - and is a Live and a Neutral. They - obviously - go from the L&N on the old 300 to the L&N on the new 510 backplate.

Then the other cable goes from the old 300's NO and COM, to the new 510's NO and COM. It really could not be more easy.

The new backplate will, of course, need screwing to the wall in place of the 300, but I suspect the same screws can be used.

('NO' or 'N/O' stands for 'Normally Open'. And COM stands for 'Common'. These are just the two wires going to an internal 'switch' inside the receiver, and this switch is 'normally open' - ie 'off'. It 'closes' when the stat sends a signal to it to turn on the boiler.)

If there is an earth wire on the old cable, just put that in an equivalent place on the new one - an earth 'park'. Don't connect it to a terminal unless that terminal is clearly for 'earth'.

The Hive is wired essentially the same way, but it's to N, L, 1 (COM) and 3 (NO). :

Page 12  https://assets.ctfassets.net/mijf9lz5yt3u/6PXpzt5QO5v4Mvov3kVh7V/85014cbc1523668920d916fc682c3073/Hive_Active_Heating_2_Wireless_Thermostat_User_Guide_Installation_Guide.pdf

You ONLY do this if you 100% understand it, and are 100% certain you won't mess up. What %-age are you at...?

DocQuincy

Wow, such a detailed response, thank you!

I would not be 100% at this stage but I will have a think about it. I'm torn as if it is a quick job for an electrician I might play it safe.

Thanks again, I really appreciate the time you've taken.

Jeepers_Creepers

A very quick, very straight-forward, job for a sparky. Half-hour.

You are at less than 100%, so you know what to do...

Jeepers_Creepers

(Check out the Hive - it is really nice...)

DocQuincy

I will do, thank you!