Tracing thermostat wiring

[Gareth Davies]

I'm stuck so any advice would be appreciated.

I have an old Honeywell room thermostat attached to a wall with internal wall wiring. The thermostat used to be connected to a warm air heating gas boiler. This boiler was replaced by previous owners with a hot water central heating system. There is no room thermostat control for the new boiler i.e. the room thermostat is not connected to the new boiler and the thermostat is basically a relic from the warm air heating system.

I want to install a new thermostat and I've looked at battery operated wireless options but I want to use, if possible, a self powered wired control panel.

The problem is that I can't see any exit point for where the current and no longer used thermostat would have connected with the old boiler.

Would it have likely connected directly to the boiler, through a lighting circuit (sounds silly but that's all I can think of) or something else?

[Roger Mills]

Have you looked near the old boiler location for any signs of cables which have been chopped off at the point where they emerge from the wall?

Is there/would there have been a control panel/junction box anywhere else, where all the heating wiring is/was brought together?

What is your objection to wireless stats? They work perfectly well, and may well be your simplest solution unless you are prepared to install some new wiring.

[Harry Bloomfield]

It happens that Gareth Davies formulated :

BT have a little gadget which you clip on one end of a wire, then a portable pen like very sensitive receiver able to trace wires under floor and in walls, back to the other end. The first part injects a radio frequency, the second is just a receiver.

[Jon Connell]

Do you have a link to such a gadget? Sounds useful.

[Andy Burns]

[Harry Bloomfield]

They are very useful, mine is the proper BT item and detects around a couple of feet away, at maximum sensitivity setting. I paid a couple pounds for it at a boot sale, in a case.

They are OK to connect to a live phone cable, but not mains live.

[The Natural Philosopher]

normally goes to a motorised valve

[Heliotrope Smith]

Gareth Davies wrote in news:52d500ac$0$1161$5b6aafb4 @news.zen.co.uk:

As the old stat conrolled a warm air unit the wiring would most likely gone direct to the heater.

Hunt around in the cupboard where the old heater was. The heater may well have been a slot in type in which case the old location may have boarded over. In this case you may be unable to find any remaining wires.

[Gareth Davies]

I fear you are correct about the original location being boarded up with the wires boarded up too.

The new boiler is sitting on a wooden board against an outside wall which is obviously where the old warm air boiler was fitted. There's no sign of the old wiring which must have been fed directly to the warm air boiler.

Oh well.

[Gareth Davies]

Yes, I've used a wireless thermostat before and found it to be very good to the extent that I questioned why anyone would freshly install the wiring for a non wireless thermostat.

I was looking in ot fitting a Nest WiFi thermostat for remote use. Oddly the Nest Thermostat isn't wireless in the sense that it does need a hard wired connection to the boiler control.

I'm unlikely to be able to find or use the old wiring (likely boarded up behind the new boiler) so I think I'll have to pass on the idea of installing a Nest thermostat.

The Nest may be more trouble than it is worth anyway with UK incompatibilities (for example ? 24V relay inside) that can be overcome but not really on a diy basis.

[Andy Burns]

Because I assume anything without wires or with batteries* will fall prey to interference or flat batteries at the most inconvenient time.

I had a CH timer once that ran on AA batteries, got rudely awaken at dark o'clock when the batteries had reached such a level that the controller was switching the boiler and pump on/off at several Hz

• Granted not all wireless stats are battery operated.

[Lobster]

On 14 Jan 2014, Harry Bloomfield grunted:

Blimey, I've heard of those but had no idea they were so cheap! I'd always envisaged a big briefcase-sized oscilloscope-type device costing 100s - with hindsight I really don't know why. When I think of the time I could have saved over the years if I'd had one of those in my collection...

[Bill]

In message , Harry Bloomfield writes

Do BT realise that their kit was on sale at a boot sale? I hope it came with reliable provenance.

These devices are very good for cable tracing, I have 3 pairs, keeping at least 1 in the car kit for when I'm on site.

The receiver section is also very good for detecting live cables in walls.

[Andy Burns]

Does yours :-P

Is the BT one (no doubt with some cryptic internal equipment number) a rebadged version of one of these?

[Bill]

Yes.