Replacing Satchwell TLX 2356 tempstat with Honeywell CM907 Temp?

[Jim Chisholm]

I've a Satchwell TLX 2356 and am considering a Honeywell CM907 7 day programmable tempstat

I've a Honeywell wiring panel in heater cupboard.

The wiring panel (Honeywell 42005748-001) has at ROOMSTAT block:

1) Red E) earth 2) Blue 3) Yellow ( I installed this to replace a rats-nest over 20 years ago!)

The Satchwell TLX 2356 has:

blue, red, empty, yellow terminals (right to left)

The CM907 (installation instruction downloaded from web) says it can replace ANY roomstat but I can't see what to connect what to connect to what!

Help?

Jim Chisholm

[JohnW]

It would be helpful if you could let us know what number terminals the wires go to.

AIUI

CM907 terminal A is common, on the TLX it is terminal 3 CM907 demand is terminal B which is TLX terminal 1 CM907 satisfied is terminal C which is TLX terminal 2

TLX terminal 4 looks to be spare for a neutral which is not used on the CM907 and needs to be insulated.

so if on the TLX the blue is on 4, red on 3 nothing on 2 and yellow on

1 Connect Yellow to B, Red to A, and insulate the Blue

John

[Jim Chisholm]

cheers

I hadn't mapped the numbers on the plastic cover to the terminals as there are no numbers on the black plastic body

but your description is very useful, and the colours maop to terminal numbes as you predict.

I'd feared damaging the CM907 if I connected it incorrectly!

Jim

[Roger Mills]

I'm assuming that the current stat is a manual bi-metallic one, which has a built-in accelerator heating resistor, and thus needs a neutral connection in addition to live and switched live. The most likely scenario is that red is live, blue is neutral and yellow is switched live - but you need to verify this because *function* is more important than *colour* and you can't necessarily rely on what the last bloke did

- unless it was you!

The Honeywell programmable stat just needs a live and switched live - connected to whichever two of the three available terminals are connected together by the stat when heating is required, and separated when the demand is satisfied. DO NOT connect the neutral or earth wires to any of the terminals!

Sorry to be slightly vague about which terminals and colours are which - but if you can't work it out, you shouldn't be doing it!

[fred]

In article , Jim Chisholm writes

If you have any doubt, the safe option is to link the 2 terminals that you think should connect for 'call to heat' with a switch or wire link. If you have the connection correct then the boiler will fire when the switch or link is made and not when it is open. In the event of an error then a fuse may blow but your expensive thermostat will be saved.

Not suggesting this as a trial and error substitute for proper research (as you are doing here) but as a final check before connecting the stat.

[Jim Chisholm]

Thanks for that

After a delay in getting unit (7 day programmable Room Thermostat) it's now installed and working.

After removing old thermostat, I discovered wire just came out of wall with no box. Installed shallow box as more professional job. It was more than a 5 min job as I hadn't a suitable box.

Now means that stat can be at lower temp for breakfast and even lower during day when we should be active. Also means if temp drops very low (12degC) at night boiler will have a burn.

I recon it should both be able to save on heating and make environment more comfortable.

Jim Chisholm

[fred]

In article , Jim Chisholm writes

Glad it worked for you.

I have one of these and didn't like some of the default settings:

1. It is set to cycle 6 times per hour which I just don't want, I want long slow burns (for efficiency) but the minimum cycle you can set it to is 3.

1. Minimum on and off times were 1min (I think). To me this is just daft, by the time the pipes are getting warm, it's cycling off again. Think I set it to 3mins minimum.

Other than that it does work well but I would have preferred if proportional control could have been turned off in some circumstances eg. when you have it set to control at a setback temperature of say

14degC I don't need it to cycle the boiler repeatedly to be exactly between 13.9 and 14.1, I'd be happy to have it broadly controlled between 13.5 & 14.5 and perhaps not cycle so much.

Just my thoughts but it is still prob one of the best and easiest to uses stats on the market.