broken thermostat?

[paul b b]

hello all,

customer phoned to say they thing there stst is broken, i just wanted to confirm any checks to do to confirm.

do test for voltage between L & SL ?

many thanks

paul

 

[sellers]

i'd say try incoming live, then turn stat up and see if it clicks in and outgoing switch live becomes live.

went to one of these a couple of weeks back, cable had come out of central heating junction box.

 

[paul b b]

thanks sellers,

now did the old stats only have twin & earth? do i need to replace stat for one the same if so? or can i 'link out' on a stat that is for use with 3C & E

 

[Theorysparky]

I would replace like for like,,,i keep one of each

had a problem like this a few weeks back,,,no volts at stat,,it turned out to be programmer

so need to check

volts on incomer of stat when call from programmer

volts on output on stat selection

check valve opens for demand and boiler fires up

 

[sellers]

im not 100% clued up with boiler controls, but the ones i've used need a 3core, L+N in, and SL out, which mean the stat must be electrically controlled.

I guess stats with a 2core must be mechanically switched with just a live in and switch live out, someone will probably be able to confirm this.

 

[paul b b]

I would replace like for like,,,i keep one of eachhad a problem like this a few weeks back,,,no volts at stat,,it turned out to be programmer

so need to check

volts on incomer of stat when call from programmer

volts on output on stat selection

check valve opens for demand and boiler fires up

oh bugger its getting complicated now lol

how do i check valve opens?

also, do i need to do a MWC?

thanks

 

[ProDave]

The 3 core to most stats is to provide a neutral to power an "accelerator heater" that reduces the hysteresis of mechanical thermostats.

If you only have 2 core & earth, with no neutral, than just leave the neutral terminal in the new thermostat disconnected, but there will be a noticeable temperature difference between it turning off, and back on again. If you do only have 2 wires, best to fit an electronic thermostat as that won't have the same hysteresis as a mechanical stat.

 

[paul b b]

thanks chaps, should i go with honeywell?

 

[sellers]

thanks dave!

To check valves they have a little lever for manual operation, when they are being operated under normal use the levers will go slack.

Call for heating and check power to the stat first, and check the outgoing becomes live.

 

[paul b b]

thanks, the outgoing will be the blue sleeved brown right? though i suppose i could turn it down see witch is live so the other is switch live?

errr, basic question coming, to test voltage i would need a netral? or would it work live to live? i have a T100 so little led lights up when probe is on live terminal but not the amout of volts shown un less othere end is connected to N. confusing myself now

is this 12V or 230?

thanks chaps

 

[sellers]

a neutral or an earth. if you've got neither then put your probe on the nearest socket, switch or rad (if its earthed)!

 

[Lurch]

thanks, the outgoing will be the blue sleeved brown right? though i suppose i could turn it down see witch is live so the other is switch live?errr, basic question coming, to test voltage i would need a netral? or would it work live to live? i have a T100 so little led lights up when probe is on live terminal but not the amout of volts shown un less othere end is connected to N. confusing myself now

is this 12V or 230?

Hmm, maybe you should turn the job down.

Cable could be any colour, but a bit of common sense will tell you what's what, if it's troubling you and you feel unsure don;t do it. Also, how do you test voltages, not going to respond to that.

 

[batty]

Siemens stats only need two core and earth.

 

[paul b b]

sorry lurch, lack of sleep and thinking to hard, once i go to look i'm sure all will make sense! just confusing myself thinking about it before i have seen it so dont know whats what,

thanks chaps

 

[Lurch]

Don;t overthink it, it'll only muddy the waters. All you need to do is use common sense and methodically test what's what. I've spent hours on some heating systems trying to trace cables and faults, just make sure you have the relevant diagrams and you should be fine.

 

[sellers]

go to honeywells website and print out all the different plans for wiring, then if your fault is deeper you will be able to trace it properly. I always keep some copies in the van

 

[paul b b]

thanks sellers will do that