Wiring Heaters to thermostat.

[V.Cassidy]

Hi all! My current dilemma:
What was three small offices is now one large one. So I have x3 DB's feeding x3 electric heaters on their own timers and built in stats. I need all 3 heaters on a single stat and timer to operate together and be tamper proof.
My thoughts are to stick all 3 on one 25A circuit, feeding the one thermostat with timer (password protected), that switches all 3 rads via single phase 25A 3 pole contactor. Any other recommendations?
Would the built in stats affect the operation of the single room stat?
Any help much appreciated.

 

[Wilko]

Hi - heater kW ?

 

[V.Cassidy]

Hi - heater kW ?

Ah 1kW each.

 

[Bobster]

Why not leave it as is? Will likely be more energy efficient.

 

[V.Cassidy]

The problem is the room gets far too hot as people constantly play with the built in stats, and so a single tamperproof stat is what has been asked for. ‍

 

[static zap]

Do think of some redundancy if stat fails , cold drafts past stats.
--2 stats in different locations minimum ?--
( Time ration heating as well ... stats if it ever gets too warm ? )

 

[davesparks]

Unless you fit heaters without built in thermostats you will have problems from the two thermostats being in series.

 

[static zap]

...... two thermostats being in series......

I'm not suggesting in series , but not having all eggs in one basket. Similar to Robs strategy.
If premises are large , air flows un-even ,local conditions will vary.

 

[TJ Anderson]

I'm not suggesting in series , but not having all eggs in one basket. Similar to Robs strategy.
If premises are large , air flows un-even ,local conditions will vary.

Dave meant the stat switching into the contactor coil will be in series with the integrated stats in the heaters.

I understand what you are suggesting too.....having 2 stats in parallel controlling the coil so that if either closes then it will bring on the heaters (if internal stats are closed).

OP, why not just have the password protected timer controlling the contactor and leave the heaters in place with their integrated stats. They will only then operate in the times permitted and the people in different areas can have it how they like it

 

[MJPD29]

Run them through the timeclock which switches the stat and then use stat to control contactors to bring on heaters

 

[V.Cassidy]

Ok thanks all so far. I've done a wiring diagram for the proposed set up. Could someone have a look to see if all looks ok before I put it forward?
Thanks​

 

[Charlie_]

You got it a$$ about face..
The thermostat should be switching the contactor, not the load

 

[V.Cassidy]

You got it a$$ about face..
The thermostat should be switching the contactor, not the load

Is that not what’s happenening here? Feel free to scribble adjustments.

 

[davesparks]

Is that not what’s happenening here? Feel free to scribble adjustments.

No, you've got a permanent live going to A1 so the contactor will be closed all of the time the mcb is closed.
Also I don't see any suitable fusing down for the coil circuit.

 

[Charlie_]

Is this a real life scenario or a college question?

 

[V.Cassidy]

Is this a real life scenario or a college question?

Real life

 

[Bobster]

We cant give out step by step instructions, its against forum rules sorry.

 

[V.Cassidy]

That's fine, thanks for pointing out the obvious mistake with the supply line to A1, think I've got it now. In regards to fusing though, it would just be a fused TB in line with supply and timer right, to protect the control circuit?