Help! New central heating system blows timeswitch every time

[brightspark19]

Hiya any help would be appreciated. I have just installed (electrically) a central heating system (Y-plan) and when I press the boost button on the timeswitch to get power to the boiler, it blows the timeswitch and trips off the circuit breaker in the DB.

I have double and triple checked that the connections are sound and going to the correct place.

The only difference between the diagram and my system is that the room stat on the diagram has three terminals and mine has 4.

I'd be grateful for any help - this is the first central heating system I've wired up from scratch.

 

[D_Hailsham]

The only difference between the diagram and my system is that the room stat on the diagram has three terminals and mine has 4.

Which thermostat do you have and what is each terminal connected to?

 

[Boilerman2]

It's my guess that you have put a Live wire onto the Neutral in the Room Stat (a common cock up!!)

 

[brightspark19]

The only difference between the diagram and my system is that the room stat on the diagram has three terminals and mine has 4.

Which thermostat do you have and what is each terminal connected to?

It is a Danfoss RMT230 - the one with 4 terminals

http://media.photobucket.com/image/rmt230/johnp68/rmt230.jpg

On the diagram it says T6360B which is a Honeywell with 3 terminals - could this be the problem?

I can't remember offhand which terminal went where, hopefully I haven't sent a live into a neutral terminal!

 

[brightspark19]

Hiya sorry to bump this, just hoping someone can tell me for definate, as I'm going back there at 7.30 tomorrow and I'd rather get it sorted tomorrow - I have it running on a timerswitch off the sockets at the moment (which, to be fair, does the job quite well).

 

[tamz]

Thermostat is wired 1 com 2 call 4 neut.

You have a dead short somewhere so try tracing it.
What does it trip with? HW or CH or both? If you find no trace of short you may have mixed the L & N on time switch. Clock will still display until you switch it. Easy done. Most timers are N L 1 HW off 3 HW on 4 CHon

Here are a few diagrams that will be handy to keep

http://www.honeywelluk.com/lib/pdf/Wiring-Guide-Issue-14.pdf

 

[brightspark19]

Handy collection of docs, theyve been favouritised.

I'm fairly sure now that it's because I'm using the wrong stat - I followed the diagram which said to take the neutral to number 2 in the stat, but on the stat I'm using the neutral goes to number 4, which is empty as the moment.

Will I have to go and get the correct stat or is there any way I can use this 4 terminal one instead, putting a 5-core flex in instead?

 

[tamz]

You are not using the wrong stat, just a different make. A stat is a stat just different connections. You might have done the stat in tho. Try it and see.

Just wire it as i have said. Change the wire you have in 2 (the neutral) to term 4
Term 1 (com) should join with the CH on from the time clock
Term 2 (call) should join with the white from the valve.
No need to change the cable.

Handy collection of docs, theyve been favouritised.

Don't just bookmark it. It's a PDF so save the file too.

 

[brightspark19]

Oh right I see and it just switches between the 2 and 3.

Nice one bud.

 

[tamz]

No it switches between the 1 and 2. The neutral (4) is just there to help it react faster to temp changes. It would still work without one.

 

[brightspark19]

What does the 3 do then?

 

[tamz]

On this particular stat, switch the heating on when it is hot and off when it cools. The opposite of what you want.
All stats can be wired to operate on temp rise or fall.