2 x 2KW Optical Wall Heaters tripping 20A MCB

[Revved Up Sparky]

Hello everybody. I am coming to the end of a big job, rewiring a 500 year old Anglican church. I have installed four 2KW wall mounted quartz optical heaters using two radial circuits wired in 2.5mm twin and earth and protected by 20A type B MCB's. The runs are quite long, maybe 30M each. The two heaters on each circuit (which have their own 13A FCU next to them) are switched on via a 20A DP switch near the consumer unit.

With each local FCU switched off you can flick on the 20A DP switch then switch on the heaters one at a time without any problems, however, when you flick the DP switch with both heaters in circuit the MCB trips. The same thing happens on both circuits. I have tested the IR and both circuits are clear.

Does anybody know if these heaters have high start up currents ?. The actual design current is 17.4 amps. I am wondering if fitting type C MCB's will fix this problem.

Any input gratefully received, thanks all.

 

[Andy™]

resistance will be lower when cold, so it would use more power until it heats up. how much extra power that is im not sure. but C type may be a fix if your Zs will comply

 

[Hefferl]

Could you not switch one of the FCUs off and measure the start up current for just one heater and then multiply by 2?

 

[PC Electrics]

If you've fitted a Hager board, you could fit a 25A mcb if your installation method will allow.

 

[Andy™]

bit OTT, but you could always use on delay timers...

 

[Manator]

[quote name='Andy

 

[revjames]

High start up current. Type C or a 25A (if it complies).

 

[kerching]

Not a help to you really but, back in the day T&E was not allowed in churches. It had to be Pyro or sometimes conduit. All listed in a book called 'The Lighting and Wiring of Churches' by church house publications. Also you could not use bare Pyro on new Oak, or drill beams, etc te ctec . Since it is Eons/EDFs/ Scottish Powers since I did a Church I was wondering if things have changed.....just curious....... :coat

 

[Revved Up Sparky]

Thanks for the comments. I will try the type C MCB's and hope the Ze is low enough to allow the Zs to comply. The DB is a Crabtree Loadstar so 25A MCB probably not an option. In my 20 years as a spark I've never known T&E to be prohibited from use in churches.

 

[revjames]

Thanks for the comments. I will try the type C MCB's and hope the Ze is low enough to allow the Zs to comply. The DB is a Crabtree Loadstar so 25A MCB probably not an option. In my 20 years as a spark I've never known T&E to be prohibited from use in churches.

And the rest...........

 

[batty]

Probably a heritage thing they generally are quite old so inconspicuous wiring is a must usually.

 

[Manator]

Not a help to you really but, back in the day T&E was not allowed in churches. It had to be Pyro or sometimes conduit. All listed in a book called 'The Lighting and Wiring of Churches' by church house publications. Also you could not use bare Pyro on new Oak, or drill beams, etc te ctec . Since it is Eons/EDFs/ Scottish Powers since I did a Church I was wondering if things have changed.....just curious....... :coat

You are actually correct, it used to all be pyro and was a stipulation on any tender. I think this rule has now been relaxed due to many reasons I guess.

 

[SLIPSHOD & SLAPDASH]

Stick an Rcd on it and dont worry about the Zzzzzzzz

 

[Phoenix]

You are actually correct, it used to all be pyro and was a stipulation on any tender. I think this rule has now been relaxed due to many reasons I guess.

I saw some installation work done in a church where no doubt this was specified on the tender and the installers obviously didnt use it often, It was a new board to feed new disabled toilet tucked away at base of bell tower stairs and new sockets and water heater circuit to coffee and biscuits serving area for the community events. Was a bit of a mess, all in red sheathed, poorly supported in some areas, thrown into bits of plastic 25x16 trunk in others, some places they'd wrapped red tape around the gland because they wanted to make up for a shroud they'd forgotton to put on, in the toilet a water heater spur had the MI comming in the back of the K/O box, pot sat in the back and was being pushed against by the back of the spur, not a single one of the terminations to an accessory had a coupler to provide a safe space for the pot. And to top it all, the new board was supplied by a poorly clipped bit of 10mm / 16mm twin (presumably they decided against trying to work with MI in this size) dogged in with the tails in the main board....

Might have the pics somewhere still if I can find them

 

[Revved Up Sparky]

Well I switched to type C 20A MCB's which did the trick and the Zs was within accepted limits.

 

[PC Electrics]

Well I switched to type C 20A MCB's which did the trick and the Zs was within accepted limits.

cool

 

[Revved Up Sparky]

Thanks PC and thanks to everyone who commented on this thread