Electric Water tank heater (inside a jewellers warehouse )

[Sav]

Hi everyone,
Just a quick one and for a bit of advise.

A friend of mine is currently decorating a small warehouse for a jeweller and has advised me of the following problem.

They have 7 tanks which they use for silver, gold and nickel plating. Inside the tanks they have a heater (similar to what you get in a gold fish tank, but slightly larger ).

The heater are 1000w (1kw ) and currently run from a 20amp double pole switch via a fuse carrier to the heaters. The fuse carriers have 3amp fuses inside. The problem he said was that the fuse carriers get really hot when the heaters are turned on (one actually scalded the inside of the fuse carrier ). I took a look today and this is the set up.

20amp RCBO from c/unit, 2.5 mm radial to the 1st fuse carrier, then linked to the others (7 in total ) and controlled by a 20amp d/pole switch and all the switches are in their own grids marked 1 to 7 . Not all heaters are 1kw, some are 400w. I called the company today who supply the heaters and the tech guy advised me to change the fuse to 13amp (3amp is too low anyway for 1000w heater I advised ) as the heaters require quite a bit of "juice" when heating up. I did this and it has helped, but is that correct, or is 13amp too high ??? Also, I think I will change the radial circuit into a ring and upgrade the RCBO to 32amps, that should help I think with regards to the "juicing of the heaters (tech guys words by the way ).

Thanks and regards,
Sav

 

[Spudnik]

The type of circuit wouldnt really affect the temp of the isolator.

Mind you, nothing would surprise me these days.

Also, when you push the plate back, try and dress the cables so there are no sharp kinks in them.

 

[rocker]

Another top tip is try and work all day... when they are locking up at night, try and spy the alarm codes. Simply email me the codes and hey presto!

 

[Sav]

Nice one Rocker !!!!

Just like the Italian job eh !!!lol

Now read the post and help me !!!! ( you were only supposed to blow the bloody doors off ) !!!
Sav

 

[UNG]

Sounds to me like everything is undersized if all the load is turned on at the same time. I am wondering what the volt drop is in the circuit as this would also have an effect on the loading and it is possible the 2.5 is on its limit. As you have said the 3A fuses are too small and should be replaced with 5A as a minimum

 

[malcolmsanford]

For me it all depends if these heaters are portable or fixed.

If fixed I would run surface conduit/trunking to FCUs and connect each unit up to an individual FCU. This way I would split the load over 2 circuits dividing it so to split what could be a 5kw load, which is quite a lot for a 32amp ring final circuit.

By runing surface and using FCU takes the RCD out of the circuit and an MCB can be used. Both circuits could be then perhaps 16amp and run in 2.5mm^ singles.

Just my way but sure therte are plenty of others

 

[Darkwood]

Also to give you understanding the heaters are probably thermostatically controlled in some way with a PID controller, this will allow the heating elements to run up to initial temperature until preset is reach then pulse the power into the elements intermittently to give accurate stable temp, so your 3amp fuses are overloaded at start up by 1.5times until temperature is reached but then power pulsed thereafter, so the overload doesn't last long enough to blow fuses using current/time curve but will get hot, then the pulsed power will stop the overloaded fuses from blowing, but agree with other post your supply circuit requires redesign in accordance with possible total load as all elements will be on together first thing.