Immersion Heater Switching/Absent Electrician

[pimpdaddydog123]

Hi chaps, I wonder if anyone has come across this before.

Customer has two old wylex fuse boxes with rewireable fuse, one board is for lighting, socket outlets, cooker etc and the other is economy 7 for immersion heater and storage heaters.

Customer wants both boards replacing but the previous electrician has wired the immersion to a 2 way switch so the customer can switch the immersion heater onto the main board to boost the hot water.

There is a neutral coming back to each board so obviously there are going to be issues with RCD tripping as it's currently using a shared neutral.

Are there switches available that will allow the user to power the immersion from the economy 7 board but switch to boost when needed and do it safely?

Thanks in advance!

 

[RandomGrinch]

Could the immersion heater element be changed to a twin element unit?
I.e.
https://www.cef.co.uk/catalogue/products/1144757-27-dual-element-twin-thermostat-immersion-heater

 

[bernardgreen]

Something like this

https://www.rapidonline.com/Europa-Components-LBC404P-Changeover-Switch-4-pole-40A-28-4370
Switch position 1..............2.........3
Pole 1............Live 1........OFF...Live 2.......to immersion heater
Pole 2............Neutral 1...OFF...Neutral 2..to immersion heater
Pole 3........... Live 1 to indicator lamp(s) ( useful to remind which supply or no supply ( position 2 ) is connected )
Pole 4 is a Spare ( cannot find a three pole version )

 

[EFLImpudence]

There are purpose made devices for two supplies to one element.

Horstmann Economy 7 Quartz being one.

 

[flameport]

If the E7 consumer unit is switched by the meter (so is only powered overnight), then the BX2000 is what you want.
https://www.tlc-direct.co.uk/Products/HOBX2000.html

2 supplies in, one from the E7 and one from the 24h consumer unit.
Single element connected.
Has a boost timer from the day CU for 1 or 2 hours, and will automatically use the E7 when that is available.
The two supplies are never connected together so no problems with RCDs.

 

[sparkwright]

I still envisage problems with there being a shared neutral.

 

[SUNRAY]

Assuming the 24hour side is cheaprate too, all that's required is a time switch on the 24 hour circuit and an override of some sort.

I have a Horstman E7Quartz unit (https://www.directtradesupplies.co....S4dQ6JhP1syco6j0_gvyPhb6wt3kYQMBoCjLsQAvD_BwE) in one of my rental properties does just this.

 

[SUNRAY]

I still envisage problems with there being a shared neutral.

There is no reason it could not be implemented using a pair of double pole, electrically and mechanically interlocked contactors, a timer module and a 'start' button.

 

[flameport]

That's basically what's in a BX2000.

 

[SUNRAY]

That's basically what's in a BX2000.

I'm sure it must be, the same is true of the Quartz too with the addition of a time switch and 1hr timer.

 

[333rocky333]

I still envisage problems with there being a shared neutral.

I dont get what he said though


"There is a neutral coming back to each board so obviously there are going to be issues with RCD tripping as it's currently using a shared neutral"

 

[EFLImpudence]

"There is a neutral coming back to each board

As it is written, I would think that means there are two neutrals.

"A neutral coming back to both boards" could be different.

The OP says the lines are wired to a two-way switch; does he mean a light switch?

Although if there are two lines - from separate boards - then surely there will be two neutrals available.

 

[SUNRAY]

As it is written, I would think that means there are two neutrals.

"A neutral coming back to both boards" might be different.

The OP says the lines are wired to a two-way switch; does he mean a light switch?

Although if there are two lines - from separate boards - then surely there will be two neutrals available.

I don't see any way of doing this safely without bringing neutrals from both boards to the heater, after that It all depends on whether it's a single pole or double pole 2 way switch.

Without further information from OP...

 

[333rocky333]

Ah, Maybe thats what he means, there are 2 unswitched Neutrals joined together and thus the load is shared between the two boards, hence the concerns about new rcds problems.
Thats an easy issue to resolve though.

 

[SUNRAY]

Ah, Maybe thats what he means, there are 2 unswitched Neutrals joined together and thus the load is shared between the two boards, hence the concerns about new rcds problems.
Thats an easy issue to resolve though.

Indeed linking neutrals between fuseboxes without RCD's was extremely common and E7 installations have traditionally been got at by DIYers as half the time they don't understand the system.