Double immersion hot water tank.

[Pauldicker]

Dear all,
Has anyone come accross a double immersion hot water tank. How did you supply it 2x16A circuits. Maybe a 32A circuit split into 2 with 2x 20A double pole switches. I have only come across singles before, so im trying to find the best solution as i only have 1 spare way at present.

 

[Pauldicker]

Im after ideas. I was simply asking if i could have run two radials from one mcb to two fcu but it sounds like i may have to run a 4 or 6mm cable to i fcu and then 2.5 from that to a second.

 

[westward10]

Run a radial to a small consumer unit then two 16A radials.

 

[Deleted member 26818]

I would run a 6mm2 cable to an adaptable box with some connector blocks, then two 2.5mm2 cables to two SFCUs.

 

[telectrix]

nothing wrong with feeding 2 x 13A SFCUs with a 32A circuit (4.0mm) and then feeding each element in 2.5mm.

 

[Wilko]

These 2 element ones do get used in shops/restaurants to get more hot water volume. If it's that use, then it warrants a little over specing in my view as they will likely run them continuously. I'd like to put each on their own B16 / 2.5mm / isolator / 2.5mm heat flex if possible.

 

[GBDamo]

These 2 element ones do get used in shops/restaurants to get more hot water volume. If it's that use, then it warrants a little over specing in my view as they will likely run them continuously. I'd like to put each on their own B16 / 2.5mm / isolator / 2.5mm heat flex if possible.

Even though the Immersion heaters are for back up I agree with over speccing it.

Whatever fancy piece of kit is supplying the primary hot water, when it fails businesses are unlikely to fix it immediately. Then this temporary situation gets forgotten about and become permanent until they burn the elements/stats out.

Personally I like 4/6mm to a small DB then two 2.5mm radials from 16A MCBs to 20A DP switches. If kept local to the cylinder it's all obvious in the event of breakdown.

Done something similar to supply a three element tank.

When called out all three elements were on individual FCUs all off the same 6mm cable. Every FCU was burnt out in the terminals due to poor termination, all back boxes smashed and all the FCUs were loose on the wall.

Used the 6mm to feed a DB, then 2.5mm radials to 20A DP switches.
Also upgraded the final flex as was only 1.5mm running through an insulated wall, managed to pull the insulation out through the back box holes and use 2.5 3093Y flex.

In the end a much easier job for £60 in parts.

 

[Pauldicker]

Even though the Immersion heaters are for back up I agree with over speccing it.

Whatever fancy piece of kit is supplying the primary hot water, when it fails businesses are unlikely to fix it immediately. Then this temporary situation gets forgotten about and become permanent until they burn the elements/stats out.

Personally I like 4/6mm to a small DB then two 2.5mm radials from 16A MCBs to 20A DP switches. If kept local to the cylinder it's all obvious in the event of breakdown.

Done something similar to supply a three element tank.

When called out all three elements were on individual FCUs all off the same 6mm cable. Every FCU was burnt out in the terminals due to poor termination, all back boxes smashed and all the FCUs were loose on the wall.

Used the 6mm to feed a DB, then 2.5mm radials to 20A DP switches.
Also upgraded the final flex as was only 1.5mm running through an insulated wall, managed to pull the insulation out through the back box holes and use 2.5 3093Y flex.

In the end a much easier job for £60 in parts.

Sounds like a plan. Although its a Domestic property.

 

[Toneyz]

Never come across a horizontal cylinder before but I would have thought it would be the same as a conventional cylinder. Have you googled the MIs?

It is if you google Megaflow

only seen one once during a loft conversion and it was put into the dormer/eaves part.

 

[Toneyz]

If this is only for domestic back up depending upon the elements in the horizontal cylinder you could consider an MK (or some other manufacturer) sink and bath switch

As this should only be used for a few days until boiler repaired.

 

[GBDamo]

Sounds like a plan. Although its

If this is only for domestic back up depending upon the elements in the horizontal cylinder you could consider an MK (or some other manufacturer) sink and bath switchView attachment 47550

never seen one of they before, what it's for?

 

[Toneyz]

never seen one of they before, what it's for?

You have one supply 16A left switch is D.P isolator and the other switches between the two elements usually it is used with vertical cylinders where the top element heats the top of tank enough H/W
for a couple of sinks.If it is switched to the bath it heats the whole cylinder as I posted I don't know if it works in a horizontal.

 

[MJPD29]

I thi k 2x 16a radial circuits would be the best option I my opinion. Do a lot of work in a restraunt where they have wired 6 immersion heaters in 3 tanks, each 2 split over a 6mm cable on 32a mcb. Switches keep burning out as they are in 24/7 and terminating 2x6mm cables into a switch is a nightmare

 

[GBDamo]

You have one supply 16A left switch is D.P isolator and the other switches between the two elements usually it is used with vertical cylinders where the top element heats the top of tank enough H/W
for a couple of sinks.If it is switched to the bath it heats the whole cylinder as I posted I don't know if it works in a horizontal.

I get it, but it wouldn't work with a horizontal as the upright relies on the fact heat rises to allow the top element to heat a relatively small volume of the tank.

With a horizontal the elements are too close together to allow this effect to work.

 

[Toneyz]

I get it, but it wouldn't work with a horizontal as the upright relies on the fact heat rises to allow the top element to heat a relatively small volume of the tank.

With a horizontal the elements are too close together to allow this effect to work.

Then that's a fair point in this situation as posted I wasn't sure upon the element layout.

 

[Pauldicker]

If this is only for domestic back up depending upon the elements in the horizontal cylinder you could consider an MK (or some other manufacturer) sink and bath switchView attachment 47550 As this should only be used for a few days until boiler repaired.

I see what your saying. But will this work both 3Kw elements or just one requiring two switches. And is it rated as a 40A switch if both elements are working.
Ive not seen this switch before.