On/off peak immersion questions

[PaulWooder]

Hi, I have a Water tank with two immersion heaters. The off peak switch heats the bottom immersion and the on peak switch heats the top immersion. my problem is the top immersion does not give enough water for a bath in the evening. can I rewire the on peak wire into the bottom immersion heater too? So that when I do flick the on peak switch a whole tank is heated. I know this will cost me more but I need a tank full early evening. I have also purchased a timer so I was going to do the rewiring as above and put a timer on the on peak switch. any advice would be much appreciated.

 

[Mike Jackson]

Consult an electrician because you could potentially be allowing the bottom immersion to draw 6kW which could result in a fire.

 

[PaulWooder]

Thanks, would it be better to just rewire by wiring the on peak to the bottom immersion on its own Nd then using a timer to control it? Does the on peak switch shut itself off during economy 7 hours would you have thought?

 

[snowhead]

No you can't do as originally proposed.
The MCB feeding the top heater will trip, it and the cable and the switch are not rated for a total of 6kw (2 x3kw).

A timer won't help.

The simplest fix would be to swop the supply to the top and bottom so E7 off peak heats the top and on peak heats the bottom.

 

[snowhead]

Thanks, would it be better to just rewire by wiring the on peak to the bottom immersion on its own Nd then using a timer to control it? Does the on peak switch shut itself off during economy 7 hours would you have thought?

No it stays on

 

[steadyon]

If the cylinder is cold in the evenings because all the hot water has been drawn off by other users, then you might have to consider using the bottom (whole tank) immersion heater on full rate electricity, and using a timer to control the heating times as far as possible. You would have to have the cheap rate wiring disconnected from the lower immersion heater altogether.

If however there is a tank full of hot water at the start of each morning, and it is not used up by others by the evening, then the heat is being wasted heating the air. Additional insulation (being careful not to cover the immersion heater caps) might well provide evening hot water at little additional cost. If there is not a tank full of hot water at the start of each morning then the lower immersion heater or its thermostat may need replacement.

As Mike Jackson has said, connecting the two elements in parallel would create a draw of 6kw, which could not be satisfied by either on peak or off peak circuit alone.

 

[PaulWooder]

Thanks all. Very helpful.

 

[PaulWooder]

No you can't do as originally proposed.
The MCB feeding the top heater will trip, it and the cable and the switch are not rated for a total of 6kw (2 x3kw).

A timer won't help.

The simplest fix would be to swop the supply to the top and bottom so E7 off peak heats the top and on peak heats the bottom.

If I do this do you think I would have enough for two people to shower in the morning? Surely by convection the lower part of the tank would heat too over a 7 hour e7 period