sink/bath immersion heater switches

[shackec]

I have installed a sink/bath immersion heater. The combined rating of the two elements is 5.5KW; drawing, perhaps, 22 amps. The standard, and readily available, sink/bath switch is rated at 20A. Does anyone know of a source of sink/bath switches with an higher rating?
I realise that I may have to simply replicate the sink/bath switch operation with two separate switches. If this is the case then, for neatness sake, I would like to use a 2 gang 32A rated switch. Does anyone have a source for one of these please?
While I am on this topic I have been asked to place a mechanical timer in the circuit to separately control the smaller element (2.7KW). Is there any reason why a typical 16A mechanical timer should not be used? I have an older model Grasslin MIL 72a which is think is rated 16A. (something I need to check!)
Look forward to hearing from someone; many thanks, Chas

 

[Taylortwocities]

I have installed a sink/bath immersion heater. The combined rating of the two elements is 5.5KW; drawing, perhaps, 22 amps

The two elements should never ever be energised at the same time. So your energy calculation is probably half, and your issue has gone away.
You would use a standard 20A switch for the purpose,

and only need one 13A supply from the consumer unit.

 

[JohnW2]

The two elements should never ever be energised at the same time.

... and the 'sink/bath switch' will presumably ensure that the two can never be on together.

If the stated desire to also include timer-control of one of the elements is in addition to having that element still controlled by the 'sink/batch' switch, that would obviously raise a number of issues.

Kind Regards, John

 

[shackec]

Thanks John, a very useful reply. I have re-read my correspondence with the immersion supplier. It is ambiguous ; he implied that when the "bath" is switched on there is a boost to the heating because of the two elements. However, it is likely,I suppose, that the "boost" comes from moving from a 2.7KW element to an 3.0KW element.
If the switch takes place after the smaller element has been operating then I daresay it would not take the larger element that long to heat the entire tank.
I can also see that it would be a simpler switch that switches from one element to another rather than switching from one to the two combined!!

It also means that I could place the mechanical time switch before the Sink/Bath switch so that the timer controls whatever power supply has been set for the heater

All-in-all a much simpler affair. Thanks again for your help.
Regards. Chas

 

[Taylortwocities]

Thanks John, a very useful reply.

My pleasure

 

[Harry Bloomfield]

However, it is likely,I suppose, that the "boost" comes from moving from a 2.7KW element to an 3.0KW element.

The boost comes from the length of the element, the longer the element, the more of the cylinder water contents is heated. Heated water rises, so the hot remains at the top of the cylinder. Sink is the shorter reach element, just heating the upper 1/4 part, bath heats the entire upper 3/4 of the cylinder.

 

[JohnW2]

Thanks John, a very useful reply.

It was really TTC - I merely qualified his useful answer.

I have re-read my correspondence with the immersion supplier. It is ambiguous ; he implied that when the "bath" is switched on there is a boost to the heating because of the two elements. However, it is likely,I suppose, that the "boost" comes from moving from a 2.7KW element to an 3.0KW element.

As has been said, the 'boost' is not anything to do with the power of the element (the difference between 2.7 kW and 3kW is trivial), nor the speed at which water would be heated - but, the longer element used in the 'bath mode' reaches closer to the bottom of the cylinder, and therefore heats nearly all of the water in the cylinder (i.e. enough for a bath), whereas in 'sink' mode it uses a much shorter element, which only heats a small amount of water at the top of the cylinder.

Roughly speaking, only the water in the cylinder above the end of the element will get appreciably heated.

If the switch takes place after the smaller element has been operating then I daresay it would not take the larger element that long to heat the entire tank.

As above, the 'sink' element will only have heated a pretty small amount of water, whereas the bath water will heat all of the water in the cylinder, so it could still take a substantial time - anything up to a couple of hours to bring all of the water up to temperature (depending upon size of the cylinder)

It also means that I could place the mechanical time switch before the Sink/Bath switch so that the timer controls whatever power supply has been set for the heater

Yes, there would be no electrical problem in doing that - but the user would then have to make sure that the sink/bath switch was always 'left' in the desired mode. If (per what you originally wrote) the primary desire was for the sink supply to be supplied by the time switch (which would make sense), they would need to be careful to always switch it into 'sink' mode after it had been used in bath mode - otherwise the timer would result in a whole tank of water being heated when they only wanted a small amount - with possible appreciable effects of electricity bills

Kind Regards, John