Can Immersion heater be supplied by mains plug?

[JohnW2]

Yes there own thermostat. The bottom one would continue heating.

It would, but have the two heaters would not do much to help the whole tank of water to heat up faster, since the top one would not often be 'on'.

Kind Regards, John

 

[AndyPRK]

If they switch on together with a cold tank they would each heat their surrounding water.

The top one switching off slightly earilier.
They wouldn’t fit them for no reason.

 

[SUNRAY]

I'm surprised at the lack of info that has come out so far.

https://www.cef.co.uk/catalogue/pro...x5mriAE8JpoK3Tl_PRUaApcrEALw_wcB&gclsrc=aw.ds
To name but one control device for dual heaters.

And a timer for E7 use and a boost for the top heater:
https://www.tlc-direct.co.uk/Produc...udlTXavfSHxJcfBvFj0Pei50sr79R_UoaAm77EALw_wcB

 

[JohnW2]

If they switch on together with a cold tank they would each heat their surrounding water. The top one switching off slightly earilier.

Water heated by the lower one would immediately rise to the top, hastening the switching off of the top one.

They wouldn’t fit them for no reason.

As I said, I have no experience of large unvented cylinders, so I don't know the reason. It might just be a means of getting some hot water available as quickly as possible when starting from cold - since, initially, both heaters would be on and the hot water from both would rise to the top and be available for draw off. However, as I've said, if the lower one is on, the top one will not stay on for long if it has its own integral thermostat.

With dual-immersion conventional (vented) set ups, the top one is normally used when one just wants to heat a relatively small amount of water, rather than the whole tank - although, as described above, if both were switched on together, that small amount of water would heat up to temp even quicker (hopefully roughly twice as fast!).

Kind Regards, John

 

[SUNRAY]

Water heated by the lower one would immediately rise to the top, hastening the switching off of the top one.
As I said, I have no experience of large unvented cylinders, so I don't know the reason. It might just be a means of getting some hot water available as quickly as possible when starting from cold - since, initially, both heaters would be on and the hot water from both would rise to the top and be available for draw off. However, as I've said, if the lower one is on, the top one will not stay on for long if it has its own integral thermostat.

With dual-immersion conventional (vented) set ups, the top one is normally used when one just wants to heat a relatively small amount of water, rather than the whole tank - although, as described above, if both were switched on together, that small amount of water would heat up to temp even quicker (hopefully roughly twice as fast!).

Kind Regards, John

Very unusual to use both high and low heaters at the same time, the supply is normally a single 16A [or even 13A] MCB or fuse for both heaters.

 

[ericmark]

Sorry Willis

and yes external heats from top down so longer you leave it on the more hot water you get.

 

[JohnW2]

I'm surprised at the lack of info that has come out so far. (click) ... To name but one control device for dual heaters. .... And a timer for E7 use and a boost for the top heater: (click) [/url]

This thread is, of course, not actually about dual immersions - it was an aside from Andy which started the recent exchanges.

However, yes, those two devices are for exactly the conventional use of dual immersions that I described - to use the top one to heat small amounts of water and the lower one to heat the whole tankful (particularly if/when off-peak electricity available). However, Andy seemed to be suggesting that the situation/purpose was different from this with large unvented cylinders.

Kind Regards, John

 

[SUNRAY]

Thid thread is, of course, not actually about dual immersions - it was an aside from Andy which started the recent exchanges.

However, yes, those two devices are for exactly the conventional use of dual immersions that I described - to use the top one to heat small amounts of water and the lower one to heat the whole tankful (particularly if/when off-peak electricity available). However, Andy seemed to be suggesting that the situation/purpose was different from this with large unvented cylinders.

Kind Regards, John

Sorry I've only seen the second page.

 

[JohnW2]

Very unusual to use both high and low heaters at the same time, the supply is normally a single 16A [or even 13A] MCB or fuse for both heaters.

You are again describing the conventional system, such as i have described. As I have just written, Andy seemed to be implying that things were different with large unvented cylinders - and, as I said, I have no experience thereof, and therefore don't know if that's the case.

Kind Regards, John

 

[JohnW2]

Sorry Willis - and yes external heats from top down so longer you leave it on the more hot water you get.

Ah, if I understand, that's not heating the water in the cylinder directly at all, As you say, it's heating the water external to the cylinder - so, when it enters the cylinder, it will, if course, rise to the top and therefore the water in the cylinder will 'get hot' (not 'be heated') 'from top down'.

That's essentially the same as if one has a cylinder with the heating happening externally in, say, a boiler or 'back boiler'.

Edit: I should perhaps have added a 'statement of the obvious' - that, no matter how, where or with what the water is heated (within or exterior to the cylinder), the water in the cylinder will obvious heat up 'from the top down', since the top is where the hottest water will rise to!

Kind Regards, John

 

[SUNRAY]

OK looked at the beginning of the thread now...

Others have already mentioned that 13A plugs will not sustain 3KW for extended periods and I will confirm that with the greatest of ease. It's not just due to the fuse rating but yes 13A plugs do fail with sustained 3KW loads.
Much better to use a 15A plug/socket or even a 16A if you can.

All of this aside I recall discussions in class when I did my 16th that plug & socket are not permitted for water heaters but I've not looked it up in the last 10 years.

 

[SUNRAY]

Scrub this, it relates to uninsulated heating elements

In 16th it says:

554-05-03 ... shall be directly connected to that switch without the use of a plug and socket...

This is of course totally impossible if the only source of power is a generator whos output is a socket.

 

[JohnW2]

Others have already mentioned that 13A plugs will not sustain 3KW for extended periods and I will confirm that with the greatest of ease. It's not just due to the fuse rating but yes 13A plugs do fail with sustained 3KW loads.

Indeed, and I was one of the people who mentioned that. However, it's not universal - I've seen immersions that have been powered via BS1363 plugs/sockets for years without any obvious signs of thermal damage.

Much better to use a 15A plug/socket or even a 16A if you can.

... but even better (and, as is the 'usual') not to use a plug/socket at all. Even if, as per the OP, there is a desire to be able to switch supply from the main installation to a genny, that can be done (hard-wired) with a changeover switch.

Kind Regards, John

 

[Bodgedbuild]

I used to have a sink/bath switch on my old tank and could get enough water for a quick shower in about 10 minutes. I'll take everybody's advice on not running a mains plug on a 3kw element though and probably plump for a 2.2 or even 1 kw one.
Thanks all.

 

[winston1]

OK looked at the beginning of the thread now...

Others have already mentioned that 13A plugs will not sustain 3KW for extended periods and I will confirm that with the greatest of ease. It's not just due to the fuse rating but yes 13A plugs do fail with sustained 3KW loads.
Much better to use a 15A plug/socket or even a 16A if you can.

All of this aside I recall discussions in class when I did my 16th that plug & socket are not permitted for water heaters but I've not looked it up in the last 10 years.

Kettles are water heaters?