Correct immersion heater size for 1050x450 cylinder?

27" is the normal size for a top entry IH
Tappy,

 

If you only fit a 12" immersion in the top it will still heat the entire cylinder.

If you want the cylinder heated in stages then a side arm willis is used.

 

Could you just run through the physics of that Ryluer, I'm a little confused.

 

Sorry, the physics of your first statement.

 

It was my plumber who told me this but he didn't explain why and I didn't ask him because I felt stupid enough.

 

I have 2 immersions in my cylinder. One 12" at the top and the willis side arm. The electrician will be fitting a manual change over switch (which I have asked for) that switches between either immersion.
Will be commissioned in a few weeks so will be able to see more accurately what is happening.

I suspect when a hot water cylinder has the top half at 70c and the bottom at about 20c and then left to stand for hours the top and bottom eventually mixes.

 

I suspect not! Mind you I have no idea what a willis side arm is, sounds vaguely military!
No, your plumber is stupid. The hot water sits at the top as it is less dense. That is why on all electric heating the boost immersion heater is near the top of the cylinder and the off peak is at the bottom.
So if the OP wants a cylinder of hot water he needs an immersion heater that extends to the bottom of the cylinder.

 

26 years in the trade so I suspect not.

 

The willis side arm heats from the top down.

 

YOu should ascertain what size of immersion you have fitted first.

 

But you don't know. My plumber says a 12" top entry immersion will heat the entire cylinder. This guy has been in the business 26 years.

 

Ryluer, are you the guy who has been in business 26 years perchance?
I googled your willis side arm and got hits on pop stars but no plumbing so what is this thing?
A top entry 12" immersion heater may well heat the entire cylinder, eventually, but in terms of your usual day to day requirements it can't possibly be fast enough. Your basic physics is against you - just ask Scottie.
"26 years in the trade so I suspect not" sadly the world's moved on so unless your plumber has kept abreast . . . .

 

My view is/was the same as yours. Till I had this guy in my home.

"Side arm" is a term used when the immersion or other heat exchange type device is external to the cylinder. Willis heating and plumbing invented this device and also the solar syphon.
I'll post an image when its finished. Would have been doing this myself but unable.

 

27" will do.
Just ask for a 27" immersion heater.

 

Side arm heat exchanger...

 

And works very well. Outputs @ about 65c straight to the top of the cylinder.