Draining down a sealed unvented direct cylinder

[Count de Monet]

I have an unvented hot water system (all electric home with storage
heaters for central heating)

The hot water cylinder is a Kingspan Range Tribune TD180 with two
immersion heaters. The lower heater (off peak) has failed. I have
replaced a few top mounted heaters in the past (I'm a sparks) but never
on a sealed system.

It looks like I can isolate the cylinder from the rest of the cold water
system. Is it enough to close this valve then open the drain cock to
drain the cylinder. Then change the immersion heater, re-fill the
cylinder and open a couple of hot taps to vent any air.

A couple of pictures of the system can be seen here:

http://usera.ImageCave.com/Barneyrubble/Cylinder.jpg
http://usera.ImageCave.com/Barneyrubble/Cylinder1.jpg

Any help would be appreciated

Martyn

--
If you don't like your job you don't strike. You just go in every day,
and do it really half-assed. That's the American way!!.

Homer Simpson

[Heliotrope Smith]

"Count de Monet" <zen98NO...@zen.co.uk> wrote in message
news:4a87e8c7$0$2493$db0f...@news.zen.co.uk...

> I have an unvented hot water system (all electric home with storage
> heaters for central heating)
>
> The hot water cylinder is a Kingspan Range Tribune TD180 with two
> immersion heaters. The lower heater (off peak) has failed. I have
> replaced a few top mounted heaters in the past (I'm a sparks) but never
> on a sealed system.
>
> It looks like I can isolate the cylinder from the rest of the cold water
> system. Is it enough to close this valve then open the drain cock to
> drain the cylinder. Then change the immersion heater, re-fill the
> cylinder and open a couple of hot taps to vent any air.

You are correct. Shut off the supply to the cylinder and drain down, fit
the new immersion heater and refill with a hot tap open at the same time
until water comes out air free.

[The Natural Philosopher]

Remember it wont drain unless air can get in, so open a hot (or cold!)
tap as well..

Or indeed, flush a loo..

I turned off the mains, and set to work on the hot system, opened hot
tap. some came out. Then flushed a loo downstairs, and flooded the
bathroom! Once the mains side could suck air in, down came all the water
from the loft mounted tank!