Cold water system connected to the CH system?

[hjalfi]

I have an elderly gas CH system and low-pressure cold water system feeding the bathroom. While replacing some radiators, I've noticed that if the cold-water system is switched on, then water continuously dribbles out of the bottom of the CH system (when the stop-cock's open, of course).

This strikes me as being wrong.

The only place where the CH system meets the hot water system is in the hot water tank, which is isolated (I've got the feed valve turned off because I don't want the sludge in the cold water tank drawn into the hot water tank). This means that the only other possible explanation I can think of is that there's a system in place to top up the CH fluid from the cold water tank system.

Has anyone ever heard of such a thing? Because I haven't, and it sounds decidedly suspicious to me. (If the CH system needs topping up it means there's a leak that needs seeing to!) Can anyone offer any advice?

 

[bripl]

try primatic if you only have one cwst

 

[CopperCylinderMan]

EITHER you have a leak in your coil in the HWC OR, as bripl says, its a 'single feed indirect' - primatic is a trade name (used a bit like 'hoover').

The heat exchanger (its not a coil) is designed to let the CWST fill both the cylinder and the CH system but not allow any CH system water back into the HWC.


http://www.mcdonald-engineers.com/assets/docs/Macmatic data sheet.pdf

http://rangecylinders.co.uk/products/primatic/index.html

Hope this helps.

 

[hjalfi]

Hmm. Thanks. The picture in the last link certainly looks familiar --- I'll check out what's written on the tank and report back.

Incidentally --- CWST? Cold Water Storage Tank?

There is another tank in the loft, that I assumed was the CH header tank; however, I haven't been able to reach it yet (it would involve a major expedition, including breathing mask, special clothing and getting hosed down afterwards). However, I don't know if it's actually connected to anything.

Is the hot water heating loop normally part of the CH system, or is it isolated and circulates seperately?

 

[hjalfi]

Is the hot water heating loop normally part of the CH system, or is it isolated and circulates seperately?

D'oh --- memo to future self: read both links before posting.

The boiler's control panel has seperate switches for CH and HW, and the heating cupboard has a number of valvey pumpy things. If this is a primatic tank, then I suspect the installer has been trying to be clever.

 

[hjalfi]

I do indeed have a single feed indirect cylinder. (Question: how does this approach avoid the need for an expansion tank for the CH fluid?)

However, I'm reasonably certain that my circuit doesn't look like the one in the diagram. There does seem to be a CH header tank, which is fed by two pipes that appear to run directly up from the boiler. There are some complicated valve and pump arrangments in the heating cupboard, and the boiler certainly believes it's supplying seperate hot water and CH feeds.

I think my system might be a bit bodged together...