zone valves on s plan

[Readingplumber]

Hi quick question -

I notice honeywell do 2 types of 2 port zone valves

normally open and normally closed

Am i right in saying for a heating system the normally closed is the right one?

Also when would a normally open one be used?
Thanks!

 

[Toddyplumb]

Normally closed for a standard S plan.

 

[BLOD]

Normally open = valve open if power is cut so makes it safer when using solid fuel

 

[tamz]

Normally you would use a normally closed valve but, if you were fitting one to a solid fuel system, normally you would fit a normally open valve as the heat source can not normally be shut off.
That is the normal way of doing it