draining down to replace motorised valve

[mickma]

I want to replace a two port motorised valve, Honeywell V4043, to the central heating circuit. The valve is on the top floor by the hot water cylinder. Do I need to drain the whole system or can I just drain the top floor? Must I latch the valves open during draining and refilling? Finally when the motorised body is removed is the valve left in open or closed position?
Thanks
Mickma

 

[jackthom]

I want to replace a two port motorised valve, Honeywell V4043, to the central heating circuit. The valve is on the top floor by the hot water cylinder. Do I need to drain the whole system or can I just drain the top floor? Must I latch the valves open during draining and refilling? Finally when the motorised body is removed is the valve left in open or closed position?
Thanks
Mickma

You are talking about removing the motorised body. If that's all you are replacing it isn't usually necessary to do any plumbing work.

To answer the question you only need to drain down the water to the level of the motorised valve and it's probably best if the valve is open when draining and filling.

The V4043H valve is normally closed until the motor is powered. The V4043B valve is normally open.