Confused about motorised valve setting

[lesyork]

Hi guys,

Just a curious student here, no knowledge of CH/DHW systems. We've got a two port zone valve on one of the hot pipes near the cylinder, but it's been set on the MAN OPEN position. Just wondering what the point of it is if someone's left it open? It's a 'normally closed' valve.

I only ask because the rads get hot when the water goes on, even when we don't want it to - no idea what type of system is installed, happy to provide pics of copper if that helps.

Many thanks.

 

[kevplumb]

post the pics then its either a c plan
s plan
or w plan
the w plan is a trick question btw

 

[lesyork]

I don't know what's relevant, forgive my ignorance

http://i.imgur.com/Fwifc.jpg
http://i.imgur.com/4NSfI.jpg

 

[kevplumb]

nuts thats where i left my henry

dont worry about ignorance bonny lad we all had to learn

whats the zone valve feedingthe 2 port on the left of your pic ?

 

[lesyork]

The zone valve (one on the right) doesn't feed the 2 port. The two port is fed by/to the cylinder boiler flow (not return) - this is the two port which is set to MAN OPEN. That seems odd to me, though probably makes perfect sense?

 

[matt1e]

Its likely to be installed as a safety device and it shouldn't be manually held open
I am presuming your cylinder is unvented

Matt

 

[lesyork]

It is unvented (Telford Tempest cylinder). Would a cock not be more appropriate than a motorised valve for safety?

 

[twgas]

Looks like you've got an unvented cylinder, which should be supplied by the 2 port even if there is a 3 port on the system. 2 port needs to be open to get hot water, if the 2 port has packed up (motor not working) then it would have to be opened manually, not the right thing to do as the 2 port is a safety device.

 

[kevplumb]

right if yer gonna do this silly thing shouldnt it be spring return

not an argumunt btw