HW Calling heating gets hot

[johnmcgivern]

System y plan but megaflo unvented cylinder controlled by 2 port v/v.
Fitted new 3 port mid position v/v rads still getting hot when HW calling only.
Why this system has a 3port v/v instead of 2 off 2port v/vs I dont know.
Any suggestions.
Many thanks, John.

 

[linkyplumb]

Would of had 3 port originally, then megaflo added with its own 2 port. If it didnt have 2 port then 3 port springs back to hot water, not safe.

 

[cross thread]

2 port is a over heat cut off for safety,heat and hw controlled by 3 port.if you have changed the 3 port it may be a clock issue this will be easy to diagnose if you have a decent heating eng look at it

 

[J_N30]

What position is the the power head in when on HW demand. Is the system sludged? have you fitted the mid pos valve the right way round?

 

[johnmcgivern]

Hi Lads, thanks for replying.

Checked all voltages all ok on 3 port v/v.
When first fitted only hot water was supplied all ok.
Then call for heating all ok.
Then when HW calling valve is staying in mid position.
Why would programmer be at fault?
Customer said worked ok I only fitted 3 port v/v changed wire for wire double checked everything all voltages ok.

V/v right way round default to HW.
Apparently recently serviced by BG so assumed not sludged but could be but I cannot imagine a new 3port v/v would sludge up few hrs after installation.