2 port valve no hot water nest thermostat

[Denis00]

I have a y plan system with an additional two port valve because i the hot water water tank to unvented cyclinder, installed a nest thermostat but with the two port valve connected hot water doesnt work, when removed and it then works. How can i include the two port valve the system amd stillvhave hot water?

 

[Wilko]

Hi - I’m a bit lost as to why there is an additional 2 port valve, sorry.
But you can manually open the 2 port valve with it’s lever (pop it into the retainer at the end of its travel or it will close again due to the return spring). This holds the valve open and water will move in the boiler pipes to heat the hot water tank when the 3 port valve permits.

 

[Denis00]

I have a y plan system with an additional two port valve because I had changed the hot water water tank to an unvented cylinder, The problem i have is when I installed a nest thermostat i get no hot water but with the two port valve disconnected hot water the hot water works. How can i include the two port valve the system and still have hot water?

 

[Denis00]

Hi - I’m a bit lost as to why there is an additional 2 port valve, sorry.
But you can manually open the 2 port valve with it’s lever (pop it into the retainer at the end of its travel or it will close again due to the return spring). This holds the valve open and water will move in the boiler pipes to heat the hot water tank when the 3 port valve permits.

Sorry for the typo in the original question its because I changed the hot water tank to a unvented cylinder,

 

[James]

I think a diagram of the setup sketched out would be helpful.

 

[Sparkingmad]

Denis if you have added a 2 port valve because on the unvented hot water cylinder is it because it was included in with the cylinder? Only asking because my one had a 2 port valve in with it. Did you need to have the valve as you already have a 3 port valve installed? Is the cylinder in the same place as old one or moved location? Can you not replace 3 port valve with 2x 2 port valves incorporating your new one on cylinder?

 

[Timbo]

Post a sketch of how you have wired it up.

 

[Zerax]

How can i include the two port valve the system amd stillvhave hot water?

Why do you want a 2-port valve in a Y Plan system ?

 

[Timbo]

Why do you want a 2-port valve in a Y Plan system ?

It's a G3 requirement, the y plan doesn't shut off the water flow to the cylinder under fail condition.

 

[Zerax]

It's a G3 requirement, the y plan doesn't shut off the water flow to the cylinder under fail condition.

I thought the requirement was that the cylinder couldn't be heated to >100°C... but if the MIs deem you need one... have you checked out John Ward's wiring diagram;

 

[Zerax]

I'd make sure that you have some sort of bypass on the boiler flow/return if you intend to create a situation where the boiler might be pumping to nothing. Some boilers have this built in.