Y Plan + 2 port valve wiring

[AndyPRK]

Could someone please tell me the standard way to wire in this new requirement 2 port valve into a Y plan system please.


What is the plumbing alternative to not fitting one?

Thank you

 

[muggles]

Eh? What are you trying to achieve?

 

[AndyPRK]

Plumber wants to fit an additional 2 port value due ti new regulations.

I would like to see how it's wired in.

 

[stem]

A 'Y' plan system has a 3-port valve, which can only close off one outlet port at a time, meaning there is always one outlet port open.

If you then add an additional 2-port valve, when that valve opens for whatever it is supplying (you haven't told us what that is) and it switches the pump & boiler on, one of the outlet ports fed by the 3-port valve will also allow water to flow through it whether it is required or not. So, using a combination of 3-port and 2-port valves on the same system doesn't work. For multiple zones you would need an S-Plan.

So as muggles says, you need to explain what you are trying to achieve with this additional valve.

due ti new regulations.

What regulations are you referring to?

 

[picasso]

Its fairly common to have a 3 port and a two port on the same system, normally used when an old cylinder has been replaced by an unvented cylinder, megaflop used to print a diagram in there instructions on how to wire it up.

https://irp-cdn.multiscreensite.com/7d2b88c7/files/uploaded/megaflo he manual.pdf

 

[AndyPRK]

I'm having an unvented cylinder replaced with another due to leak.

I assume the 2 port goes to the HW but you tell me what the new method is

 

[stem]

I'm having an unvented cylinder replaced with another due to leak.

Ah good, some useful information at last. Based on your previous information (and probably because I have done one or two recently) I thought that you were splitting your upstairs and downstairs heating into two zones to meet the new building regulations. However now you have explained what you are doing, AndyPRK is quite correct.

 

[muggles]

I'm having an unvented cylinder replaced with another due to leak.

I assume the 2 port goes to the HW but you tell me what the new method is

Ah, got there in the end. Yes, the 2-port goes on the flow to the cylinder. You need a G3-Registered installer to fit the cylinder for you and register the installation with Building Control, it's not a DIY job. A competent installer will know how to wire it up correctly

 

[AndyPRK]

Yeah the only snag is that I modified the standard wiring a few years ago, so I would like to understand if the 2 port valve will work with my modified system or whether I need to convert it back. Trying to avoid giving the poor plumber a head ache

 

[AndyPRK]

https://irp-cdn.multiscreensite.com/7d2b88c7/files/uploaded/megaflo he manual.pdf

Thank you.
I think they just recommend 2x 2port valves.

It is probably a sensible way ahead.

I'll see if I can hunt a diagram down though

 

[picasso]

There is a diagram on page 22 showing how to wire up a 3 port and a 2 port.

 

[AndyPRK]

picasso or anyone. Could you please explain the requirement for this additional valve?

Would just like to know what they were trying to achieve?

Thank you

 

[flameport]

anyone

Prevents water flowing to heat the cylinder in the event of various failures. A standard 2 port valve will be closed due to a spring inside if power is removed or the valve motor fails.

Can't be done using a Y / 3 port valve as that defaults to HW open which could result in the cylinder being overheated.

 

[MeldrewsMate]

It's to isolate the heat input to the hot water cylinder. It means that the valve will fail to its closed position and stop the cylinder from overheating. I suppose the G3 regs people wanted to avoid overheating if a solid fuel heat source is used.

 

[AndyPRK]

So if the thermostat in the cylinder fails its still no help.

If the boiler decides to keep going (when not requested) this new valve will help. Somewhat unlikely failure mode.