Is this an unusual configuration of motorised valves?

[Question]

I have two motorised values in my heating system.  One is a three port and the other is a two port.  The three port has one flow pipe for the hot water and the other for the radiators.   I would have thought that was enough, i.e. be a Y plan.   However, there is also a two port valve between the three port and the hot water cylinder, and I can't understand why it is there.   Picture below shows flow of water and 2 and 3 port motorised valves. 

 

Can you see a reason for the two port motorised valve? 

 

 

[ProDave]

Is the 2 port normally open or normally closed?

 

Is there any other source of heat e.g. a stove?

[Marvin]

Hi @Question

 

I have never seen such a configuration. However it could be that the 3 port valve is not working or its the wrong type. Can you read the code on the 3 port valve? 

 

I have a 3 port valve that either supplies to one port or the other but not both however the norm is a mid position valve that when not energised supplies to both ports.

 

At the cable end of the 3 port valve there is the ability to prop the valve open it goes all the way to the right as you face the cable end and is then lifted up to latch it open. Is it latched?

 

and what @ProDave asked (see if you can see the code on the honeywell home valve)

 

Good luck

 

Marvin

[JohnMo]

10 hours ago, Question said:

One is a three port and the other is a two port

Sound reason for this.

 

Couple of assumptions you have an unvented cylinder and the 3 port valve is a mid point valve. A Y plan will be a mid point valve.

 

NOTE: mid point valve - No power - With no power applied, the spring holds the valve in position B, so water only flows to the hot water cylinder.

 

With a mid point valve to comply with G3 you need a fail close valve to protect the cylinder from the heat source. The 2 port should be a normally closed valve and energised to open.

 

Do not remove this valve, it ensures compliance with G3 regulations. All Y plan installs with an UVC should have this valve. S plan does not need the additional valve.

[Question]

23 minutes ago, JohnMo said:

Sound reason for this.

 

Couple of assumptions you have an unvented cylinder and the 3 port valve is a mid point valve. A Y plan will be a mid point valve.

 

NOTE: mid point valve - No power - With no power applied, the spring holds the valve in position B, so water only flows to the hot water cylinder.

 

With a mid point valve to comply with G3 you need a fail close valve to protect the cylinder from the heat source. The 2 port should be a normally closed valve and energised to open.

 

Do not remove this valve, it ensures compliance with G3 regulations. All Y plan installs with an UVC should have this valve. S plan does not need the additional valve.

Thanks very much.  I couldn't find a configuration like this when I googled (yes I have an unvented cylinder).   If I drain the system, would I put both valves manually into open?

Edited August 20 by Question

[JohnMo]

57 minutes ago, Question said:

 If I drain the system, would I put both valves manually into open

If draining, mid point when depowered moves to the open position for the cylinder and 2 port would need to be over manually. But drain the radiators etc you would move the 3 port valve position.