Multi Zone heating problem

[Mark kennerley]

I have just had an extension completed with a separate UFH zone added meaning i have 1 zone for the radiators in the house and 2nd zone for the UFH.
Unfortunately it seems that when the UFH comes on it also turns the house radiators on too and they are uncontrollable meaning the house becomes a complete sweat box. I have had a 1 month period where it seemed to work all ok but then i bled 2 radiators and the problem has come back.
The plumber who installed the UFH has said that he thinks the return is in the wrong place. He has said ideally it should be behind the HW return but it is not there.
There seems to be no problem when the HW comes on and the 3 way port has recently been replaced.
I am hoping someone maybe able to offer either confirmation of what i am being told or another explanation, i am no longer certain that the original installation of the UFH has been completed correctly. Thanks very much.

 

[ShaunCorbs]

You need to change the 3 port for 2 2 ports

Also do you know where has he taken his pipes from ??

Any chance of a few pics of the install ?

 

[townfanjon]

I think we need some pics , you would put a 2 port on every circuit , and a seperate pump and mixer on your ufh

 

[townfanjon]

Hes done me again !!!! Lol

 

[Mark kennerley]

Thank you for your thoughts, the plumber also mentioned today changing the 3 port for 2 2 ports. I have attached photos of the pipe work I can see, not sure where he has taken his feed from, sorry bit dense in this field.

 

[ShaunCorbs]

You need to ask him where has he taken his feed from

If he's taken it from the rad circuit there's your problem

 

[Mark kennerley]

He has taken it from the primary flow

 

[Ric2013]

On the last photo, why does the 3 port feed a 2-port valve? Something to do with the unvented? Is that usual, anyone?

 

[PhoenixServices]

Yeah that’s usual for unvented as can’t allow the 3 port to continue flowing round the coil.

 

[Msk]

3 x 2 port valves needed
Htg htw ufh

 

[Mark kennerley]

Thanks everyone for the advice. How would 2 2 ports help and why does the system work sometimes and not others!?

 

[Ric2013]

EDIT Sorry, can't help as page formatting ruins my text base diagram.

 

[ShaunCorbs]

EDIT Sorry, can't help as page formatting ruins my text base diagram.

??

 

[Ric2013]

I tried to explain why a 2pv and a 3pv cannot do what 3 no 2 pvs would, but it relied on a sort of flowchart like you'd do an a typewriter, but the stupid computer thing made everything aline left, ignoring my intentional indenting, and I couldn't find the button to delete my post and I'm too tired to argue with a computer's idea of formatting, sadly.

 

[ShaunCorbs]

I tried to explain why a 2pv and a 3pv cannot do what 3 no 2 pvs would, but it relied on a sort of flowchart like you'd do an a typewriter, but the stupid computer thing made everything aline left, ignoring my intentional indenting, and I couldn't find the button to delete my post and I'm too tired to argue with a computer's idea of formatting, sadly.

I get what your saying and yep no way around it

 

[Mark kennerley]

I tried to explain why a 2pv and a 3pv cannot do what 3 no 2 pvs would, but it relied on a sort of flowchart like you'd do an a typewriter, but the stupid computer thing made everything aline left, ignoring my intentional indenting, and I couldn't find the button to delete my post and I'm too tired to argue with a computer's idea of formatting, sadly.

Thanks for trying anyway, do you think it will help the issue!

 

[Mark kennerley]

I think we need some pics , you would put a 2 port on every circuit , and a seperate pump and mixer on your ufh

Should this have been done with the initial UFH install?

 

[Ric2013]

Yes.

 

[leesparkykent]

The three port will always be open one way. When the UFH is calling the flow is also going around your rads. As said above changing to three two ports is the way forward. You only need the pipe work re-jigging and one more 2port as you already have one on the UFH and another on the HW.

 

[Mark kennerley]

The three port will always be open one way. When the UFH is calling the flow is also going around your rads. As said above changing to three two ports is the way forward. You only need the pipe work re-jigging and one more 2port as you already have one on the UFH and another on the HW.

Thanks very much, I will get that sorted ASAP, and thanks to everyone else you made comment. All I have to deal with now is the 130mm of screed the builders out on top of the pipes, not much I can do to change that!

 

[Mark kennerley]

What is the default resting position of the 3 port? It seems that when call for heating comes to the 3 port nothing happens but when HW is called for the port moves. Is this the wrong way round?

 

[Ric2013]

_Normally_ motors quietly to the heating position, with a noisy whee- pa! spring return noise to the hot water position.

 

[doitmyself]

What is the default resting position of the 3 port? It seems that when call for heating comes to the 3 port nothing happens but when HW is called for the port moves. Is this the wrong way round?

The ports of a mid-position valve are labelled: AB, A, and B. AB is the inlet, A the outlet to radiators, and B the outlet to HW cylinder.

When the valve has no power to it, it will be at rest with port B open. The status of the valve when powered depends on which wires are live and the sequence in which they are turned off.

White live: valve in mid-position (A & B open): CH and HW both on
White and grey both live: A only open: CH only on.

If CH is then satisfied, power is removed from the white but grey remains powered. This means the valve remains with port A open, so the rads will get heated, uncontrolled, as you have found out.

There are two ways of removing power from the grey wire: turn power off at the main switch, or a call for heat from the HW cylinder. As the first is not practical and the second cannot be guaranteed, the only solution is to replace the mid-position valve with two zone valves.

 

[Mark kennerley]

The ports of a mid-position valve are labelled: AB, A, and B. AB is the inlet, A the outlet to radiators, and B the outlet to HW cylinder.

When the valve has no power to it, it will be at rest with port B open. The status of the valve when powered depends on which wires are live and the sequence in which they are turned off.

White live: valve in mid-position (A & B open): CH and HW both on
White and grey both live: A only open: CH only on.

If CH is then satisfied, power is removed from the white but grey remains powered. This means the valve remains with port A open, so the rads will get heated, uncontrolled, as you have found out.

There are two ways of removing power from the grey wire: turn power off at the main switch, or a call for heat from the HW cylinder. As the first is not practical and the second cannot be guaranteed, the only solution is to replace the mid-position valve with two zone valves.

Brilliant explanation thank you, thought this would be the case but did not know why.