Underfloor Heating Help with a Y Plan system.

[chris202]

Hi all,

Literally just joined and to hopefully I can get some help with the following problem. I hope this will be a success!

I believe this is possibly a common problem, but hopefully there is a standard solution?

Ok, here goes. I have a one pipe system with a conventional boiler that is wired up exactly to a Y Plan design. The components are: Boiler, three way valve, tank stat, room stat, pump, programmer.

I have purchased an under floor heating kit that I have installed for just the kitchen heat supply. This consists of a separate pump, 2 way valve and a room stat and a manifold.

I have managed to find a wiring diagram to incorporate this in to the system but have a problem. I intend to wire the under floor heating side in as a completely separate system that can be used when everything else is off. The problem I have is when I wire into the switch live for the boiler (to fire the boiler), this connects the two pumps and in the case where the central or domestic water is not being heated, and the under floor heating calls for heat, this will send a live to the main pump and allow it to switch on. I can not see any other logical way of wiring so it does not do this.

This means the main central heating pump will be rotating but with no where for the flow to go as the three way valve will be closed (because neither the tank / room stat will be calling for heat).

I suppose I have two questions:

1) Is it ok to have the central heating pump rotating but with the three way valve closed and the flow going no where?

2) If not, how can I wire so the CH pump does not switch on when the under floor heating calls for heat. (I am thinking some sort of relay).

Any help would be very gladly received.

Thanks,

Chris.

 

[dcawkwell]

Hi all,

Literally just joined and to hopefully I can get some help with the following problem. I hope this will be a success!

I believe this is possibly a common problem, but hopefully there is a standard solution?

Ok, here goes. I have a one pipe system with a conventional boiler that is wired up exactly to a Y Plan design. The components are: Boiler, three way valve, tank stat, room stat, pump, programmer.

I have purchased an under floor heating kit that I have installed for just the kitchen heat supply. This consists of a separate pump, 2 way valve and a room stat and a manifold.

I have managed to find a wiring diagram to incorporate this in to the system but have a problem. I intend to wire the under floor heating side in as a completely separate system that can be used when everything else is off. The problem I have is when I wire into the switch live for the boiler (to fire the boiler), this connects the two pumps and in the case where the central or domestic water is not being heated, and the under floor heating calls for heat, this will send a live to the main pump and allow it to switch on. I can not see any other logical way of wiring so it does not do this.

This means the main central heating pump will be rotating but with no where for the flow to go as the three way valve will be closed (because neither the tank / room stat will be calling for heat).

I suppose I have two questions:

1) Is it ok to have the central heating pump rotating but with the three way valve closed and the flow going no where?

2) If not, how can I wire so the CH pump does not switch on when the under floor heating calls for heat. (I am thinking some sort of relay).

Any help would be very gladly received.

Thanks,

Chris.

The underfloor kit is pumped in effectlively as a big radiator driven
from the flow and return of the main central heating. You NEED the main central heating pump to switch on otherwise there will be no flow from the boiler. If you have plumbed in the underfloor before the central heating pump that isn't correct.
Look here for some diagrams and wiring

http://www.ukunderfloorheating.co.uk/technical/plumbing-and-wiring-diagrams/

 

[chris202]

Hi,

Thank you for the response, are you saying do away with the second pump I have installed PURELY for the under floor heating and then run the whole lot of just the one existing CH pump then?

You say no flow from the boiler but, currently, I thought there would be flow from the boiler as the underfloor heating pump should ensure this... no?

I still am concerned that if we run the central heating pump simultaneously with the under floor heating pump, the flow has no where to go. As it draws it through the feed pipe with both outlets on the 3 way valve closed it has no where to go.

Sorry, need some nursing on this one!

Thanks...

 

[D_Hailsham]

This means the main central heating pump will be rotating but with no where for the flow to go as the three way valve will be closed (because neither the tank / room stat will be calling for heat).

On a Y plan at least one port is always open.

If you want to be able to have only the underfloor heating on, you will have to replace the 3-port valve with two 2-port (S Plan).

Back to the drawing board!

 

[chris202]

Ah, Got you - thank you.

I may have to accept I have to run it with the rest of the CH; which I suppose isnt too bad!

Thanks again........

 

[dcawkwell]

Ah, Got you - thank you.

I may have to accept I have to run it with the rest of the CH; which I suppose isnt too bad!

Thanks again........

as default you will have underfloor and hot water without inserting a zone valve before the 3 port valve. best way to do it would be 3 zone valves