Polypipe ZRU installation issue

[furtive]

Hi, this is my first post and I'm fairly clueless when it comes to plumbing.

My builder has installed Polypipe Overlay underfloor heating in my kitchen and has connected the ZRU to a separate flow and return from my boiler (so it is not part of the existing heating circuit. As he didn't put a flow control valve on the UFH circuit the floor gets hot when the hot water is on but not the heating, so he is going to add a 2 port zone valve to the flow before the ZRU.

My question is how will this need to be wired up so that the UFH can turn the boiler on when it calls for heat if the main heating circuit is not calling for heat.

I have got a Honeywell CM907 programmable thermostat on the main heating circuit which happily controls the boiler, and am going to get another one for the UFH zone which will be connected to the 2 port zone valve.

Do I need some sort or box to link the two thermostats up together so that they can both independently call for heat and fire up the boiler? Or do I just wire both the new 2 ports zone valve for the UFH and the existing one for the main heating to the boiler controller?

I have the heating controller set to be permanently on so that the programmable room stat controls the heating, but I want each zone to be able to independently control the boiler.

I hope all that makes sense.

 

[furtive]

Anyone?

 

[Norcon]

Your installer should know the answers to your questions.
Electrics are not something to play around with if you don't know what you are doing.
You say you are clueless with plumbing. So in all probability it will follow that you are clueless with electrics also.
Sorry but get some one in who knows what they are doing.
That won't necessarily be an electrician as quite a few of them are clueless with heating wiring also.

 

[furtive]

Thanks for the helpful informative post

 

[furtive]

That was sarcasm, by the way

 

[D_Hailsham]

How many motorized valves do you have at the moment (i.e ignoring the one for the u/f heating)?

Is the heating controller which is permanently on the timer built into the boiler?

 

[furtive]

Currently one motorised valve for the main heating circuit.

And the timer is not built into the boiler, it's a separate Danfoss unit

 

[D_Hailsham]

Currently one motorised valve for the main heating circuit.

Is it this type of valve (one inlet, two outlets)?

View media item 5946

And the timer is not built into the boiler, it's a separate Danfoss unit

OK

 

[furtive]

Yes

 

[D_Hailsham]

Yes

One outlet goes to the heating and the other to the hot water cylinder.

If you want to have a valve for the u/f heating, you will have to replace the existing valve with two valves like this (one in the existing heating circuit, the other in the hot water circuit). So you will need three valve in total.

View media item 11762
See the Sundial U plan on page 14 of the Honeywell wiring Guide

 

[furtive]

Sorry, the existing valve is a 2 port one like that. I need to add another 2 port one to the flow going to the UFH, but it's the wiring I'm not sure about.

I assume the existing valve will have a wire going to the boiler/timer. Can I have another wire from the 2nd UFH valve going to the same timer and connect them in parallel so that they can both call for heat individually?

Looking at those wiring diagrams it is an S Plan I have currently and an S Plan Plus system I should be aiming for. Or is it a U plan?

 

[D_Hailsham]

Have you read the Technical Installation Guide (click to download)?

There is a diagram at the bottom of page 44 showing how you plumb in so you can control rads and U/F separately. I assume this is what you want. It is just an S Plan Plus, you don't need the complications of a U plan.

If you look at the S plan plus wiring diagram in the Honeywell book, you will see that the valve has four wires. Brown and Blue control the opening of the valve via the programmer and room thermostat. Grey and Orange supply voltage to the boiler, via a microswitch in the valve, so the boiler runs when the valve opens.

You can run the rads and U/F from the same timer or from separate timers. You could also use separate programmable stats if you wanted.

The S Plan plus wiring in the Honeywell book uses a two channel programmer for the HW and one rad zone (with separate stats) and a programmable stat for the other zone. There are many options available, it's just which one meets your specific requirements.

 

[furtive]

Excellent, many thanks for your help.

 

[D_Hailsham]

Just a thought

You mentioned that you had a two port zone valve and assumed it was an S Plan. Can you confirm that you actually have two valves, one in the rad circuit, the other in the HW cylinder circuit?

 

[furtive]

Hmm, good point. Will have to have a look. There might only be one valve in the airing cupboard.