Wiring UFH system help

[alexm1992]

Hi guys,

I have a set up with rads upstairs and UFH downstairs. I have installed the manifold for the UFH along with 2x Honeywell 2port values, one near the manifold and the other on the radiator side. I will be using Nest 3rd gen thermostats to control both the upstairs radiators and downstairs UFH zones - 1 thermostat upstairs and 3 thermostats downstairs.

I am just getting my head around the wiring for the complete system and have put together a quick diagram to show where im at with things. Note that I have not yet shown the wiring of the actuators and heatlinks (for the nests) into the UFH wiring center (Danfoss FH-WC). Before I proceed with this I would like to check with you kind folks that what I am proposing so far wiring wise makes sense?

There are 4 questions/points on the attachment that I am unsure about, and of course if there is anything else which is wrong it would be great to know.

Thank you very much for any help provided 🙂

Parts/materials:

Danfoss FH-WC wiring center
Honeywell Home 2 port valve
Nest 3rd gen thermostat
Worcester 36CDI combi boiler

Alex

 

[ShaunCorbs]

1 correct link the lives

2
Brown your switch / call
Blue neutral
Green / yellow earth
Orange switch live
Grey perm live link to lives

3 answered above

Lr on your Worcester combi is your switch

 

[alexm1992]

1 correct link the lives

2
Brown your switch / call
Blue neutral
Green / yellow earth
Orange switch live
Grey perm live link to lives

3 answered above

Lr on your Worcester combi is your switch

Really do appreciate the quick response Shaun, thank you

I have made the amendments and attached again with the 2port valves connected to LR and perm live.
With the 2 port valve rad side the wiring does not make complete sense to me - the pdf will explain this better.

Does all the wiring so far look correct Shaun?

 

[ShaunCorbs]

1 needs to go into sl orange goes to the boiler / pump etc also you can’t have multi feeds need to feed it all off one fused spur

 

[fowlerboi]

Yeah the grey/brown being the wrong way is stupid, it still catches me out and have fitted loads of them.

Wiring diagram as per manual below. If you're using programmable room stats then ignore the programmer wiring and go straight to the stats. If you're using 2 separate programmers or twin channel then wire them between terminal 4 of the wiring center and the stats (or the equivalent using a new terminal in the box)

Whats the plug 4a fused in the top left?

I'll try and do my own drawing as I'm a little lost with yours (just the way my brain works)

What you're proposing to do only a small percentage of plumbers would normally do and a lot of electricians would say they can't do it because they don't understand it.

 

[alexm1992]

1 needs to go into sl orange goes to the boiler / pump etc also you can’t have multi feeds need to feed it all off one fused spur

Understood with the spur, I have changed this. Made changes to 2port wiring too, hope I follow you correctly - see attached.

Hopefully this is getting closer!

 

[alexm1992]

Yeah the grey/brown being the wrong way is stupid, it still catches me out and have fitted loads of them.

Wiring diagram as per manual below. If you're using programmable room stats then ignore the programmer wiring and go straight to the stats. If you're using 2 separate programmers or twin channel then wire them between terminal 4 of the wiring center and the stats (or the equivalent using a new terminal in the box)

Whats the plug 4a fused in the top left?

I'll try and do my own drawing as I'm a little lost with yours (just the way my brain works)

What you're proposing to do only a small percentage of plumbers would normally do and a lot of electricians would say they can't do it because they don't understand it.
View attachment 84000

Cheers Fowler! Glad i'm not alone with the confusion. I am only an apprentice electrician so it is a bit of a learning curve.

If its possible to do a drawing that would be amazing - Unless I have cracked it with the last version.
Its tricky but love to learn new stuff 🙂

 

[fowlerboi]

Not gone into details about how each control is wired but thats where the wires go between each.

The supply can go to the wiring center or the boiler depending on where it is. If it goes to the wiring center then the 230v out from the boiler can be made redundant.

I’ve done the diagram on how i would do it with an airing cupboard upstairs hence the wiring center would be there and why the ufh zone valve is wired off the ufh wiring center which would be next to it. Saving you just running a 5 core between the wiring center and ufh center. I’ve also forgotten the actuator wiring but thats straight forward. Anything written as LNE is all taken from 1,2,3 on the wiring center unless shown

Obviously duplicate zone 1 for the 3 zones, stats, actuators

Remember to remove the link from the boiler when using external controls

 

[alexm1992]

View attachment 84004
Not gone into details about how each control is wired but thats where the wires go between each.

The supply can go to the wiring center or the boiler depending on where it is. If it goes to the wiring center then the 230v out from the boiler can be made redundant.

I’ve done the diagram on how i would do it with an airing cupboard upstairs hence the wiring center would be there and why the ufh zone valve is wired off the ufh wiring center which would be next to it. Saving you just running a 5 core between the wiring center and ufh center. I’ve also forgotten the actuator wiring but thats straight forward. Anything written as LNE is all taken from 1,2,3 on the wiring center.

Obviously duplicate zone 1 for the 3 zones, stats, actuators

Remember to remove the link from the boiler when using external controls

This has helped me BIG time!!


I had removed that 230V supply from the boiler end as I realised that with my old circuit, if the spur was turned off the circuit was still energised... what a noob!

I have studied how your circuit works and compared to the one I was working on (attached). Fundamentally as far as I can see both work in the same manner. The exceptions I can see is that a seperate spur is currently feeding my circuit and you are using the boiler power, which makes complete sense. (I might make this change!)

My boiler and the 2port rad valve are next to one another in one room and quite some distance away is my manifold, which is next to the pump and 2 port UFH valve. There is a 2.5mm and also a 5 core cable between the two which I can utalise.

My next step is proably to tidy up my circuit and make it as efficent as possible with cables going to each component.

Regarding the link: I have attached a photo of the current boiler wiring, this is currently connected to an old honeywell thermostat which will be replaced with my nest heatlink. I premume the link that needs to be removed is already removed?

Last thing... Might be a stupid question but how does the hot water work?

Thanks so much

 

[fowlerboi]

The link has already been removed because of the external controls already fitted.

The link there is for the hot water which is operated by a flow switch within the boiler, the link stays in unless you have external controls to decide what times the pre-heat function works (pre-heat keeps the water in the heat exchanger hot to reduce time to get hot water to the taps, personally I have mine off because it wakes me up when it comes on.) You could use your nest for this.

It looks like it may be wise to have a wiring center next to the boiler and then take that 5 core across to the UFH.

Its definitely best practice to have one spur feed the lot so the plumber can isolate it safely to carry out work. You can add additional isolators and its common to put an isolator for the entire UFH, I typically see fan isolators for this because its 3 pole for the L/N/SL (terminal 10 in my drawing)

I was also wrong you only need a 3 core between UFH center and main wiring center.


To clarify your drawing;

Spur at the UFH is an isolator?

Personally I wouldn't be wiring straight into the boiler with the oranges, try and put a junction box or better the main wiring center next to the boiler. Try and keep just 1 cable going to the boiler if possible 2 max

Your grey on the UFH 2 port valve wants to be into a permanent live. You currently have the brown from the 2 port connected to the permanent live and going into the pump terminals of the UFH wiring center (basically a link wire) this looks like it should be removed?

2 port valve neutral wants to go to the main neutral not the one on the boiler relay (I think based on other wiring diagrams and presuming the boiler relay is acting as a SL to fire the boiler)

 

[alexm1992]

The link has already been removed because of the external controls already fitted.

The link there is for the hot water which is operated by a flow switch within the boiler, the link stays in unless you have external controls to decide what times the pre-heat function works (pre-heat keeps the water in the heat exchanger hot to reduce time to get hot water to the taps, personally I have mine off because it wakes me up when it comes on.) You could use your nest for this.

It looks like it may be wise to have a wiring center next to the boiler and then take that 5 core across to the UFH.

Its definitely best practice to have one spur feed the lot so the plumber can isolate it safely to carry out work. You can add additional isolators and its common to put an isolator for the entire UFH, I typically see fan isolators for this because its 3 pole for the L/N/SL (terminal 10 in my drawing)

I was also wrong you only need a 3 core between UFH center and main wiring center.


To clarify your drawing;

Spur at the UFH is an isolator?

Personally I wouldn't be wiring straight into the boiler with the oranges, try and put a junction box or better the main wiring center next to the boiler. Try and keep just 1 cable going to the boiler if possible 2 max

Your grey on the UFH 2 port valve wants to be into a permanent live. You currently have the brown from the 2 port connected to the permanent live and going into the pump terminals of the UFH wiring center (basically a link wire) this looks like it should be removed?

2 port valve neutral wants to go to the main neutral not the one on the boiler relay (I think based on other wiring diagrams and presuming the boiler relay is acting as a SL to fire the boiler)

Very interesting with the pre-heat function I wll look into this, it can take some time for hot water to start flowing 🙂

Wiring center next to the boiler is an interesting option, I will give it some thought. The thing I like about it been by the manifold is that the manifold is under the stairs, its a hidden space with lots of room to mount wiring center, heat links etc. At the boiler end, things are a lot more visible and there is not a lot of room. Will think it all through!

I have tidyed up the drawing and will take another look tomorrow including only taking one cable to the boiler which I think was a nice point you raised!

The spur at UFH was an isolator correct, this is now gone.

I have changed the wiring to the 2 port UFH valve and pump to the relays in the new drawing, Let me know if you think this is correct? I presume that when the heatlinks are eventually wired into each UFH zone bank that when one of the heatlinks at any zone 'calls' for heat it causes the relays to switch on which intern powers the 2 port valve (UFH), pump and it also sends a signal to the boiler for heat. Note that I have put a permanent link across the two L on both relays as they are volt free. Hopefully this is correct.

Again, thanks very much for your time 🙂

 

[fowlerboi]

The volt free part is beyond my knowledge but it doesn't look right.

Where is the adaptable box going to be placed?

Where is the fused spur?

Rest looks great, what are you using to do the drawings?

 

[alexm1992]

The volt free part is beyond my knowledge but it doesn't look right.

Where is the adaptable box going to be placed?

Where is the fused spur?

Rest looks great, what are you using to do the drawings?

I will try and work out if the volt free part is correct, if anyone knows, let me know.

I was planning on placing the adaptable box next to the boiler which is next to the 2port valve for the rads.

The boiler is connected to a fused spur so as L and N is fed from the boiler to the components the whole system is fused from this place.

I'm a designer and use Adobe illustrator day to day so I used this to do the drawings, it's not a specific software for circuit design but hopefully its good enough to communicate my lack of knowledge ha.

 

[fowlerboi]

Volt free looks fine now, its what I've used on a number of relays just didn't understand the terminology. L terminals have a link to the permanent live and the N is basically the switch live.

If the adaptable box is going near the boiler then that will effectively be your main wiring center. Run everything through here before the boiler. This will allow you to get the boiler cables down to 1

Actuators and heat link wiring is missing from the UFH wiring center but should be straight forward

 

[alexm1992]

Volt free looks fine now, its what I've used on a number of relays just didn't understand the terminology. L terminals have a link to the permanent live and the N is basically the switch live.

If the adaptable box is going near the boiler then that will effectively be your main wiring center. Run everything through here before the boiler. This will allow you to get the boiler cables down to 1

Actuators and heat link wiring is missing from the UFH wiring center but should be straight forward

This is perfect Fowlerboi - very clear diagram. I really am greatful for you expertise and time.
Attached is my final drawing, I have followed everything through and it looks the same as yours, do you agree?

The only thing to note is that I have used 5 core cable between the Heat link (rad side) and the boiler (via wiring center) This is so I have a core to connect the hot water SL 'call for heat' to the boiler incase I decided to use the pre-heat hot water feature you mentioned.

I think it is nearly time to go to the wholesalers to pick up some materials... exciting!

If there are any last min issues you can see let me know buddy!

 

[fowlerboi]

Good idea with the 5 core.

You need to have a 3 pole isolator for the UFH because that orange wire will be live in certain situations while the isolator is off and it would be dangerous for anyone working on it to assume its all isolated.

Are you hard wiring the nests or having them on a stand and charging via usb? If you're hard wiring you'll need to allow provisions for those cables too. T1 T2 on the heat link.

Other than that it looks good to go, I'm no electrician though so take that with a pinch of salt.

 

[alexm1992]

Good idea with the 5 core.

You need to have a 3 pole isolator for the UFH because that orange wire will be live in certain situations while the isolator is off and it would be dangerous for anyone working on it to assume its all isolated.

Are you hard wiring the nests or having them on a stand and charging via usb? If you're hard wiring you'll need to allow provisions for those cables too. T1 T2 on the heat link.

Other than that it looks good to go, I'm no electrician though so take that with a pinch of salt.

I think you meant a 4 core isolator, but you are definitely correct with this all 4 cables need isolating!

I will have 2 nests which can be easily hardwired. I will allocate a cable to power these and the other two will be on stands.

Many thanks 🙂 will send a photo when it's done!