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

 

[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!