Unvented wiring .

townfanjon · Apr 21, 2019

Strange request for Easter Sunday lol , its just in my head .
have any of you fine chaps got a wiring diagram for a y-plan with a new 2 port wired in for an upcoming unvented installation.
I usually change them to an s-plan but the boiler is miles away from the cylinder and would cause a load of work getting perm lives to the 2 ports .
Cheers in advance

EvilDrPorkChop · Apr 21, 2019

Creates more hassle than it's worth IMO. Have you checked the wiring, you usually have enough wires to do it anyway, especially if theres already a pump overrun.

Aire · Apr 21, 2019

Can you add a 2 port to a y plan? With the 3 port keeping one zone permanently open, what happens when the 2 port calls for heat? You'll get unwanted heating of a zone.

EvilDrPorkChop · Apr 21, 2019

Craig Watson said:
Can you add a 2 port to a y plan? With the 3 port keeping one zone permanently open, what happens when the 2 port calls for heat? You'll get unwanted heating of a zone.

Yes you can. It's on the HW side, so you can leave your 3 port in situ and have the 2 port for thermal cut out for the Unvented after the 3 port valve. It's doable but for everyone that i've come across it's not worth the hassle and easier just sticking two 2 port valves in.

Aire · Apr 21, 2019

EvilDrPorkChop said:
Yes you can. It's on the HW side, so you can leave your 3 port in situ and have the 2 port for thermal cut out for the Unvented after the 3 port valve. It's doable but for everyone that i've come across it's not worth the hassle and easier just sticking two 2 port valves in.

Ok, I get what your saying, but if the 2 port acts only as a thermal cut out, what happens when the cylinder stat on the first cylinder is satisfied but the thermostat on the second isn't? You could end up with unbalanced temperatures.

townfanjon · Apr 21, 2019

EvilDrPorkChop said:
Creates more hassle than it's worth IMO. Have you checked the wiring, you usually have enough wires to do it anyway, especially if theres already a pump overrun.

Ancient boiler pal , so no spare wires but just realised there must be a hw off wire , but really need 2

townfanjon · Apr 21, 2019

Craig Watson said:
Ok, I get what your saying, but if the 2 port acts only as a thermal cut out, what happens when the cylinder stat on the first cylinder is satisfied but the thermostat on the second isn't? You could end up with unbalanced temperatures.

I have never done it but a 2 port should be fitted on to a y plan unvented installation, yes a right pita

EvilDrPorkChop · Apr 21, 2019

townfanjon said:
Ancient boiler pal , so no spare wires but just realised there must be a hw off wire , but really need 2

If you've got a HW off wire then you're sorted. Change that for a perm live, you'll already have Neutral and Earth there, along with HW on and CH on.

It's when you haven't got a HW off wire that's the issue (So when they have to have HW and CH at the same time)

Aire · Apr 21, 2019

townfanjon said:
I have never done it but a 2 port should be fitted on to a y plan unvented installation, yes a right pita

So your not having 2 cylinders? Why do you have to a 2 port on a yplan when feeding an unvented?

townfanjon · Apr 21, 2019

EvilDrPorkChop said:
If you've got a HW off wire then you're sorted. Change that for a perm live, you'll already have Neutral and Earth there, along with HW on and CH on.

It's when you haven't got a HW off wire that's the issue (So when they have to have HW and CH at the same time)

I have not looked , I just thought of it as I was typing

townfanjon · Apr 21, 2019

Craig Watson said:
So your not having 2 cylinders? Why do you have to a 2 port on a yplan when feeding an unvented?

In case it goes *** up , spring return valve closes supply to cylinder

EvilDrPorkChop · Apr 21, 2019

Craig Watson said:
So your not having 2 cylinders? Why do you have to a 2 port on a yplan when feeding an unvented?

Part of the G3 regulations. Must have a thermal cut out, as a 3 port valve is always open in some form that doesn't meet the requirement.

See so many Unvented cylinders on 3 port valves, it's worrying! Had one where the High limit stat kept cutting out, so cylinder must have been about 85/90oc!

townfanjon · Apr 21, 2019

EvilDrPorkChop said:
If you've got a HW off wire then you're sorted. Change that for a perm live, you'll already have Neutral and Earth there, along with HW on and CH on.

It's when you haven't got a HW off wire that's the issue (So when they have to have HW and CH at the same time)

Wheres yer GS badge ??? Admin still in the boozer

EvilDrPorkChop · Apr 21, 2019

townfanjon said:
Wheres yer GS badge ??? Admin still in the boozer

Must be!

Aire · Apr 21, 2019

EvilDrPorkChop said:
Part of the G3 regulations. Must have a thermal cut out, as a 3 port valve is always open in some form that doesn't meet the requirement.

See so many Unvented cylinders on 3 port valves, it's worrying! Had one where the High limit stat kept cutting out, so cylinder must have been about 85/90oc!

Good to know, I suppose if I had my g3 I would have known that

EvilDrPorkChop · Apr 21, 2019

Anyway to answer the original question, just looking at a diagram you'd still need a perm live anyway for a 3 port plus 2 port.

townfanjon · Apr 21, 2019

EvilDrPorkChop said:
If you've got a HW off wire then you're sorted. Change that for a perm live, you'll already have Neutral and Earth there, along with HW on and CH on.

It's when you haven't got a HW off wire that's the issue (So when they have to have HW and CH at the same time)

I am no sparks , is it acceptable to use the one perm live and split to supply both 2 ports ? Assuming there is one lol

EvilDrPorkChop · Apr 21, 2019

Craig Watson said:
Good to know, I suppose if I had my g3 I would have known that

Many of the 3 ports that i've seen have been left in/fitted that had their G3 qualification.

It's daft really, the Manufactures instructions clearly state that a 2 port is needed, along with them sending one with the cylinder. If it comes with the cylinder then you'd be thinking I have to fit this thing!

Riley · Apr 21, 2019

townfanjon said:
Wheres yer GS badge ??? Admin still in the boozer

Ha ha

townfanjon · Apr 21, 2019

EvilDrPorkChop said:
Anyway to answer the original question, just looking at a diagram you'd still need a perm live anyway for a 3 port plus 2 port.

I cant find one anywhere lol

EvilDrPorkChop · Apr 21, 2019

townfanjon said:
I am no sparks , is it acceptable to use the one perm live and split to supply both 2 ports ? Assuming there is one lol

Yeah you can use the same live, you don't need separate lives for each valve.

townfanjon · Apr 21, 2019

EvilDrPorkChop said:
Yeah you can use the same live, you don't need separate lives for each valve.

Sound , after all this I am praying theres a Hw off wire , assuming yes I will go S-plan , cheers

EvilDrPorkChop · Apr 21, 2019

Here you go.

ShaunCorbs · Apr 21, 2019

wire the port valve into the stat but you need a neutral

EvilDrPorkChop · Apr 21, 2019

ShaunCorbs said:
wire the port valve into the stat but you need a neutral

Isn't as simple as that unfortunately. As the HW Stat on a 3 port fires the boiler when it's just HW only. If the heating was running on the 3 port (So Live on the Orange wire on the 3 port) , it would back feed and hold the HW 2 port valve open. Therefore defeating the object of a thermal cut out.

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Unvented wiring .

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