Underfloor Heating And Combi Boiler System
- Thread starter davenellie
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you dont have an off signal to control the 3 port valve correctly
not if you know what you are doing and use a relay
but it is easier with the correct programmer to start with
well yer, but the numpties that installed it are having problems knowing what they are doing with a normal programmer, and stats
HTF would they cope with a relay???????
The whole point of the UH2 is it has its own programable room thermostats so you only require a trigger to call the boiler.
Most systems would use 2 X 2 Port Zone Valve's for each, so UFH and Rads with water on demand due to Combi or 3 X 2 Port for standard boiler, S Plan would be simple, Y Plan with 2 heating loops would be better with 2 X 2 Ports.
A Single Channel for rads and the UFH UH2 takes care of itself.
Most systems would use 2 X 2 Port Zone Valve's for each, so UFH and Rads with water on demand due to Combi or 3 X 2 Port for standard boiler, S Plan would be simple, Y Plan with 2 heating loops would be better with 2 X 2 Ports.
A Single Channel for rads and the UFH UH2 takes care of itself.
Do you have a make and model number for the valve?
davenellie
Active member
So, I gather from responses that a Y plan was always going to be difficult. And two port isolator to make s plan is what's called for unless you use complicated relays?
This will mean more plumbing to remove the 3 port and add at least one two port. Or can I just use the 3 port as a 2? If I could get the 3 port to use the MID position and UFH only I would have CH and UFH in Mid and only UFH when CH is off. As long as I can get the CH to return it to UFH only with the cancel signal??
I believe it's a Drayton BGMVSP-23 mid position valve
This will mean more plumbing to remove the 3 port and add at least one two port. Or can I just use the 3 port as a 2? If I could get the 3 port to use the MID position and UFH only I would have CH and UFH in Mid and only UFH when CH is off. As long as I can get the CH to return it to UFH only with the cancel signal??
I believe it's a Drayton BGMVSP-23 mid position valve
you will need to either alter the wiring to suit the 3 port valve, or replace it with 2x 2 port valve and alter the wiring to suit (but the wiring to suit S plan may be easier than Y plan)
davenellie
Active member
There's the thing, how do I alter the wiring to suit the three port valve I have. Instead of re plumbing and purchase of two port valves I don't have!
And is my builder going to cover the cost, since I still don't have a system that works?
And is my builder going to cover the cost, since I still don't have a system that works?
you should call someone who knows how to wire a heating system and they can design something to suit what you have. too many variables to plan much from here, but you are basically missing an off signal to the valve
you really only need the UH2 if you have more than 1 UFH zone,
other than that its pretty much a waste of money,
I fitted a load of them in flats where they had only wired for one stat, 4 zones, so everything had to be on at once, some rooms too warm, some too cold,
tried to explain to the electrical contractors , but apparently that is what the architect had specified, beggars belief sometimes.
the really easy simple way to do it is either
1 x 2channel programmer and 2 stats on a mid position valve
or
1 x 1 channel programmer and 2 stats with UFH permanently on a mid position
or, and this is better
1 x 2channel programmer and 2 stats on 2 x 2port valves
you could also have a 1channel programmer on 2 stats with 2 x 2ports with UFH permanently on,
personally it all depends if you want it to either
just work,
or
work properly and efficiently.
but, its not going to be a remote fix, you need someone on site to see just what cables you have going to where, and that actually knows what they are doing,
sounds like your builder and plumber are bluffing their way around this,
why on earth they have all those programmers/clocks is beyond me........
other than that its pretty much a waste of money,
I fitted a load of them in flats where they had only wired for one stat, 4 zones, so everything had to be on at once, some rooms too warm, some too cold,
tried to explain to the electrical contractors , but apparently that is what the architect had specified, beggars belief sometimes.
the really easy simple way to do it is either
1 x 2channel programmer and 2 stats on a mid position valve
or
1 x 1 channel programmer and 2 stats with UFH permanently on a mid position
or, and this is better
1 x 2channel programmer and 2 stats on 2 x 2port valves
you could also have a 1channel programmer on 2 stats with 2 x 2ports with UFH permanently on,
personally it all depends if you want it to either
just work,
or
work properly and efficiently.
yes, you can alter the wiring to get it to work with what you have,
but, its not going to be a remote fix, you need someone on site to see just what cables you have going to where, and that actually knows what they are doing,
sounds like your builder and plumber are bluffing their way around this,
why on earth they have all those programmers/clocks is beyond me........
I installed my own system a few years back.
Combi boiler.
2 x 2 port valves (s plan) 1 for downstairs UFH the other for upstairs radiators.
2 x single channel programmers -1 upstairs the other downstairs.
6 x thermostats for UFH
Works perfectly.
I cannot see how a Y plan will not work either. Could it be that you are using the incorrect type of valve (It is not the same valve as that which is installed inside the combi).
It can only be a wiring fault if the valve is the correct one.
Combi boiler.
2 x 2 port valves (s plan) 1 for downstairs UFH the other for upstairs radiators.
2 x single channel programmers -1 upstairs the other downstairs.
6 x thermostats for UFH
Works perfectly.
I cannot see how a Y plan will not work either. Could it be that you are using the incorrect type of valve (It is not the same valve as that which is installed inside the combi).
It can only be a wiring fault if the valve is the correct one.
a 3 port valve needs a DHW off signal to put the valve in the correct place. a the moment, there isnt one, so the valve will never work correctly
if you have 2 port valves as S plan, DHW off signal isnt req'd
if you have 2 port valves as S plan, DHW off signal isnt req'd
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I may have missed some points already covered..
or I may be repeating what has already been said...
Either way the crux of the problem as I read it, (and Step's & Andy have already pointed out), is that domestic heating wiring is NOT complicated..
as long as you understand what you want a system to do..
and you also understand how the components you have got work..
On the face of it it sounds like the builder/plumber & electrician all have either partial or no knowledge about how the controls/valves/stats operate..
A lot of builders/plumbers/electricians just want a drawing they can copy saying put blue wire here,
red wire there, yellow wire in another place etc.. etc..
I suspect they don't understand how a 3port mid position valve works or how it is controlled.
If you can get a few basic facts into your head you may be able to figure out for yourself what you need..
Consider a traditional Hot water & Central Heating set up...
As you don't need water cuz your combi will do that bit for you..
then as you suggest, you should be able to use the old hot water port for your UFH control...
1/ The 3port valve has letter designations on its pipe outputs 'A' & 'B'
'A' is connected to the heating system
and 'B' is connected to the hot water
(so you would need to make sure you have A-> rads b-> UFH)
2/ The 3port valve has two trigger input wires used to position the valve where you want it:
The White wire and the Grey wire.
3/ The 3port valve has one output wire to send a call for heat signal to the boiler:
The Orange wire.
4/ The 3port valve always lets water though in one of three combinations..
'A' only, 'B' only or 'A' & 'B'
Unlike a 2-port valve a 3port IS NEVER OFF preventing any water flow.
5/ With NO voltage on any of the trigger wires the 3port sits with the 'B' outlet open as the 'A' is closed by a return spring:
This is normally the hot water only position and the call for heat comes direct from the cylinder stat to the boiler,
bypassing the valve wiring (i.e. not via either white or grey wires!)
This you would need to configure to come off your UFH stat/programer..
6/ With a voltage only on the 'White' the valve moves to the mid position to supply both heating and water, ports 'A' & 'B' are both open.
The White wire would be trigged from your normal central heating thermostat..
House cold->voltage out from stat to White wire of 3Port.
(the white wire also outputs a call for heat to the boiler via the orange wire output from the 3port)
7/ With a voltage on BOTH 'White' & 'Grey' the 3port move motor drives the valve fully over to close 'B' and leave 'A' only open.. Heating only.
The White wire signal is still coming from the room thermostat for the bog standard heating..
The 'Grey' wire signal would be coming from either the water OFF or the cylinder stat tank already hot signal..
This is the bit Andy mentions..
You probably don't have a voltage input onto the 3port Grey wire when your UFH is OFF or floor already warm.....
UNLESS you have got the valve fitted arse about face & 'B' & 'A' are reversed !!??.
In all honesty it shouldn't take very long for a competent person with a test meter to suss out how it is currently wired and to amend it to get it working how you want..
The biggest problem with all remote heating problems is that..
There is NO standard colour code as how any one person wired their system..
so your red/yellow/blue or brown/black/grey 3 core cables could be using any of the colours for any of the trigger wires..
We cannot tell you what your colours are meant to be doing as we cannot see both ends of the cables!!
But you need:-
A voltage from your traditional heating stat onto the White of the valve when you want normal heating ON
A voltage from your UFH stat/programmer onto the Grey of the valve when the UFH is OFF or warm enough.
A voltage from the UFH stat direct to the boiler when you want the UFH ON and the floor is cold.
The Orange from the valve must be connected to the boiler call for heat.
If you cannot get these voltages with the existing controllers a simple relay set up should achieve what you want.
opcorn
or I may be repeating what has already been said...
Either way the crux of the problem as I read it, (and Step's & Andy have already pointed out), is that domestic heating wiring is NOT complicated..
as long as you understand what you want a system to do..
and you also understand how the components you have got work..
On the face of it it sounds like the builder/plumber & electrician all have either partial or no knowledge about how the controls/valves/stats operate..
A lot of builders/plumbers/electricians just want a drawing they can copy saying put blue wire here,
red wire there, yellow wire in another place etc.. etc..
I suspect they don't understand how a 3port mid position valve works or how it is controlled.
If you can get a few basic facts into your head you may be able to figure out for yourself what you need..
Consider a traditional Hot water & Central Heating set up...
As you don't need water cuz your combi will do that bit for you..
then as you suggest, you should be able to use the old hot water port for your UFH control...
1/ The 3port valve has letter designations on its pipe outputs 'A' & 'B'
'A' is connected to the heating system
and 'B' is connected to the hot water
(so you would need to make sure you have A-> rads b-> UFH)
2/ The 3port valve has two trigger input wires used to position the valve where you want it:
The White wire and the Grey wire.
3/ The 3port valve has one output wire to send a call for heat signal to the boiler:
The Orange wire.
4/ The 3port valve always lets water though in one of three combinations..
'A' only, 'B' only or 'A' & 'B'
Unlike a 2-port valve a 3port IS NEVER OFF preventing any water flow.
5/ With NO voltage on any of the trigger wires the 3port sits with the 'B' outlet open as the 'A' is closed by a return spring:
This is normally the hot water only position and the call for heat comes direct from the cylinder stat to the boiler,
bypassing the valve wiring (i.e. not via either white or grey wires!)
This you would need to configure to come off your UFH stat/programer..
6/ With a voltage only on the 'White' the valve moves to the mid position to supply both heating and water, ports 'A' & 'B' are both open.
The White wire would be trigged from your normal central heating thermostat..
House cold->voltage out from stat to White wire of 3Port.
(the white wire also outputs a call for heat to the boiler via the orange wire output from the 3port)
7/ With a voltage on BOTH 'White' & 'Grey' the 3port move motor drives the valve fully over to close 'B' and leave 'A' only open.. Heating only.
The White wire signal is still coming from the room thermostat for the bog standard heating..
The 'Grey' wire signal would be coming from either the water OFF or the cylinder stat tank already hot signal..
This is the bit Andy mentions..
You probably don't have a voltage input onto the 3port Grey wire when your UFH is OFF or floor already warm.....
UNLESS you have got the valve fitted arse about face & 'B' & 'A' are reversed !!??.
In all honesty it shouldn't take very long for a competent person with a test meter to suss out how it is currently wired and to amend it to get it working how you want..
The biggest problem with all remote heating problems is that..
There is NO standard colour code as how any one person wired their system..
so your red/yellow/blue or brown/black/grey 3 core cables could be using any of the colours for any of the trigger wires..
We cannot tell you what your colours are meant to be doing as we cannot see both ends of the cables!!
But you need:-
A voltage from your traditional heating stat onto the White of the valve when you want normal heating ON
A voltage from your UFH stat/programmer onto the Grey of the valve when the UFH is OFF or warm enough.
A voltage from the UFH stat direct to the boiler when you want the UFH ON and the floor is cold.
The Orange from the valve must be connected to the boiler call for heat.
If you cannot get these voltages with the existing controllers a simple relay set up should achieve what you want.
opcorn
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even better guide to how Y systems work
http://s26.photobucket.com/user/jimjohn2/media/threeportwiring.swf.html
http://s26.photobucket.com/user/jimjohn2/media/threeportwiring.swf.html
davenellie
Active member
Special location,
Thanks for your very clear description of how the 3port valve actually works. It's answered a lot of my missing knowledge. With what I have already working I should be able to work out which colours are at least signal wires. Looking at my diagram I think I'm nearly there anyway. (What do you think?)
The valve could well be reversed! It's something I've thought of but not checked yet. (Going to in a minute now I know which port should be water. )
Dave
Thanks for your very clear description of how the 3port valve actually works. It's answered a lot of my missing knowledge. With what I have already working I should be able to work out which colours are at least signal wires. Looking at my diagram I think I'm nearly there anyway. (What do you think?)
The valve could well be reversed! It's something I've thought of but not checked yet. (Going to in a minute now I know which port should be water. )
Dave
or do what we used to do in the olden days, :slap
put a 5amp switch on it......
put a 5amp switch on it......
davenellie
Active member
This is the airing cupboard with what I think is what!, plenty of space for a S plan I supose!
davenellie
Active member
Ok then, this seems quite simple to me! All I need is a signal from CH via from the stat via the programmer to the white valve wire or both white and grey. That will get the valve to the CH only or BOTH position when CH is finished sending signal valve should revert to W only. UFH stat just needs signal to boiler only. That way when CH has finished with boiler UFH can remain calling and the valve should revert to W port B only!
Looking at j box, I can see now why when CH stops valve remains at H because the UFH is sending signal to grey valve wire and only switching it off gets the valve to revert to W only!!
The grey signal wire could go to the orange terminal to signal boiler...
Is it that simple or am I over simplifying it??
Dave
Looking at j box, I can see now why when CH stops valve remains at H because the UFH is sending signal to grey valve wire and only switching it off gets the valve to revert to W only!!
The grey signal wire could go to the orange terminal to signal boiler...
Is it that simple or am I over simplifying it??
Dave
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