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Discuss Care home UFH wired incorrectly in the Water Underfloor Heating Installations area at PlumbersForums.net

I’m an electrician, a plumber has asked me to look at wiring in a care home for UFH with a system boiler.
Only way to get it to work is run everything constantly.
The wiring center was a mess, i’ve rewired and now working as expected.
However, it appears to me there is an unnecessary valve. On the heating side there is a master valve (S-Plan), then behind this two manifolds with thier own valves. The master valve was wired to be constantly open.
I’ve rewired for it to only open when one of the UFH valves is calling for hot water.
I’ve been told UFH was installed by one company and boiler by another. So I wonder if boiler engineer installed S-Plan, and UFH just fitted to this.
I can’t see any reason for the master valve (S-Plan). I’m gonna suggest to plumber to remove as I just can’t see any reason for it and I think this will simplify installation, what do you think, am I missing something.
To be clear I’m ignoring hot water in this post, that all works fine.
 
Photographs might help if you have any?
Unfortunately I’m not back for a while, but photos probably won’t help anyway as the installation is spread out across the property.
To put it another way, the installation has two valves in series. Is that normal with UFH?
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Zone valves wired in series ?
 
Here's a brief diagram, hopefully this makes more sense than my text.
To recap, I don't see why you need a "Master Valve"

20190226_074439061_iOS.jpg
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
You sure it’s not a 3 port would make sense
 
You sure it’s not a 3 port would make sense
When you say "3 port" I guess you are referring to Harvest Fields suggestion as opposed to a 3 port valve?

It would then make sense if this was the case. I will double check when I am back, but I was lead to believe there is only UFH.
If this is the case, do you agree the "Master Valve" is superfluous ?
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
When you say "3 port" I guess you are referring to Harvest Fields suggestion as opposed to a 3 port valve?

It would then make sense if this was the case. I will double check when I am back, but I was lead to believe there is only UFH.
If this is the case, do you agree the "Master Valve" is superfluous ?
No it could be a 3 port zone valve or are you 100% it’s a 2 port
 

Harvest Fields

Esteemed
Plumber
Gas Engineer
Advent Win
I am confused by what you mean by a master valve? Are there just 2 zone valves. If so you have to have these otherwise the under floor would only come on with the water and they will want the underfloor on by itself .
 
I am confused by what you mean by a master valve? Are there just 2 zone valves. If so you have to have these otherwise the under floor would only come on with the water and they will want the underfloor on by itself .
Master valve is my terminology as it governs the subordinate vavles, look at the diagram, it's in series with the manifold valves. The manifold valve triggers the boiler when any of the thermostats call for heat. All the thermostats are wired into a relay for this purpose.
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Remove it then
 

Harvest Fields

Esteemed
Plumber
Gas Engineer
Advent Win
Could be an old valve or it could be for a heating circuit. You need to double check it is for the UFH only.
 
I’ll double check again to be sure there is no third circuit, but otherwise I’ll unwire and leave manually open, then tell plumber to remove when he next drains.
Thanks guys,
 

Harvest Fields

Esteemed
Plumber
Gas Engineer
Advent Win
I’ll double check again to be sure there is no third circuit, but otherwise I’ll unwire and leave manually open, then tell plumber to remove when he next drains.
Thanks guys,
You need to make sure that it is definitely open all the time and cannot close at all or it needs removing at the same time.
 

oz-plumber

Esteemed
Plumber
It may be wired in with the DHW valve.
When the DHW valve is opened - the valve in question might close.
May have been done to simplify the wiring?
 

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