Mid position valve and underfloor heating

[Mork]

Hi all, just installed a polypipe under floor heating system to an existing Y plan, the valve is a V4073A,with this system the UFH stat should independently operate the UFHeating from the existing central heating, the snag is with the time clock off and the UFHeating stat on both the UFH & the central heating come on, I've checked the wiring and I know Im back feeding the orange of the zone valve, but it appears that this in turn is back feeding the white (heating on). Q; Does this valve allow for back feeding? Is the valve itself at fault? Many thanks if you can help, cheers Mork.

 

[davesparks]

No a 3 port mid position valve shouldn't backfeed from the orange to the white, otherwise the heating would come on every time the cylinder stat calls!

How is the new ufh connected in to the system both hydraulically and electrically?

 

[Mork]

I'm not sure exactly how its plumbed, the plumber assures me has the same system working fine elsewhere, electrically the call wire from the UFH control is connected to the orange.

 

[Mork]

davesparks what I also note is that this valve has a pcb style connection and not the old switch type.

 

[davesparks]

Sorry you said you installed the system, I assumed you meant you had installed the system rather than just connected the electrics!

But either way did you not check how it had been plumbed in before connecting the wiring to ensure that your controls would be correct for the way it is plumbed?

So does this ufh have it's own programmer, stat and valve?

 

[davesparks]

davesparks what I also note is that this valve has a pcb style connection and not the old switch type.

Eh? I don't know what you mean by this?

All 3 port valves will have a small pcb in them for the mid position function along with 2 micro switches.

 

[Mork]

Sorry , should have made that clear.The sytem has a programmable room stat but no separate 2 port valve installed at the manifold, there is a 2 port at the cylinder end, this ive wired to come on/off with the cylinderstat.

 

[Mork]

Eh? I don't know what you mean by this?

All 3 port valves will have a small pcb in them for the mid position function along with 2 micro switches.

Is that right! I could swear theres no micro switches in this valve.

 

[davesparks]

Is that right! I could swear theres no micro switches in this valve.

When I get near my laptop I'll post the internal wiring diagram of the 3 port valve

 

[davesparks]

Sorry , should have made that clear.The sytem has a programmable room stat but no separate 2 port valve installed at the manifold, there is a 2 port at the cylinder end, this ive wired to come on/off with the cylinderstat.

So the 2 port is controlling the hot water in series (hydraulically) with the 3 port valve then?
I assume this is due to it being an unvented cylinder?

Is there no valve at all for the underfloor?

 

[Geordie Spark]

This may help ...... internal wiring diagram of the 3 port valve - Google Search

 

[Mork]

Sorry, yes there is a 2 port at the manifold, I think if im getting a back feed off the valve then it must this that's faulty----I think?

 

[davesparks]

This may help ...... internal wiring diagram of the 3 port valve - Google Search

Thanks, that saves me putting the dog in the treadmill to power up the laptop!

 

[davesparks]

Sorry, yes there is a 2 port at the manifold, I think if im getting a back feed off the valve then it must this that's faulty----I think?

But you just said there isn't one there and there is an extra one by the cylinder which you connected to the cylinder stat?

Draw a diagram showing exactly how you have connected this system and then we might be able to give useful advice.

You can't just go assuming that something must be faulty, you need to test the system in all operating conditions and make an informed diagnosis. But first you have to understand how the system should work otherwise you'll be on a hiding to nothing

 

[Mork]

Thanks, that saves me putting the dog in the treadmill to power up the laptop!

Thank you both this really helps, there are 2 micro switches,must be blind! And yes it is unvented.

 

[Leesparkykent]

The two port for the underfloor heating, where Is the orange connected

 

[davesparks]

Thank you both this really helps, there are 2 micro switches,must be blind! And yes it is unvented.

Why did you disassemble the valve head in the first place?
Everything you need to access to test and diagnose the fault will be available at the joint box.

 

[Geordie Spark]

I'm surprised Scouse Tel isn't jumping all over this thread.

He knows all there is to know about UFH heating!

 

[Mork]

I wanted to check that the internal wiring wasn't shorting out etc and curiosity.

 

[Leesparkykent]

How have you wired the two port for the underfloor heating?

 

[Geordie Spark]

I wanted to check that the internal wiring wasn't shorting out etc and curiosity.

Curiosity killed the bat. ....... or something like that.

 

[Mork]

Also when the UFHeating switch wire is disconnected from the orange, the system as it originally was works perfectly, hey ho looks like im back on site tomorrow continuing to isolate the problem.

 

[Mork]

If any one does have any suggestions Id be glad to get your responses, but the football is on now so wont be replying.

 

[davesparks]

Also when the UFHeating switch wire is disconnected from the orange, the system as it originally was works perfectly, hey ho looks like im back on site tomorrow continuing to isolate the problem.

Eh? Which switch wire from which orange?

Draw out a diagram of the wiring and post it here if you want the best advice we can give.

From what you have described so far there must be 3 orange wires to fire the boiler, one from the three port, one from the ufh and one from the 2 port valve providing the positive shutoff for the unvented cylinder.

 

[davesparks]

If any one does have any suggestions Id be glad to get your responses, but the football is on now so wont be replying.

If you can be bothered to reply, don't expect anyone else to!

 

[D Skelton]

I'm surprised Scouse Tel isn't jumping all over this thread.

He knows all there is to know about UFH heating!

I'm surprised that the op didn't rip out the 3 port valve and replace with three 2 port valves?!

Or at least get the plumber to do the job right in the first place?!

 

[davesparks]

I'm surprised that the op didn't rip out the 3 port valve and replace with three 2 port valves?!

Or at least get the plumber to do the job right in the first place?!

It is an odd one, as they appear to have installed an unvented cylinder aswell as the ufh so the 2 port used for the positive shutoff means the plumber must have installed an automatic bypass into the system now.
The bypass isn't needed with just a 3 port as it spring returns to HW open, but you need a shutoff in the flow to the cylinder if unvented so that the flow stops if the overheat stat trips.

So all the advantages that I understand a 3 port to give have now been lost.


Bug then you can't trust a plumber to do the right or sensible thing can you?
The last Y plan system I wired the plumber had neglected to install the 2 port for the unvented or a bypass and I had to explain to him his mistake and point out the relevant parts of the MIs and draw a diagram for him!

 

[Geordie Spark]

I'm surprised that the op didn't rip out the 3 port valve and replace with three 2 port valves?!

Or at least get the plumber to do the job right in the first place?!

That would be my choice as well.

 

[Mork]

If you can be bothered to reply, don't expect anyone else to!

Absolutely right ,appologies , the orange wire is from the 3 port zone valve connected to it are the input from the underfloor heating and the output to the boiler, when im calli g for heat from the ufheating the valve on hot water opens and 3 port allows the rads to heat up , its seems to be the case that when 230v is applied to the orange from the ufheating the white from the 3 port valve also livens up !

 

[Anthony S]

To do it properly you need to Zone Valve UFH, CH, HW, its that simple.

 

[davesparks]

To do it properly you need to Zone Valve UFH, CH, HW, its that simple.

Although it's a bit odd the setup he has can be made to work if connected properly