Discuss Faulty new Honeywell valve? in the Valves & Taps area at PlumbersForums.net

Jones82

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Hi guys just exploring a possibility

I’ve replaced a 3 port valve and it’s passing into the heating circuit when hot water is on. Could an electrical fault cause this problem? There is no call for heat on the heating circuit, proved with my multimeter. The heating pipe work next to the valve is barely warm so definitely not open. Just passing ever so slightly.

I’m leaning towards a possible reverse circulation. Caused by a diy addition to the heating system, the heating return for two rads in the loft may be piped in too close to the cyclinder return.

Just wondered if anyone had ever had an electric fault that caused this symptom.

Ah one more fact it’s a 3 port and a 2 port on the supply to the unvented cylinder just incase that’s relevant. Once again. There is definitely no 240 voltage on the heating wiring
 
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ShaunCorbs

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Did you change the body as well ?
 
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Jones82

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Yep drain down and full valve
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Also I blew down the old valve, whilst it was out and it did pass a little bit then I manually closed it and it didn’t pass.. maybe reverse circulation is forcing it open?
 

ShaunCorbs

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prob always happened then

any reson why you didnt convert to s plan esp as theres already 2 port there?
 
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Jones82

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Quickness! Customer just wanted a valve, but now looking at repiping some of the rads so yeah I’ll convert to s plan too
 
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When you said no voltage on the heating wiring - where are you taking the reading.


Can you confirm volts on the white and the gray wires to the three port - the combination controls the 3 port.

You don't mention what position the 3 port indicates.

Is it on H or midpoint or on W?

What happens when you demand heating?

Does the 3 port move to H?

I realise you may have converted to S plan but if not would be interested
 
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Jones82

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No voltage on the white, or room stat, ch programmer etc gray is permenant live if I remember right?

Its mid position so turns to open heating when there's demand. The additional 2 port is wired into the cylinder stat to provide another interlock for the unvented cylinder

Not there at the the moment. I asked customer to turn off two radiators, which I suspect are reverse circulating. Not heard back yet, I suspect this has stopped the problem so looking at re-piping the rads.
 
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Thanks for your response.

here is the cheat sheet on position of valve.
No power (on valve) = HW only (port B open)

240V on white wire = HW + CH (mid position)

240V on white & grey wires = CH only (port A open) & 240V output on orange wire

240V on grey wire = Valve held in last position (but if last position was CH, approx 100V output on orange wire)

You said that the unit was in mid position so that obviously allows hot water to pass into the rads. Provides HW and heating. The hot water may be prevented by the two port.

Switch off the mains. The three port should got to HW.
If it doesnt then the spring inside is broken or unlikely you have 240 on grey!



Switch on mains and ask for HW.

The three port of first in series with the two port should stay on HW.

Switch off HW

Three port still on HW and grey shows 240

Switch on Heating. Port should move to Heating and 240 on white and grey.

Switch on HW as well and port should move to mid-position and white should be 240

This assumes that the two port is after the three port electrically

Try this if you can and check the power going to the boiler and the two port if you can . The live and the blue wire shows what it is up to!

I will think out the interaction of the two port later today!

And a final check for today.

Wiring

I'm assuming it is being treated as a y plan system though the two port may invalidate this. I can visualise where the two port is starting the boiler and pump and the 3 port is not pointing in the right place!

Need to consider who is in charge of the boiler & pump.

The grey wire should be connected to:

The programmer requesting no hot water and the cylinder stat "not called for" terminal

For a 3 port to function this wiring is required and is quite often missed.

The white wire should be connected to the "called for" terminal of the room stat.



Hope this helps.
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Now think of the two port.

Perhaps the idea was to implement an S Plan using the 3 port as a two port for heating and the two port for HW.

Plumbing might show this:

Layout

Scheme 1
Boiler- pump- 3 port in- 3 port to rads- back to boiler
-3 port to HW-2port in-2port to HW coil
- back to boiler

Scheme 2
Boiler-pump- 3 port in - 3 port to rads-back to boiler
- where does the HW port go to 2 port or back to
boiler?
- 2 port in - 2 port to HW coil-back to boiler

Each separate line being a tee.

Or another schema.

You have two logical choices.

Turn it into an S Plan by replacing the 3 port with a two port.
Would need a bypass return valve (better for future as noted in previous post)

Turn it into an S Plan by removing the two port .
Doesn't normally need a bypass return valve.

So can you explain what the flow is round the system.
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Importantly is there a tee in the system that provides water to the 2 port without needing to go through the 3 port
 
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