Potterton Suprima 40l | Not operating according to programmer

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Hi Folks,

I have a problem with my boiler/CH/HW setup which I am having difficulty troubleshooting.

There are two scenarios:

The programmer/timer is off for both CH and HW: Boiler is running, and continues to do so until next program change or reset (button or mains power off/on)

The programmer/timer is On for both CH and/or HW, thermostats under desired temp: Boiler does not run, resetting does not help. Strangely if I manually activate the motorized zone valve the boiler kicks in to life.

Recently had Hive installed (by a qualified electrician) but this problem existed with the previous programmer. Since Hive has been installed I have replaced both the hot water tank thermostat and motorized zone valve.

Symptoms I have noticed:
  • Hive Off for both CH and HW | Boiler is running | Motorized valve light on for CH and in the correct position for CH only | 235v supply on the CH and HW circuit. In this scenario the hot water tank thermostat had reached temp and explains why the motorized valve was set for CH only.
  • Hive On for both CH and HW | Boiler is not running | Motorized valve lights on for both CH and correct position | 235v supply on CH circuit but only ~55v on HW circuit? | Thermostats under desired temp.
There other variations of the above symptoms which I can't fully recall at the moment and won't try to guess as it will just muddy the waters. The above two I have seen this week.

The boiler was installed in 2003 when the house was built, I believe it has the newer Siemens PCB going by the front panel. The boiler doesn't show any fault lights or lockouts.

Any troubleshooting pointers I would appreciate.

Thanks,
Gordy
 
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You don't say what type of system you have. Do you have two 2 port valves (S Plan), or one 3 port valve (Y Plan)

If you have a Y Plan, it sounds as if the cylinder thermostat connections may be transposed.

The 'call for heat' wire should go to the boiler switched live
The 'satisfied' wire should go to the grey wire on the motorised valve
The 'common' wire should go to 'hot water on' from the programmer
 
Hi Stem,

It's one 3 port valve (Y). I'll have a look at the wiring when home. I'll take a picture too.

Thanks,
Gordy
 
Photo's of the wiring often don't help unfortunately. They just show wires of varying colours which would have been chosen according to the original installers personal preference connected to terminals. It's what each of them is connected to at the other end that is important.

If the cylinder thermostat is wired wrongly it must have been like that from day one and the symptoms would have always been there. I know you changed the cylinder thermostat, but I guess you made a straight swap of the wires as they were. Although having given it more thought, if it was just the cylinder thermostat wiring that was transposed, it doesn't quite fit the symptoms you describe.

Has the system always had this fault? or did it suddenly appear? anything else happen / change at the same time?

Something else to check is the 'hot water not required' wire this should be connected to the Hive terminal 1 (hot water off) is there a wire present on this terminal? If so where does it go?
 
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I'm interested in the indicator lights on the valve, what model valve do you have?
 
Stem, common and satisfied wires swapped at cly stat?
when ch and hw on valve moves to correct mid position as room stat powers white, boiler doesn't start as no power from cly stat, when ch and hw are set to off the hw off signal sends power directly to the boiler, the valve moves to ch only as it gets the hw off signal direct from the programmer, though it would only go to ch only with both off if the hw was switched off before the heating. If the ch was switched off first the boiler would still run but this time the valve would be in hw only mode. If that isn't the case it would seem as you said there are 2 (or more!) faults.
 
Stem - Correct, the cylinder thermostat was a straight swap of the wires. This fault happened suddenly around a month ago, before Hive was installed, the system worked perfectly up until this point - I walked in one day and the house was melting, the boiler had kept running all day when the programmer was set to off. I'l' check the wire on terminal 1 and trace it out, will get back to you.

Echo - the valve is a Myson MPE322 link
 
Just been up looking at the wiring again and realised I have a made an error - discount the second symptom I gave you for now, I was checking the wrong wire. When the fault state reproduces again I will re-check the voltages.

I had correctly checked the CH circuit (white wire) but not the HW circuit - I had checked the grey wire instead of orange, the grey wire was giving me ~55v. Sorry for the confusion.


As a side note, another thing I have noticed is that the HW light on Hive always comes on when CH comes on even if HW is not scheduled to be on. HW can be independently of the CH but not the other way around. If I manually switch HW off on the Hive app, the light still remains on on the contoller.
 
If the HW light always comes on with CH the hive will be set to gravity mode. This is sometimes used as a fudge to get a y plan system working when no hot water off wire is available from the programmer to the valve.
 
Trying to give you as much accurate information as I can just now.

Current state:
  • Hive manually set to on for HW an CH link
  • Boiler is not running - sitting with the standby light (solid amber) link
  • Motorized valve light on for CH only link
  • Motorized valve at mid position (CH and HW)
  • Hive thermostat under desired temp link
  • Hot water cylinder thermostat up to temp
Cylinder stat install says:

Terminal 1 = Common contact
Terminal 2 = (N.C.) CLOSED when the water temperature is below the selected set point.
Terminal 3 = (N.O.) OPEN when the water temperature is below the selected set point.

CupboardWiring.png


CupboardWiring.png

If the HW light always comes on with CH the hive will be set to gravity mode. This is sometimes used as a fudge to get a y plan system working when no hot water off wire is available from the programmer to the valve.

That makes sense, it is set to gravity mode. Thanks
 
Something else to check is the 'hot water not required' wire this should be connected to the Hive terminal 1 (hot water off) is there a wire present on this terminal? If so where does it go?

There is a wire on Hive terminal one (yellow), which I presume is the wire going to position 9 on the block connector.

20161221_001405.jpg
 
I was close! Swap Brown and blue wires in the cylinder stat.

Terminal 4 in your wiring centre is heating on from programmer to the room stat.
 
Swap Brown and blue wires in the cylinder stat.

Yep, that was my thinking. Com (1) and Call (2) are transposed.

It should be:

1 Common = Brown
2 Call = Blue
3 Satisfied = Yellow

And you can take the Hive out of gravity mode you don't need it, and are restricting your available functions.

This fault happened suddenly around a month ago
This put me off the scent a bit. Wires don't normally move themselves!
 
Last edited:
I was close! Swap Brown and blue wires in the cylinder stat.

Terminal 4 in your wiring centre is heating on from programmer to the room stat.

Yep, that was my thinking. Com (1) and Call (2) are transposed.

It should be:

1 Common = Brown
2 Call = Blue
3 Satisfied = Yellow

And you can take the Hive out of gravity mode you don't need it, and are restricting your available functions.

Thanks guys, I really appreciate the help so far. I will try this as soon as I am home from work and report back.

Stem - can you explain why I don't need Hive in gravity mode? I thought it needed to be as I have a cold water tank in the attic.

This put me off the scent a bit. Wires don't normally move themselves!

I think I might know what has happened. During the summer I had some work done in the airing cupboard (shelves, etc.) and wiring was moved around. I never noticed a fault during the summer as the CH was never on and HW always worked? Around a month ago it's been cold enough for the heating to be used and hey presto this strange behavior has appeared? I've then replaced the cylinder stat but kept the wiring the same.

Sorry for leaving this detail out - it never came to mind.
 

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