Sunvic Zone valve query

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Hi there everyone.
I am currently trying to trace through and fault find issues with my central heating / hot water system.

First off i have been confirming Zone valves actuator are operating correctly.
Central Heating Zone valve is Sunvic SZM 1801
Hot water zone valve is a honey well 272848

With the covers off i can see both valves operate on demand.
1st question is regarding the Sunvic valve. Do the motors only drive in 1 direction? Is seems to drive 90deg from closed to open then another 270deg in the same direction to go back to closed. Meaning when you ask it to close it goes from OPEN to CLOSED to OPEN to CLOSED before the actuator stops.

2nd question: Arrow on the valve body is in wrong direction of flow. I think this may be contributing to the valve passing into the CH loop when HW system is being heated. Is this likely to be causing any flow restrictions being in the wrong flow direction.

Regards,
Stu
 
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The Sunvic is a momo, motor on, motor off, not spring return.
 
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As @Chris_W correctly says , you have 1 x spring return valve and 1 x MOMO valve very unusual, guessing your HW is an unvented cylinder
 
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It is an Indirect system.

Oil fired boiler in the garage with the supply split in the loft to the 2 actuated zone valves.
Central heating circuit has a header tank in the loft.

Hot water cylinder is as ianmcd guessed = unvented.

Could the configuration of 1 MOMO and 1 Spring return valve give any issues?

Next question is what may be causing the boiler to not fire / trip out.

There are 2 scenarios which seem to cause the problem, but it is not every time and cant 100% confirm.

1/ HW and CH come on together as per timer. CH goes off 1st then HW timed to go off a bit later. I suspect at some point in the switch off sequence the boiler trips. Don't notice until the next timer cycle so cant confirm.

2/ Heavy Hot water use when the cylinder is not being heated. If someone takes a long shower when the cylinder is not being heated the boiler often does not come on when demanded by the timer. What could cause this?
 
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Could the configuration of 1 MOMO and 1 Spring return valve give any issues?
Not if wired correctly, I got the unvented Cyl bit because you cant have a MOMO controlling the heat source on an unvented it has to be spring return (well yes you can but you would also need a spring return too, before all the trolls jump in ) has this problem just started ? it could be that the origional valve was a MOMO and has been replaced by a spring return, some have the same wiring but not all, hence why it is unusual but can be done
 
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has this problem just started ? it could be that the origional valve was a MOMO and has been replaced by a spring return, some have the same wiring but not all, hence why it is unusual but can be done

The spring return valve fitted when the previous valve stopped working about 3 years ago - and i think it may have been a MOMO valve previously as i recall the same casing on it.

We have had spurious trips over last couple years. It was very infrequently but last few months it has been occuring more regular. Dont know if it is because changes to the Timings have caused it be more noticeable. If the HW and CH timings come on and go off together the issue is a less frequent.

Boiler is serviced annually.
 
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When you refer to 'trips', is this the boiler overheat stat or the burner lockout?
 
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Both types of valves simply make aswitch when in the open position, this switch sinals the boiler to come on, no compilation would cause the boiler to lock out, the only thing that could do this, is if the valve closed but the switch stuck in the made position, then the boiler would continue to fire and would lock out on overheat, as both valves closed the heat has no where to go
 

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So could be locking out with the valve being positioned the wrong direction of flow then?
 
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So could be locking out with the valve being positioned the wrong direction of flow then?
Only times I have had problems with zone valves the wrong way round is they can be noisey when closing, they make a clunking sound
 
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When you refer to 'trips', is this the boiler overheat stat or the burner lockout?
TBH i had forgot there was other 2 reset switches on it. Sometimes the lock out light is on, sometimes it is not. But we have just got in the habit of hitting the lockout reset.
The lockout light has not always been on when going to reset it so i guess that suggests the Fault conditions are combo of Boiler overheat and Lockout
 
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Sunvic valves are renowned for having problems, (I'm not saying this is the cause of your issues, but it might be worth knowing in the grand scheme of things.) This Guy actually tackled Sunvic about the issue, dont think they were too impressed with his findings! Rather a lot of reading, so if insomnia is an issue, it may be of help. Sunvic motorised valve failures (seered.co.uk)
 
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