High voltages on closed valves

[catalin]

Hello,

there are two UTP cat5e cables going from my controller to the valves; they are used for carrying 24VAC. One of the cable that leads to 4 valves – all fine.

The other remaining 4 valves do not work, so I have unplugged the cable from the valves side. I have measured between 16 and 23+ VAC at the OS controller side with the valves idle. Opening them reads 25+ VAC. Slots 5 an 6 are at one voltage level; slots 7 and 8 are at another common voltage level.

Next thing I have tried was to take out one of the hot wires (valve 8) and measured again for the 8th slot – pretty much the same behaviour. Does this mean some parts inside the OS controller have gone bad ?

Thank you

[catalin]

I have managed to reduce the non-working valves number to 2. Still there is the issue with high voltage on non-actuated valves, even higher when no cable attached to the two respective IO port.

I have unfolded a secondary 2-wire cable just to test the two non working valves some more. I have left the return path on the the old cable and made various combinations between the 2 IO ports, the 2 wires in the secondary test cable and the 2 valves. Results: both valves working on only one of the ports. I am now stuck. Help!

[Mike]

Hi Catalin,

If you disconnect all of the wiring for all of your valves from the OS, what voltage measurements do you get at each of the 8 stations when they’re off and again when they’re on? Something like the table below. It’s not clear to me from what you’ve described above if you’ve tried that or not. It could help you narrow the problem down to your wiring/valves or the OS itself.

	1	2	3	4	5	6	7	8
Off VAC	0	0	0	0	0	0	0	0
On VAC	24	24	24	24	24	24	24	24

Mike

[catalin]

Hello Mike,

Thanks for dropping in. I may have found something:

1. Pretty fluctuating outputs; see the image (the arrows inside the orange shapes indicate fluctuating values; actually i think they all fluctuate, not just the ones with arrows to their left). Input does fluctuate as I move the measuring sticks but not as much.
2. output 5 appears to be bad. See the gray rectangles (output 5 vs output 8). Checked the same setup for outputs 6 and 7 and it was the same outcome as for output 8. 5 stands out. 5 is the presumably dead output that has failed my previous test cable experiment.

I have only disconnected the second cable (5 – 8, COM) as the first cable (outputs 1 – 4, COM) does not exhibit any problems.

Attachments:

1. 

   OS_second_cable_off.jpg
   

[catalin]

I have now replaced the old cable with another one. This would be the third tested cable. All good except for the 5th output mentioned above:

2. output 5 appears to be bad. See the gray rectangles (output 5 vs output 8). Checked the same setup for outputs 6 and 7 and it was the same outcome as for output 8. 5 stands out. 5 is the presumably dead output that has failed my previous test cable experiment.

If only I knew what part to replace…

[Ray]

To make sure we are on the same page:
1. when measuring voltage, you should be using your multimeter to measure AC voltage (not DC) from the COM (common) terminal to a zone port. You should NOT measure voltage from GND to a zone port as that’s not how the solenoid driver circuit works.
2. if you remove the zone wires (or simply remove the common wire), and measure voltage as step 1 describes, and turn on each zone one after another. When a zone is turned on, it should measure about 24VAC. When a zone is turned off, the voltage may float (not 24VAC but also not 0), that is normal.

[catalin]

Hello Ray,

thanks for the tips. I managed to identify and replace the faulty part in the meanwhile – the output triac. Case closed.

[Author]

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