Solar controller relay sticking

[Barlidge]

Looking for thoughts on this little problem ...

I've got two solar controllers controlling panels to heat the kids above ground pool, one is a Resol deltasol B and the other is a Resol deltasol BS. The outputs of both controllers are connected to laptop style 240v to 24v transformers which one then controls a 24v solenoid while the other controls three small 24v pumps. One is locate in my lean to style conservatory and the other is 20m away in the garden shed.

The problem I'm having is that the output relay is intermittently sticking on, this is happening on both controllers seemingly randomly. the controller display signals it should be in the off position but there is still power being output and a quick tap on the relay releases it.

The manual states the controller has an output capacity of 1A and measuring the transformer draw shows 0.19A so shouldn't be overloaded.

Any ideas?

The relay

 

[rtbcomp]

Instead of tapping it, will it drop if you remove power from the unit? If so it looks like there is some leakage current holding it on.

Without a circuit diagram it's a bit difficult to suggest a fix, but check all power supply connections as a starter.

 

[Barlidge]

Instead of tapping it, will it drop if you remove power from the unit?

If so it looks like there is some leakage current holding it on.

Sorry, forgot to mention, powering it off doesn't work, as soon as power is reapplied to the controller then power is output from the relay

Without a circuit diagram it's a bit difficult to suggest a fix, but check all power supply connections as a starter.

Do you mean a circuit diagram of the controller or my setup?

 

[daleyd]

Are the relays switching dc? they say they are rated for 6 amps 240volt ac but this rating usually comes down considerably when switching dc.

 

[rtbcomp]

Sorry, forgot to mention, powering it off doesn't work, as soon as power is reapplied to the controller then power is output from the relay

Do you mean a circuit diagram of the controller or my setup?

So the relay stays on when power is removed or does it drop off and come back on when you re-apply the power?

 

[rosinante]

Possibly as the output relay is switching an inductive load (motors) the contacts have been damaged by back emfs and are partially welded, replace relays and put buffer relays in line so main load switching is done by heavier duty relays, or solid state relays with zero load switching,this phenomenon is common , if fitting ssrs put a varistor across to ensure switching is positive, hth Chris

 

[Robotstar5]

Replace with solid state relays.

 

[Barlidge]

Are the relays switching dc? they say they are rated for 6 amps 240volt ac but this rating usually comes down considerably when switching dc.

No, they are switching 240vac to 24vdc transformers which are drawing 0.19A in use.

So the relay stays on when power is removed or does it drop off and come back on when you re-apply the power?

Drops off and come back on when power is re-applied.

Possibly as the output relay is switching an inductive load (motors) the contacts have been damaged by back emfs and are partially welded, replace relays and put buffer relays in line so main load switching is done by heavier duty relays, or solid state relays with zero load switching,this phenomenon is common , if fitting ssrs put a varistor across to ensure switching is positive, hth Chris

They are not directly switching motors but transformers, are they classed as inductive? And could they also give back emfs?

 

[Barlidge]

I'l replace the relays as advised and see how they get on.

All advice much appreciated as always.

 

[rtbcomp]

"Drops off and come back on when power is re-applied."

In which case I'd suspect the relay driver circuit. Can you remove the input signals to the controller, or supply dummy signals to test it?

 

[daleyd]

"Drops off and come back on when power is re-applied."

In which case I'd suspect the relay driver circuit. Can you remove the input signals to the controller, or supply dummy signals to test it?

I'd agree with this ^^. If the relay drops out (are you sure the contacts open when you remove power, or are you removing the power from the output side as well, this could lead you down a false path if you get this bit wrong!!) when you remove power, but comes back on when power is put on again then something is "telling" the relay to turn on, rather than the relay sticking.

 

[Barlidge]

"Drops off and come back on when power is re-applied."

In which case I'd suspect the relay driver circuit. Can you remove the input signals to the controller, or supply dummy signals to test it?

The controller does have a 'manual' mode or I could connect sensors directly to the inputs and warm one up to trigger the controller but in testing this all worked fine, its only intermittently plying up in use so hard to re create on demand.

I'd agree with this ^^. If the relay drops out (are you sure the contacts open when you remove power, or are you removing the power from the output side as well, this could lead you down a false path if you get this bit wrong!!) when you remove power, but comes back on when power is put on again then something is "telling" the relay to turn on, rather than the relay sticking.

No I'm not sure at all if the contacts open when the power is removed, the power feed supplies both the controller and the output (I've done a little diagram below).

It looks like the relay is triggered by 12v so if I was to remove the original relay and and take the 12 trigger outside of the box via a short piece of wire and hook up an external relay with a 12v led in line that would tell me if it was sticking or getting a false trigger feed, does that make sense?

 

[rosinante]

My diagnosis may well be wrong, relays may be being energised on by spurious signals as said in previous posts, yes transformers are an inductive load, I believe any thing with a coil is.That's how they work by inducing a current in a secondary coil.you will have to dig deeper, you could try disconnecting transformers from outputs and measuring output contacts with a voltmeter switched to appropriate range wrt ground.
If you can hear or feel the relay operating when removing or applying power to device will tell if the relay is being called for,however it does not necessarily mean the out contacts have opened, remove or simulate the input to the controller to enable you to switch at will whilst checking output contacts with a meter.
I have had this problem a few times with small relays and the answer was always a replacement in my experience, for longevity a slave switching device is advised.
The last event was a contactor welding and causing an ammonia cracker to heat to 1000C gulp.
hth
Chris

 

[daleyd]

The controller does have a 'manual' mode or I could connect sensors directly to the inputs and warm one up to trigger the controller but in testing this all worked fine, its only intermittently plying up in use so hard to re create on demand.



No I'm not sure at all if the contacts open when the power is removed, the power feed supplies both the controller and the output (I've done a little diagram below).

It looks like the relay is triggered by 12v so if I was to remove the original relay and and take the 12 trigger outside of the box via a short piece of wire and hook up an external relay with a 12v led in line that would tell me if it was sticking or getting a false trigger feed, does that make sense?

View attachment 89710

Yes, that would do it. Really you just need to determine whether the relay is genuinely "sticking", which is a real possibility, or whether your box of tricks is still telling it to be energised. If there is any sort of logic in between the input and output then it could be held on for any number of reasons...

Another way could be to put a switch inline with the relay and disconnect power to the coil, if the output is still on then you can be pretty sure it's a sticky relay. (There are a multitude of different ways of doing the same thing, you could put a multimeter on the relay coil etc so whichever one you are more comfortable with...)