Mitsubishi S-N12 Magnetic Contactor - Chatter

[Mattd]

Morning, I recently had to have the salt water chlorinator unit & cell replaced on my swimming pool due to a cell failure and it made economical sense to replace all.

The original unit was a Viron V25 (Astralpool) which had a built in electronic timer for the pump start and stop functions.

 

The new unit is an Emaux SSC50-T, with a built in timer clock for the pump start and stop functions.

 

Motor is a single phase, 220v, 1.5hp Astralpool Alaska Plus model.

 

The power from the chlorinator unit goes directly to a Mitsubishi S-N12 Magnetic contactor and motor overload relay, before going to the pump.

 

Since replacing the chlorinator unit, the pump starts up perfectly OK, runs for the 4 hour cycle with no issues, however, at the end of the cycle instead of going off the contactor starts to chatter, as if the voltage feeding it has dropped to a point where the coil is on the edge of being neither properly on, or properly off, eventually the contactor de-energizes and will be fine until the end of the next cycle, this chattering only happens at the end of each cycle, it does not chatter when starting the pump or at any time during the run cycle.

With the Viron V25 unit, this never happened, it is only since the Emaux model has been fitted.

 

If the pump is manually started and stopped by either the on/off switch on the control box panel, or on the chlorinator unit, it works correctly, with no chattering of the contactor.

Turning the pump on via the timer for say 15 minutes, it turns off correctly, with no chattering of the contactor.

It seems to only do it after the full cycle of 4 hours.

I have checked all of the electrical connections to make sure they are all tight and are making good contact.

 

Has anybody ever experienced this, or have any suggestions as to what could be causing it?

 

My thoughts are the following, but really do not know if the truth be known.

 

1. Polarity - Perhaps when the new unit was fitted, the polarity has been reversed on either the input to the unit, or on the input to the contactor (Being AC, would this matter and if it did, then surely the contactor would not energize?)

2. Heat related, the pump room is small and not ventilated, so heat builds up, especially at this time of the year, thinking maybe that when the timer reaches the end of the cycle the power is not fully released due to expansion of something internally?

 

I can solve the ventilation fairly easily, by drilling holes in the wall and fitting a wall fan to cool the chlorinator unit and will probably do this anyway.

 

Worst case, I can purchase and fit a new contactor and overload relay, although this model has been replaced with the S-T12 version and I'd have thought that if this was at fault it would show the same symptoms when starting or running?

[tjo o tjim]

Usually contact chatter is a function of low coil voltage; that contactor is rated down to 85% of nominal voltage. 
 

It does look like the contactor is marginally rated, especially if you have low voltage.  This could also cause issues. Temperature rating is 55C, so I would be surprised if that is your issue, but possible. 

[Metropolitian]

Are you able to do some measuring with a voltmeter?

If yes; At the end of the 4hours run check what the emaux is feeding to the contactor on pen A1 and A2.

 

If not; Do you feel a ticking at the end of the 4 hours run at the timer altogether with the chatter of the contactor ?

Assuming that your model is the one with the round-dial-timer.

 

 

 

It seems to me that the contacts in the contactor are a bit 'wielded' after 4 hours run (that's why with a short -test- it wont chatter).

But very unlikely, because the contactor is rated on 3.5kw and the pump is 1.5kw.

Still not impossible, and only if there is no feed from the timer switch.

 

 

[Fruit Trader]

Many moons back I repaired one of these chlorinators with integral clock and recall a connection between the 220v clock contacts and the main PCB. This would be to signal the electronic control that pump is on so start making chlorine.

 

My guess is that there is a low current leak from the PCB circuit to the pump output connection which is enough to chatter the contactor. This might be worse when the electronics has the cell powered up and the clock goes off. 

 

My suggestion would be make sure the live and neutral of the whole system is connected correctly and the chlorinator is properly grounded so that any filter circuits dont go looking for alternate paths.

[Mattd]

Thanks for the replies, I will take some measurements later on today and let you know what they are.

Tried to buy a new contactor / overload relay earlier, but the shop only have the S-T10 in 200-240v range, this might be slightly underpowered, although it does state it is ok for 1P motors up to 1.5hp on the side of it, guess it would do no harm to try it.

2 hours ago, Metropolitian said:

Are you able to do some measuring with a voltmeter?

If yes; At the end of the 4hours run check what the emaux is feeding to the contactor on pen A1 and A2.

 

If not; Do you feel a ticking at the end of the 4 hours run at the timer altogether with the chatter of the contactor ?

Assuming that your model is the one with the round-dial-timer.

I'll do some measurements later, not sure if there is ticking, it is not easy to hear much other than the contactor and pump when it is chattering, yes, it is the one with the round timer.

[Mattd]

As an update, I ended up having to do away with using the built in timer in the Emaux Chlorinator to operate the pump, this was the issue, basically when this timer got to the end of the run cycle, sometimes it would switch the power off completely, other times there was still 180v on it for 30 minutes or so before it went off completely, can only imagine the internal switch is faulty.

 

I fitted a new S-T12 magnetic contactor and 6.6A overload relay, wired with the live to A1 & negative to A2, a separate live feed to L1, separate negative feed to L2, the pump is wired to T1 & T3 on the overload relay with a jumper between L3 on top of the contactor & T2 on the overload relay, to balance.

 

To get around the chlorinator salt cell only working using the built in timer, I have placed the chlorinator in to the on position, as opposed to auto, otherwise the salt cell only powers up and produces chlorine when the built in timer is set to the run cycle.

 

The chlorinator unit is now powered from the load side of the new external timer, so only powers up during the run cycle, as a precaution, I got a cheap wall fan and this also comes on during the run cycle only.

 

So far so good.

 

Lessons learnt, either buy a better chlorinator unit, or the Emaux one without the built in timer!

 

Oh and did away with the old fashioned porcelain fuse (10A) and fitted a single pole breaker instead.