[Opinion] MCE product review

[ians]

Stay away from this brand ... The plant was down again yesterday ... burnt contactor coil this time

They dont have an issue with replacing the junk ... however the plant standing time ... electrician cost to replace the contactor and get the plant up and running again ... this product is burning my reputation.

[GQE]

Hi Guys, I think its not great to throw a supplier under the bus with comments about MCE products.

I have had great success with the other products in their range, but I would not use a contactor from them in a factory, there I go with bigger brand names.

[ians]

Hi Guys, I think its not great to throw a supplier under the bus with comments about MCE products.

I have had great success with the other products in their range, but I would not use a contactor from them in a factory, there I go with bigger brand names.

I learnt the hard way ... I have just had an overload fail on a cooling tower ... and on the o/l relay the blue pin has popped out.

I would agree ... I made the mistake by using this product in a factory on an essential part ... I suppose I shouldnt blame the manufacturer for my own stupidty ... I should know better ... I did check with the wholesaler prior to purchasing the product ... they did mention that they sold hundreds of these contactors and havent had any issues ... so I took a chance and lost.

So should we agree tha this is a DIY product ... and has a place in the market ?

[ians]

Lets talk about ...

the first 3 contactors ... where replaced without an investigation ... so we will move on from them ... however this is starting to cost me moeny and my reputation.

The overload (sent in still attached to the contactor)... sent in for an investigation.

The normally open contact is not working ... you press the overload btton the normally closed ... opens .. the result ... the pumps stop and because they are all linked the pumps and fan stop ... the normally open is connected to a light and siren ... overload trips ... no warning.

The other overload with an issue ... but working ... the oveload pin doesnt stay in ... so it is held in with prestik.

The contactor ... sent in for investgation.

The coil is burnt out completely ... the contactor is one of 3 connected in parallel ... the other 2 are still operating (this plant runs at least 5 days 24/7) ... replaced blown one with a bigger contactor even though the total load is only 3.7 amps.

If the power was an issue all 3 contactors running together should have burnt out ... why only the one coil? I even made a point of leaving a gap between them to reduce heat ... just thought about it ... I am going to site this morning with my thermal imager to check the temp insid ethe panels.

[ians]

This has got me into investigation mode...

I uploaded the thermal scans I took of the pump control panel.

1/ The temp of the contactor (fan ... problem one) is less than both the pump conatactors.

2/ The only difference between the pump contactors and the fan contactor is the clear cover supplied on the contactors ... to prevent accidentally pushing in the contactor.

I am going to go to site ... measure the voltage from the top to the bottom of the contactor ... then from the bottom of the contactor to the bottom of the overload ... then test the voltage on all the coils ... do a thermal scan of the panel again ... load test the pumps and the fan and record everything.

[ians]

I am open to any suggestions to get to the bottom of this and determine if it is the power or control gear.

I agree it is not fair to throw a supplier under the bus without a fair investigation ... so lets investigate

I look forward to the report from the supplier ... for the record the units were handed in a week ago 12/11/2020.

[ians]

Back to site yesterday AGAIN

I want to give this product the benefit of the doubt ... however yesterday I purchased 4 new brand new MCE 12 amp contactors (230 VAC coils) ... 1 out of the 3 faulty out the packaging ... yes I know they will replace it free but come on.

I did some tests on the units ... top to bottom of the contactor ... on average 20 mVAC ... top of contactor to the bottom of the o/l relay on average around 300 mVAC.

Did thermal tests on the units while running ... depending on the load and type of enclosure ... and the applications ... between 30 and 70 degrees C.

A note ... some of the contactors ... are used for dryers which have a set point of 85 degrees C and switching often ... the temperature in the panel is around 50 degrees C.

Averything seems normal if you take into consideration the application.

However something I did notice while carrying out the test ... the blue flashes as the units switch ... not normal ... it reminds me of crabtree plugs switches back in the 90's.

I need to find a data sheet for this product and check if the model is correct for the constant switching and load.

I decided to contact the technical department if we can resolve these issues.

[ians]

So what did we learn today:

AC1 - resistive loads
AC3 - inductive loads
and all the others in between ... there are numerous AC rating for diffirent applications ... but for now the 2 above are the most common.

As with the CBI ASC -

30 amps is for a resistive load - AC1 ... yes you can switch a 4 kw geyser without a contactor ( or should I say .. in theory)
10 amps is for inductive loads - AC3 ... yes you can use it to switch a 1,5 kw pool pump motor.

The same with contactors ... if you are using it to switch on/off heaters you should in theory be able to use an AC3 contactor with at a lower rating to switch heating elements.

In my application ... I am using one contactor to switch a small 3 phase fan and the other to switch heater on/off.

So I need a small AC 3 contactor to run the fan motor (less than an amp) no issues with the contactors used for this application.

An AC1 contactor to switch the heaters (2.2 kw ... 400 volts) ... the small 9 amp contactor should do the job with ease ... I have 12 amp AC3 contactors installed at the moment and the blue flash when making and breaking the contact ... with this size I would have thought there would be minimul flash.

Looking at the control circuit -

Careful consideration is required when selecting the control transfomer ... 400/230 VAC ... 50 va looks like a fair size transformer ... however it can only handle around 217 mA full load current ... which shouldnt be running at more than 80 % of its capacity ... taking into consideration inrush current when the contactors are energising and de-energising ... It was advised that some form of suppression is used across the contactor coils.

The next question would be fuse protection for the control transfomer ... would you fit a fuse (1 or 2 amp) on each phase of the prmary side of the transfomer and one fuse (250 - 300 mA) on the secondary side of the transfomer ... to allow for the inrush current ...

I see in the manual supplied wih the dryers shows 300 mA 400/230 VAC transfomer with 1 amp fuses on each phase on the primary side and one 2 amp fuse on the secondary side ... with 0.75 mm wire ... I have always taking the wire size into consideration when selecting currnet ratings for protection devices.

At what point would it become a problem and cause the transfomer to burn out ... and how do you protect the transfomer from burning out ... a 2 amp fuse on the primary side would surely be too big.

The next step is to calculate the power for each component in the panel ... lights ...switches with lights ... temperature controllers ... contactors ...timers etc ... taking into consideration ( the bigger AC3 contactors being used ... which will in time be replaced with smaller AC1 rated contactors) add it up and verify that the transfomer is big enough.

[Justloadit]

Another issue that is never considered, is the inductance introduced into the circuit by the connection of cables.
If long cables are wound up in a coil to make it look neat, introduce inductance into the circuit, even if it is a resistive load.

I am sure that you have seen/experienced extension cords heating up/burn out when coiled up and supplying a fair number of amps.

There will always be arcing in physical contact environments, unless the contacts are sealed in a vacuum chamber or a sealed chamber filled up with an inert gas. Many of the expensive 'Relays" are manufactured like this. Most of the cheap relays are open to the environment.

One way to reduce the arcing is to place what is called a suppression capacitor (Type X2) across the load. The capacitor absorbs the back EMF reducing arcing. Of course capacitor value does influence the maximum amount of arcing it can suppress. Very much like the capacitors your (should) see on florescent lights. A typical general value is a 470nF 275V X2 capacitor. Introducing a few of these into the circuit, makes huge improvements, and also reduces noise in electrical systems. An interesting article here

The better quality contactors have this suppression capacitor already included in the contactor coil inside the frame.

An interesting point you may not be aware is that by introducing capacitors into motor circuits which are not supplied by a VSD, will reduce the current the motor draws, and reduces the amount of arcing when the contacts are opened. The reason for this is that the capacitors reduce the phase angle that the inductance of the motor introduces during operation, known as Power Factor Correction.

An interesting article here about Power Factor Correction

Hope this helps.

[ians]

Doing some research and comparing various contactors ... it seems MCE has the highest inrush current of 80 VA ... which in most cases would not even be a concern ...but when you have a 50 VA transfomer ...every VA adds up ... throw in a lot of switching on the contactor and you now have a situation which reuires attention.

Collected all the info on each component and the VA ... it is around 30 VA ... then you have to take into consideration the inrush current and frequency of operation.

I also looked into overload protection for the transfomer ... but as indicated by more exprienced people in this field ... the protection in a 50 VA transformer would be only for short circuit protection ( to prevent a fire)

I am gong to look into solid state relays and see if it is not more practical and cost effective in the long run.

[ians]

This weekend I decided to pull all MCE contactors ... the stock I bought to try keep the site going ... I will be returning.

It is just not worth it ... everytime I loose a contactor ... the ripple effect in the control circuits using control transfomers with low VA ratings is far out weighs the couple of rand saving using MCE ... even if I was the maintenance electrician at the factory ... the machine downtime ... production losses ... all this requires consideration.

After wasting many hours trying to find a solution to protect the transformers ... I learnt a lot but at the end of the day ... not worth hassle.

The blue flash as the contactor makes and breaks ... the high inrush current ... the higher running current compared to other contacotors I researched ... may not be an issue if you have a neutral from the DB sealed the decision.

Maybe the product is good for other applications ... as mentioned by others ... but not in my case.

You live and learn.

[ians]

So we had another 2 contactors fail today ... I have contacted a another supply company company to try a different brand to see if it is the product or the design and installation.

I spent a few hours going through the thermal scans of the control panel ... and found something rather interesting ... the ambient temperature in the panel ... around 30 degrees C ... above the contactors around 53 degrees ... considering there are coils which generate heat ...would seem a little high but ok ... also considering it is the same above all the contactors and evenly spread... but here is the kicker ... 97 degrees between the contactor and overload ... if I look at the thermal scans facing down towards the overload ... the heat seems to be coming from the overload ... yes I have removed the contactor and overload and checked the connection are correct and that the pins are behind the steel plates ... you would see if there was a loose connection or if the overload pin was in front of the plate ( a common problem I pick up when doing thermal audits for companies) by an uneven thermal profile across the terminals.

I have checked and rechecked the voltages and load balancing across the motors ... if there was a problem the overload should ave tripped ... the load tests are lower than the rated amps on the motor name plate ... the contactors and overloads are slected correctly for the motor size ... I have checked and double checked.

Please feel free to comment or offer advice ... I am all ears ... I need to find a solution and soon ... this fiasco is starting to cost me a lot of money.

I am still waitng for the reports from MCE ... and the next 2 will be sent off tomorrow for investigation.

Something else I found interesting ... when the motors are started in the morning and switched off in the evening or run for a couple days without stopping ... there are no issues ... however if the motor is stopped during the day and the motors are restarted soon afterwards ... bang that is when the coils in the contactors pop and the circuit breaker trips ... looking at the overload temperature profile ...could that be the problem.

[ians]

Just to clear up any confusion ... the contactors and overloads are being used for various applications ... some run heaters ... motors ... pumps ... fans ... of diferent sizes ranging from 0.5 watts to 5.5 kw.

For example #12 is not the same panel as #8 ... the only thing common is the replaced switched gear.

[Justloadit]

Note that motor overloads consist of resistance wire, whose resistance value is proportional to the amount of heat generated in a bi-metal trip switch. In other words, heat must be generated in order that the overload can detect when there is an excess amount of current being drawn by the motor.

Now this could be a few watts depending on the amount of current flowing through the resistance element wire.
Add the heat created by the contactor coil, also a few watts, add the heat generated in cabling from the main breaker, add the the heat generated by the wire from the overload to the motor, and there is a fair amount of heat generated by each motor control circuit. Now add a number of these circuits, all inside a closed control panel, and running for hours and hours, and all of a sudden you have a nice heater box, now add one more variable into this mix, ambient temperature which at the coast could be around 40°C, and you have a situation in which there is going to be failures because of the heat buildup.

Had a situation like this some 40 years back, We had measurements of approximately 90°C when the panels were closed, and doors closed, by the way these were free standing 2 meter high control panels. Our final solution was to split the number of motor circuits across 2 DBs, in other words reduce the amount of switch gear by half, and increased the wire size to reduce the heat generated in the wire, and the problem did go away. Was a huge job to rewire the DBs.

You could consider using electronic overloads, as the amount of heat generated by these detectors is equivalent to the transformer wattage.

[ians]

I moved the contactors and overloads in the DB ... but too scared to switch off and restart to test... the plant closes today so I can do the mods over the weekend.

When the plant closes I will be removing the D curve breakers and overload relays ... replacing them with motor starter breakers mounted in the main DB (reducing the amount of gear in the DB and control panel) ... Replacing the Contractors with a diffrent brand and modifying the wiring to suit ... lets hope this will resolve the issues.

We live and learn.