Greetings. I’m having issues with blowing fuses on my jet wash machine (basically an industrial dishwasher for washing transmission/engine parts). I had a problem a couple years ago where the fuse block melted. Originally, the machine used the tiny cartridge fuses I couldn’t find anywhere but an industrial supply store. I replaced the fuse holder with the kind that take much larger fuses, and ones I can find at a hood hardware store. As a added bonus the fuse holder has LED that illuminates when the fuse is blown. I assumed my problem was dolled, until yesterday.

Once again, it blew 3 fuses. Always the same fuse, and very inconsistent when it does blow. I have checked the heating element resistance (10 ohms) which seems acceptable. When I replaced the fuse holders I also replaced all the wire (I used 8 gauge which should be plenty for a 30 amp load, on a5 foot run) the entire machine is feed by a 60 amp circuit wired with 6 gauge.

Im wondering what this “controller” is? Is it a fancy relay? It’s obviously been pretty warm judging from the screw discoloration. I’m wondering if maybe the internal contacts are pitted and causing excessive resistance.

Notice the dark screw on the right side.

 

That is an electric disconnect switch, motor starter, big relay, or whatever you want to call it. You can remove power from the circuit, take the center section apart and check the contacts. What size fuses are installed? They need to be 1.5 times the circuit load.

 

It's a Magnetic Contactor & rather than attempting to explain it myself, I'll simply post what it is.

What is a Magnetic Contactor?
Magnetic contactors are the same as the electrical relays which are used in a number of electric motors. Magnetic contactors are used in the electric motors to balance the change in frequency of the motor or the state of the motor which can be termed as the switching of the motor from ON and OFF state. The change in frequency of the motor is due to the different parameters of the power sources which are direct power sources and due to the high load of electrical motors. Magnetic contactors act as a safeguard to protect the power supply and the motor. Magnetic contactors are sometimes considered as circuit breakers due to their similarity of shape with the circuit breakers but their functionality is different than that of circuit breakers. When the circuit between the motor and the power source is in short state the connection is cut off to safeguard the appliance. The magnetic contactors can be easily removed from the motors and the work on the motor can be performed easily. With the removal of the magnetic contactor from the motor, the possibility of live current passing to the motor is reduced to 0%. Relays and magnetic contactors are taken as the same equipment at the industrial level but there are a lot of differences between the relays and the magnetic contactors. Relay is used for loads up to 10A or less than 10A whereas a magnetic contactor is used for loads greater than 10A. Relays are typically used in single-phase appliances whereas a magnetic contactor is used in three-phase appliances. Relay has a common contact for the connection to the appliance while the magnetic contactor has 2 poles for its connection with an appliance.

SOURCE: https://www.electgo.com/magnetic-contactor/

 

Measure the Volts & Frequency on both legs. Balanced?
Looks like your burning the contacts. This means overvolt/over amps
Do you have a clamp-on amp meter? See what each leg pulls on the line an load side. Even? Too high? Lugs tight?

 

I kinda figured it was some sort of relay.

no, I don’t have a clamp on meter. The real pisser is I had one in my hand at a garage sale just last week. I thought about buying it, but figured I’d probably never use it. Now I wish I had, it’s like so many tools you have that you never have a need for once you own it.

 

I'm not a electrician... Many years ago I worked as a maintenance man for a large office/ garage building. I was the younger guy, my older partner had more of a electrical background. We had a breaker or contactor that would keep blowing, it could be reset but then would blow again. I told my partner about it and he said make sure and check for loose connections as they can get hot and make the breaker blow.( I wanted to replace the breaker). Well I thought he was full of crap, but I did tighten the screws the wire connected with, one of them was a little loose and looked like it had gotten hot.... Guess what, no more blown breaker. He was right. I guess sometimes wires loosen up due to vibration, heat-cold, etc. Check out your connections- might work.

 

That's just a contactor. Like you guessed, contactors are basically relays: a small current controls contacts that control large current. What makes something a "contactor" is multiple parallel contacts controlled by a single control voltage. In this case, all three power legs are controlled by the single control signal.
Contactors only have a few parameters. You can get them from the local A/C supply house or readily from Amazon or wherever.
# poles: usually 2 or 3. You're only using 2.
power rating: higher the rating, the bigger and stouter the unit. You can go bigger, don't go smaller.
control circuit: the coil can be driven by AC, DC, a wide variety of voltages, have interesting internal shortcuts or whatnot. e.g. an A/C condensor contactor is controlled by 24V A/C from the thermostat (transformer is usually located inside the furnace). This unit uses a 110v coil.

Not sure what "definite purpose" is trying to convey. Are there "indefinite purposes"? Industrial marketing got ahold of it.

Separately there are devices called "motor starters" which is a contactor plus an overcurrent protection. Has nothing to do with starting the motor, but that's what they're called. The overcurrent protection is there if the motor gets overloaded. It'll pull more than its rated current, but it's not a short circuit so it won't throw a breaker. They usually have a dial so you can set the trip current just slightly higher than the motor's rated current. It'll cut out the control signal to the contactor if the current exceeds the trip current for more than a bit of time.

Anyway, as said, you can pop the cover off that contactor and see what the contacts look like. Like relays, they do get pitted. Obviously do this with power cut off at the panel.
Given what you've said I would first guess loose connection or some sort of vibration issue in the motor(s). I assume there's a spray pump and maybe a separate turnstile motor? Also note that you'll need to use "slow blow" fuses. Or could use a breaker or resettable fuse. But, the manufacturer put that there so you'd know something wasn't right.

 

This is pretty good

 

Keith - That's a great video. It also (more or less) speaks to what defines a DP (Direct Purpose) Contactor. Historically, a DP Contactor was employed in the HVAC industry (from what I understand). The DP meant the contactor was designed for electrical motors employed in the HVAC industry. I don't believe it was meant to suggest a contactor could not be used elsewhere, but if it was stated as a DP Contactor, I believe it meant its design (obviously identified by the Cat.No., as well) was specifically designed for the Direct Purpose of its designed application.

 

At 14.42 of the video it explains the need for an over load device which may be the missing piece in this circuit especially if the motor or motors involved in this circuit have multiple stop/start cycles and experiencing that 6to8x inrush often. Possible the amount of weight being pulled through is too heavy or even a pulley has too much drag or bearing that is bad. I agree with everyones replies and each one needs to be checked so the full load current is not being exceeded. If the fuse block was melted at one point it indicates a pretty significant issue.

 

The machine has 2 of these controllers, one for the electric pump, the other for the heating element. It seems the original part is obsolete, Siemens has a number that crosses over. Nobody in town has one, I’m so sick of hearing “supply chain issues”.

If my original can be taken apart for inspection, I might try that. Since this is a single phase system, I thought about using the unused 3 contacts instead of the burnt contact. Or I might at to hell with it and just wait the 2 days for a new one to come in.

Thanks!!!

 

You can use the unused contact or you can swap parts around once you take it apart to clean.

 

I've had a couple experiences w/ these (years ago) - not identical to yours, but same type contactor (commercial concrete mixer(s), commercial wet saw, rock/polishing tumbler). As has been suggested already, in my experiences removing the contactor, opening them up & cleaning them and very importantly ensuring the lugs/wires are tight resolved the issues. I only ever had to replace one, and they do become faulty with vibration and oxidation. It's not a big deal to open them up, clean them well & reassemble. I only put them back together as they were wired and they worked fine. I found one vendor who has the exact same contactor for sale with same load specifications. The only thing I'm unsure of is the pole wiring - and, I'm not certain it relates to the pole wiring to be honest. Some of these use bi-metal, others use springs - is the bi-metal same? springs same? pole wiring identical? - I can't speak to those parameters. Others may be able to assist if this one will work or not. You might call the vendor to see if all of them are X347 or he/she may have an X133, but as you suggested there probably are updated/cross-reference replacements available. Good Luck.

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