# Allen Bradley 150 B360NBDB Soft-Start



## micromind (Aug 11, 2007)

Background; this soft-start controls a 300 HP vertical hollowshaft pump motor. It is a stand-alone unit, no bypass contractor. It is installed in a cubicle 90" high, 20" deep and 36" wide with 2 refrigerated coolers mounted in the door. Both of them work. 

This system has been in operation for several years and every once in a while it will fault into overtemp. This occurs anywhere from once few days to once every day. Never at the same time of day, it's random. This happens more frequently as time goes on. The fan at the bottom of the S/S works, lots of very warm air coming from the top of the heatsinks. 

The motor is 340 amp FLC, 1.15 SF. The actual current is 343, 343, 345. (It's about 1/4 mile from a POCO substation, hence the balanced currents. Voltage was very close to 473 on all 3 phases. 

I'm inclined to believe that cooling for the S/S was marginal from the start and is now a bit worse with age.

I'm considering adding a bypass contractor and separate O/L but cannot find whether or not this S/S will allow it and if it will, what terminals to connect it to. 

Or maybe add more cooling in the form of fans at the bottom blowing upward, and/or seeing if I can direct more cold air from the coolers upward into the S/S. 

This system needs to limp by for another 2-3 years, then it will be replaced by a VFD and the SCADA upgraded to accept analog I/Os. 

Advice?


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## dawgs (Dec 1, 2007)

Just leave the MCC door open and use a fan to circulate air on it like everyone else does. Just kidding.

Can you duct the coolers toward the bottom of the soft start more? What's the ambient temp in the gear room?


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## micromind (Aug 11, 2007)

The ambient is pretty cool, like 70 or so during the summer. 

Yes, I'm seriously considering directing the cooler airflow toward the bottom of the S/S. 

This would certainly be the least costly, and it may very well work.


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## dawgs (Dec 1, 2007)

micromind said:


> The ambient is pretty cool, like 70 or so during the summer. Yes, I'm seriously considering directing the cooler airflow toward the bottom of the S/S. This would certainly be the least costly, and it may very well work.


Worth a try. Even if you just temporarily do it to see if it works.


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## emtnut (Mar 1, 2015)

micromind said:


> Background; this soft-start controls a 300 HP vertical hollowshaft pump motor. It is a stand-alone unit, no bypass contractor. It is installed in a cubicle 90" high, 20" deep and 36" wide with 2 refrigerated coolers mounted in the door. Both of them work.
> 
> This system has been in operation for several years and every once in a while it will fault into overtemp. This occurs anywhere from once few days to once every day. Never at the same time of day, it's random. This happens more frequently as time goes on. The fan at the bottom of the S/S works, lots of very warm air coming from the top of the heatsinks.
> 
> ...


Did it trip once and a while since new, and more frequent now ? Or the trips started recently, and now even more frequent ?

I'm thinking the same as you... may have been marginal to begin with.

Did you consider the refrigerated coolers as a possible problem ?


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## JRaef (Mar 23, 2009)

All soft starters reject around 4-1/2 watts/running load amp as heat. So your unit is putting out 1500W of heat, like a 6' baseboard heater. Close and seal the door and it's an oven. The amount of cooling that box needs is fairly extreme. According to the Hoffman Air Conditioner on-line calculator, you would need an AC unit with a capacity of 8,000 BTUs, so unless those two coolers are 4,000 BTUs each, they are not going to cut it. That's assuming 70F ambient, only the back and bottom of the box unable to dissipate heat. Any worse ambient conditions and it's even worse. In general, it's too expensive to use AC units on soft starters, because it's far far cheaper to just use a bypass contactor. 

The old SMC Dialog Plus units like yours didn't come with one. To add one however, you need to buy an accessory unit that goes ahead of it which monitors the current externally from the soft starter. Without it, if you just bypass the soft starter after it's done, it will trip on current loss when the bypass closes, so it would have to be reset every time, and would not be able to soft-stop, which might be important on a pump application. It is called an 825-MCM20 Converter Module. Although the SMC Dialog Plus is no longer supported, they still sell the Converter Module because it's used on other things. It going to cost you around $1,000. 

If you chose to ventilate, you will need a minimum of 500CFM of air flow and the bottom cutout must be a minimum of 5x20" (100sq.in.), more if you use filters.


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## emtnut (Mar 1, 2015)

JRaef said:


> All soft starters reject around 4-1/2 watts/running load amp as heat. So your unit is putting out 1500W of heat, like a 6' baseboard heater. Close and seal the door and it's an oven. The amount of cooling that box needs is fairly extreme. According to the Hoffman Air Conditioner on-line calculator, you would need an AC unit with a capacity of 8,000 BTUs, so unless those two coolers are 4,000 BTUs each, they are not going to cut it. That's assuming 70F ambient, only the back and bottom of the box unable to dissipate heat. Any worse ambient conditions and it's even worse. In general, it's too expensive to use AC units on soft starters, because it's far far cheaper to just use a bypass contactor.
> 
> The old SMC Dialog Plus units like yours didn't come with one. To add one however, you need to buy an accessory unit that goes ahead of it which monitors the current externally from the soft starter. Without it, if you just bypass the soft starter after it's done, it will trip on current loss when the bypass closes, so it would have to be reset every time, and would not be able to soft-stop, which might be important on a pump application. It is called an 825-MCM20 Converter Module. Although the SMC Dialog Plus is no longer supported, they still sell the Converter Module because it's used on other things. It going to cost you around $1,000.
> 
> If you chose to ventilate, you will need a minimum of 500CFM of air flow and the bottom cutout must be a minimum of 5x20" (100sq.in.), more if you use filters.


I take it that your an Engineer JR .... I have to say, in my whole career I've worked with 100's of Engineer's, I have respect for maybe 3 of them.
Since I've been here, I've seen a few of your posts ...

I now have respect for 4 of them :thumbsup: 

Nutz


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## micromind (Aug 11, 2007)

emtnut said:


> I take it that your an Engineer JR .... I have to say, in my whole career I've worked with 100's of Engineer's, I have respect for maybe 3 of them.
> Since I've been here, I've seen a few of your posts ...
> 
> I now have respect for 4 of them :thumbsup:
> ...


You're not the only one.......


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## micromind (Aug 11, 2007)

emtnut said:


> Did it trip once and a while since new, and more frequent now ? Or the trips started recently, and now even more frequent ?
> 
> I'm thinking the same as you... may have been marginal to begin with.
> 
> Did you consider the refrigerated coolers as a possible problem ?


I know its history for the past 4 years, as that's how long the guys who are responsible for it have worked for the city. 

It has always tripped randomly, but they say it's getting worse. But still not bad enough to be a problem.

I think more than anything else, they feel that if it keeps tripping, it'll burn up........and they may very well be right.


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## micromind (Aug 11, 2007)

JRaef said:


> All soft starters reject around 4-1/2 watts/running load amp as heat. So your unit is putting out 1500W of heat, like a 6' baseboard heater. Close and seal the door and it's an oven. The amount of cooling that box needs is fairly extreme. According to the Hoffman Air Conditioner on-line calculator, you would need an AC unit with a capacity of 8,000 BTUs, so unless those two coolers are 4,000 BTUs each, they are not going to cut it. That's assuming 70F ambient, only the back and bottom of the box unable to dissipate heat. Any worse ambient conditions and it's even worse. In general, it's too expensive to use AC units on soft starters, because it's far far cheaper to just use a bypass contactor.
> 
> The old SMC Dialog Plus units like yours didn't come with one. To add one however, you need to buy an accessory unit that goes ahead of it which monitors the current externally from the soft starter. Without it, if you just bypass the soft starter after it's done, it will trip on current loss when the bypass closes, so it would have to be reset every time, and would not be able to soft-stop, which might be important on a pump application. It is called an 825-MCM20 Converter Module. Although the SMC Dialog Plus is no longer supported, they still sell the Converter Module because it's used on other things. It going to cost you around $1,000.
> 
> If you chose to ventilate, you will need a minimum of 500CFM of air flow and the bottom cutout must be a minimum of 5x20" (100sq.in.), more if you use filters.


It sounds like the cost of the module plus the cost of a 400 amp contractor would be fairly close to a new soft-start. 

It feels like 1500 watts of heat, maybe more. 

I'm going to recommend increased airflow and redirecting the cold air from the coolers, maybe more fans under the S/S. Hopefully this will get them by until the big SCADA upgrade and it'll be replaced by a VFD.


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## JRaef (Mar 23, 2009)

If the tripping is increasing, it might be that the heat sinks are loading up with crud and reducing their ability to dissipate the heat. The thermal sensor is just a little klixon snap switch attached to the heat sink, set for (usually) 185F, because the point at which the SCRs will short is typically around 200F. So if the heat sinks can't radiate and dissipate fast enough, the sensor trips.

Or if there are filters, they are clogged, or the fans, although working, are dirty, which increases air drag on the blades and reduces flow. It doesn't seem like much, but if the design was marginal to begin with, any slight losses in cooling efficiency might be pushing it over the edge. I'd start with a very thorough cleaning too.


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## just the cowboy (Sep 4, 2013)

*I agree*



JRaef said:


> If the tripping is increasing, it might be that the heat sinks are loading up with crud and reducing their ability to dissipate the heat. The thermal sensor is just a little klixon snap switch attached to the heat sink, set for (usually) 185F, because the point at which the SCRs will short is typically around 200F. So if the heat sinks can't radiate and dissipate fast enough, the sensor trips.
> 
> Or if there are filters, they are clogged, or the fans, although working, are dirty, which increases air drag on the blades and reduces flow. It doesn't seem like much, but if the design was marginal to begin with, any slight losses in cooling efficiency might be pushing it over the edge. I'd start with a very thorough cleaning too.


I was just going to suggest dust on heat sink, I have some lenze drives that don't like dust on the heat sinks. It is surprising how dust likes to hide there even in a closed system.


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## JRaef (Mar 23, 2009)

I like some things dirty, but not my heat sinks.


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