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All Replies on Is it possible to run a 2hp Dust Collector and Saw on a single 240v/30amp dryer circuit?

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View JonCrafting's profile

Is it possible to run a 2hp Dust Collector and Saw on a single 240v/30amp dryer circuit?

by JonCrafting
posted 03-29-2021 06:44 PM


31 replies so far

View HokieKen's profile

HokieKen

19418 posts in 2386 days


#1 posted 03-29-2021 06:51 PM

In short, yes. I see no reason you can’t run both of those on a single 30A circuit. Even with startup loads, the spike should be short enough that it wouldn’t throw the breaker. Running a second outlet is the same as running a 115V outlet with the exception that there’s an extra wire and the wire will be larger. Just use a pigtail to split the line at the first outlet and run it to the second outlet.

This of course is dependent on local codes. I think in most locations that multiple outlets are allowed on a single 230 circuit but you should check and make sure for your locale.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View misbeshavings's profile

misbeshavings

32 posts in 3892 days


#2 posted 03-29-2021 08:01 PM

Absolutely you could do that. You could also put a junction box there, take out the dryer plug, and run conduit and 220 receptacles closer to your machines. That’s what I did in my first garage shop. Second one didn’t have a dryer outlet, so I had to run a line all the way across the house from the outside box. Still worth it!

View WhyMe's profile

WhyMe

1414 posts in 2809 days


#3 posted 03-29-2021 08:31 PM

Are both the dust collector and tablesaw 120V? If so and the dryer circuit is 4 wire, 2 hot, neutral and a ground you can split the circuit into two 20A 120V circuits with a shared neutral. The 30A breaker will need to be changed to a 2 pole 20A breaker or two single pole 20A breakers with a handle tie. Obviously the circuit will no longer be used for a dryer. If you are on the International Residential Code multiple outlets on a single circuit are not allowed if over 20A.

View Ruscal's profile

Ruscal

120 posts in 426 days


#4 posted 03-29-2021 08:48 PM

You are only supposed to use 80% of the circuit, so 24A. 12A (DC) + 7.5A (TS) – you are fine. The DC will have a higher start load for an instant to get the blower wheel turning. You may have to run the machines in that order: Start DC first, then start TS.

-- Have a hobby? You should have a business.

View CaptainKlutz's profile

CaptainKlutz

4910 posts in 2742 days


#5 posted 03-29-2021 08:58 PM

- Yes.
Per NEC 430, need 125% of FLC (not FLA) for a motor circuit. (2) 2HP motors have 12A FLC * 125% = 30A

- NEC code only allows multiple receptacles on 20A building wire circuits.
Can not make a permanent circuit with more than one 30A receptacle, though you can permanently connect more than one machine with dedicated wiring to a circuit greater 20A, that meets code requirements.

You can use a temporary cable with 30A plug, and several 15/20A receptacles.
Leviton makes this easy with a #5822 duplex 2 wire 240v 20A receptacle. They also make #16462 Decora version. Can place one of these in an outdoor junction box, and use 10-3 SOOW cable with a 30A matching dryer plug on end. If cord length exceeds 120ft, then suggest 8-3 SOOW cord to avoid voltage drop.

PS – Not an licensed electrician. Only a EE that has played with power and learned some codes.
If any of the above does make sense, hire a professional to help you.
YMMV

-- If it wasn't for bad luck, I wouldn't have no luck at all, Doom, despair, agony on me… - Albert King - Born Under a Bad Sign released 1967

View WhyMe's profile

WhyMe

1414 posts in 2809 days


#6 posted 03-29-2021 09:38 PM

”- NEC code only allows multiple receptacles on 20A building wire circuits.”
There is no such NEC restriction. The IRBC limits multiple outlets to 20A.

View JonCrafting's profile

JonCrafting

17 posts in 440 days


#7 posted 03-29-2021 10:02 PM

Thanks for all the responses and advice.

@WhyMe I’m so sorry, I thought I had clarified in my post that both the DC and TS would be running on 240v, but apparently not.

@HokieKen, @Ruscal That would be great if i don’t have to worry about timing the start up times. I guess the only way to tell would be to test and see.

@misbeshavings I like this idea, and imagine it would be better/safer than long dropcords.

@CaptainKlutz I like the idea of the duplex receptacle, but it is unclear if the 20A rating on the receptacle is signifying the output or input. I could be wrong, but as the circuit is 30A, I would be hesitant to put anything rated less than 30A in the line.

View ibewjon's profile

ibewjon

2653 posts in 4041 days


#8 posted 03-29-2021 10:05 PM

A 2 hp motor on 240 v draws 12 amps, so your table saw is not 2 hp. Is it a Craftsman where they sell you ‘developed’ hp? A 1 hp draws about 8 amps on 240. I would have a sub panel installed with separate breakers for each motor, as long as you have a grounding conductor. In rush / start up current for a motor is about 3x running current.

View HokieKen's profile

HokieKen

19418 posts in 2386 days


#9 posted 03-29-2021 10:18 PM

As WhyMe and CaptainKlutz stated, you can’t add outlets to that circuit. I was unaware there was a 20A cap when I originally replied. I think I would pull another 20A circuit or make a pigtail extension cord to plug the machines in. Having a code violation could be bad if there’s a fire or something even if it’s totally unrelated.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View WhyMe's profile

WhyMe

1414 posts in 2809 days


#10 posted 03-29-2021 10:21 PM

The building wiring is governed by the NEC, so a 240V 30A dedicated single outlet circuit needs to have a 30A or greater amp outlet. A 20A outlet on a 30A circuit is a no go. Using an adapter cord going from a 30A plug to a 20A socket end is an option. The correct way is to mount a small subpanel fed by the 30A circuit and have two 240V 20A circuits from that subpanel. Or one 240V 20A with multiple 20A outlets.

View ibewjon's profile

ibewjon

2653 posts in 4041 days


#11 posted 03-29-2021 10:39 PM

An adapter cord with a 20 amp female is not an option without changing to a 20 amp breaker. There are adapter plugs at big box stores that allow plugging a 20 amp cord into a 15 amp receptacle. It is not UL listed.

View TopamaxSurvivor's profile

TopamaxSurvivor

22441 posts in 4924 days


#12 posted 03-29-2021 11:17 PM

I could be wrong, but as the circuit is 30A, I would be hesitant to put anything rated less than 30A in the line.

- JonCrafting


That is correct. 20A outlet needs to be protected by a 20A breaker or fuse.

Edit: The only place that overrated fuse protection is allowed is branch circuits with several 15 amp outlets protected by a 20 A breaker. If the 15 amp outlet is on a circuit by itself. it would require 15A protection.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View JonCrafting's profile

JonCrafting

17 posts in 440 days


#13 posted 03-29-2021 11:26 PM

Thanks for the additional comments.

@iblewjon Not sure, where your info comes from, but “2 HP, 120V/240V (prewired for 120V), single-phase, 15A/7.5A ” is strait off of the grizzly website, for the Shop Fox W1837. I can’t argue based on personal experience, I’m just going off of the specs that have been made available.

@HokieKen If by “cap” you mean maximum capacity, your first understanding is correct and the cap is 30A not 20A. I was however responding to CaptainKlutz’s who linked a 20A receptacle as a possible solution to put on my 30A circuit.

@WhyMe I agree that the best scenario might be to create a 240v/30A sub panel in the garage. That does sound a bit more costly though, so I will need to price it out to see.

View TopamaxSurvivor's profile

TopamaxSurvivor

22441 posts in 4924 days


#14 posted 03-29-2021 11:44 PM


Thanks for the additional comments.

@iblewjon Not sure, where your info comes from, but “2 HP, 120V/240V (prewired for 120V), single-phase, 15A/7.5A ” is strait off of the grizzly website, for the Shop Fox W1837. I can t argue based on personal experience, I m just going off of the specs that have been made available.

- JonCrafting


That is probably the National Electrical Code rating. About 15 or 20 years ago all the power tools HP doubled. I believe they started using locked rotor current instead of full load to rate HP ;-((

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View JonCrafting's profile

JonCrafting

17 posts in 440 days


#15 posted 03-29-2021 11:52 PM


Thanks for the additional comments.

@iblewjon Not sure, where your info comes from, but “2 HP, 120V/240V (prewired for 120V), single-phase, 15A/7.5A ” is strait off of the grizzly website, for the Shop Fox W1837. I can t argue based on personal experience, I m just going off of the specs that have been made available.

- JonCrafting

That is probably the National Electrical Code rating. About 15 or 20 years ago all the power tools HP doubled. I believe they started using locked rotor current instead of full load to rate HP ;-((

- TopamaxSurvivor

Thanks TopamaxSurvivor. So you are saying that either the HP or the Amp draw listed on the Grizzly website is not accurate and is based on an older formula? I can understand companies picking and choosing the formula they use for different specs in order to improve marketing, but was not aware this was the case for Grizzly/Shop Fox.

View ibewjon's profile

ibewjon

2653 posts in 4041 days


#16 posted 03-30-2021 12:31 AM

2 hp is 2 hp. Amps should be close to the same for both motors. Companies can claim what they want to sell. Who will challenge them? That is how sears Craftsman shop vacs are rated 5 hp, and able to run on 15 amp 120 volt circuit. My info comes from a starter / breaker / fuse calculator put out by Square D, a very reliable electrical equipment manufacturer. Much more trustworthy than Griz or Craftsman. Kind of like milage for a car. Do you ever get what is on the window stickerr? The tag on my 2 hp dust collector states 2 hp, 12 amps on 240 volts.

View WhyMe's profile

WhyMe

1414 posts in 2809 days


#17 posted 03-30-2021 01:15 AM


An adapter cord with a 20 amp female is not an option without changing to a 20 amp breaker. There are adapter plugs at big box stores that allow plugging a 20 amp cord into a 15 amp receptacle. It is not UL listed.

- ibewjon

Why is the 6-30 to 6-20 adapter not an option? You can buy them; and what code prohibits their use? No they are not UL listed. Not the best option, but it is an option.
PS: If the saw and dust collector motors have their own overload protection (reset buttons) I’d run then on a 30A circuit with no concerns. If they don’t have independent overload protection I don’t recommend plugging them into a 30A circuit.

View TopamaxSurvivor's profile

TopamaxSurvivor

22441 posts in 4924 days


#18 posted 03-30-2021 01:27 AM

I am IBEW too. ;-)) I use the same data Square D publishes based on the National Electrical Code requirements. Power is basically Amps x Volts with lots of other minor factors for AC vs DC. Like ibewjon points out a Sears Craftsman shop vac rated at 5 hp can’t run on 15 amp 120 volt circuit. 5hp at 120 volts draws 56 amps and 28 on 240. When my Sears 5 hp-peak vacuum started on my 15 amp circuit remodeling the bath last year it dimmed the lights slightly starting. My electrical panel is Cutler Hammer. They have thermal (as most do) and magnetic (most don’t expect Square D) overload protection. Square D and CH breakers trip so quickly on overload you cannot see a spark with a dead short most of the time. There is no way that vacuum will run drawing 5 hp worth of amps (56) on 120 v. I did not measure it, but I doubt it is drawing more than 9 or 10, a 1/2 hp worth on 120 v.

Your 2HP/12amp dust collector should be 2 old-fashioned hp at 240 v. or 3/4 at 120v. The 2HP/7.5amp table saw could be 1 old-fashioned hp at 230 volts or a 1/3 old-fashioned hp at 120 v.

I have no idea how they claim a 5 hp vac can run on a 15 amp circuit. I suppose they use lock roto amps or may peak staring amp, but those are not really measurment so of horse power produced.

Edit: Many many moons ago a customer had a 5n hp compressor I wired. There is not enough room in the top of my Sears Craftsman shop vac for a 5 hp motor ;-))

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Lazyman's profile

Lazyman

8000 posts in 2635 days


#19 posted 03-30-2021 03:39 AM

While we are on the subject…what is the difference between a 6-15 and 6-30 receptacle? I know one is rated for 15 amps and the other 30 but they look like the same plugs on the charts? Is there a subtle difference that prevents the 6-30P from plugging into a 6-15R or even 6-20R receptacle?

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View TopamaxSurvivor's profile

TopamaxSurvivor

22441 posts in 4924 days


#20 posted 03-30-2021 04:41 AM


While we are on the subject…what is the difference between a 6-15 and 6-30 receptacle? I know one is rated for 15 amps and the other 30 but they look like the same plugs on the charts? Is there a subtle difference that prevents the 6-30P from plugging into a 6-15R or even 6-20R receptacle?

- Lazyman


They are not interchangeable. One is a little bit more heavy-duty than the other. Easier to see if you google the plugs rather than the receptacles.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View ibewjon's profile

ibewjon

2653 posts in 4041 days


#21 posted 03-30-2021 12:35 PM

The difference is physical size and blade spacing. As for the adapter to plug a 20 into a 30, it is allowing a 20 amp receptacle on a 30 amp breaker which is a code violation. It is not UL listed because it is not safe. If I have no assets, I can sell you an adapter to put a 20 into a 200 amp receptacle because I have nothing to lose. A maintenance man at a papermill hooked 14 wire, rated at 15 amps, to a cable fused for 400 amps. Just because he did it doesn’t make it safe. In that case, the wire would have vaporized, possibly starting a fire. As I stated back at the start of this, the safest way is a small sub panel.

View Lazyman's profile

Lazyman

8000 posts in 2635 days


#22 posted 03-30-2021 02:41 PM

That confuses me. You can plug a 15 amp plug into a 20 amp receptacle (and circuit) and that is not considered unsafe. Why would plugging in a 20 amp plug (with adapter) into a 30 amp receptacle be unsafe? That is not the same thing as using a 15 amp rated to wire a 400 amp circuit. I’ve always heard that the breaker is there to protect up to the receptacle not what is plugged into it.

I guess it just the dang black magic. :-)

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Fred Hargis's profile

Fred Hargis

7240 posts in 3741 days


#23 posted 03-30-2021 03:34 PM


That confuses me. You can plug a 15 amp plug into a 20 amp receptacle (and circuit) and that is not considered unsafe. Why would plugging in a 20 amp plug (with adapter) into a 30 amp receptacle be unsafe? That is not the same thing as using a 15 amp rated to wire a 400 amp circuit. I ve always heard that the breaker is there to protect up to the receptacle not what is plugged into it.

I guess it just the dang black magic. :-)

- Lazyman

What you just asked is a good question, I don’t see a problem running something on a circuit that’s rated higher than need be. My BS (3.6 HP, 30 amp) runs on a 50 A welder circuit all the time. It does have overload protection.) In my mind it goes back to the fact that the circuit breaker’s job is to protect the wiring, not the tool.

-- Our village hasn't lost it's idiot, he was elected to congress.

View ibewjon's profile

ibewjon

2653 posts in 4041 days


#24 posted 03-30-2021 03:38 PM

I guess it is magic. You can’t see it but you sure can feel it. And it can kill you or burn your house down. But look at the work it can do, and it is kind of magical. The NEC, which was started by insurance companies, and has many experts contribute to it, from engineers, manufacturers, electricians, and even you can contribute content. Which must be approved by others. But the rule is a 15 amp on 15 amp breaker. A 15 or 20 on a 20 amp breaker. A 30 amp receptacle on a 30 amp breaker, but no 15 or 20 amp receptacles on a 30 amp breaker. The rules were written from experience, injuries, property damage, and deaths. We want none of those. One of the worst things that happened in terms of electrical safety, in my opinion, is electrical parts being easily available to anyone without any or limited electrical knowledge and experience.. It scares me when I hear an employee at a big box or hardware store giving electrical advice. The maintenance man I mentioned did not try to run a 400 amp load with a 15 amp wire. He connected 15 amp wire to the larger wire for a small load. The wire was large enough to power what he was running, but would have vaporized if a fault occurred because of the large fuses on the line he connected to.

View HokieKen's profile

HokieKen

19418 posts in 2386 days


#25 posted 03-30-2021 04:06 PM

It is magic. Among engineers, Electrical Engineers are known as “black magicians” or “masters of the dark arts” ;-P And those are in no way meant as insults. Just a little playful banter to acknowledge that anyone that understands electricity is far smarter than us lowly mechanical guys.

I imagine that the NEC rules for what size plugs can go to what circuits/receptacles have a lot to do with total wattage and the derating of the materials used for said plugs. The total wattage jump from a 15 to 20 amp circuit at 115V is only 575W. But the jump from a 20 to 30A circuit at 230V is 2300W. And like ibewjon said, some portions of the code are based on empirical data rather than actual calculations so that makes it even more confusing. Personally, I just go with. I have no doubt there are good reasons behind it, even that parts that strike me as not making any sense ;-)

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View Lazyman's profile

Lazyman

8000 posts in 2635 days


#26 posted 03-30-2021 05:41 PM

Thanks guys for the clarity. One of the things that has always bothered me about my Grizzly 2 HP/220V band saw is that it does not have built in overload protection. Can anyone recommend a good after market upgrade for that? I know that band saws are not as prone to overloading as a table saws but still, I would feel better if it had it. I know that Grizzly has a magnetic switch on some of their versions of the same band saw that include overload protection but it is a $120 part.

BTW, I was looking at adapter cords and noticed this 6-30P to 6-20R adapter with 20 amp breaker built in. They have some other plug variations as well. Perhaps this is a safer way to go to retask a 30 amp dryer outlet for a power tool?

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View TopamaxSurvivor's profile

TopamaxSurvivor

22441 posts in 4924 days


#27 posted 03-30-2021 05:45 PM

Check the fine print on the motor nameplate. It may have internal overload protection with automatic reset.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View WhyMe's profile

WhyMe

1414 posts in 2809 days


#28 posted 03-30-2021 05:52 PM



The difference is physical size and blade spacing. As for the adapter to plug a 20 into a 30, it is allowing a 20 amp receptacle on a 30 amp breaker which is a code violation. It is not UL listed because it is not safe. If I have no assets, I can sell you an adapter to put a 20 into a 200 amp receptacle because I have nothing to lose. A maintenance man at a papermill hooked 14 wire, rated at 15 amps, to a cable fused for 400 amps. Just because he did it doesn t make it safe. In that case, the wire would have vaporized, possibly starting a fire. As I stated back at the start of this, the safest way is a small sub panel.

- ibewjon

A cord adapter is not a receptacle under the purview of the NEC. You are implying something that is not covered by the NEC. Under the NEC a receptacle is installed at the outlet for the connection of an attachment plug.

View CaptainKlutz's profile

CaptainKlutz

4910 posts in 2742 days


#29 posted 03-30-2021 06:21 PM

Interesting debate.

- Building codes like NEC, only codify permanent structures. Once the power comes out a receptacle, there are other federal regulations, like UL, or CSA that cover the appliance plugged into wall. Which means users can make all kinds of unapproved (possibly unsafe) cables/splitters.

- Motor circuits are different than standard 15/20A circuit with multiple outlet’s used for lights, radio, or other household appliances. Other NEC articles govern the rules for household power. While one can debate that circuit sharing is common, and safe; these do not apply to large motor surge loads covered by article 430.

- Codes requires all motors 1HP+ to have a disconnect, magnetic relay, and overload protection. Agency certification (UL/CSA/etc) issues are reason some mfg do not provide a power plug for their larger machines. They avoid needing certification for disconnect device, and place risk on buyer to add proper device.

- NEC treats large motors with special rules. Complicated and convoluted article 430 is enough to make your head spin. Here is summary.

- NEC Article 430 has specific rules for motors sharing current a circuit. If you want to split a motor circuit permanently per NEC, each branch must have:
- Proper rated wire to a separate disconnect switch for each branch
- Fuses/breaker protecting downsize circuit
- Magnetic relay that keeps power off in case of power loss.
- Thermal overload

The sneaky part to NEC 430 becomes when you have a 30A receptacle you want to repurpose.
NEC code doesn’t care if your temporary extension cord catches on fire due overload.
So you can use a 30A dryer plug to dual 15/20A receptacle splitter. The reason that most dryer plug to 6-20 adapters are not UL listed, is they don’t provide circuit protection for the smaller 20A circuit.

Is using 20A appliance on 30A circuit safe? Depends:

Your receptacle/plug is considered a disconnect device. As Whyme mentioned, if both devices have magnetic starter relay and overload protection, the appliance connection be reasonably safe (as it meets intent of UL requirements).

The probability of your extension cord overheating is very small, thanks to overload protection. If an overload fails, hopefully you are in shop using the tool; can see the smoke due motor failure, and disconnect power before wiring overheats. Also highly likely the motor windings will short and 30A breaker will trip before extension cord catches fire, though the 20A cord and motor will be damaged due lack of circuit protection.
Part of reason I would take this risk; is 2HP motor surge currents are relatively low. If you asked about sharing a 50A receptacle between 3-5HP motors, would recommend a sub-panel or fused disconnect solution.

Bottom line: Splitting a 30A into (2) 15/20A receptacles without breaker/fuse for each circuit can be done, but it puts some risk on user. It does not mean you can ignore the physics when setting up temporary solutions. Still need to proper rate the wiring and devices in the circuit.

+1 ibewjon – Just because anyone can buy electrical parts, does not mean you should not consult/hire a professional.

When it doubt with household wiring, hire a professional.
Be safe, not sorry.

PS – Not a licensed electrician. Just an engineer who designs, builds, and sells electrical appliances.

-- If it wasn't for bad luck, I wouldn't have no luck at all, Doom, despair, agony on me… - Albert King - Born Under a Bad Sign released 1967

View ibewjon's profile

ibewjon

2653 posts in 4041 days


#30 posted 03-30-2021 07:00 PM

The cord with breaker is fine, but limits you to the 20 amp circuit. You need the sub panel to run both tools. I don’t care what possibly unsafe adapters are sold, many without UL testing and listing. I will not use them in my house or shop, and would never tell anyone to use one in theirs. Is the wire in that un protected and adapter 10 or 12 or 14 wire? We do not know without cutting it apart. There is a reason for the testing and listing. As for getting deep into the NEC sections about motors and fusing and using smaller conductors on breakers sized larger to not trip on start up, that is beyond understanding to people that are not familiar with code language. I don’t understand computer language. Everyone has their expertise. As for magnetic motor starters, any name brand is fine. Square D, Allen Bradley, Siemens, ABB, Cutler Hammer. Whatever is available and fits your budget. There are switches with overload protection, but not being magnetically held, the motor can restart after a power interruption.

View TopamaxSurvivor's profile

TopamaxSurvivor

22441 posts in 4924 days


#31 posted 03-30-2021 07:35 PM

Good summary CaptK, well done. Minor correction, manual motor starters with overload protection meet code requirements. Magnetic starters not required in all circumstances.

In my experience troubleshooting commercial and industrial systems, most motor overloads are oversized. The excuse made by those who knowingly do it is to prevent nuisance tripping. Properly sized overloads do not nuisance trip, they indicate a problem, overloaded motor. Unfortunately, most do not take the time to properly size the overloads. Many motor starters used to be shipped with NEC-sized OL heaters based on the NEC generic circuit requirements if the specific motor amps are not available. They are supposed to be changed when the motor is connected. Most motor’s full load amp will be 5 to 10% lower than the NEC generic values. When the systems are connected, the oversized overload heaters are left because the installer either doesn’t know or doesn’t make the effort to make it correct. Electrical inspectors cannot check every detail, they approve if overload protection is provided. Bottom-line, most of the motors I found burned up were because they did not have proper OL protection when the bearings went out or other issues overloaded the motor. Puget Power used to have issues in the Green River Valley constantly during the conversion from rural to industrial. Lots of motors could have been saved with proper overload protection ;-))

A computer tech wrote a program error that did not turn off a fan motor after it started. It burned up running all night. The electrical contractor blamed him. He asked me about overloads. If the electrical contractor had the proper overload heaters installed in the motor starter, it would have tripped and saved their motor.

The reason that motor was so fragile running all night is it was not a continuous duty rated motor. Motors have a service factor of 1.0, 1.15, or 1.25. 1.25 is rare. 1.15 was normal for most of my career. 1.0 is nearly all motors I saw in my last 15 years in the trade. The 0, 15, and 25 are the percentages of overload the motor is designed to handle.

That programming error mention above reminds me of another when energy management was in its infancy. The job was adding the boilers in an elementary to their computer-based energy management system. Programming error would not allow the boiler to turn off after it started. The engineer’s interface wiring design bypassed the high temp cutout and other safety devices. Fortunately, the pressure relief valve worked. Hot water under pressure expands at a ratio of 1600 to 1 when released to the atmosphere ;-( There isn‘t enough room for that expansion in a school full of kids!

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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