Industrial Oven Help

[Micscience]

Hello guys, I work for a hotel and we just received an industrial oven. I have a few concerns. I am trying figure out if the circuit is setup for 3 phase or single phase. The old oven uses like 35amps but this new oven is 3 phase 35 amps, single phase 50 amps.

The new oven did not come with a power cord from what I was told. The circuit to the breaker looks like 10awg so I am thinking we might need a new circuit. Any help my way is greatly appreciated. Pics are attached.

 

[RPH]

Tags on both ovens would be very useful here. Plus any wiring schematics on new oven. Then the question can be answered.

 

[LXCam]

What rph said, a picture of the tag showing the voltage and load values. It might only show Kw but we can do the math. Also do you know if your service is 120/208?

 

[Micscience]

First pic is from the old oven. Second Pic is the new oven's tag the brand name is Mainstreet. I also uploaded the diagram from the manual. I am almost positive it's not 120volt since the wire thickness looks like 10 gauge when I removed outlet plate to see how thick the wire was.

 

[LXCam]

You’ll need to have a new circuit installed. #8 wire and a 40A breaker and id suggest it being hardwired even though they do make a receptacle and plug for this configuration.

 

[wyliesdiesels]

looks like both ovens can do either 1Ø or 3Ø. you most likely have to change the way the elements are wired....

 

[dogdog]

it requires 6AWG for single phase 240V stuff... so probably a 50AMP...

OPs first two pic says it only have 30AMP with L15-30R.....

The inside wiring might be only 10Ga... and each element might only uses upto 30AMP... but combined all 3 heating elements... probably would be more than what the current circuit can handle.

 

[Micscience]

Ok that was what I was thinking if the oven was going to be wired for single phase though since I have little to no experience with 3 phase I was wondering if converted to 3 phase configuration the existing outlet might work but I had no clue so I'm just going to recommend they install a new circuit. Thanks a bunch guys Garage Journal always comes through.

 

[LXCam]

It’s a really simple conversion and I’d lay odds the elements are already terminated for three phase since it’s a commercial appliance. Since you already have three phase there’s no reason to incur the additional expense for a larger circuit required for single phase operation. Plus that might play hell on your overall load balancing.

 

[Norcal]

Not going to be cheap or quick though, those breakers are 22K interrupting rating & any replacement or addition needs to be the same & most likely QOB.

 

[dogdog]

Ok that was what I was thinking if the oven was going to be wired for single phase though since I have little to no experience with 3 phase I was wondering if converted to 3 phase configuration the existing outlet might work but I had no clue so I'm just going to recommend they install a new circuit. Thanks a bunch guys Garage Journal always comes through.

It says your 3phase requires minimum 8 awg sized wire. Seems to me you don’t have any problem reading diagrams but wanted a confirmation on not to rewire. Just make sure your current wiring supports that minimum requirement. You mentioned only 10gauge ?

 

[Micscience]

Where did you see 8awg? I haven't seen anything like that in the manual. The only wire size requirement I saw was from the old oven's tag.

 

[dogdog]

Where did you see 8awg? I haven't seen anything like that in the manual. The only wire size requirement I saw was from the old oven's tag.

This is your pic?

https://www.garagejournal.com/forum/attachments/20240613_141742-jpg.2129819/

This one says 3 phase 34amp one phase 55 amp?

https://www.garagejournal.com/forum/attachments/20240611_120231-jpg.2129820/

 

[micromind]

If possible, always go with 3Ø, lower current is better than higher. Less trouble plus having a 55 amp load on 2 legs of a 3Ø system might cause enough of a voltage imbalance to have a bad effect on 3Ø motors. Especially refrigeration compressor motors.

 

[walta]

Just to be 100% clear since you have a 3-phase service you want to buy only equipment that will use the 3phase power and connect it as 3 phase loads to keep your load balanced.

You are almost certainly being billed on a commercial rate plan you are very likely to be penalized if your if you have unbalanced loads. What that means is if you pull different amounts of power from the 3 phases you get charged as if all 3 equaled the highest one. So, this oven likely cost 3 times as much to operate when connected to a single phase.

You need to learn about power factors not a problem with this oven but if you have big motors it will be.



Walta

 

[Micscience]

This is your pic?

https://www.garagejournal.com/forum/attachments/20240613_141742-jpg.2129819/

This one says 3 phase 34amp one phase 55 amp?

https://www.garagejournal.com/forum/attachments/20240611_120231-jpg.2129820/

Yeah that is the old oven's tag that has been replaced. The weird thing I discovered was the power cord to the old oven was 10 gauge. They used the wrong wire size.

 

[Micscience]

Just to be 100% clear since you have a 3-phase service you want to buy only equipment that will use the 3phase power and connect it as 3 phase loads to keep your load balanced.

You are almost certainly being billed on a commercial rate plan you are very likely to be penalized if your if you have unbalanced loads. What that means is if you pull different amounts of power from the 3 phases you get charged as if all 3 equaled the highest one. So, this oven likely cost 3 times as much to operate when connected to a single phase.

You need to learn about power factors not a problem with this oven but if you have big motors it will be.



Walta

I wasn't aware that I had a 3 phase service. I thought it was a single phase service though I wasn't sure. That is why I made this thread.

 

[micromind]

A 3 pole breaker in the panel usually indicates a 3 phase service.

There are 2 types of 3 Ø service that have 120;

1) 120/208 3Ø 4 wire Y. This one has 120 from any phase to neutral/ground and 208 from any phase to any other phase.

2) 120/240 3Ø 4 wire ∆. This one has 120 to neutral/ground on 2 phases and the other one will be 208 to neutral/ground. It has 240 from any phase to any other phase.

Usually, the ∆ system will have blank spaces in the panel in seemingly odd locations. This is because the spaces with the high leg (208) cannot be used for 120 loads so they stay blanked off.

 

[Norcal]

A 3 pole breaker in the panel usually indicates a 3 phase service.

There are 2 types of 3 Ø service that have 120;

1) 120/208 3Ø 4 wire Y. This one has 120 from any phase to neutral/ground and 208 from any phase to any other phase.

2) 120/240 3Ø 4 wire ∆. This one has 120 to neutral/ground on 2 phases and the other one will be 208 to neutral/ground. It has 240 from any phase to any other phase.

Usually, the ∆ system will have blank spaces in the panel in seemingly odd locations. This is because the spaces with the high leg (208) cannot be used for 120 loads so they stay blanked off.

And the high leg cannot be used for 240V load unless the breakers are rated for 240V, 3 pole are, 2 pole are not normally unless a special order.

 

[walta]

I made the assumption you have 3 phase service based in this photo you posted showing a 3 pole breaker. Note the 3 red arrows.

I would think your power meter and bills would both say 3 phase also if I am correct.

Walta

 

[LXCam]

I made the assumption you have 3 phase service based in this photo you posted showing a 3 pole breaker. Note the 3 red arrows.

I would think your power meter and bills would both say 3 phase also if I am correct.

Walta

It was a good and rightful assumption since the receptacle was also 3ph.

 

[walta]

The best thing to do would be to get a volt meter out and measure the voltages between the 3 legs and to the ground the 6 numbers will tell us what flavor of 3 phase you have.

Please post a wider photo of the pannel.

Walta

 

[wyliesdiesels]

I made the assumption you have 3 phase service based in this photo you posted showing a 3 pole breaker. Note the 3 red arrows.

I would think your power meter and bills would both say 3 phase also if I am correct.

Walta

thats also a straight rated 240v breaker like what Norcal was referring to

 

[Micscience]

The best thing to do would be to get a volt meter out and measure the voltages between the 3 legs and to the ground the 6 numbers will tell us what flavor of 3 phase you have.

Please post a wider photo of the pannel.

Walta

I don't have my multimeter with me ATM but I will get a reading ASAP. I did attach more photos of the panel though.

If this circuit happens to be 3 phase then wouldn't it be ok to make a power cord and install it to the 3 phase configuration and just plug it in?

 

[Norcal]

I don't have my multimeter with me ATM but I will get a reading ASAP. I did attach more photos of the panel though.

If this circuit happens to be 3 phase then wouldn't it be ok to make a power cord and install it to the 3 phase configuration and just plug it in?

A closeup of the data plate in the middle photo above would clear up everything about that SQ D panelboard.

 

[micromind]

Judging from the pics, that panel is 120/208 3Ø 4 wire Y.

There are 4 - 3 pole breakers, strongly suggesting 3 phase and more than 3 single pole breakers next to each other so it cannot be a high-leg ∆. The only other choice is a Y.

The old oven 3 pole breaker is 30 amps. That won't work for the new oven, it will need to be a 45 or 50.

Also, since the cover is vented, it's most likely 400 or 600 amps. Since the available fault current (maximum current during a short-circuit) is likely pretty high, they used breakers rated at 22,000 AIC (amps interrupting current). 10,000 amps is normal but this panel most likely can exceed 10,000 amps during a short-circuit.

Turning on a breaker that's rated at 10,000 amps and has a short-circuit and the panel can produce more than 10,000 amps will very likely result in a fair-size explosion that might require surgery on your hand.

Also, the breakers in that panel are almost certainly bolt-on rather than stab-in although that panel will accept either one.

Not something to mess with unless you know what you're doing.........

 

[micromind]

The new oven cannot use the same breaker, wire or receptacle as the old one, they are all too small.

50 amp receptacles are available, they're expensive and larger than the existing one. Same with the plug that goes on the end of the cord.

Whether you use a receptacle and cord or hard-wire it, you'll need a 45 or 50 amp breaker and # 8 wire.

 

[Micscience]

Well the new oven on the plate says 30-35 amps when connected to 3 phase circuit. I took a pic of the plate it is definitely a 208y 3 phase circuit.

 

[walta]

That sure looks like 3 phase to my eye.

Given the numerous single pole breakers and the fact that they seem to be connected to all 3 phases, my bet is the panel is 208 volt service. And when you put a meter on it will read about 9% high or 226 volts.

Seems unlikely you will be moving the oven around so I would avoid the plug and receptacle and hard wire it with a nearby disconnect. I would run 8 gage in conduit with a 50 amp breaker but 45 would be better if the price and lead time seems reasonable

Walta

 

[wyliesdiesels]

I don't have my multimeter with me ATM but I will get a reading ASAP. I did attach more photos of the panel though.

If this circuit happens to be 3 phase then wouldn't it be ok to make a power cord and install it to the 3 phase configuration and just plug it in?

as said above, has to be 208Y/120 3Ø since circuits 30-42 are single pole breakers for receptacles. you would see skipped spaces if it was 120/240∆ 3Ø...