engine block heaters dilemma

[coolbreeze]

Commercial building that need 34 outlets for engine block heaters (1200w each @ 120v). 200A 120/208y 3p system to feed circuits from.

My questions are the following:
1. Are these considered continuous loads? (it's if they are hooked up for 3 hours or more right?) ? so, could you put on a timer and/or temperature switch controlling a relay to stay under the 3hrs which would also save lots of electricity?
2. Total load calculation for the 34 loads at 1200w each (how this is addressed/calculated under the 120/208y 3ph system). My understanding is that the 200a 120/208y 3p system can handle 71,968 watts of load. Therefore, the 34 loads with a total rating of 40,800 watts can be supplied with this loadcenter, even though, I have 34 loads at 10a each or 340A of load @ 120v.
3. Can a 30A protected circuit be used supplying 2 loads together (each load on a GFCI receptacle)? Assuming I am using #10 copper
4. Can a 20A GFCI receptacle be used when using a 30A overcurrent device supplying 2-20A GFCI (each with a so-called dedicated 1200w load for a truck engine block heater)?

At the receptacle, each driver will use an extension cord to plug into his truck heater

Thanks for any input.

 

[petersonra]

Commercial building that need 34 outlets for engine block heaters (1200w each @ 120v). 200A 120/208y 3p system to feed circuits from.

My questions are the following:
1. Are these considered continuous loads? (it's if they are hooked up for 3 hours or more right?) ? so, could you put on a timer and/or temperature switch controlling a relay to stay under the 3hrs which would also save lots of electricity?

IMO they are not continuous loads as the heaters have themostats built in to cycle them on and off.

2. Total load calculation for the 34 loads at 1200w each (how this is addressed/calculated under the 120/208y 3ph system). My understanding is that the 200a 120/208y 3p system can handle 71,968 watts of load. Therefore, the 34 loads with a total rating of 40,800 watts can be supplied with this loadcenter, even though, I have 34 loads at 10a each or 340A of load @ 120v.

If you balance it out, it is a maxiumum of 120A on one L-N, and 110 on the other two.

3. Can a 30A protected circuit be used supplying 2 loads together (each load on a GFCI receptacle)? Assuming I am using #10 copper
4. Can a 20A GFCI receptacle be used when using a 30A overcurrent device supplying 2-20A GFCI (each with a so-called dedicated 1200w load for a truck engine block heater)?

A 20A receptacle has to be on a 20A branch circuit. I am not sure this is actually a dedicated circuit. IMO, it is just an outlet, since there is nothing to prevent someone from plugging something else into it. As a practical matter though, you have to account for the real loads that it will see.

At the receptacle, each driver will use an extension cord to plug into his truck heater

I am not thrilled with the idea of an extension cord. Chances are they will get left out and a snow plow or other vehicle might damage them over time.

 

[coolbreeze]

Not really sure how else to handle getting from the wall 30ft away from the heater other than an extension cord. Mounting a bracket on the wall to roll up the cord and hang it when not being used.

Open to any suggestions on how to handle this problem of the extension cords as well as the problem of (1200w @ 120v) loads. Trying to avoid having to run several conduits or 1 large conduit to accomodate 34 circuits (47 wires minimum).

Also, would I be better of using GFCI breakers and single twist-lock receptacles that only the extension cords with appropriate twist-lock can be used on it?

 

[coolbreeze]

Thanks for the response Bob.

the 30A GFCI breaker and using 30A twistlock receptacles and twistlock cord ends should solve the issue of putting 2 1200w loads per circuit instead of using a 20a GFCI receptacle.

As long as the extension cord is #14, it can be used on a 30A circuit, correct?

 

[hurk27]

I have done several around here, and for the most part not all the receptacles will get used at the same time, except where the truck will be back every night, one thing I will point out is using twist Lock's is not a good idea, they will drive off with them attached, straight pullout receptacles and plugs are the best, use nothing but HD cord ends with 12/4 SJOWHD cord. some of these block heaters come with right angle plugs, make sure there is a pull apart after a right angle plug.

People proofing jobs like these will go along way to having a satisfied customer.

 

[bluesmoke...oops]

they will drive off with them attached

I wondered how long I would read into this thread before seeing that brought up.

 

[petersonra]

Thanks for the response Bob.

the 30A GFCI breaker and using 30A twistlock receptacles and twistlock cord ends should solve the issue of putting 2 1200w loads per circuit instead of using a 20a GFCI receptacle.

As long as the extension cord is #14, it can be used on a 30A circuit, correct?

Where did you get this idea from what I posted?

If you have 20A GFCIs, the maxmium OCPD that can be used on that circuit is 20A.

You can't put a 15 or 20A plug on a branch circuit with a 30A breaker protecting it.

I suppose you could change out all the plugs on the heaters so they were 30A plugs, but that does not seem real safe either.

IMO, the extension cords are not covered by the NEC.

My first thought would be some kind of cord reel that hangs in front of where the trucks park, so the cord is not laying on the ground. For various reasons that might not be practical.

The other option is some kind of pedestal near where the trucks park.

I do not one bit like the idea of 34 thirty foot long extension cords being used on a daily basis in a parking lot.

 

[coolbreeze]

Where did you get this idea from what I posted?

I never said it was you who stated this nor did I derive the information from your words. I was only suggesting some other scenarios and asking for input. Sorry, if you took it so personal. Was only looking for input from others that's all. I used your information to see I could not do what I wanted, then read some more of the NEC and got an alternate scenario which I posted for more input from the forum. That option won't be acceptable either so this is my next option below.

Anyhow, I think the best option may be to put an inline fuse rated at 20A in front of the GFCI receptacle, that way, everything is fused at 20A (receptacle, extension cord, heater plug, etc.) and still be able to put 2 loads on 1 circuit to keep my branch circuit numbers down.

 

[petersonra]

Anyhow, I think the best option may be to put an inline fuse rated at 20A in front of the GFCI receptacle, that way, everything is fused at 20A (receptacle, extension cord, heater plug, etc.) and still be able to put 2 loads on 1 circuit to keep my branch circuit numbers down.

If by "in front of" you mean downstream of, it is certainly closer to being code legal.

I don't know that you gain all that much. Why is so important to reduce the number of circuits? It might be easier to just install some smaller panel boards with the GFCIs installed inside them near where the trucks are parked.

 

[iceworm]

Responses imbeded

edit to add: I'm a slow poster. So following (and adding to) other posters' comments

Commercial building that need 34 outlets for engine block heaters (1200w each @ 120v). 200A 120/208y 3p system to feed circuits from. My responses are based on the outlets are for company trucks - not POVs.

My questions are the following:
1. Are these considered continuous loads? (it's if they are hooked up for 3 hours or more right?) – They are where I live. Generally speaking, If one lives where the heaters are needed, then they are continuous. If however, if you live where they are not needed - say it rarely gets below 0F, then they are not.

so, could you put on a timer and/or temperature switch controlling a relay to stay under the 3hrs which would also save lots of electricity? Absolutely you can. Most I deal with use two temp switches, a timer, and a main contactor (200A) feeding a dedicated panel. Above 20F, all are off. 20F to -20F, half hour on - half hour off. Colder than -20F, on continuous.

3. Can a 30A protected circuit be used supplying 2 loads together (each load on a GFCI receptacle)? Assuming I am using #10 copperI likely would not (more later)

4. Can a 20A GFCI receptacle be used when using a 30A overcurrent device supplying 2-20A GFCI (each with a so-called dedicated 1200w load for a truck engine block heater)?I wouldn't (more later)

At the receptacle, each driver will use an extension cord to plug into his truck heateryes

IMO they are not continuous loads as the heaters have themostats built in to cycle them on and off.
I've never seen a block heater or sidearm heater with a thermostat. Nor have I seen oil pan heaters or transmission pan heater pads with thermostats. Generally if the block heaters go dry, they overheat and burn up. However, I have only seen a few thousand. It is likely there are models made that have integral thermostats and I just have not seen them.

Not really sure how else to handle getting from the wall 30ft away from the heater other than an extension cord. Mounting a bracket on the wall to roll up the cord and hang it when not being used.Yes, each needs a cord. You don't want twist locks. If the truck leaves with out unpluging (hard to believe but it happens), you want the cord to just pull out. One method is to hardwire the cord at the bull rail, with a 20A cordcap. Use strain reliefs. Make the cord long enough to reach the truck pigtail sticking out of the grill. Use a 15A cordcap on the truck. That way you can plug it in anywhere, using a standard extension cord.

Open to any suggestions on how to handle this problem of the extension cords as well as the problem of (1200w @ 120v) loads. Trying to avoid having to run several conduits or 1 large conduit to accomodate 34 circuits (47 wires minimum).
The norm is to run enough conduit to give each a separate circuit on it's own gfci cb. The idea is to limit the number of trucks that won't start if you lose a circuit. Trucks that aren't running aren't making any money - and the drivers and loading crews are standing around waiting. Starting a truck at -20F is a bear. It takes blankets and df/propane space heaters and a couple of hours. At -40F, it isn't twice as hard, it more than four times a hard.

Also, would I be better of using GFCI breakers and single twist-lock receptacles that only the extension cords with appropriate twist-lock can be used on it?

the 30A GFCI breaker and using 30A twistlock receptacles and twistlock cord ends should solve the issue of putting 2 1200w loads per circuit instead of using a 20a GFCI receptacle.

As long as the extension cord is #14, it can be used on a 30A circuit, correct?

GFCI receptacles tend to break easier that a high end nylon federal spec. So, I recomend each circuit on it's own 20A gfci CB, terminating in a 20A nylon federal spec receptacle. Use a #14 cold temp extension cord, with 15A ends. Select a cord that has a lighted cord cap.

OR

Terminate in a #12 cold temp spec cord hardwired at the rail. Use a 20A lighted cord cap long enough to reach the truck pigtail.

The minor money one saves running commoned-up (is that even a word) circuits really goes away fast the first time a truck doesn't start cause the circuit went out. Having a truck out of service because a circuit failed is a bummer. Having two trucks OOS cause one circuit failed could easily be considered poor design.

It's -25F this morning. I plugged my truck in about 3 hours ago. I run 5-30 synthetic this time of year. It should start okay.

You guys and girls have a great day. later

ice

 

[BJ Conner]

Some heater experience.

Some heater experience.

Commercial building that need 34 outlets for engine block heaters (1200w each @ 120v). 200A 120/208y 3p system to feed circuits from.

My questions are the following:
1. Are these considered continuous loads? (it's if they are hooked up for 3 hours or more right?) ? so, could you put on a timer and/or temperature switch controlling a relay to stay under the 3hrs which would also save lots of electricity?
2. Total load calculation for the 34 loads at 1200w each (how this is addressed/calculated under the 120/208y 3ph system). My understanding is that the 200a 120/208y 3p system can handle 71,968 watts of load. Therefore, the 34 loads with a total rating of 40,800 watts can be supplied with this loadcenter, even though, I have 34 loads at 10a each or 340A of load @ 120v.
3. Can a 30A protected circuit be used supplying 2 loads together (each load on a GFCI receptacle)? Assuming I am using #10 copper
4. Can a 20A GFCI receptacle be used when using a 30A overcurrent device supplying 2-20A GFCI (each with a so-called dedicated 1200w load for a truck engine block heater)?

At the receptacle, each driver will use an extension cord to plug into his truck heater

Thanks for any input.

1. Yes- they are generally on all the time. Also there might be oil heaters, battery heaters and sometimes a small space heater in the cab ( not legal but I hav seen it done).
2 & 3. One circuit per outlet is the only way to go. I have not seen a heater that didn't have a NEMA 5 plug on it. If you go to twistlock you'll have to have custom cords that may not be legal.
There are pedistals and boxes that have the recepticals in them made especially for car heaters. The last one I used had eight receptical and were positioned in the center of eight cars.
Nothing will Pi_ _ you off like someone stealing your cord. IF these are company trucks you can try ty-wrapping them to the grill and makeing a bracket to wind it on while on the road, or make sure the driver keeps it in the cab when it,s on the road.
One great thing about heaters is you get in the car and the car heater and defroster work immediately. OR (idf someone has stolen your cord or the circuits triped ) you can drive the first 4 or 5 miles with cold air blowing on you, frost on the window and watch your coffee freeze in the cup.

 

[BILLY101]

An alternative method would to run (2) 100 amp, 3 phase,4 wire, 208/120 volt feeders out to the truck stations. From the source to central point then each feeder would service 17 of the 34 stations.
Assuming each station would be at least 20 feet wide to park a truck that would be 340 feet plus the home run for each feeder. Given the load is 1200 watts x 120 volts that gives us 20.4 kw @ 208 volts x 1.73 = 57 amps connected load. But at 100 amp feeder capacity that easily covers any voltage drop issues.
At each station a 20 amp GFI breaker would be tapped to the feeder according to the NEC tap rule requirements.
Each GFI breaker would feed a receptacle.

BILLY

 

[glene77is]

I have done several around here, and for the most part not all the receptacles will get used at the same time, except where the truck will be back every night, one thing I will point out is using twist Lock's is not a good idea, they will drive off with them attached, straight pullout receptacles and plugs are the best, use nothing but HD cord ends with 12/4 SJOWHD cord. some of these block heaters come with right angle plugs, make sure there is a pull apart after a right angle plug.

People proofing jobs like these will go along way to having a satisfied customer.

Agree. Hurk has the idea!

We did a set of 80 for a bus company.
They setup two parking rails, bus parked on both side, 2 rows.
We ran conduit to each rail, weatherproof disco box (sub-panel),
conduit down the rail,
then one receptical at each bus,
with pull-out plugs and cords hanging out for each vehicle (6' long),
with pull-aparts right at the vehicle (so the extension cord remained at the receptical).

Which reminds me, it is 15 F here, and my 42 year old VW transporter needs to start this AM. I normally use a 250 W light bulb to warm the underside of the crank case, with two (installed) batteries, and a shot of ether on these cold days. That is a trick I learned QuoQuo country in New York in the 1960's.