Use Resistor To Reduce Output On Heating Element

[Ravenvalor]

Hello,

I have a restaurant customer who has a single phase 208volt food warming system consisting of 6 different wattages and lengths of heating elements on a single circuit. They want to slightly reduce the heat output of one of those elements. Will a resistor in series with this element solve this puzzle for them?

Thanks,

 

[Besoeker]

Hello,

I have a restaurant customer who has a single phase 208volt food warming system consisting of 6 different wattages and lengths of heating elements on a single circuit. They want to slightly reduce the heat output of one of those elements. Will a resistor in series with this element solve this puzzle for them?

Thanks,

It would but where it is a practical proposition is another matter.

 

[GoldDigger]

Hello,

I have a restaurant customer who has a single phase 208volt food warming system consisting of 6 different wattages and lengths of heating elements on a single circuit. They want to slightly reduce the heat output of one of those elements. Will a resistor in series with this element solve this puzzle for them?

Thanks,

Yes and No.
A series resistor will reduce the heat output of the element. But if you want to "slightly" reduce the heat output, then to a good approximation the resistor itself will have to dissipate the same amount of heat that you are reducing from the element. Usually not very practical.
More reasonable possibilities, at least theoretically, include putting a buck transformer winding in series with the element, changing the element to one of lower wattage (probably best), and installing an SCR/Triac dimmer capable of driving the element.
What is the wattage of the element?
If the system is configurable for either 208V or 240V use using different elements, just replace the one 208V element with a 240V element of the same nominal wattage.

 

[JFletcher]

See if you can find a lower wattage element and just replace it. Another option would be to find a 120V element run at 120V instead of 208V.

You could also use an element made for 240V; at 208V, it will produce ~75% the power of a 208V rated one

 

[Besoeker]

See if you can find a lower wattage element and just replace it. Another option would be to find a 120V element run at 120V instead of 208V.

You could also use an element made for 240V; at 208V, it will produce ~75% the power of a 208V rated one

I think that is a practical suggestion.
Or just change the element to a lower wattage at the same volts if one is available.

 

[Ravenvalor]

After calling Powerohm.com and finding that yes a resistor will work but it will also heat up just like an earlier reply to this post suggested (Thanks),
I am going to try a 4 x 4 blank coverplate installed about 1" in front of the element hoping it may reduce the temperature going to the surface sufficiently (a degree or two). If not one cover then another about 12" away from the first one. If two does not work then another one another 12" away.

Thanks for all of the great replies.

 

[JFletcher]

After calling Powerohm.com and finding that yes a resistor will work but it will also heat up just like an earlier reply to this post suggested (Thanks),
I am going to try a 4 x 4 blank coverplate installed about 1" in front of the element hoping it may reduce the temperature going to the surface sufficiently (a degree or two). If not one cover then another about 12" away from the first one. If two does not work then another one another 12" away.

Thanks for all of the great replies.

If you need just a degree or two temp difference, maybe try a more accurate thermostat or mounting the existing one in a different location.

 

[infinity]

I like Golddigger's idea of using a transformer to low the voltage sent to the units.

 

[Besoeker]

I like Golddigger's idea of using a transformer to low the voltage sent to the units.

I prefer the idea of fitting a lower wattage heater.

 

[Ingenieur]

https://www.mccombssupply.com/wp314...MIuKrmjKyD2QIVlFqGCh1MCwpxEAQYBCABEgIWW_D_BwE

how about something like this?
used to control stove top elec htg elements
drill a small hole, install knob, variable adjustment

 

[hbiss]

A
I am going to try a 4 x 4 blank coverplate installed about 1" in front of the element hoping it may reduce the temperature going to the surface sufficiently (a degree or two). If not one cover then another about 12" away from the first one. If two does not work then another one another 12" away.

I would be careful here. Placing a baffle in front of the element can cause dangerous heat build up and overheating. This is electrical equipment designed and listed for use as it is. What you propose voids the listing and makes you responsible for any damages, fires, etc.

Further, these warmers are used in the preparation of food for public consumption. Putting galvanized J box covers in a position where they will get very hot near food could result in the galvanizing flaking off and oxidation forming that could flake off and contaminate the food. This is not something that the Health Department inspector will want to see.

You haven't told us exactly what kind of warmer this is, but if you can't figure out the proper way to do this (perhaps move warmer farther from food, checking if the thermostat can be adjusted) then I would refer them to a restaurant equipment repair tech who knows the equipment.

-Hal

 

[infinity]

I prefer the idea of fitting a lower wattage heater.

That might be best but I think that before we talk about modifying the existing equipment finding an electrical solution would be better.

 

[Ingenieur]

a $13 range top element control switch/pot will do it
they are rated 240 vac up to 1600 w down to 500
they also act as an on/off switch
measure the R of the element or get its W rating, adjust for 208 vac
nice clean install too

 

[hbiss]

Burner controls are not potentiometers or rheostats (way too small). They work like a variable speed Christmas light flasher. The shaft rotation biases a bi-metallic strip with a cam, "flashing" faster or slower. They just vary the duty cycle like variable speed windshield wipers.

OP might try placing a diode in one side of the line instead of the resistor he was thinking of using. I've done that in a box with a switch to shunt the diode for large soldering irons to make them "duel wattage".

-Hal

 

[kwired]

For slight reduction in element output use a 50 foot 18AWG extension cord instead of the 10 foot 12 AWG cord.

Don't leave it all coiled in one spot near combustibles though.

 

[Ingenieur]

Burner controls are not potentiometers or rheostats (way too small). They work like a variable speed Christmas light flasher. The shaft rotation biases a bi-metallic strip with a cam, "flashing" faster or slower. They just vary the duty cycle like variable speed windshield wipers.

OP might try placing a diode in one side of the line instead of the resistor he was thinking of using. I've done that in a box with a switch to shunt the diode for large soldering irons to make them "duel wattage".

-Hal

thanks for the explanation
would they work on a resistive htg element like the op's?

the diode idea is clever
about a 20% reduction in power

 

[Besoeker]

That might be best but I think that before we talk about modifying the existing equipment finding an electrical solution would be better.

Surely a lower wattage element is an electrical solution?

 

[Besoeker]

OP might try placing a diode in one side of the line instead of the resistor he was thinking of using. I've done that in a box with a switch to shunt the diode for large soldering irons to make them "duel wattage".

-Hal

That would make it DC of course. Might be an issue if the element is inductive or somewhat inductive.

 

[LarryFine]

When my son was little, I connected a diode across the bathroom light switch so it was dim instead of off.

Surely a lower wattage element is an electrical solution?

Don't call me Shirley.

 

[Besoeker]

Don't call me Shirley.

Wouldn't dream of it!
And I don't see how that relates to the topic anyway.
Pronunciation maybe?