hot dimmer switch

[rb8jm]

Have dimmer switches controlling lights in church. There are two dimmer switches in one switch box and they work separatately but appear to be wired( ganged?) together. One switch controls a couple of lights on one side of the church and the other controls the other lights.

The problem is one of the dimmers is getting really hot but it still works O.K. There is no noticeable bad or loose wires.

What do you think is making this dimmer switch get so hot?

[pushkins]

Dimmer switches will get hot with standard use, make sure they/it isn't causing any deformation to the cover plate, that would indicate way too hot as well as any discoloration of the wires or switches themselves.
The "appearing to be wired together" is most likely a hot line feeding power to the switch.

[jnaas2]

Dimmer switches are rated , if you have a 600 watt dimmer it will handle 6 100 watt bulbs, check how many lights and the watts of all the bulbs and add them together, then check the dimmer swith to see if its rated for the wattage that needs to be dimmed

[HayZee518]

yes, dimmers are rated by wattage. if your switches are covered by plastic plates, change the plates to metal. the metal will increase the heat dissapation area of the dimmers.

[manhattan42]

Professional Required

By virtue of the fact that dimmer switches use resistance to dim the lights, heat will be a by-product of these types of switches.

Dimmer switches should NEVER be hot to the touch, however, when they are operating properly. They should merely be warm to the touch.

If they run hot, you need a qualified electrician to look into this situation immediately before you have a fire.

Two main reasons that dimmer switches overheat:

-There is too much load for the switch (IE. Too many light fixtures for its rating)
-The switch is undersized for the load.

Dimmer switches also have removable flaps on either side of their metal bodies under the plate which should be removed to increase air circulation around them when warm.

There can also be other reasons that a switch will overheat which includes using the wrong size or temperature rating for the conductors that are attached to the device, or having improperly sized conductors for the load.

Remember: Lighting loads in a commercial occupancy like a Church is considered a continuous load so the overprotection device (breaker) must be rated at 125% of the load and the load must only be sized for 80% maximum ampacity.

You really should have a professional electrican check this out.

The situation is very dangerous and poses a serious risk of fire in an occupancy where large groups of people congregate.

A very dangerous mix.

[HayZee518]

those removable flaps are to increase or decrease the heat area exposed to dissipate heat. air is stagnant within a box.

[manhattan42]

Breaking off the tabs for a dimmer can have the immediate effect of making the dimmer run hotter, but this is normally only a concern when other dimmers are ganged together. In such a case the dimmer's capacity may actually need to be derated because of the increased heat.

But when a dimmer is installed in a single box or ganged boxes with devices other than dimmers, removing the tab(s) can actually increase the air flow around the dimmer and have a net effect of cooling it.

And yes, there is air flow in most boxes especially when the cavity is uninsulated and there are openings in the box where cables enter.

_______

But again, if a dimmer is running HOT, there are serious other problems that need to be addressed and whether or not tabs are intact or broken off will normally be the least of one's concerns.

[rb8jm]

These are two 600 watt dimmer switches one (switch) controls about 24 25watt bulbs, the other switch controls the same. The metal cover on th dimmer switch gets real hot but the plastic body of the dimmer feels relatively normal.The two are wired together (one gets power from the other). The wires and switch cover plate all appear to be in good shape, no burns or anything but the metal part of the switch doesget really hot.

Will changing the switches to 1000 watt switches solve this heat problem?

[HayZee518]

you got to figure out the wattage draw of the fixtures per dimmer. nameplate on the dimmers say 600 watt. don't go over 600 watt or you'll shorten the lifespan of the dimmer. for banks of lights an autotransformer is often used. the name of the device is POWERSTAT.

[manhattan42]

These are two 600 watt dimmer switches one (switch) controls about 24 25watt bulbs, the other switch controls the same. The metal cover on th dimmer switch gets real hot but the plastic body of the dimmer feels relatively normal.The two are wired together (one gets power from the other). The wires and switch cover plate all appear to be in good shape, no burns or anything but the metal part of the switch doesget really hot.

Will changing the switches to 1000 watt switches solve this heat problem?

It should.

Since this is a commercial building with continous lighting loads, a dimmer rated at 600w can only be loaded to 80% of capacity.

Thats a mere 480 watts maximum capacity.

Your 600 watt dimmer is already overloaded by 20% since you are loading it to 600 watts (24 25 watt bulbs) and this would account for it running hot without even considering other contributing factors.

Upsizing to an 800 watt dimmer would work with your 600 watt load since you would be loading the 800 watt dimmer to only 75% of maximum...but a 1000 watt dimmer will also work.

That is, "will work" provided there are not other causes contributing to the overheating.

You'd still do best to have a professional assess the situation.

[larepair20]

Have dimmer switches controlling lights in church. There are two dimmer switches in one switch box and they work separatately but appear to be wired( ganged?) together. One switch controls a couple of lights on one side of the church and the other controls the other lights.

The problem is one of the dimmers is getting really hot but it still works O.K. There is no noticeable bad or loose wires.

What do you think is making this dimmer switch get so hot?

The reason dimmer switches get hot is fairly simple. Some dimmers get hotter than others because of their design. Old dimmer switches typically were rheostats that varied the amount of voltage going to the light bulbs. As the rheostat was turn down to lower the voltage, the electricity was changed into heat. These old dimmers wasted lots of energy.

[Digital1]

Professional dimmers

Wall dimmers get hot because they have to dissipate an amount of heat equal to 1.5 x load in Amps. So if you have a 600 watts load ( 5 Amps on 120 VAC ) the heat generated inside the dimmer is equal to : 1.5 x 5 = 7.5 watts . it is like having a 7 watts lamp inside the wall switch.
To avoid these heating issues low voltage controls and remotely placed dimmers are used in commercial and higher load applications.
In this case you would have a keypad to raise and lower the levels that sends a low voltage signal to the Dimmer pack placed in line between the lights and the breaker panel.
This way the user interface have no Line voltage and no heat.
visit Digitallighting.com for more information.