240v Heater not working

[Rst277]

I have an old temro electric heater I found in my dad's shop and have used for the last 10 years or so. The thermostat never worked, I just plugged it in as needed. Now it is not heating for some reason. There is power to the elements but the elements fo not get hot. The elements have a metal tube surrounded by ceramic, covered with light metal fins. Could the tubes be rusted out? What are those 2 doodads on top?


Thanks, Ralph in Winnipeg

 

[eddieK]

Probably one is a limit switch. both might be if one has a longer sensor. Just guessing. Most likely if the thermostat was not working the elements got too hot and shorted. Ohm the element(s).

 

[ambenz]

I would ohm out the elements...turn off the power to the unit, verify no wires are energized!
After removing the wires to the elements, measure the resistance between the connections.
If you get an open and no resistance, the elements are broken inside.
If you get resistance, the elements are good!
You did mention you had power to the elements but you didn't mention how you know this.
Maybe you are missing ground to the elements, the relay to engauge the power to the elements is missing one leg of the power, one fuse is blown, over temp safety snap switch is broke, etc.
Not enough info.

 

[Bert_]

"There is power to the elements" as in you measured 240v across the terminals of each element(s)?

 

[Rst277]

Ambenz / Bert - the ground wire is screwed to the body of the heater. With my tester I confirmed there is power from the body to each element. I tested the elements - we have resistance! Thanks for the help guys! What is the next step?

 

[Alchymist]

Ambenz / Bert - the ground wire is screwed to the body of the heater. With my tester I confirmed there is power from the body to each element. I tested the elements - we have resistance! Thanks for the help guys! What is the next step?

Testing from one end of the element to the body will not confirm full voltage. Test from one end of the element to the other, it should read 240 volts. If one leg of the 240 is missing, both ends of the element will still read 120v to the body.

 

[Rst277]

Hmmmm. I tried one end of the element to the other and got 0. Wouldn't I need a ground to complete the circuit and get a reading?

 

[Alchymist]

Hmmmm. I tried one end of the element to the other and got 0. Wouldn't I need a ground to complete the circuit and get a reading?

No, if you have a 240 volt heater and 0 volts across the element but each end reads 120 volts to ground, you have lost power on one of the legs. Only way to tell which one is to remove one lead from the element and secure it safely, then turn power on and check each lead to ground to determine which leg failed. With both leads attached and one leg missing you will still see 120 to ground on both leads, as it will feed through the element.

 

[Milton Shaw]

240 volt heaters don't use a ground or neutral most of the time, just 240 volts across the element. If you have 0 across the element you need to go back in the circuit and see where you have an open. Most likely it will be one of the thermal limits you posted pictures off or thermostat. Somewhere you have 240 across a component. Be very careful looking for that 240 volts as it will kill if you get across it the right way. Sometimes you have components that will show 0 ohms across them but will still not carry the current required for heaters.

 

[Bert_]

Hmmmm. I tried one end of the element to the other and got 0. Wouldn't I need a ground to complete the circuit and get a reading?

Ground is for safety only in this case, it does not have any effect when the heater is operating normally. Your reading means the element is likely fine but it is not getting power.

Have you checked to see that you have 240v coming in to the heater?

If you do have 240 coming into the heater but still no heat,
Use your meter to check across any switches, thermostats, or high limits. These things should all read zero if they are turned on and working correctly. If you find one of these things gives you a 240v reading when you measure across it, then you have located the problem.

 

[Rst277]

Victory! Thank you for all the help gentlemen. One of those two doodads on the top was holding up the current. I have eliminated those from the circuit and voila, fan and heat! I manually plug this heater in occasionally to quickly raise the temp in my garage that I keep above freezing all winter, so while I have eliminated some safety features, it will do the job.

Thanks again,

Ralph in Winnipeg

 

[PWC Repair]

I'm assuming you jumped out the "L200". That's a 200 degree limit switch that has failed. Roughly $10 at the HVAC supply house. The other "doodad" is a 110 degree fan switch that cycles the fan.

 

[zmaxmotorsports]

I'm assuming you jumped out the "L200". That's a 200 degree limit switch that has failed. Roughly $10 at the HVAC supply house. The other "doodad" is a 110 degree fan switch that cycles the fan.

 

[Bronson]

DO NOT bypass safeties.
Why risk your shop, or life?
Replace both limit switches and be done with it.
Take them with you to the HVAC supply house.

 

[Rst277]

Good point! First thing Monday.