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Bobice

Basic Troubleshooting of Electric Heat

7 posts in this topic

ELECTRIC HEATING TROUBLESHOOTING CHART Problem Possible cause Solution Furnace won't run 1. No power. 1. Check for blown fuses or tripped

circuit breakers at main entrance

panel, at separate entrance panel,

and on or in furnace; restore circuit.   2. Switch off. 2. Turn on separate power switch

on or near furnace.   3. Motor overload. 3. Wait 30 minutes; press reset

button. Repeat if necessary. Not enough heat 1. Thermostat set

too low. 1. Raise thermostat setting 5°.   2. Filter dirty. 2. Clean or replace filter.   3. Blower clogged. 3. Clean blower assembly.   4. Registers closed

or blocked. 4. Make sure all registers are open;

make sure they are not blocked

by rugs, drapes, or furniture.   5. System out of

balance. 5. Balance system.   6. Blower belt loose

or broken. 6. Adjust or replace belt.   7. Element faulty. 7.Replace element. Furnace turns

on and off

repeatedly 1. Filter dirty.

2. Motor and/or

blower needs 1. Clean or replace filter.

2. If motor and blower have oil

ports, lubricate.   lubrication.     3. Blower clogged. 3. Clean blower assembly. Blower won't

stop running 1. Blower control

set wrong. 1. Reset thermostat from ON

to AUTO.   2. Relays faulty. 2.Replace relay. Furnace noisy 1. Access panels

loose. 1. Mount and fasten access

panels correctly.   2. Belts sticking, worn,

or damaged. 2. Spray squeaking belts with

fan belt dressing; replace worn

or damaged belts.   3. Blower belt too

loose or too tight. 3. Adjust belt.   4. Motor and/or blower

needs lubrication. 4. If motor and blower have oil

ports, lubricate.       Problem: Electric heat will not come on or fan will not come on. 1. First and most important, Please make sure your electrical power is turned off before trying to repair or inspect any type of electrical appliance. I would recommend that you purchase a Multi Meter for some of the troubleshooting procedures listed. 2. Inspect the inside of the air handler or electric furnace for burnt wires. I find this to be a major problem. Electric furnaces use lots of electricity. Any connections that are the least bit loose inside the furnace will cause a heat build up, arcing and eventually a completely burned off connection. Before long the entire wire will be burnt off. Please see picture (compliments from one of our nice customers) below of a burnt heat sequencer. You can see where the heat build up and arcing has caused the terminals to completely burn off the left side! This looks like a three stack sequencer, because of the divisions in the layers of the sequencer:

3. Check your breakers or fuses inside the air handler. Again, make sure your power is off. A good multimeter would be nice to test your fuses. ·        Set the meter to the Rx1 scale (horseshoe), place one lead on each end of fuse. If the fuse is good, you should read zero. If the fuse is bad, you should read infinity (no reading at all).     4. If you still are not getting electric heat then you should test your sequencers to make sure they are working. You can make yourself a tester so you could get portable 24 volts without having the furnace power turned on by using a fan center connected to a junction box. [align=center] [/align] When 24 volts is applied across the two bottom connections (coil) on most sequencers, you should get continuity (a closed circuit) between the two terminals the one on the left M1 and the one on the right M2. You should also have continuity between M3 & M4. This might take 30 to 90 seconds after the 24 volts is applied before you get the continuity. If you do not get continuity then, the sequencer is no good. [align=center] [/align]  

What do we check if our electric heat is not working? There are a few basic things to check yourself. Other steps require an expert.

  • Is the thermostat asking for heat? Be sure you know where all of the thermostats for your electric heat are located. Some heaters such as flush-in-floor electric heaters may use a wall-mounted thermostat while other electric baseboard heaters may have individual thermostats on each baseboard unit. In a bathroom with electric radiant heat in the floor, Is electrical power on to the heater? Check the fuses or circuit breakers that supply each electric heater. If the electric furnace does not seem to be making heat, the electrician or heating technician will use an ammeter to test each of the heating elements to see if one or more of them is not working. She will also check first to confirm that electrical power is on to the unit. If one or more of the staged electric heaters in the furnace has failed, the furnace may make warm air, but not enough warm air in very cold conditions. Check the air temperature rise across the electric furnace. When the furnace has been operating for 20 minutes or longer, typically the temperature at the return plenum (the lower thermometer in the sketch) will show about 70 deg .F. and the supply plenum temperature will be between 120 deg .f. and 125 deg .f. If the supply plenum temperature is too high (over130 deg .f.) something's wrong and you should call a heating service technician. Check radiant heat ceiling panels for wire interruptions. If someone drove an nail into a radiant panel or in the attic above they damaged a wire or heating panel, you may find that that room no longer has heat. We use a hand-held infra-red thermometer scanner to quickly check radiant heat floors and ceilings.
The following is for experienced technicians.
 
  • Does the fan start up even with the fan lead removed from the thermostat ?  A grounded heater coil can cause this to happen. 

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Need appliance parts? Call 877-803-7957 now!

Electric Heat How does electric heat work? Having a basic understanding of what is happening greatly increases your ability to diagnose and repair these heaters. All of them basically work the same. Just as an air conditioner A-coil needs a certain amount of freon flowing through it, Air must be traveling over the heating coils at a certain rate or they will simply heat up and disentergrate in a very short time. But if the fan comes on straight away then only cold air will come out of the vent!. So how do they do it? The manufacturer installs a sequencer to bring on the heating coils in stages. sequencer.jpg   Typical sequencer with 4 stages   This does 2 things. Pre warms the heater and keeps the breaker from tripping. A heating coil is first brought on to heat up the furnace and then 30 seconds later another one comes on 30 seconds later the fan and another one kicks in. Each coil is approximitly 5000 watts the typical furnace for a 3 bedroom. These coils will break individually and instead of 15000 watts you have 10000 or even 5000. Many times people would bring the heat strip to me with all 3 coils broken. Can you imagine that? The good news is each coil can be restrung

  gibsonfrig%20elec%20coil.jpg    typical restring kit   and the heater can be brought back up to normal. When restringing any element you must have the coils evenly spaced and you cannot have any gaps or they become weak spots and burn out. You must take care not to let the coil touch the heater chamber also.  

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Thanks for the photos JW :D

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[user=43030]Bobice[/user] wrote:

Thanks for the photos JW :D

Them's good'ns!  Verlly helpful post, too, Bobice.  Domo!

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Maintaining the all electric house, I have to deal with a 30 year old furnace. I have gone to using tricks and tips from the aviation world the keep things flying right.

When I decided to install all new wiring due to 1 or 2 wires blowing out every single year, first I sourced wire that was correctly rated, and as I cut each individual wire, I coated each end with a film of DOW compound #4 then installed properly rated crimp connects, coated them with DOW4 then installed onto the proper connections.

The DOW4 is a silicone compound that is non drying, and will prevent the corrosion that leads to the high resistance areas that heat up when power is applied, and blow apart the wire.

Since I did this I have had 4 years of trouble free operation, which is much better than awakening at 3 AM to find the beer freezing in the fridge with a temp inside the house of 45 and having to fix the heater (in the garage) with a garage temp of 15.

I use DOW 4 on all of my electrical connections, no matter what they are, since it helps by keeping voltages stable by keeping humidity from causing corrosion.

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Thanks for the info guys. Since semi-retiring here 1.5 yrs. ago , I have been up close and personal with my 15 yr. old furnace twice :1 fuse and 1 relay and also my neighbors for a relay. Did not fully understand operation  - so thanks again..

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I love to help as many people as I can. In these tough economic times I believe everyone appreciates it and knows when their limit is reached and call in a professional.

I also try and educate as there are too many "Salesmechanics".

Funny I am at this over forty years and never had to sell people repairs they did not need to stay around.

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