I have 2 hvac units running an electric heating element for the heater. Both limit controls are set the same. One is ignited the flames and continuing with flames for close to 3 min. The other is taking longer to ignite and only running 1min 45 sec. Do I need to replace the complete limit control or is there some other sensor which could be causing the long delays and short heat cycle. ( I did switch electronic flame sensor and no change)

Why Does My Electric Water Heater Reset Button Keep Tripping? So the red reset button on your electric water heater keeps popping out and needing to be reset.
Here's the most likely problem: The water in your water heater is getting too hot.
When the water temperature in your water heater exceeds 180°, the red reset button (also known as the high-limit switch) trips. This tripping protects you from getting scalded or burned when using hot water in your home.
OK, but then what's causing the water in your water heater to get so hot? The most likely cause is a bad thermostat.
How a bad thermostat causes your water heater reset button to trip Electric water heaters have a lower and upper thermostat-one for each heating element.
The thermostats are responsible for controlling the heating elements. When the water has cooled off, the thermostats kick on the heating elements to heat the water. And once the water has reached your desired temperature, the thermostats shut off the heating element.
(This is very similar to the way your heating and air conditioning thermostat controls your home HVAC system.)
But these thermostats can go bad. When they do, they sometimes get stuck in the "on" position. This means that that the heating element continues to heat your water, eventually causing the high-limit switch to trip.
The fix: The bad thermostat needs to be replaced. A plumber can use a multimeter to test the thermostats and find out which one is bad.
Other problems that can cause your high-limit switch to trip While a bad thermostat is the most common reason your water heater's reset button may trip, it's not the only one. Other common causes include:

• A shorted heating element-It may be that the thermostat is working just fine and shutting off the heating element. But a short in the element is causing it to continue to heat your water.
• Loose wiring-A loose wire in the water heater can generate heat that can cause the high-limit switch to trip.
• Bad high-limit switch-The switch itself may be malfunctioning and tripping when it shouldn't be.

Get a professional plumber's help

Do you live in the Minneapolis-St. Paul area and need a reliable plumber to help you troubleshoot your water heater problem? Contact MSP Plumbing. We can usually fix the problem the same day.

Many things could bring this on. Most commonly a high limit is open tEllington the unit that the furnace has a cracked heat exchanger.

Hello there and welcome to fixya there are several things that could make this dryer not heat up
Here are the most common things

Thermal Fuse

If the dryer doesn\'t heat, but the drum
turns, check the thermal fuse(s). The thermal fuse protects the dryer
from overheating and helps to prevent fires. If the thermal fuse is
blown, it will have to be replaced.




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Gas Valve Solenoid

The gas valve has two or more electric
solenoids which open the valve to let the gas flow into the burner
assembly. If the dryer doesn\'t heat one or more of the solenoids may be
defective. If the igniter glows for 90 seconds but the burner flame
doesn\'t light, replace these coils as a set.


Dryer Igniter


If the dryer doesn\'t heat, the igniter might
be burned out. Check the igniter for continuity with an ohm meter. Dryer
igniters burn out over time, similar to a light bulb.

Heating Element

The heating element on an electric dryer can
burn out over time. If the dryer doesn\'t heat, the element should be
checked for continuity. The heating element cannot be repaired and must
be replaced if defective.

Heating Element Assembly

the heating element assembly on an electric
dryer can burn out over time. If the dryer doesn\'t heat, the element
assembly should be checked for continuity. The heating element assembly
cannot be repaired and must be replaced if defective.

Flame Sensor



Gas dryers have a flame sensor to detect the
heat given off by the flame. If the dryer doesn\'t heat, the flame sensor
might be defective. Check the flame sensor for continuity. This is not
as common as a burned out igniter or thermal fuse.


High Limit Thermostat


Although not common, if the dryer doesn\'t
heat the high limit thermostat can be defective. It can be checked for
continuity. If the thermostat is "open" the dryer doesn\'t heat.


Cycling Thermostat




The cycling thermostat regulates the
temperature of the air in the dryer. If the dryer doesn\'t heat it may be
caused by a defective cycling thermostat. This is not common.


Main Control Board

The main control board is normally not at
fault when the dryer doesn\'t heat. Check all of the other components in
this troubleshooting guide before replacing the main control board. The
main control board cannot be tested easily and must be replaced if it is
defective.


Timer
The timer is normally not at fault if the
dryer doesn\'t heat. In many situations where timers are replaced they
end up being returned. Check all of the more common components in this
troubleshooting guide before replacing the timer

Hello there and welcome to fixya

Here are the most common things that will need to be checked with a meter to ensure there is continuity on these parts no continuity means that the part is bad and needs replacement ok?

Thermal Fuse

If the dryer doesn't heat, but the drum turns, check the thermal fuse(s). The thermal fuse protects the dryer from overheating and helps to prevent fires. If the thermal fuse is blown, it will have to be replaced.


Enter your model number to see parts for your dryer.
Help me find my model number

Gas Valve Solenoid

The gas valve has two or more electric solenoids which open the valve to let the gas flow into the burner assembly. If the dryer doesn't heat one or more of the solenoids may be defective. If the igniter glows for 90 seconds but the burner flame doesn't light, replace these coils as a set.


Enter your model number to see parts for your dryer.
Help me find my model number

Dryer Igniter

If the dryer doesn't heat, the igniter might be burned out. Check the igniter for continuity with an ohm meter. Dryer igniters burn out over time, similar to a light bulb.


Enter your model number to see parts for your dryer.
Help me find my model number

Heating Element

The heating element on an electric dryer can burn out over time. If the dryer doesn't heat, the element should be checked for continuity. The heating element cannot be repaired and must be replaced if defective.


Enter your model number to see parts for your dryer.
Help me find my model number

Heating Element Assembly

The heating element assembly on an electric dryer can burn out over time. If the dryer doesn't heat, the element assembly should be checked for continuity. The heating element assembly cannot be repaired and must be replaced if defective.


Enter your model number to see parts for your dryer.
Help me find my model number

Flame Sensor

Gas dryers have a flame sensor to detect the heat given off by the flame. If the dryer doesn't heat, the flame sensor might be defective. Check the flame sensor for continuity. This is not as common as a burned out igniter or thermal fuse.


Enter your model number to see parts for your dryer.
Help me find my model number

High Limit Thermostat

Although not common, if the dryer doesn't heat the high limit thermostat can be defective. It can be checked for continuity. If the thermostat is "open" the dryer doesn't heat.


Enter your model number to see parts for your dryer.
Help me find my model number

Cycling Thermostat

The cycling thermostat regulates the temperature of the air in the dryer. If the dryer doesn't heat it may be caused by a defective cycling thermostat. This is not common.


Enter your model number to see parts for your dryer.
Help me find my model number

Main Control Board

The main control board is normally not at fault when the dryer doesn't heat. Check all of the other components in this troubleshooting guide before replacing the main control board. The main control board cannot be tested easily and must be replaced if it is defective.


Enter your model number to see parts for your dryer.
Help me find my model number

Timer

The timer is normally not at fault if the dryer doesn't heat. In many situations where timers are replaced they end up being returned. Check all of the more common components in this troubleshooting guide before replacing the timer

There are several things that can prevent a dryer from not heating.. Unplug Power Before checking.
Electric Models
1- Power- Your dryer runs on 220volts. 110 runs the entire dryer and 110 runs just the element. Your breaker may have half tripped. Check to see if you are getting the correct amount of power by using a ohm meter. Also check the power cord for burn marks on the plugin and the cord itself.
2- The thermal fuse can prevent this from heating. The thermal fuse is a sensor on the blower housing the measures the temperature of the air. There is a cycling thermistat near the thermal fuse. If the dryer temp gets over 190-220 degrees the thermal fuse will blow to cut power to the element to prevent fire. You can test this by using a continuity tester.
3- High limit and/or thermal cutoff. These are both sensors on the heating element housing. Thermal cutoff is at the top and the high limit is near the bottom above the heating element connectors. Test these with a continuity tester.
4- Heating element- Just below the high limit on the heater housing. Test for continuity.
5- Motor- The motor has to reach a certain rpm to activate a sinfrigrial switch inside the motor. If the rpm is not reached it will not allow current to go to the element.
6- Timer- Make sure you are trying this on timed dry. Sometimes people use air fluff and forget to change it back. The timer could also not be sending current to the heater.

Gas models
1- Electric ignitor- Inside the flame tunnel inside of dryer near where gas line hooks up. Usually if it glows than it is still good but check to see if it is sending and amp signal to the heat coils.
2- Heater coils are two valves that open up when the ignitor send signal saying the ignitor can ignite the gas. Heat coils will not open to send gas if it does not receive a signal from the ignotor. They look like two round disk with two wires running from ignitor.
3- Flame sensor- Change if you change the heater coils. The flame sensor could not be detecting the flame inside so it shuts down the ignitor.
4- Motor- See above
5- Timer See above

If you have any further questions or need further assistance please feel free to comment me back

There are several things that can prevent a dryer from not heating.. Unplug Power Before checking.
Electric Models
1- Power- Your dryer runs on 220volts. 110 runs the entire dryer and 110 runs just the element. Your breaker may have half tripped. Check to see if you are getting the correct amount of power by using a ohm meter. Also check the power cord for burn marks on the plugin and the cord itself.
2- The thermal fuse can prevent this from heating. The thermal fuse is a sensor on the blower housing the measures the temperature of the air. There is a cycling thermistat near the thermal fuse. If the dryer temp gets over 190-220 degrees the thermal fuse will blow to cut power to the element to prevent fire. You can test this by using a continuity tester.
3- High limit and/or thermal cutoff. These are both sensors on the heating element housing. Thermal cutoff is at the top and the high limit is near the bottom above the heating element connectors. Test these with a continuity tester.
4- Heating element- Just below the high limit on the heater housing. Test for continuity.
5- Motor- The motor has to reach a certain rpm to activate a sinfrigrial switch inside the motor. If the rpm is not reached it will not allow current to go to the element.
6- Timer- Make sure you are trying this on timed dry. Sometimes people use air fluff and forget to change it back. The timer could also not be sending current to the heater.

Gas models
1- Electric ignitor- Inside the flame tunnel inside of dryer near where gas line hooks up. Usually if it glows than it is still good but check to see if it is sending and amp signal to the heat coils.
2- Heater coils are two valves that open up when the ignitor send signal saying the ignitor can ignite the gas. Heat coils will not open to send gas if it does not receive a signal from the ignotor. They look like two round disk with two wires running from ignitor.
3- Flame sensor- Change if you change the heater coils. The flame sensor could not be detecting the flame inside so it shuts down the ignitor.
4- Motor- See above
5- Timer See above

If you have any further questions or need further assistance please feel free to comment me back.

Check the reset inside the dryer. You will need to open the machine. The part looks like this one. If this is ok, then check the heater element for continuity with a multimeter. If you need the heater element, here is a link to the part.

If it does not dry them all then the element is a good guess or the thermostat.

If it dries them but not all the way check that the moisture sensor is not turned down too far.

The following should help you.

How to Repair Heating Elements A dryer sometimes won't heat or heats too slowly because of a variety of reasons. By following the guidelines below, you can inspect the heating elements on a gas or electric dryer to pinpoint the source of the problem.

Troubleshooting the Gas Heater

In a gas dryer, heat is provided by a gas heater that is controlled by an air shutter. The gas heater is generally the source of no-heat or drying problems. You can often correct such problems by adjusting the air shutter on the gas burner, which is located along the bottom of the dryer.

To adjust the shutter, take out the screws and remove the panel that covers the gas flame. Turn on the dryer so the flame is burning. If the flame has a deep blue color and you hear air whistling around the burner, the air/gas mixture is receiving too much air. If the flame has a yellow tip, the mixture is not receiving enough air. Turn the thumbscrew or loosen the two screws slightly to increase or decrease the flow of air to the burner. Keep turning until the flame is a light blue color, without any yellow, and the whistling stops.

Gas dryers use an electric ignition device rather than a pilot light to light the gas heater: An element becomes hot and glows like the filament in a lightbulb. Electric ignition systems are always sealed; you can't adjust or repair them. If an electric ignition device fails, call a professional service person for replacement.

©2006 Publications International, Ltd.
In a gas dryer, heat is provided by a gas heater, controlled by an air shutter.
Electric dryers have self-contained electric heating elements.
Servicing the Electric Heating Elements

Electric heating elements, found in electric dryers, are self-contained units located in the back of the dryer. A defective heating element is frequently the source of no-heat or drying problems. Remove the back service panel to gain access to the elements.

The heating elements are located inside the heater ducts. If you think a heating element is faulty, test it with a volt-ohm-milliammeter (VOM) set to the RX1 scale. Disconnect the leads from the power terminals and clip one probe of the VOM to each terminal. The meter should read about 12 ohms. If the reading is higher than 20 ohms, the heater is faulty and should be replaced. Replace a faulty heater with a new one of the same type and electrical rating. A heater connected to a 115-volt line usually has an 8.4-ohm resistance; a heater connected to a 220-volt line usually has 11 ohms resistance.

The heater may also malfunction because it's grounded. To test for this, set the VOM to the RX1 scale and remove the leads to the heater. Clip one probe of the VOM to a heater terminal and touch the other probe to the heater housing. The meter needle should jump to a fairly high reading. If the needle flicks back and forth at a low reading, the heater is probably grounded and should be replaced. Here's how to replace the heater:

Step 1: Remove the back of the dryer. If necessary, also remove the cabinet top.

Step 2: Disconnect the leads and remove the screws that hold the duct in position. Then lift the entire heater unit out of the dryer.

Step 3: Remove the screws that hold the heating element in the duct.

Step 4: Slip the new heating element into the heating duct the same way the old one came out. Be careful not to damage the resistance coils. Replace the screws that hold the heating element in the duct, reconnect the leads, and screw the unit back into position.

Servicing the Fan

The most common dryer fan problem is lint clogging the air passages through the heater and through the dryer drum. To clear a clogged air passage, remove the back service panel of the dryer and back out the screws holding the air duct in place. Then reach into the duct and remove all the lint and dirt possible. Reassemble the parts.

Also inspect the fan for a loose screw connection where the motor shaft is set on the dryer's drum. Remove the back service panel, tighten the screw, and replace the panel.

I would start by sanding the flame sensor. It will be located in the path of the flame.

Your Heating Elements could have problemA dryer sometimes won't heat or heats too slowly because of a variety of reasons. By following the guidelines below, you can inspect the heating elements on a gas or electric dryer to pinpoint the source of the problem.

Troubleshooting the Gas Heater

In a gas dryer, heat is provided by a gas heater that is controlled by an air shutter. The gas heater is generally the source of no-heat or drying problems. You can often correct such problems by adjusting the air shutter on the gas burner, which is located along the bottom of the dryer.

To adjust the shutter, take out the screws and remove the panel that covers the gas flame. Turn on the dryer so the flame is burning. If the flame has a deep blue color and you hear air whistling around the burner, the air/gas mixture is receiving too much air. If the flame has a yellow tip, the mixture is not receiving enough air. Turn the thumbscrew or loosen the two screws slightly to increase or decrease the flow of air to the burner. Keep turning until the flame is a light blue color, without any yellow, and the whistling stops.

Gas dryers use an electric ignition device rather than a pilot light to light the gas heater: An element becomes hot and glows like the filament in a lightbulb. Electric ignition systems are always sealed; you can't adjust or repair them. If an electric ignition device fails, call a professional service person for replacement.

©2006 Publications International, Ltd.
In a gas dryer, heat is provided by a gas heater, controlled by an air shutter.
Electric dryers have self-contained electric heating elements.
Servicing the Electric Heating Elements

Electric heating elements, found in electric dryers, are self-contained units located in the back of the dryer. A defective heating element is frequently the source of no-heat or drying problems. Remove the back service panel to gain access to the elements.

The heating elements are located inside the heater ducts. If you think a heating element is faulty, test it with a volt-ohm-milliammeter (VOM) set to the RX1 scale. Disconnect the leads from the power terminals and clip one probe of the VOM to each terminal. The meter should read about 12 ohms. If the reading is higher than 20 ohms, the heater is faulty and should be replaced. Replace a faulty heater with a new one of the same type and electrical rating. A heater connected to a 115-volt line usually has an 8.4-ohm resistance; a heater connected to a 220-volt line usually has 11 ohms resistance.

The heater may also malfunction because it's grounded. To test for this, set the VOM to the RX1 scale and remove the leads to the heater. Clip one probe of the VOM to a heater terminal and touch the other probe to the heater housing. The meter needle should jump to a fairly high reading. If the needle flicks back and forth at a low reading, the heater is probably grounded and should be replaced. Here's how to replace the heater:

Step 1: Remove the back of the dryer. If necessary, also remove the cabinet top.

Step 2: Disconnect the leads and remove the screws that hold the duct in position. Then lift the entire heater unit out of the dryer.

Step 3: Remove the screws that hold the heating element in the duct.

Step 4: Slip the new heating element into the heating duct the same way the old one came out. Be careful not to damage the resistance coils. Replace the screws that hold the heating element in the duct, reconnect the leads, and screw the unit back into position