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No Heat

No Heat

NO HEAT – The space temperature drops more than 3 degrees below the thermostat's heating setpoint.

Scenario 1 – Cool Air Blowing from Registers

A heat pump has two stages of heat. The primary (1st) stage is the heat pump itself. If the heat pump is unable to produce sufficient heat to satisfy the thermostat temperature setting, the auxiliary heat (2nd stage) is activated to work in conjunction with the heat pump. The majority of the "no heat" calls with a heat pump, the auxiliary heaters have failed to operate.

POSSIBLE PROBLEM & DESCRIPTION

Clogged Air Filter/Dirty Coil/Restricted Ductwork

All new York air handlers have a feature which disables the auxiliary heaters if the over-temperature device is activated three times during a run cycle. This "lock-out" also energizes the fan to run continuous until manually reset.

The most common cause of this failure is low airflow across the heaters. The most common source of low airflow is a clogged air filter, but can also be caused by a dirty indoor coil or closed/restricted ductwork.

Once the source of the airflow restriction is eliminated, reset the lock-out by cycling high-voltage power to the air handler.

Loss of Power to Auxiliary Heaters

Many air handlers have more than one breaker that provide power. For instance, on an air handler with 15kw heaters, one breaker powers the blower and one heater while another breaker powers the remaining two heaters. Check the breaker panel and the air handler itself for any tripped or turned-off breakers.

Return Ductwork Issues

If the return duct system has openings or has come loose (especially in an unheated attic or crawlspace), it will draw-in cold air and, even if the heat pump is operating normally, blow cool air from the supply registers and may not heat the space. This condition is easiest identified by checking the return air temperature entering the air handler. An extremely cool return air temperature would indicate ductwork problems.

Failed Auxiliary Heater Controls - Qualified Technician Recommended

All air handlers have some type of control to energize the auxiliary heaters. Most newer air handlers use an electronic control board to cycle the heaters. Older air handlers use mechanical heat sequencers to power the heaters. It is not uncommon for control boards and sequencers to fail over time.

Bad Thermostat - Qualified Technician Recommended

A less likely, but possible, cause of "no heat" on a heat pump system is a bad thermostat. We have seen instances on newer electronic thermostats where the relay outputs fail to energize the auxiliary heaters even though the thermostat display shows that "Aux Heat" is activated.

Heat Pump Failure - Qualified Technician Recommended

Another unlikely, but possible, cause of "no heat" on a heat pump system is a failure of the heat pump itself. The reason that this is an unlikely cause is the fact that the auxiliary heaters should energize to keep the space warm even if the heat pump stops working.

Some York units have a feature which disables the electric heaters above a certain outside temperature (usually around 35-40 deg). If the outside air temperature is above this point, a heat pump failure may cause "no heat".

Scenario 2 – No Air Blowing from Registers

POSSIBLE PROBLEM & DESCRIPTION

Thermostat Set Incorrectly

Many "no heat" calls, especially early in the heating season are the result of thermostats that are not set correctly. Make sure the system setting is set for either "Heat" or "Auto" and the desired temperature is set higher than the space temperature.

Loss of Power to the Air Handler

Many air handlers have more than one breaker that provide power. For instance, on an air handler with 15kw heaters, one breaker powers the blower and one heater while another breaker powers the remaining two heaters. Check the breaker panel and the air handler itself for any tripped or turned-off breakers.

Bad Thermostat

A less likely, but possible, cause of "no heat" on a heat pump system is a bad thermostat. It is possible for the thermostat to fail to energize the heating outputs.

Try turning the thermostat to the "Off" position, then back to "Heat" or "Auto".

If you have an electronic thermostat, you may also want to try installing new batteries.

Failed Blower- Qualified Technician Recommended

If the blower motor or the blower motor control fails to start, the heat pump and auxiliary heaters will still attempt to operate. This condition is generally accompanied by a burning or hot smell from the supply registers.

In this condition, you should turn the thermostat to the "Off" position and contact a qualified technician to diagnose.

Our focus and specialty is quality installation, service and repair of heating and air conditioning systems - both residential and commercial.

For more than 45 years, GHAC, Inc. has been the trusted name in HVAC for customers all across the Tri-State.

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