Geothermal: Heating
Re: High Electric Bill / Running Aux Ht
When a customer with a geo-thermal unit reports an electric bill that is much higher than normal, that typically means that the heat pump is not heating properly and the auxiliary heaters are operating more than normal.
► The blower and auxiliary heaters are typically working normally or the customer would also be experiencing no heat.
Qty |
Possible Causes |
2 |
Refrigerant Charge |
1 |
Bad Expansion Valve |
1 |
Bad Capacitor |
1 |
Thermostat Issue |
|
Water Flow Problem |
|
Low Water Temperature |
|
Bad Compressor |
|
Ductwork Problem |
|
Bad Control Board |
CHECKOUT:
1. Check Unit Status
- Set the thermostat to call for heat.
- Inspect the geo-thermal heat pump to see if the compressor is operating.
- Check for 24VAC between "Y" and "C" on the unit control board.
- No Power = No Call from the Thermostat --> Check Thermostat
- Power Present--> Compressor should start within 5 minutes.
- Check the control board for active Diagnostics.
- LED Flashing = Control in Lockout due to active diagnostic --> Short TEST pins to show diagnostic code.
2. Check Compressor Operation
- Compressor Hums but Doesn't Run = Bad Capacitor, Locked-up Compressor, or Burnt Compressor Wiring
- Compressor Does Not Try to Start --> Re-Check for 24VAC between "Y" and "C" on the control board.
- No Power = No Call for Compressor --> Re-check Thermostat
- Power Present + No Diagnostics + 5 Minute Delay + No Contactor = Bad Control Board or Bad Contactor
- Check for 24VAC across both contactor coil wires.
- Power present but contactor doesn't pull-in = Bad Contactor
- No Power --> Suspect Bad Control Board
3. Check Loop Water
- Pumps
- Use an Amp Probe to check amperage on each loop pump to ensure that they are operating.
- Pumps should start with the compressor.
- Each pump should draw .7 to .8 amps.
- Pressure Drop
- Use a Pressure Gauge to check the water pressure drop through the unit.
- Use performance chart to calculate and record the GPM/Ton.
- No Pressure or Negative Pressure = Low Water
- Temperature Drop
- Use a thermometer to check the water temperature drop across the unit while the compressor is operating at full capacity.
- Check and record the inlet water temperature.
- Check the outlet water temperature.
- Calculate and record the water temperature drop.
4. Check Refrigerant Pressures
- Hook-up refrigerant gauges to the pressure ports on the unit.
- Blue --> "True Suction" Low Pressure
- Red --> High Pressure
- Place an insulated temperature sensor on the liquid line between the evaporator coil and expansion valve.
- Monitor and record the pressures as the system operates.
- Calculate and record the "Sub-Cooling".
- Check "Saturation Temperature" from the discharge pressure gauge.
- Subtract the Actual liquid line temperature reading.
- Sub-Cooling = Saturation Temp - Liquid Line Temp
- (Split-Systems) If a Liquid-Line Sight Glass is installed, observe for bubbles in the sight glass in-lie of checking sub-cooling (after the system has been operating for at least 5 min.)
- Bubbles = Low Refrigerant Charge
5. Check Air Temperature Rise
- With the auxiliary heaters disconnected (remove "W" from the low voltage terminal block):
- Check the Return Air Temperature near the unit or in the filter compartment.
- Abnormally Low Return Air Temperature --> Check Return Ductwork for Cold Air Infiltration
- Check the Supply Air Temperature.
- Calculate and record the air temperature rise.
- RE-HOOK THE "W" WIRE ON THE CONTROL BOARD.
6. Check Thermostat Aux Settings (New VisionPro 8000)
- Check the Aux Heat Control Setting
- Under Installer Setup, go to Setup #301
- Change from "Basic" to "Advanced"
- Press Next to advance to Setup #309 - "BACKUP HEAT DROOP"
- Change from "comfort" to "2.0" or "3.0"
- Press Next to advance to Setup #311 - "UPSTAGE TIMER FOR BACKUP HT"
- Make sure value is set to "Off".
- Press Done to save changes.
- This change doesn't allow Aux Ht operation unless the indoor temperature drops [#309] degrees below setpoint.