Heat pumps / VRF faults
Heat pumps and variable-refrigerant-flow systems.
Six rules for heat pumps and VRF: auxiliary heat running without an outdoor lockout, excessive defrost, compressor short-cycling, reversing-valve and mode mismatches, indoor units fighting each other, and one unit carrying the whole outdoor unit. Aux heat alone can double a heat pump’s winter bill.
How to read it. A day and a half at a heat pump. Blue is the outdoor temperature; the dashed green line is the temperature below which auxiliary electric heat is allowed. The two bars show when the compressor and the auxiliary heat are running. Red blocks are auxiliary heat running on mild afternoons, above the lockout, when the heat pump alone should carry the load.
The rules
- HP-01
Auxiliary heat without lockout
Electric resistance / auxiliary heat runs while it is warm enough for the compressor to carry the load.
Capacity-basedBAS trends - HP-02
Excessive defrost
The outdoor coil is defrosting far more than it should.
Capacity-basedBAS trends - HP-03
Heat-pump compressor short-cycling
The heat-pump compressor is starting far more often than a healthy unit should.
Capacity-basedBAS trends - HP-04
Reversing valve / mode mismatch
The unit says heating but the supply air is colder than return (or the opposite in cooling).
Capacity-basedBAS trends - VRF-01
VRF indoor units in conflicting modes
On a heat-pump (non-heat-recovery) VRF system, some indoor units call for heating while others call for cooling.
Capacity-basedBAS trends - VRF-02
VRF indoor unit runtime imbalance
One indoor unit runs several times longer than its siblings.
Diagnostic · reliabilityBAS trends
What is short cycling costing?
Estimate the energy wasted on starts, and remember the wear is the bigger bill.
Enter positive numbers to see an estimate.
Each start costs roughly a couple of minutes of full-load energy before the unit is doing useful work. Extra starts above a sane rate, times that penalty, times the unit size and the affected hours. Energy Agent counts the starts from status trends.
Screening estimate. Energy Agent measures the real fault hours and load from your trends and prices them at your tariff.
See these rules run on your building.
Send twelve months of interval data and a BAS trend export. Energy Agent returns a ranked list of what is wasting money, what each item is worth per year at your tariff, and what to do about it.