A heat pump is blowing a fuse because a short circuit, overload or ground fault is occurring.
This could be occurring inside the heat pump, inside the outdoor unit, in the heat pump switch, in the switchboard or even in the cable between the heat pump and the switchboard.
This post will go into common reasons why a heat pump is blowing a fuse and what can be done about it.
Let’s first discuss why a fuse will blow in the first place.
What Is A Blown Fuse?
Electrical faults have the ability to cause fires and electric shocks. A ‘blown fuse’ or tripped circuit breaker is a protective mechanism designed to protect people and property from electrical faults.
They work by shutting off power to a circuit when the fault occurs.
Breakers are designed to operate on specific types of faults.
For example, an RCD is designed to trip when a ground fault occurs and a MCB will trip when a short circuit or overload occurs.
Ground Fault
This occurs when current from a live wire leaks to earth. This has the potential to give someone a fatal electric shock or damage sensitive electronic equipment.
An RCD is used to shut off power when this occurs.
Overload Fault
An overload occurs when a cable draws more current than it is designed to handle. This ‘overloading’ of the circuit causes the cable to heat up and potentially cause a fire.
A MCB will trip when this occurs. Overloads can be caused by having too many appliances on a single circuit. It can also be caused by mechanically overloading motors.
Short Circuit Fault
This occurs when the live wire crosses the neutral creating a ‘short circuit’.
This is an explosive event generating a lot of heat and smell. Short circuits are known to cause fires and MCB’s are designed to shut off power when they occur.
A heat pump will trip a breaker for these three key reasons. Taking a look inside the switchboard will reveal what type of fuse has tripped and therefore what kind of fault has occurred (Ground fault, short circuit or overload).
An RCD has a distinct appearance compared to a MCB. With this in mind let’s look at where the fault may be occurring.
Where The Heat Pump Could Have A Fault?
As mentioned above a fuse will blow or trip for three key reasons (short circuit, overload or ground fault) knowing where this is occurring will help determine the cause of the problem.
Here are some locations where a heat pump could have a fault.
1. In The Heat Pump Itself
The heat pump could have a short circuit or ground fault somewhere in the unit.
A short circuit will give obvious signs such as weird smells, presence of black carbon, melting or disfiguration around the heat pump.
If the heat pump hasn’t been serviced in a while, this may also be why.
2. In The Outdoor Unit
Signs include wear and tear of the outdoor unit or deterioration of the outdoor unit or cabling.
This could include seeing exposed cables and damaged conduit which occurs as a result of being exposed to the weather for long periods of time.
3. In The Switch
Water could have gotten inside the isolator or switch for the heat pump.
Insects such as ants are known to get into switches and cause short circuits and ground faults.
4. In The Cable Between The Heat Pump And The Switchboard
Damage to the cable due to rodents, sharp objects or general deterioration can cause the cable to short circuit/ground fault and blow a fuse. Overloading the circuit is also possible if new outlets or appliances have been installed on the same circuit.
5. Switchboard
Loose cables in the switchboard can also cause fuses to blow.
Determining Where The Fault Is Located
- Visual Inspection
Visually inspecting the above components will sometimes reveal exactly what is causing the fault. Some obvious giveaways include recent wet weather events causing water to get inside electrical components.
Other signs include ant activity in the home around switches or rodents in ceiling cavities. These clues make it easier to find the cause of the fault.
Weird smells or any signs of fire such as black carbon or melting around components such as the heat pump switch or unit also give clues.
- Electrical Testing
If the fault isn’t obvious by this stage, an electrician can do tests to find exactly where the fault is occurring. This includes testing the earthing system, testing the insulation of the cables (insulation resistance test), testing RCD’s, cable polarity and others.
Electricians Perspective
A heat pump blowing a fuse is most likely due to a short circuit or ground fault somewhere in the circuit.
This could be in the heat pump, outdoor unit, switch, switchboard or even in the cable between the heat pump and switchboard. We Fix Faults is an electrical blog dedicated to finding faults. If you have information you’d like to share send us a message above.