News

Heat pumps keep showing up problems that were already there

We’re getting a lot more calls and enquiries about heat pumps at Power Capacitors these days. Not because the heat pump itself has failed, but because something else on site has started misbehaving after it was switched on.

Banks, hospitals, warehouses and offices are all swapping “old fashioned” gas boilers for air-source or ground-source heat pump units. It all makes sense on paper - lower carbon emissions & predictable running costs. The trouble is that these machines are full of inverters, and once you put another inverter-based load onto a site that already has solar, EV chargers, VSDs and LED drivers, the electrical network can start behaving in ways the original designers never expected.

In a lot of cases the heat pump isn’t creating a new problem. It’s just changing the way existing harmonic currents flow, and suddenly equipment that had been limping along for years starts tripping or shutting down.

What we actually see on site

The complaints are usually the same: lifts stopping for no obvious reason, random trips on distribution boards, intermittent faults that vanish when the heat pump is turned off. The heat pump itself is often running perfectly. It’s the older kit on the same supply that objects.

One recent banking HQ was a classic example. The customer replaced the gas heating system with an air-source heat pump unit. Within weeks the lift VFDs began dropping out. Everyone naturally assumed the lifts were the problem until someone noticed the trips only happened when the heat pump was running. Our Power Quality Survey showed elevated voltage harmonics that hadn’t been an issue before. The extra load had shifted the resonance enough to push the drives over the edge. An active harmonic filter sorted it out and the lifts have been fine since. Magic.

Another job was a hospital that was about to install a heat pump near sensitive imaging equipment. The contractor was nervous enough to call us in before they commissioned anything. We found the existing harmonic levels were already higher than ideal, so we fitted a filter first. The heat pump went in cleanly and nothing else has complained.

Why these sites are fragile

Most of the buildings we look at aren’t just adding a heat pump. They’re also adding solar, EV charging, battery storage and LED lighting upgrades at the same time. Each piece of kit might meet its own standards in isolation.

Put them all on the same busbars and the interactions become hard to predict from a simple ‘desktop’ study.

That is exactly why we keep recommending power-quality surveys both before and after the heat pump goes in. The baseline measurement tells you what you’re starting with. The second set of measurements - after commissioning - shows whether anything has altered. The top-of-the-range analysers we use pick up the harmonics, flicker, transients )and the odd network interaction) that would otherwise stay hidden until something trips at 3.30 on a Saturday morning!

Bottom line

Heat pumps are going to keep arriving on commercial and public-sector sites. So are PV arrays, chargers and storage systems. The electrical environment is getting more complicated, and power quality is no longer something you can leave until the snagging list.

If you’ve had unexpected trips or shutdowns after a heat pump went live, the fastest way to find out what’s actually going on is usually a proper power-quality survey. In our experience the heat pump is rarely the villain - it’s just the thing that pointed out the problems that were already there.