Why is my heat pump not turning on? Experts explain what you can do to solve it — and when to call in a professional

If you’re currently scratching your head and wondering, ‘Why is my heat pump not turning on?’ you’re not the first person to ask this question. After all, heat pumps run like well-oiled machines 99% of the time, but that extra 1% can leave you feeling stressed and confused.

Although heat pumps aren’t as popular as gas central heating just yet, there’s no doubt that they’re rising in popularity - and for good reason. As one of the most efficient ways to heat a house, they can help you save energy and money throughout the year, while cutting down your carbon footprint simultaneously. But they’re not foolproof, and one of the most common heat pump problem is it not turning on.

As Michael Zohouri, founder of The Retrofitters explains, ‘Often, the cause is something relatively simple. There are a few things homeowners can check before calling in a professional.’ Below, we’ve outlined 5 of the possible reasons why a heat pump isn’t turning on - and what you can do about it.

1. There’s an error code

Although heat pump units and their components may seem daunting and impossible to understand, the control panels of these heating systems tend to offer all of the information you could need to know. So, if your heat pump isn’t turning on, your first step should be to check the control panel for any error codes or messages.

This is echoed by David Leviseur, CEO and co-founder of heat pump specialist Fornax. He says, ‘It may have an error code displayed indicating a fault which would prevent it from operating. You can look up the error code online and/or in the equipment manuals provided by the installer when the system was put in.’

However, David advises that you don’t try and rectify this error code yourself. ‘As a first step, contact the engineer who installed the system originally; it may be under workmanship or equipment warranty and they can diagnose and repair at no cost or, if it's out of warranty, quote for doing so.’

2. The thermostat isn’t in the right mode

Like gas central heating, heat pumps also come with thermostats, allowing you full control over their heat output - and they even help if you decide you want to turn off your heat pump at night. But just as your central heating won’t turn on if your thermostat is off, a heat pump won’t turn on if the thermostat isn’t in the right mode.

Michael says, ‘Make sure it’s set to the right mode—heating or cooling—and that the temperature is set higher or lower than the current room temperature.’ The best case scenario is that your heat pump will turn on again once it’s in the right mode.

If your heat pump still isn’t turning on, it’s time to check the thermostat itself. Charles McAlpine, HiiLIFE’s climate solutions expert and Technical Sales Director, explains, 'Smart thermostats can also require periodic attention. Ensure their batteries are charged and that the system is properly synced with the heat pump.'

He adds, 'If the connection between the two has been disrupted, consult the product manual or seek professional assistance to re-establish the link. Regular checks and maintenance can prevent these issues from arising and keep your heat pump running efficiently.'

3. There’s been a power surge or power cut

Although heat pumps have the power to redefine how you keep your home warm in winter, they’re also electrical appliances attached to the mains electrics at your property. So, any electric change could result in your heat pump not turning on - including a power cut or power surge.

Michael suggests to, ‘Check your fuse box. A power surge or overload might have tripped the circuit breaker linked to the heat pump. If that’s the case, resetting it could solve the problem. But if the breaker trips repeatedly, that’s a sign of a more serious electrical fault that needs professional attention.’

If you haven’t had a power cut and you know for certain that the circuit breaker hasn’t tripped, it’s a good idea to visually inspect the wiring of a heat pump. However, it’s vital that you don’t start poking your fingers around the wires if you suspect there could be a problem with the wiring.

‘Over time, connections can become loose, especially in older systems. But this is definitely something a qualified electrician should handle,’ warns Michael.

4. It’s low on refrigerant

Although most people use heat pumps to heat their homes, they can’t work their magic without a constant supply of refrigerant. And if your heat pump is low on refrigerant, it might not turn on at all and you may be left scratching your head.

Michael says, ‘Without enough refrigerant, the heat pump can’t function properly.’ Thankfully, there is an easy fix if your heat pump is low on refrigerant.

A top-up of refrigerant is something a heat pump engineer will include in their service of your heat pump, so you shouldn’t need to do anything. But if levels are running especially low and you don’t think you’ll be able to last until your next service, contact your installer or a qualified engineer to get it done as soon as possible.

5. The air filters are blocked

Many electric appliances have air filters, and heat pumps are no different. But if you find that your heat pump isn’t turning on, you might want to check whether the air filters are blocked or need cleaning. In some cases, you can use one of the best vacuum cleaners to suck up any excess dirt or dust.

Michael explains, ‘Blocked filters restrict airflow, which can cause the system to overheat and automatically shut down as a safety measure. Cleaning or replacing the filters regularly can prevent this from happening.’

However, if your heat pump engineer continues to clean your filters during its annual service, it may be that blocked air filters aren’t the problem.

That’s why Michael advises, ‘If the system still refuses to turn on, it might be a faulty compressor or even a frozen outdoor coil. These kinds of faults are more complex and really need a trained heat pump engineer to diagnose and repair. Heat pumps are sophisticated systems, and sometimes, it takes an expert to get to the root of the problem.’

FAQs

How do you reset a heat pump?

If you want to reset a heat pump, you should first consult your manual to ensure you follow the required steps. In general, though, the best way to reset a heat pump is to turn it off at the thermostat or circuit breakers and then wait around 10 minutes.

Then, turn it back on to reset your heat pump. If this doesn’t work, you should reach out to your heat pump installer or a registered heat pump engineer to help you.

How do I fix my heat pump not heating?

If your heat pump is not heating, your first step should be to check the thermostat and ensure that it’s in ‘heating’ mode rather than ‘cooling’ mode. You should also check whether the temperature is set correctly, and not too low.

If this doesn’t solve the problem, it’s a good idea to check the air filters and inspect the exterior unit for any signs of damage or blockage. However, most experts would advise trying to fix your heat pump yourself. Instead, call in a professional.

If your heat pump wasn’t turning on, you should hopefully have an idea as to why now - and what you can do about it.