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    Air Source Heat Pumps

    Installing an air source hot tub heat pump could shave hundreds of pounds off your hot tub running costs each year.

    How do air source heat pumps work?

    An air source heat pump takes heat from the air, boosts it to a higher temperature using a compressor, and then transfers that heat to your hot tub. Here’s exactly how it works:

    • The heat pump’s fan draws air over tubes full of refrigerant, which is warmed up and turned into a gas.
    • This gas is then compressed using the electric pump, which significantly increases its temperature. Then it’s passed into a heat exchanger which transfers that heat to your hot tub.
    • The refrigerant gas inside the heat pump then cools and turns back into a liquid upon passing through the pressure valve, starting the process again.

    The warmer the weather, the more efficiently an air source heat pump works, as it can take more heat from the air. But heat pumps still work in temperatures as low as -15°C – it just takes them longer to heat your hot tub up.

    How much can I save?

    Air source heat pumps have an efficiency rating of around 350% – significantly higher than standard hot tub heaters.

    This can lead to some serious savings on heating costs. For example, it costs 20.06p per kWh to heat a home and/or hot tubs with standard electric heaters compared to just 5.73p per kWh with a typical air source heat pump. In initial tests with hot tubs we have seen hot tubs that were costing £2 per heat per day see that cost drop to £1 per day with a heat pump added.

    When it comes to your hot tubs’ electricity costs, it’s typical for an air source heat pump to save you in the region of £300 to £500 per year in reduced running costs. And the higher energy costs rise, the bigger those savings become.


    How quickly do heat pumps heat the water?

    How quickly your heat pump gets your hot tub up to temperature will depend on a few different things.

    Firstly, every heat pump is rated with a COP – a “coefficient of performance”. If a heat pump has a COP of four, that means it produces four kilowatts of actual heat for every kilowatt of electricity it uses. So, the higher your heat pumps’ COP, the faster it will heat up your hot tub (and the cheaper it will be to run).

    The ambient air temperature also plays a big part in how quickly a heat pump will heat up your spa. The less ambient heat that’s in the air, the harder a heat pump has to work to get up to temperature. So, you can expect your heat pump to heat your hot tub up slower – and cost more to run – during winter than in summer (while still being more cost-effective than a standard heater, even in winter).

    Last but not least, how well insulated your hot tub is will play a big part in how fast it gets up to temperature. The more heat your hot tub leaks, the slower it will heat up (and the more expensive it will be to keep it hot).


    What’s the payback period of a hot tub heat pump? 

    Since an air source heat pump costs a few thousand pounds and typically shaves around £500 off your energy bills a year, they usually pay for themselves after two or three years. After that, expect it to save you thousands of pounds over the years on the cost of heating your hot tub.


    Are there different types of air source heat pumps?

    There are two main kinds of hot tub heat pumps: those that use on/off technology and those that use inverter technology.

    As the name suggests, on/off models have two modes: on and off. These tend to be cheaper models, but because they don’t have variable speeds, they aren’t the most energy efficient.

    Inverter models, on the other hand, are powered by a variable-speed fan. A lot of top-end inverter heat pumps have smart tech within them that checks the ambient air temperature and adjusts the fan speed to get the best efficiency out of the heat pump. These models, therefore, tend to cost more upfront but cost less to run.


    Are heat pumps suited to the UK’s climate?

    While we think of ourselves as having lousy weather here in the UK, compared to a lot of other countries we have quite a mild environment.

    Our average temperatures are around 9 and 12°C, which is well within the working parameters of a good air source heat pump. In fact, some heat pumps can carry on heating water in temperatures as low as -15°C.

    As long as you make sure to buy a heat pump that can handle cold temperatures it will have no problem heating up your spa.

    Most air source heat pumps from good brands can operate down to -5°C, but look out for models that are only designed for summer use and actually only work down to 10°C.


    Do heat pumps still work in winter – and down to what air temperature?

    An air source heat pump from a good quality brand will heat your hot tub in temperatures as low as -15°C. That means they’re more than capable of handling our winters here in the UK and will continue working even in the worst of the winter weather.

    Just be sure you’re getting a model specified to handle those temperatures. And check the specs of the model you’ve got your eyes on to make sure it goes down to those temperatures.


    How much noise do air source heat pumps make?

    As a rule, air source heat pumps aren’t noisy. A good model in good condition won’t make more than a low whirring sound.

    Every air source heat pump requires a decibel rating by law. So, you’ll be able to see how loud the model you’ve got in mind is going to be before you have it installed.


    What does a hot tub need to be compatible with a heat pump?

    The first thing you need to fit an air source heat pump to your spa is space – enough to fit the heat pump itself and for it to generate good airflow.

    You’ll also need a hot tub with a cabinet that’s spacious enough to accommodate the extra pipework that will need to be fitted to connect it to a heat pump. A good hot tub dealer will be able to point you in the right direction here. Some hot tubs are even built “heat pump ready”, so look out for those to save yourself an expense.

    Another must-have for a hot tub you want to fit a heat pump to is good water flow. A hot tub with a very low-flow system with very few water turnovers isn’t going to give you a good exchange rate through a heat pump’s heat exchanger. So, the higher the water turnover rate through the spa, the more compatible it will be with an air source heat pump.

    You’ll also need a power supply for your heat pump. Some heat pumps can be powered off the hot tub itself alone, however, most need electrical requirements of a 13amp (or higher) power supply.


    How big is a hot tub heat pump?

    A 12kW air source heat pump will generally measure a metre in length by about 500cm in depth and 700cm in height. So they can be quite big. But, the bigger the heat pump, the bigger the surface area it will have and the more money it will save you.


    What size or output heat pump will you need?

    For domestic use, a heat pump with an output of anything from 5kW up to 12kW should do the trick. But the larger the heat pump, the quicker you’ll see a return on your investment.

    If you’re looking for a heat pump for a holiday let and a fast heat-up time is your priority, a 12kW model would be the minimum you should be looking at, potentially up to one with a 17kW output.


    Will having a heat pump fitted void my hot tub’s warranty?

    If you fit an air source heat pump to your hot tub without the permission of the manufacturer it will void your warranty.

    However, a good hot tub dealership with contacts within the brand can be worth its weight in gold here, as they can often get you authorisation to retrofit an air source heat pump to a model without voiding its warranty.

    If you would like more information would you like to discuss your options then please call a member of our team on 01159442211

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