We Fix Our Air Source Heat Pump’s Flow Fault By Cleaning The Filter

by Mars

Our air source heat pump recently went into standby mode for two consecutive nights, during which time it refused to heat the house or hot water in order to prevent any damage to the system. We were able to diagnose the issue with Global Energy Systems, and narrowed the issue down to the fact that the flow and return filter was blocked.

We cleaned the filter on our 18kW Caernarfon air source heat pump in order to restore and maintain a flow rate of around 25 litres per minute. As a result of the blockage, our flow had dropped below 15 litres per minute, which prompted the pump to go into standby mode.

Disclaimer: What we show in the video is how we cleared the blockage in the filter of our air source heat pump in order to get it back up and running after having consulted with an engineer at Global Energy Systems. We do not recommend undertaking this work yourself and would suggest calling your installer, manufacturer or trained engineer to assist if you have a similar issue or if your pump is not functioning as it should. You must make your own judgements on any action you carry out after watching the video, but if you decide to clean the filter yourself on your air source heat pump, we will not be liable for any resulting injuries or damage to the air source heat pump system, nor will we accept any liability arising out of incomplete or incorrect information. If in doubt, please call an air source heat pump professional.


anna mycoe 18 January 2021 - 08:54

Hi there
We have had an ASHP installed on the 11th Jan,
It was -6 for two nights concurrently almost immediately after the install. It was cold, as it took a few days for the glycol to mix in the system. We replaced a 30 year old oil guzzler. I’ve found so far that I need to leave the night temp at around 18 so that it can reach 21 during the peak times when we are in (almost 100% of the day during lockdown)
Butter hot water had been excellent, no issues at all once I have set the schedule to suit us. My husband finds it cooler, but then he likes to sit in his shorts and tee shirt of an evening. The house is a really old cottage, with some modern ish extensions and the insulation isn’t superb but we are working on that as we renovate. We’ve been here 18 months and wanted an alternative to the noisy smelly oil boiler and want the space the tank used. We’re hopeful that we’ve made the right choice ! Ours is a Grant, 14Kw I believe. What’s the best way to monitor the electricity consumption?

Mars 18 January 2021 - 10:08

Thanks for the feedback Anna, and for sharing your set up. You’ve had your ASHP installed at a testing time of the year. Have you found that it’s keeping the property sufficiently warm?

A potential ‘fix’ for more consistent temperatures would be leave it at 20C all day and see what happens, as opposed to moving from 18-21C which will make the pump work harder when heating rooms up.

Monitoring electricity consumption? Good question. Our ASHP has a 4G antenna and it feeds back data to Global Energy Systems. We have a user login with them on their website where we can access our data and we can see exactly how much electricity our heat pump has used on a day-by-day basis. I don’t think that this set up is very common though, so I don’t think it’s something you’d have access to. My first suggestion would be to call your installers and ask them if the control panel for your Grant ASHP monitors and collects this data.

We also have two metres installed that we use to submit data to the RHI to get payments. One of these metres collects data on how much electricity we’ve used to generate our heat. If you have one of these metres you could, on a day-by-day basis, jot down the electricity used every day at the same time, and that would allow you to work out how much electrify the the pump is consuming over 24 hours. It’s a manual exercise, but it can be effective.

We’re also lucky in that we have solar panels with a realtime electricity usage and production, and I know that as a household we’re consuming (on average) 0.4kWh to run appliances in the house (fridges, TVs, etc.), so anything over that is usually what our ASHP is using, which allows me to see spikes in ASHP activity. You could, as another manual exercise, monitor your electricity metre. When your heat pump is off, try to work out what your average consumption is – the might be easier to do in the summer when the ASHP does not come on frequently. This will give you a base figure to work from, and you can then watch your electricity metre to work our how much power your ASHP is using.

Hope this helps.

anna mycoe 18 January 2021 - 21:01

Thanks Mars

So far I’m very impressed with the unit, I’ll see how I feel after a year and some bills to compare. However tbh, as long as it’s not more expensive to run than the old oil system I’ll be happy, it was more about energy efficiency, space saving and having little options as we do not live on the gas network. I’ll try the 20 degrees setting, thanks

Mars 18 January 2021 - 21:37

Good luck Anna. We have definitely outperformed our old oil boiler in financial terms and have saved money. December and January are always a tad heavy, but for the remaining months of the year, they are very efficient to run.

Name 26 January 2021 - 17:54

Anna, buy and install an electric meter for the pump , like the one you might have on the whole house, as a simple solution.

anna+mycoe 26 January 2021 - 20:14

Great idea ! And simple too, didn’t occur to me.
Am looking at solar panels and batteries now too
Anyone have any input ??


Mars 27 January 2021 - 19:34

Regarding solar panels, we’ve found out that roof pitch is extremely important during the winter months when the sun is low in the sky. Examine the data for October to February to see how much power you can generate.

anna+mycoe 27 January 2021 - 20:02

Great thanks will do ! Had two quotes so far very similar, we want battery storage too for the summer months. I’ll check the data out

Mars 27 January 2021 - 20:17

Nice. Do you have an idea of how large the solar PV array will be?

anna+mycoe 27 January 2021 - 20:30

Hiya, 3.5 – 3.8 Kw had quotes for 11 & 12 panels and a 4.8 battery roughly give or take

Mars 29 January 2021 - 20:40

Exciting. Let us know what you decide. Out of curiosity, what brands are the panels and batteries?

anna+mycoe 29 January 2021 - 21:31

Well, things have moved on a pace since then. We’re exploring a small wind turbine instead, we live on the foot of the moors here, small plot just over an acre. So we’re not always blessed with long days of sunshine, but there is always a breeze, even in the dark ! I’ll keep you updated

Mars 30 January 2021 - 09:02

Amazing. The wind turbine sounds like a great alternative. We were thinking of adding something along those lines and was going to do some research this summer. Please share your findings on them, and what’s involved from from a planning, installation and implementation perspective.

Adam Stanley 22 December 2021 - 12:22

I’m not actually a DIY lover guy but after reading your post, I just got the courage to do small fixing and maintenance work by myself and for the first time I have cleaned my air source heat pump today with some help from my cousin who is a HAVC professional. Congrats to me!!! and Thanks to you for sharing this nice post and video with us.

Mars 22 December 2021 - 16:25

That’s awesome Adam. I’m glad you did it and congratulations are most certainly in order.

Heat pump maintenance is actually straight forward and it certainly builds confidence and knowledge of the unit. We do our own maintenance and the next step in our evaluation will be to clean/flush the heat exchanger on the machine which is still a bit daunting. I’ll try and do that this coming summer.

What heat pump do you have and what did you clean/maintain?


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