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6 Red Flags to Avoid When Considering a Heat Pump Installation

Simon Murray · 2024-08-27T20:25:25Z

As someone that's deeply involved in the design and installation of heating systems, I want to share essential advice for consumers considering an air source heat pump. My business partner, Luke, and I run Optimus Heating, and we’ve achieved recognition in the industry, winning Vaillant’s heat pump challenge last year and being one of 10 chosen projects in Viessmann’s Top of the SCOP’s competition. We specialise in creating highly efficient heating systems, often achieving efficiencies over 500%. This guide is not a pitch for business but a genuine attempt to help consumers navigate the misinformation surrounding heat pump installations. If you’re looking for a system with long-lasting efficiency, low running costs and minimal noise, here are the six red flags to avoid when considering a heat pump installation. Red Flag 1: Design Flow Temperature If you’re being sold a heat pump with a flow temperature of 50C, be cautious. A higher flow temperature can limit the efficiency of your heat pump and shorten its lifespan. Some manufacturers offer a 7-year warranty, which is far shorter than the potential lifespan of a heat pump installed with the correct parameters. The reason for this limited warranty is that manufacturers have no control over how the heat pump is installed, particularly concerning flow temperature. Many mass-market installations are designed for 50C flow temperatures, which can significantly reduce the lifespan of the compressor and increase noise levels. Additionally, for every degree increase in flow temperature, you may experience a 3% loss in efficiency. A heat pump designed with a 35C flow temperature can be up to 45% more efficient than one designed for 50C. Lowering the flow temperature naturally enhances efficiency, reduces running costs, extends the lifespan of your heat pump and minimises noise. Always question any company promoting flow temperatures above 45C. Red Flag 2: Rooms Designed at Different Temperatures CIBSE design guides recommend different temperatures for different rooms, such as 18C for kitchens and 21C for living rooms. However, designing emitters for varying temperatures in adjacent rooms can lead to inefficiencies. According to thermodynamics, heat will always move from hot to cold areas. This means that the warmer room will lose heat to the cooler room, causing your system to become unbalanced and your heat pump to work harder than necessary. It’s nearly impossible to maintain different temperatures in different rooms unless they’re vacuum-sealed. Your home should be designed with a single consistent temperature, with a setback temperature for cooler bedrooms overnight. Always question any company that doesn’t use one consistent design temperature across your property. Red Flag 3: Third Party Controls, Zoning & TRVs Imagine a simple two-up, two-down house, where each room has a 2.5kW heat loss/load, totalling 10kW for the entire house. If you install a 10kW heat pump and then zone the house into upstairs and downstairs, shutting off the upstairs zone during the day, you’ve essentially halved the water volume in the system. This reduction in water volume can cause your heat pump to cycle on and off, reducing efficiency and potentially shortening its lifespan. Heat pumps operate most efficiently when they can modulate their power to maintain a steady temperature. However, third party ‘smart’ heating controls often act like on/off switches, which can cause the compressor to cycle inefficiently. These controls were originally designed for combustion heating (boilers) and are not ideal for vapour compression heating (heat pumps). The best approach is to use weather compensation controls, which allow your heat pump to adjust its power output based on outdoor temperatures, maintaining a consistent indoor temperature without cycling the compressor. Always question any company that suggests using third party or ambient controls. Red Flag 4: Buffers, Hydronic Separation & Fixed Speed Circulation Pumps Buffers can be useful in some cases, but they’re often unnecessary for the vast majority of domestic UK housing stock. A buffer is essentially a cylinder of water connected to both the heat pump and the central heating system. In many cases, the use of a buffer with a fixed speed circulation pump can lead to inefficiencies, particularly when the pump doesn’t modulate according to the outdoor temperature. Most heat pumps are designed to operate with a temperature differential (ΔT) of 5C between the flow and return. However, when a buffer is used, the differential can become distorted, leading to the heat pump having to work harder to maintain the desired temperature. This can result in inefficiencies and increased wear and tear on the system. Buffers are often used by installers to simplify the installation process, but this can lead to a lazy and inefficient system. Instead, consider a volumiser, which can add system volume without the need for hydronic separation, allow...

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Air Source Heat Pumps (ASHPs)

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GT22

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24/09/2024 5:48 pm

@johnmo Thank you for providing that clarification.

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GT22

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24/09/2024 5:53 pm

@editor As requested a couple of photos. Many thanks for the information. It is so helpful to get that sort of clear information.

This post was modified 7 months ago 3 times by Mars

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GT22

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24/09/2024 6:30 pm

If I had a new ASHP installed I would still have to have a hot water cylinder. I watched the relevant video on this site. But I don't need any buffer unit.

Can I get clarification on this point.

Can the ASHP External unit, supply heat for Central Heating radiators or UFH at one temperature and one set of F&R pipes and do that supply directly? Bypassing the cylinder?

Or have I got that completely wrong and need to go away and do some serious reading? 🤔

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benson

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24/09/2024 9:11 pm

Nothing like a government grant to bring out the bandits for sure. An absolute minefield and as per my other post our current installation is hardly going smoothly. The company we went with however were one of the few who didn't want a massive amount of money (in effect the whole cost of the job minus the grant) up front, so at least I have some leverage to try and ensure it is completed to a decent standard.
As for optimus heating, came across as knowing their onions but I booked an initial home survey after a fair bit of back and forth communications (mainly telling me how good they were) and after all that they didn't turn up or contact me to tell me they weren't coming. Red flag #7?

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Mars

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24/09/2024 9:22 pm

@benson Optimus didn't turn up?

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benson

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24/09/2024 9:31 pm

@editor Nope. Made a firm appointment, and they didn't turn up or make any contact. I was slightly miffed.

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Mars

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24/09/2024 9:39 pm

@benson that's very disappointing indeed.

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JamesPa

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25/09/2024 8:56 am

Posted by: @gt22

↑

Can the ASHP External unit, supply heat for Central Heating radiators or UFH at one temperature and one set of F&R pipes and do that supply directly? Bypassing the cylinder?

Or have I got that completely wrong and need to go away and do some serious reading?

ASHPs (and fossil boilers running at a low flow temperature or with weather compensation - rare in UK, common in more enlightened countries) supply at one flow temperature at any one time and thus the installation will invariably include a three way diverter valve (or two two way valves) so that space heating or dhw can be fed, but not at the same time. The unit switches flow temperature and the diverter valve according to whether space of dhw heating is required.

If you need, in addition, two flow temperatures for space heating you must supply the space heating at the higher temperature and mix down for the lower. Again same for boilers and ASHPs. The ASHP COP will be determined by the higher, because that is the temperature it is required to produce.

Hope that clears matters up.

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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GT22

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26/09/2024 9:05 pm

@jamespa Many thanks. You are adding to my education on the current ASHP approach. So different from my 2009 Sanyo configuration, hence my questions.

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JamesPa

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27/09/2024 8:32 am

Posted by: @gt22

↑

@jamespa Many thanks. You are adding to my education on the current ASHP approach. So different from my 2009 Sanyo configuration, hence my questions.

My ashp journey is only 3 years old and in that time it's clear that thinking has matured quite significantly, albeit by no means universally. I can only imagine how much change there might have been since 2009.
Please continue to ask questions, people here are very willing to help and no question is silly.

This post was modified 7 months ago by Mars

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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Erik Verne

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29/11/2024 3:51 pm

Great article! You've highlighted essential red flags to watch out for when considering a heat pump installation. One innovative idea would be to include tips on how to verify the credentials of installers, ensuring both quality and reliability in the installation process. Keep up the informative work!

This post was modified 5 months ago by Mars

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JamesPa

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29/11/2024 4:03 pm

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One innovative idea would be to include tips on how to verify the credentials of installers, ensuring both quality and reliability in the installation process. Keep up the informative work!

@mars That could be a whole discussion in itself. I don't personally think its simple!

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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