RED Heat Pump

  • Heat Pump: RED 16kW
  • Installer: SA Energy Ltd

fWe’d heard only recently about heat pumps but became interested when a resident nearby had one installed under the RHI grant scheme. This scheme ended in April 2022 (although other grants are now available). On the face of it, our house would possibly not be an ideal candidate for a heat pump due to its size and the fact that it is a 100-year-old house with less-than-ideal insulation. It has loft and cavity insulation that was done in the 90s. We topped up the meagre 100mm loft insulation to 300mm soon after we moved in (2005).

Why did we think about going for a heat pump?

Our current boiler was frequently breaking down and, although only seven years old, seemed to be a bit of a lemon. The hot water cylinder had also started to leak. A couple of plumbers said that a repair was possible, but couldn’t guarantee it, especially as the cylinder was fifteen years old and out of warranty. So we were already in the position of having to invest in a new system, and the RHI grant would mean a heat pump could probably be installed at the same cost as, or very little more than, a new gas system.

We contacted several installers to survey and quote with very mixed results. Before a heat pump can be installed, the installer needs to make quite accurate measurements and projections in regard to the amount of heat required for any particular house. It became obvious that the more conscientious installers measured up all the rooms and did the calculations, with a consensus that we need close on 16kW. This is when we discovered there may be one or two cowboys out there as one company just had a quick look round and came up with a quote for installing a heatpump that we subsequently discovered would not be adequate. Another installer suggested we needed two heat pumps.

In the end we decided on an installer who recommended a modern “new technology” pump that was super efficient and so would be adequate for a large detached house. We were further impressed by his idea to split the existing pipework into two zones: this allows the upstairs to have a different (lower) thermostat setting to downstairs. Assuming we didn’t need or want the bedrooms quite as warm as the living room, this would save energy and money.

Because heat pump systems usually require larger radiators than gas systems, prior to installation we turned down the temperature of our existing gas boiler to simulate the type of radiator temperature we would be getting with a heat pump. Although the installer will do calculations based on room volume and house efficiency, this is a good way to get a rough idea before biting the bullet and swapping out more radiators than is actually necessary for your needs.

We were all set to go for a February install in order to get the RHI grant but at the last minute, the installer called to say he could not go ahead as his refined heat loss calculations meant that this pump would not quite be adequate for the house. This is crucially important as all installers are obliged according to their MCS certification (required not only for peace of mind but in order to qualify for the RHI grant). The obvious solution was to retrofit underfloor insulation which in our case was not too difficult as we had traditional board suspended floors. After doing this, we were all ready to go ahead and had it installed mid February 2022 – catching the tail of winter to get a decent idea of how it was working.

This all went reasonably smoothly. We did need to add/enlarge some radiators – however, we decided to keep a couple of existing radiators in bedrooms that are not used regularly, and in any case we tend to prefer cooler bedrooms.

What do we think of it so far?

First of all, as made clear by the installer, with current energy pricing, a heat pump is not likely to save you money compared to a gas boiler. Looking at our bills, this year we paid about the same for electric during February and March as we did for electric and gas combined in the previous year.

We are very impressed by the two-zone system. Overall it works very well, but we quickly became aware of a couple of issues caused by fitting a new heat source to an old system of pipes and radiators.

Kitchen radiators

With our old gas system, our kitchen was heated by a kick-space (plinth) convector radiator. This is a small but powerful radiator that sits at floor level inside the cabinet plinth. It uses a fan to be able to convect a lot of heat from a small radiator. The new design to use with the heat pump added a conventional radiator but also relied on retaining the kick space heater. As it turned out, this kick space heater does not work with the low temperature of a heat pump system so we now need to either add another conventional radiator or to find a kick space heater that will deal with lower temperature.

Extension pipework

Our 1920s house has a 1960s extension with a separate shower/toilet. This now serves as a home office, but with the new system it does not quite get warm enough. The installer’s plumbers initially had various theories about this:

  • Too many isolation valves within the pipework.
  • System needs rebalancing via the valves on other downstairs radiators. They did this but no difference.
  • Pipework to extension was the wrong size – ie the plumbers in the 60s may have (literally) cut corners and should have run a separate branch from the main 22mm feed.
  • Blockage in pipework.

The plumbers then discovered that the TRV valve that came with the radiator was faulty so they changed this, however the radiator still was not heating the room adequately.

They then found a lot of gunge in the valve and cleaned it out. The radiator still was not heating the room adequately.

We found that by turning off the extension shower room towel rail, the main room gets warmer, but of course this doesn’t seem an adequate permanent solution.


The control panel was mounted on the cylinder in the loft. The installer had reassured us we would not need access to the panel as we should not mess with the settings. This soon ended up being inconvenient because we found that we needed to adjust the hot water schedule depending on whether we had house guests or not. We had also read that it is useful to adjust weather compensation settings to find the most economical setting.

No power flush?

While all this was going on, we also noticed that the hall radiator was cold at the bottom, so wondered if the system could do with a power flush. Although the installer said a power flush is not required by the heat pump manufacturer, the distributor pointed out that in older properties a power flush was essential. So this is where we are currently: we will get a powerflush and then we can re-evaluate whether the pipework to the extension is adequate. Renewing it directly from the master 22mm feed is not too much of an issue, so one way or another we are confident about getting this all working soon. Touch wood.

More installation issues.

In September the control panel (situated on the cylinder in the loft) suddenly decided to stop working. A local electrician diagnosed that the installers had cut corners when wiring it in to the mains, and did not use enough connectors so they had to jam two wires together. A strand of copper had obviously caused a short circuit which blew the control PCB, along with the manifold PCB and the heat pump PCB.


Luckily we managed to contact the installer eventually who replaced all three, however we were without heat for three weeks as the parts were not available in the UK and had to be sent from Ireland.

At this point we were getting nervous that if anything went wrong when out of the warranty period we may have real problems. We also found that after the installers two year of annual service, we could not find any company who offered heat pump service contracts who were prepared to service a RED due to it not being a traditional heat pump. Only one company said they might but as they sucked the air in over their teeth we could almost hear pound note signs racking up.

What we have learned

Always make sure that the installer does a thorough survey of the system in advance. In our case it was obvious (looking at the instruction manual) that the kick space heater was very unlikely to work with a heat pump. The extension pipework, although adequate for high temperature and flow rate from a conventional system, does appear to have been running too many radiators already, so this should have been flagged up by the installer as a potential issue in advance. And finally, insist on a power flush!

[UPDATE Jan 2023]

Some of these issues were resolved:

  • A powerflush was carried out on zone 1
  • The installer moved the control panel into the house.
  • After some more plumbing work the kick space heater does work, but depends on the flow temperature setting. This makes sense but what it means is that it will only come on when the the system temperature is high enough. Possibly this is not an issue , as it can be viewed as a “top up” to the main radiator system and may only be necessary when very cold and weather compensation causes the temperature to rise.
  • A section 15mm pipework has been replaced by 22mm to adequately serve the extension radiators.

During extreme cold < -0 degrees the system does not reach design temperature of 21 degrees. This may be due to an issue with defrost cycle. Although we would expect the design temperature to be possible this is actually higher than we would mostly require.

Potentially good news news was that Octopus had bought RED, ostensibly in order to develop their own line of heat pumps.

[UPDATE November 2023]

Further to finding a leak in the roof of the extension, the roof was replaced in Feb 2023. This meant it was better insulated due to current building regulations. We also fitted new French windows with triple glazing and the issues with the room being too cold seem to be solved. This basically due to the extension not performing as well as it could.

[UPDATE April 2024]

After attempting to get the installer to carry out the second year maintenance and not getting any responses, we presumed they were no longer interested in helping us with the system. This was very worrying as we wanted to have it regularly serviced – we had hoped that with RED having been bought by Octopus there might be a solution. But we weren’t very confident because we found that Red were developing a new line of heat pumps for Octopus and this one was no longer on the market.

Octopus to the rescue!

However, in March of this year we contacted Octopus and they told us that as part of their Red takeover, they were training up their staff to be able to work on the “legacy” Red heat pumps. Their training programme was actually a real boon, because after booking the service we got not one helpful friendly heat pump expert but three. Steve the engineer brought along Jo who was doing part of here training in the field and the area heat pump supervisor Murray also came along.

They went to great lengths to get it right, after spotting something in that heat pump that could potentially be an issue, they rang Ireland and spoke to Jason (the owner and chief developer of Red) and were able to get the information that all was well. They did however spot that there may be a leak in the system. testing showed that it wasn’t in the pump or manifold so bad news – probably under the downstairs floor somewhere. Not an easy thing to find.

However I was just in the process of showing Murray the underfloor insulation (I had left one floorboard loose) and he spotted the leak. It was on a compression fitting that the installers plumbers had not tightened up properly so Jo fixed that, all part of the service . Brilliant!

Murray also confirmed that the control panel should be easily accessed by the customer and advised us on how to adjust the thermostat and weather compensation to get the best economy. He said in all Octopus heat pump installations they take time to discuss how to do this with the customer.

(More about weather compensation and thermostat settings for heat pumps to come in a future blog)


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