In February of 2024, I decided I was going to have a go at installing my own Air Source Heat Pump.
To give me the best possible chance at doing a quality install, I’m going to go very slowly and do all the assessments and blocks of research in a sequence. I will document the journey, every step of the way, so if you want to follow along be sure to subscribe to my blog or my YouTube channel.
#1 Assessing Pipework
The first thing I did was to take an initial look at my existing pipework. Because of increased flow rates associated with heat pumps, one issue that can arise is that the existing pipework might need to be upgraded. This can obviously be an intrusive, messy and expensive undertaking depending on the pipes and where they are.
To have some idea of what to expect, this was the first thing I did. You can watch how I did this.
Outcome
Thankfully, whilst I do need to upgrade some of my pipework, it’s all accessible in the garage before the pipework branches to the upstairs and downstairs radiators. This means the disruption will be minimal!
#2 Getting an idea of Heat Loss
So, whilst the pipes appear to be big enough, what my initial assessment doesn’t cover is the pressure drop due to the flow rate. The pipes can carry enough heat, but I need to understand the exact flow rate that is required by each radiator.
To get the radiators sizes, I need to complete a room by room heat loss for the whole house. Once you know how much heat a room loses, you know how big the radiator needs to be!
Room by Room heat loss takes time, so I thought I’d start by doing a very crude whole-house heat loss, to give me a rough idea.
Outcome
Aside from taking a long time to take all the measurements, the calculations themselves weren’t too difficult. I got a figure of around 7kW as the total heat loss. This isn’t exact, as my methodology left a few things out and made some dodgy approximations, but even if I’m 10-15% out, we only talking an 8kW heat pump, which isn’t massive.
#3 Detailed Room by Room Heat Loss
With my whole home heat loss done, I next tackled a room-by-room heat loss. To perform this, I chose a tool called HeatPunk. This is a free, web-based tool, which allows you to draw out your house, room by room, floor by floor, filling in information about the windows, doors, floors and ceilings. You can add the fabric information too and once you have completed the drawing; it will give you a whole house figure and even tell you which heat pumps are suitable!
Outcome
I found the tool quite frustrating to use in the beginning, mainly because it doesn’t have any undo functionality, so every mistake required me to delete a room and start again. Took me about an hour or so to get my drawing in and the results were interesting!
Using the default temperatures and air change values, it told me that my whole home heat loss figure was around 8.2kW. If I dropped the ACH values down to 1, I got a figure of 6.2kW. Splitting the difference gives me 7.2, which matches my own whole home figure. It’s a pretty big swing based on ACH, so I’m seriously considering a door blower test.
HeatPunk also supports emitter sizing, so that will be the next thing I perform. Once I know the radiator sizes needed, I’ll be much more confident in my pipe sizing!
#4 Radiator (Emitter) Sizing
Coming!
#5 Pressure drop calculations
Coming!
#6 Choosing an ASHP
Coming!
#7 Upgrading pipework
Coming!
#8 Installing the heat pump
Coming!
#9 Panic?
Coming!
@tomasmcguinness 
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