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Can an Air Source Heat Pump Work with Microbore Pipework?
Yes, air source heat pumps can be used effectively with microbore pipes in your home, although they are not the ideal pipework for such systems. With some adjustments, microbore pipes can still ensure warm household temperatures even on the coldest days. And don't worry, no need to invest in extra jumpers just yet!
What is Microbore Pipework?
Microbore pipework consists of small pipes measuring less than 15mm in diameter, typically made of plastic or copper. Think of them as the skinny jeans of the plumbing world. If you live in a house built in the 80s or 90s, it’s highly likely your heating system has microbore pipework. You can easily identify it because it looks more like a cable, with a diameter of 10 or 12mm, and it’s often hidden in the walls almost as soon as it comes out of the radiator.
Why Use Microbore Pipework?
Microbore pipes were often chosen because they are cheaper and faster to install compared to traditional pipes. They can be easily bent by hand and run from a manifold to a radiator. While effective for boilers that transport hot water at a low flow rate, microbore pipes can be easily damaged and prone to blockages if not properly maintained.
Debunking Myths About Microbore Pipework and Heat Pumps
In the world of heat pumps, there is a tendency to cling to outdated conclusions. Every week, I hear someone claim that microbore doesn’t work with heat pumps. This idea is rubbish. The pipe size is not a barrier to heat pump installation if you do a little bit of maths and design work. Remember, folks, just because your pipes are thin doesn't mean your heating has to be!
Let's get a few things straight first. In domestic installations, no one sizes the pipework precisely; we use rules of thumb and pipe the house as we like. For instance, small rooms with small radiators need less water and should have smaller pipes, while big rooms with big radiators need more water and bigger pipes. However, in most houses, every radiator has the same size pipework.
Technical Guide: How Does a Heat Pump Work with Microbore Pipework?
Heat pumps can work with microbore pipes by splitting the heating system to operate at different flow rates and running at higher temperatures than traditional systems.
Typical air source heat pumps have a temperature difference (delta T) between the water entering and leaving the radiator. For a more efficient setup with microbore pipes, we can use a flow rate of 45°C instead of the standard 55°C. This setup lowers the temperature at which the system operates, affecting the overall efficiency.
To maintain the same level of heating output, radiators will need to be approximately 30-40% larger when operating at a flow rate of 45°C compared to 55°C. This is because the lower temperature water delivers less heat per unit time. So, for instance, if a standard radiator is 1 metre wide, you might need a radiator that is 1.3 to 1.4 metres wide to provide the same amount of heat.
Typically, radiators were not properly sized in the first place. Have you ever noticed how a radiator is almost always sized to fit under your window? This is not a coincidence that the heat loss requires the exact size as the window. It is because radiators tended to be sized aesthetically as well. So, in some cases, the radiators may not need replacing at all.
Alternatively, we can increase the output of the radiator without changing its width and height by switching from, for example, a single panel single convector radiator to a double panel double convector radiator.
Types of Radiators and Their Outputs
Type P (Single Panel, Single Convector): These are the most basic type, with one heating panel and one set of fins. They have the lowest heat output among the radiator types.
Type P+ (Double Panel, Single Convector): This type has two heating panels with one set of fins in between. It offers more heat output than the Type P without taking up more wall space in terms of height and width.
Type K1 (Single Panel, Single Convector): Similar to Type P but with a slightly different design, which can sometimes offer a marginally higher heat output.
Type K2 (Double Panel, Double Convector): This type has two heating panels and two sets of fins. It significantly increases the heat output compared to Type P and Type P+, making it ideal for rooms that need more heating power without expanding the radiator's footprint.
Type K3 (Triple Panel, Triple Convector): These radiators have three heating panels and three sets of fins. They provide the highest heat output among standard radiators, suitable for large rooms or spaces with high heat loss.
By selecting the appropriate type of radiator, you can effectively increase the heat output to match the demands of a lower flow temperature system without necessarily increasing the physical size of the radiator. So, whether you're dealing with an undersized radiator or looking to boost efficiency, there are solutions that don't involve turning your living room into a radiator showroom. And hey, who needs more radiator space when you can have more room for furniture instead?
No Need to Worry About Sizing Radiators Yourself
There's no need to worry about calculating the size of your radiators yourself. We can accurately determine the outputs of your current radiators and identify which ones can stay and which ones need upgrading using our heat pump design software, Carno. This means you can rest easy knowing that your heating system will be optimised for efficiency and comfort without any guesswork.
Why Isn’t Microbore Pipework Ideal for Air to Water Heat Pumps?
Air to water heat pumps typically require lower flow temperatures and higher flow rates, which microbore pipes restrict due to their small size. This necessitates higher flow temperatures, reducing overall efficiency.
Key Issues with Microbore Pipework and Heat Pumps
Fragility: Microbore pipes can be easily bent out of shape. Remember, if your pipes are more flexible than your yoga routine, you might have an issue.
Noise and Erosion: High flow rates can cause noise and pipe erosion.
Blockages: These pipes are prone to blockages, particularly in dirty systems. Installing filters and inhibitors, and performing powerflushes, can mitigate this.
How Does Microbore Pipework Affect Heat Pump Efficiency (SCOP)?
The small size of microbore pipes reduces water flow rates, necessitating hotter water to meet heating demands, which can lower the system’s efficiency. The SCOP (Seasonal Coefficient Of Performance) indicates the energy efficiency over time, and with proper installation, a heat pump can still achieve a SCOP of around 4.0 even with microbore piping.
Maximising Heat Pump Efficiency with Microbore Pipework
Reduce Heat Loss: Ensure your home is well-insulated to decrease heat demand and maintain efficiency. Remember, draught excluders are cheaper than cranking up the heat!
Separate Systems: Use hydraulic separation to allow the pump circuit and heating circuit to run at optimised flow rates. Renew East experts can assist with the design and installation.
Repipe the System: As a last resort, consider repiping, though this is disruptive and time-consuming. Think of it as giving your plumbing a much-needed facelift.
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