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Avoid the Heat Pump Villain: Why Low-Loss Headers and Buffers Can Sabotage Your Heat Pump's Efficiency

Mars · 2024-01-23T06:00:00Z

Heat pumps are becoming increasingly popular as they provide an efficient and eco-friendly way to heat homes, helping us save money and protect the environment. However, to work best, they need the right setup. Sometimes, parts like low-loss headers and buffers, which are supposed to help, can actually reduce the heat pump's effectiveness. This can lead to less warmth and higher running costs. It's important to understand why these parts might not always be beneficial and what you can do to get the most out of your heat pump. The Two Pillars of Heat Pump Prowess Understanding how heat pumps operate holds the key to optimising their performance. Two fundamental principles guide their efficiency: 1. Low-Temperature Symphony: Think of heat pumps as musicians, capable of raising the temperature of heat, much like conductors orchestrate notes. But here's the twist: the lower the target temperature, the less energy they need to play their magic. So, aiming for a cosy 20C instead of a sweltering 25C translates to a lighter burden on the system and a lighter burden on your wallet. 2. Flowing River of Warmth: Heat pumps move heat through water flowing through your radiators and/or underfloor heating. Imagine this water as a river, where a smooth, steady current efficiently delivers the thermal energy. Now, picture what happens if you dam the river with restrictions like narrow pipes or sluggish pumps. The flow suffers, and the heat struggles to reach its destination, leaving you feeling chilly despite the pump working overtime.The Deceitful Decoys Low-loss headers and buffers are often recommended by many installers and manufacturers as beneficial additions to heat pump systems. They are touted to enhance efficiency and comfort. However, in practice, the benefits they promise may not always materialise as expected. Let's see why: Low-Loss Header Trap: These headers aim to minimise heat loss in the pipework, but they often achieve this by reducing the water flow. Remember our river analogy? A constricted header acts like a dam, hindering the smooth flow and consequently, the efficient transfer of heat. This leads to the dreaded high delta T situation – a large difference between the temperature of the water entering and leaving your radiators. It's like the conductor demanding the orchestra play at full volume while restricting the air to their instruments. The result? Strained performance and disappointing results. The Buffer's Misdirection: Buffers are essentially storage tanks for hot water, supposedly providing you with readily available warmth and reducing the heat pump's workload. But here's the catch: buffers add complexity and introduce additional heat loss points. They essentially become thermal cul-de-sacs, where some of the precious heat gets trapped and wasted. Additionally, buffers can encourage inefficient on-off cycling of the heat pump, further negating any potential gains.Beyond the Decoys: A Path to Optimal Performance So, how do you ensure your heat pump system lives up to its full potential? The key lies in simplicity and a focus on the two core principles we discussed earlier: 1. Embrace the Flow: Ditch the low-loss headers and any other flow-restricting components. Let the water flow freely, like a well-maintained river, ensuring efficient heat transfer throughout your home. 2. Befriend the Low-Temperature Symphony: Ensure your temperature control is managed directly by the heat pump's controller, as on-off thermostats can be less efficient than a buffer. It's crucial for the thermostat to be integrated with the system for optimal efficiency, rather than relying on standalone on-off mechanisms. 3. Weather Compensation – Your Wise Companion: Utilise weather compensation, a feature that automatically adjusts the heat pump's output based on the outdoor temperature. This ensures constant comfort while minimising energy consumption. Think of it as a dynamic conductor, adapting the orchestra's performance to the changing weather conditions. 4. Delta T – The Fine-Tuning Maestro: Implement delta T control, which fine-tunes the temperature difference between the flow and return water. This further optimises the heat pump's operation, squeezing out every drop of efficiency. Consider it the musical equivalent of perfect intonation, ensuring a harmonious performance from your heating system. 5. Radiator Harmony: Use thermostatic radiator valves (TRVs) only in bedrooms, allowing weather compensation and the heat pump itself to manage the temperature in common areas. This strikes the perfect balance between individual comfort and overall system efficiency. 6. Hot Water Wisdom: Optimise your hot water production too. Let the heat pump controller handle this task. Think of it as a bonus track in the symphony of energy savings. Avoiding the Heat Pump Villain Sometimes, navigating the world of heat pump installation can feel like a quest through a confusing landscape. If you're still daunted, consider buying my b...

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Tim441

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17/02/2025 3:07 pm

@jamespa measuring with clamp-on heating pipe thermometer? I see ebay/amazon has them around £6 or £7 .. Good enough?

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JamesPa

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17/02/2025 3:15 pm

Posted by: @tim441

↑

@jamespa measuring with clamp-on heating pipe thermometer? I see ebay/amazon has them around £6 or £7 .. Good enough?

I believe so, we are looking for difference so as long as you can clamp consistently then it doesn't matter if the figure isn't perfect.

I stress there is absolutely no need to do this unless you want to.

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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Tim441

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20/02/2025 3:32 pm

Borrowed a clamp on thermometer.

Buffer tank: PAW-BTANK50L-2 buffer tank
Only 48l
According to ashp controls
leaving temp 33deg
Return 31 deg

Arr from ashp BT 34.4flow
Leave BT 34.1 flow

Arr from house BT 33.2 return
Leave 33.8 BT return

I suspect not great test right now... as mild... so not working hard
Will be better to check on cold morning.. perhaps.

Will report again once more results

This post was modified 7 months ago by Tim441

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Mars

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Topic starter 20/02/2025 10:59 pm

@tim441 the other thing to “check” is where the respective flow and returns are to see if your buffer has minimal distortion. Ideally, it’s plumbed like this:

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Tim441

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21/02/2025 9:32 am

@editor

Logically the electronic motorised valve.. I think... stops buffer being used when heating DHW/hot water tank. So will be on flow to BT?

With the pump on right on flow from BT?

Tap at bottom right ... return to BT?

So same as your diagram. but I'll try the thermometer a few times in different scenarios

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JamesPa

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21/02/2025 9:53 am

Posted by: @tim441

↑

Logically the electronic motorised valve.. I think... stops buffer being used when heating DHW/hot water tank. So will be on flow to BT?

Is it a 2 way valve or a 3 way diverter valve. Normally the (3 way) diverter valve is the only motorised valve needed.

As you say taking some temperature measurements when its working harder would be good, but your initial ones are encouraging.

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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Tim441

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21/02/2025 10:00 am

@jamespa it's 3 way

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JamesPa

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21/02/2025 10:02 am

Posted by: @tim441

↑

@jamespa it's 3 way

I presume the diverter valve then, which would make sense. As you say you would expect this to be on the inlet to the BT

This post was modified 7 months ago by JamesPa

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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Potatoman

(@potatoman)

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29/03/2025 8:59 pm

Hi, so if I wanted to make my system more efficient, It's open loop 28/22/15mm ,all rads,run via a Homely is it possible to remove the buffer tank but still comply with 7-year LG warranty requiring hydraulic separation. Thanks

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Mars

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Topic starter 29/03/2025 11:32 pm

@potatoman can you share LG's official documentation that explicitly requires hydraulic separation to maintain the 7-year warranty?

If you've got that document, it would be extremely valuable to see it.

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Potatoman

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30/03/2025 11:09 am

@editor

487221638 10163211903663552 6665514382284125271 n

Regards

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JamesPa

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30/03/2025 2:14 pm

To me that reads as 'Hydraulic separation optional but if present covered for 7 years if you take out the extended warranty', as opposed to 'Hydraulic separation mandatory'. The very last line in the table (mag filter) would seem to confirm this.

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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