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

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Mars
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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 book Bodge Buster.

Manufacturers and even some training bodies might recommend setups that prioritise their own interests over your comfort and efficiency. Remember, you're the homeowner, the conductor of your heating symphony – a poorly installed system not only strains your wallet but also leaves you in the discomfort of a cold home, bearing the full impact of such shortcomings. Don't hesitate to question proposed designs, seek information from independent sources, and prioritise simplicity and the two core principles of low-temperature operation and optimal flow.

By taking charge and avoiding the deceptive decoys, you can ensure your heat pump delivers the comfort and sustainability you deserve, turning your home into a haven of warmth and energy efficiency. So, banish the monsters and villains, embrace the flow and let your heat pump play its beautiful low-temperature symphony.

This topic was modified 4 weeks ago by Mars

Buy Bodge Buster – Homeowner Air Source Heat Pump Installation Guide: https://amzn.to/3NVndlU

Follow our sustainability journey at My Home Farm: https://myhomefarm.co.uk


   
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(@jamespa)
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Posted by: @editor

Remember, you're the homeowner,

Well said!

I (and I suspect many others) have met a fair few installers who don't seem to accept this!


   
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Toodles
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Thank you Mars, I accept that a LLH may affect the efficiency of the overall efficiency - but how can the average individual who has a system installed with a LLH know whether they would be better off without it? Ripping apart a system that has one such and a secondary pump is a little radical - and is ther any guarantee that the efficiency would improve without these components. Presumably, LLH was a concept with a purpose - is it just to protect the designer and installers? Regards, Toodles.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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(@hughf)
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@toodles It is purely there to allow the heat pump to operate without any flow errors... Primary side just sits there running into the header, microbore or TRVs closing don't have any effect on it.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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Toodles
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@hughf If a system doesn't have any variable restrictions like TRV’s, would such a system be better able to perform to the optimum without an LLH then? My system has carefully adjusted lockshield valves (constant restrictions in other words) but does have one TRV in a bedroom. There is an LLH and secondary pump - I was told this means achieving a Delta T of 5 degrees across the radiators is not crucial as the LLH is acting as an intermediary. Regards, Toodles.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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(@jamespa)
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Posted by: @toodles

Thank you Mars, I accept that a LLH may affect the efficiency of the overall efficiency - but how can the average individual who has a system installed with a LLH know whether they would be better off without it? Ripping apart a system that has one such and a secondary pump is a little radical - and is ther any guarantee that the efficiency would improve without these components. Presumably, LLH was a concept with a purpose - is it just to protect the designer and installers? Regards, Toodles.

It's a fair question

There are two approaches to answering it I can think of.

1.  Measure the flow-flow temperature drop across the llh.  For each degree you are losing 2-3% system efficiency.

2.  Plumb in  bypasses for the llh on the flow side and for the secondary pump with a couple of manual diverter valves so you can switch them in and out.  Perform the experiment 

Posted by: @toodles

Presumably, LLH was a concept with a purpose - is it just to protect the designer and installers?

In most cases it seems, yes.

Posted by: @hughf

@toodles It is purely there to allow the heat pump to operate without any flow errors... Primary side just sits there running into the header, microbore or TRVs closing don't have any effect on it

One might reasonably ask, why is the heat pump designed to register them as errors.  Answer - because the situation shouldn't occur. 

Putting sticking plaster over a red warning light doesn't make the problem go away.  However it does reduce the liklihood of call outs.  Now who does that help?

This post was modified 3 months ago 2 times by JamesPa

   
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Marzipan71
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Hi @toodles don't know if you've seen them before but there a couple of articles which may be of interest from Protons for Breakfast regarding his system performance before and after removal of the LLH (I have a LLH on my Daikin ASHP) - links here and here


   
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(@prjohn)
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Are all Low Loss Headers bad? Mine was fitted as per Samsung schematics. This I would imagine would remain part of the warranty agreement. The effect on my system seems to be negligible. I did discusses this at a resent service and the engineer comment was "if its not broken don't fix it". As my efficiency appears to be high, 2288kw/h energy use over a year as opposed to 1700litres (17000kw/h) of oil it seems my system is working OK. Another point is if by removing the LLH increases efficiency could it have an effect on the size of HP fitted? One other point, can a LLH act as a debris trap for older heating system thereby protecting the HP?


   
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Toodles
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@marzipan71 Thanks very much Marzipan, very interesting indeed. I think that that data excuses my uncertainty of LLH - Good or Bad? Regards, Toodles.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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Toodles
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@prjohn Ooooh! Mars! Did you consider you might be opening a massive can of worms with this topic?! ;-)))

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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(@hughf)
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Posted by: @hughf

@toodles It is purely there to allow the heat pump to operate without any flow errors... Primary side just sits there running into the header, microbore or TRVs closing don't have any effect on it

 

One might reasonably ask, why is the heat pump designed to register them as errors.  Answer - because the situation shouldn't occur. 

 

Putting sticking plaster over a red warning light doesn't make the problem go away.  However it does reduce the liklihood of call outs.  Now who does that help?

On commissioning, I was having a nightmare getting rid of flow errors, I suspected a faulty flow switch so just jumpered it out in the terminal strip. It has been running like that since september.

Turned out to be air in the system. Haven't had a flow error since 😀 

 

This post was modified 3 months ago by HughF

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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Mars
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Posted by: @toodles

@prjohn Ooooh! Mars! Did you consider you might be opening a massive can of worms with this topic?! ;-)))

Always good to have discussions about topics like this.

 

Buy Bodge Buster – Homeowner Air Source Heat Pump Installation Guide: https://amzn.to/3NVndlU

Follow our sustainability journey at My Home Farm: https://myhomefarm.co.uk


   
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