Your topic raises my interest for a couple of reasons.  Why, after only 7 years, has your pump died and needs replaced?  I feel sure the reasons are somewhere on this site but a brief recap would be appreciated.  I thought something more like 20 years was the likely life.

I was given a complete Ecodan 8kW system (inc the tank, controls and all the radiators) which had been installed and running for about 6 years.  The new house owner decided it was useless, didn’t heat his house as he wanted and had a COP of about 1.4.  He had it all removed and an oil boiler installed.  I now have all the kit which might be suitable for re installation in another property.  So my question is, now at 8 years old, is the Ecodan unit worth reusing, should / can it be refurbished or should it be scrapped and a new outside unit bought for any reinstal? If it’s to be scrapped, the lessons from your experience will be highly pertinent.

@davidb There will be companies that offer a recycling service at some point in the near future as the secondhand market grows, of course its worth installing it in another property if you can offer a warranty as the new customer is probably going to pay a few thousand to have it installed. Its this risk and lack or warranty that can discourage second hand units. What do you do if it lasts 18 months, would you give the customer a new (secondhand) unit for free?

These units installed and designed correctly should last 15+ years, most manufacturers are offering 7-10 yr warranties on major components and some even more. This to me this says they think it should last double that for their safe margin.

The biggest issues we see is failure on non maintained units or badly designed, having badly designed systems or a dirty blocked system on the evaporator or heating circuits shorten the life of the system, I don't mean completely blocked, as that creates a failure and it gets fixed, no heating causes the customer to call out an engineer and the issue gets dealt with, I mean 20% blocked for most of each 2,3 or 4 years making the pump work harder, heat exchange slightly inefficient so it slowly wares on the components.

This makes a 10kW system have to work much harder to produce 8kW (20% less efficient) but by its nature many of thee units can over-clock to use a CPU computer narrative, they are able to run at 11.3kW to try to produce that near 10kW and now runs that compressor and all its components much harder at its max all the time. 

We see that a system that was not looked after lasts around 3-6 years, a system that is badly design but looked after 5-10 years, systems that are well designed and looked after the data is still coming in as they are all still running 15yrs+

Posted by: @ashp-bobba

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We see that a system that was not looked after lasts around 3-6 years, a system that is badly design but looked after 5-10 years, systems that are well designed and looked after the data is still coming in as they are all still running 15yrs+

Thats really helpful real world experience. 

By 'well designed' do you mean the same 'well designed' that gives good performance, plus filter(s) or is there something else we should be asking for?  Also some systems seem to come with a mag filter and a fine gauze filter (which in my case seems to be the first to get blocked and the more difficult to flush!), and others with only the first, any comments on this?

Also is looking after doing the annual service and ensuring filters are clean, or is there anything else worth doing?

@ashp-bobba thanks for the response.  For clarity, the outline plan is for the kit to be installed for a family member with relatively few £ involved - although that’s a little down the line.

Your comments re maintenance are timely.  We had a 3.5 Aerotherm installed September 25 so annual maintenance needs to be planned.  As a homeowner, do Vaillant provide customer guidance on what to expect?  How do I check if it’s been done properly and roughly how long should the work take if done “to the book”?

I brought my old R407C water to water heat pump to the local recycling center. They accept heat pump related things, old mobile aircon units, fridges, etc. It's pretty convenient, but due to the weight and size a few friends were needed to load it into the van.

Split units are more complicated. It's illegal to vent the refrigerant, so you're not allowed to take it apart yourself, you need a qualified tech to empty the refrigerant first. But with a monobloc you can deliver the whole unit to the recycling center with the refrigerant still inside.

@davidb 

Posted by: @davidb

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So my question is, now at 8 years old, is the Ecodan unit worth reusing, should / can it be refurbished or should it be scrapped and a new outside unit bought for any reinstal?

If it's a 8 years old split, then most likely R410, you're not allowed to fill it with refrigerant, and the certified pro who can do it will cost you as much as a brand new cheap R290 monobloc, so... to the recycling center.

If it's a monobloc and you are proficient with DIY then why not? Just make a base large enough to fit its future replacement, lay a few extra conduits in case the next one requires some more communication wires, preplan the pipe layout with flex hoses so you can easily change it, and use it for as long as it lasts.

If you don't DIY it then it's probably not worth it.

Just stick your wet finger into the flow/return fittings. Finger comes out the color of rust: bad. Finger comes out clean: good.

Next I'd recommend power flushing the heat pump exchanger and see what comes out. You can do that with tap water, just make sure you don't exceed the max pressure rating. I do it with a DIY powerflushing rig which mixes compressed air with tap water, it's just a bunch of plumbing fittings and hoses. The bubbles really help flushing the dirt out. Direct the flush water to a bucket, check the color of the water, let the suspended solids settle at the bottom, get them out, and check them with a magnet. If you have access to the old installation the heat pump used to be in, you can also take a sample of the water, check what the dirt filter caught, etc.

If you get brown sludge, rust and magnetite particles, this is a strong hint the heat pump was on an installation with lots of oxygen ingress in the water and corrosion ; this is bad news because the heat exchanger is usually stainless steel brazed with copper and the copper used in these is very vulnerable to pinhole corrosion if the water is loaded with oxygen, dissolved iron, and acidic pH. If the heat exchanger develops a pinhole leak, this is usually game over, more expensive to fix than buying a new cheap R290 unit.

If the circulating pump is a modern low power one which uses brushless motor instead of the old asynchronous motor, then its rotor has permanent magnets... magnetite particles and iron shavings will stick to it, get wedged between the rotor and stator, and may stall it or destroy the bushings. So you may have to take it apart to clean it. This is not a complicated operation, if you can access it, all you need is a hex key and a toothbrush. If it is hidden deep into the bowels of the heat pump then it may turn into a caving expedition. If it's in the indoor unit then easy peasy.

On the other hand, if the water comes out pristine and clean, even better with a slight yellow tint and smell from the corrosion inhibitor, then congratulations, it'll probably last 10 years.

Same remarks apply to your installation, if it runs on brown sludge, then it'll probably destroy a heat pump in a few years.

Posted by: @davidb

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@ashp-bobba thanks for the response.  For clarity, the outline plan is for the kit to be installed for a family member with relatively few £ involved - although that’s a little down the line.

Your comments re maintenance are timely.  We had a 3.5 Aerotherm installed September 25 so annual maintenance needs to be planned.  As a homeowner, do Vaillant provide customer guidance on what to expect?  How do I check if it’s been done properly and roughly how long should the work take if done “to the book”?

Every manufacture has a guide and service list in their manuals, they are easily looked up online:

https://professional.vaillant.co.uk/downloads/aproducts/renewables-1/arotherm-plus/arotherm-plus-vwl-35-75-a-s2-installation-operation-manual-0020330791-03-2806789.pdf#:~:text=The%20manufacture r's%20literature%2C%20including%20Benchmark,Yes

As it for a family member I would say yes, its worth installing and flushing both the ASHP and home system, even if this system fails in 1,2,3 or 10 years the home will be ASHP ready and then the next system will be something like swapping out the boiler. Just check the capacity of what you have will suit the heat loss of the new home. 

Posted by: @davidb

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Why, after only 7 years, has your pump died and needs replaced?

We've started to document everything, and part 2 of the saga is on the way, hopefully landing in the next fortnight. It’s taken a fair bit of time to pull together properly, but it walks through everything that was wrong with the system in detail.

If you haven’t seen it yet, here’s Part 1:

@editor Thanks Mars.  I look forward to the subsequent episodes.  Can I assume you will post a notice when those episodes are released?