Couldnt you just replace the old Heat Pump unit, leaving everything else as it is? My 5kW Samsung cost just over 2K last year and its simple to switch units.

Thanks @bontwoody and yes, I think I probably can replace the old external pump with a new one for similar costs to yours.

Were you tempted to upgrade everything else?  

@pressure Well mine was a new installation in this house, but if upgrading I would definitely install anti frost valves if you are using antifreeze solution and replace it with water. This will improve your efficiency. Also I would install a good monitoring system maybe with a heat meter like the open energy monitor kit.

I’m not surprised an installer suggested replacing everything since he gets more work!

Your system is 16 years old so what else might need changing? Copper pipes don’t wear out. Radiators benefit from flushing muck out occasionally but do they need replacing cosmetically, badly rusting or a partner/you wanting a different design? 

The easiest option is just change the ashp, what size is it?
Do you have features like a low loss header (aka 4 port buffer?) then removing that could be wise.

Don't fall for “its old guv” line!

@judith, cynical, but possibly very true 🤣 

@pressure, I'd definitely get a second and third opinion.

Many thanks @judith.

The engineer was from Daikin rather than an installer. His comment was that if it were his money, he would possibly consider replacing both the external unit and the ASHP after 16 years. 

All the UFH, piping etc would stay the same. (No rads here.)

Even so, I suspect just getting the external unit changed might be adequate. 

I’ll report back after the Daikin visit on Thursday. 

im also going to get a quote from Heat Pump Installers in Huddersfield just to get a benchmark on a new system.

We currently have a Daikin Altherma 1 16kw split unit. No low loss header  here. 
I wonder what the oldest heat pump here is - is there anything older than a 2008 install date? I was watching a  RHH YouTube video about how long ASHPs last and the estimate was 15-20 years, which is the age band of my unit, so some people out there will be thinking about replacement…

@pressure I think you’re the record holder here by quite some distance in terms of heat pump age, and you’re definitely in the “range” for a replacement. I’m not sure our unit from Global Energy Systems has any hope of getting to double figures.

Just be mindful of installation restrictions on newer A3 class R290 refrigerant (Propane) ASHP monobloc units. There are rules to follow concerning location of the unit and adjacent openings, non-Ex certified local isolators, etc. An A2L class R32 refrigerant unit R32 doesn't have these restrictions. They are plenty R32 units available new, but R32 refrigerant is gradually being withdrawn from the market due to higher global warming potential than R290.

So an update - it's been a fun few days! Cold, but fun.

We lucked out with the engineer Daikin provided for the visit on Thursday - it was Peter, who is our favourite Daikin engineer, who we contracted with separately back in 2020 to review and fix the original install. He took out loads of pumps and other kit, and the system was much happier as a result. We definitely trust Peter.

His diagnosis as expected was that the compressor in the external unit was failing, due to mechanical wear and tear.  We then discussed the merits of repairing it compared to getting a new monobloc system which could be located right outside the plant room (and benefit from re-using arm air from the MHVR system's exhaust). This would also mean we could get rid of the internal unit and possibly re-use the space with a battery. This is still our likely course of action, but we thought we'd have plenty of time to think about it, because the system was still working.

Spoiler: this assumption turned out to be faulty :). 

Thursday night, the internal unit died, and the MCD had tripped. I reset it - and five minutes later it tripped again. And again, and again. It looks like the external unit has failed so badly that its current draw is tripping the system, a known risk for a failing compressor. The house is very well insulated but it started to cool, and warm water became scarce as the big tank depleted.  

Friday I tried to get an emergency visit from Daikin but their engineers were already occupied - I talked to both the lead tech support engineer for the north, and the northern service manager, who were lovely but there was nothing they could do. Peter couldn't help because he was on another job a hundred miles away - but he did suggest a workaround if we could get an electrician: getting on the roof, taking the cover off, turning off the power, and unscrewing the comms cable. That would allow the internal unit to run without the demand of the external compressor, and give us heating and hot water from the 3KW back up immersion inside the unit. Chris, the Daikin senior engineer agreed this would work but cautioned it needed to be done by an electrician. So we went out and borrowed some heaters from friends, bought one new one, and also picked up some electric blankets (all of which will come in handy in various ways). 

So we were most fortunate that the electrician who helped build the house for us was able to come over today. The wind in Sheffield was extremely strong today and I was worried about him going on the roof - it's only one storey up at the back and we have a decent ladder, and the roof is flat although occupied by a lot of PV - but he managed it. 

Straight away the internal unit was able to stay running. We now have lots of hot water. Heating has stabilised and gone up around 1 degree everywhere - Peter just called and said this is to be expected, it'll take a while for the immersion to get the UFH up to temperature. We are OK - and we don't have to cancel Christmas (we're hosting it this year for the family). 

So what have we learned and what's the plan?

Learnings:

• Heat pumps do in fact last perhaps 15 years, longer if you're lucky. But at around 15 years you need to think about replacement especially if the noise increases - our compressor has been noisy for a year. In comparison, the typical recommendation for boilers is replacement after 10 years so 15 years for a heat pump is not bad. I probably should have been more proactive in replacing it after 16 years. Peter has replaced a number of systems of the same vintage as our Gen 1 - most of them done a year ago or more. One has been "fixed" piecemeal and has cost £5K so far and has some other big bills coming. 
• I don't know this for sure until I get the quotes back but I suspect a replacement heat pump won't be too much more than a boiler. I will be getting a quote from Peter, and hopefully one from Heat Pump Installers (who were on one of the RHH YouTube round tables and talked sense, and were great on the phone). I am hoping heat pumps may not be vastly more expensive to replace than a quality boiler. A colleague has just got a posh boiler replaced with some other works for £8K (and is still not happy, there is more cost to come). Yes you can get cheaper, but it's a valid benchmark. 
• Heat pumps have moved on since the first gen Daikin kit in the mid 2000s. I believe that I can expect better efficiency and lower electricity usage with a third gen unit. I will also get a unit that is much easier to programme and control. The Gen 1 dot matrix interface is terrible, so hard to understand. I'm looking forward to checking status and doing settings from the Onecta app while sitting on the couch. 
• You're not just buying the kit when you're buying a heat pump: you're buying a relationship. Maintenance, support and engineer availability are very important elements of what you're buying. I have had my ups and downs with Daikin over the years (decades!) I've been a customer. I know the basic contact centre will be crap and the website will be disappointing, it needs a load of content design, and they're desperately in need of a proper CRM system and customer management processes. I also know that the sharp end will be bloody brilliant - not perfect but good people doing the right thing. I literally know the people now and they know me. That is worth a lot. So yes, I'm buying Daikin again, not Vaillant (yes I know they have men in vans now) or Ideal or Mitsubishi - although I'll look at what the quotes are like. 
• My original installer really screwed us by not getting us on the original RHI grant - that's £7.5K I'll never get back. But we knew that anyway and it's money under the bridge. 

Plans:

• This system at 16 years is end of life. It will be replaced - repair is throwing good money after bad. The rest of the system - the UFH pipes, the manifolds, the thermostats - is all AOK. I'm 57 aim to take this system into my early 70s (we're most unlikely to move) and get a decade plus of worry-free, current-spec heating.
• We'll be getting quotes by, I hope, mid January and hopefully on the way to an install around the end of January, sooner if I can get it. 
• I'll probably go Daikin Altherma 3 Monobloc, on the ground, in a light well at the back of the house right outside the plant room. The big question is if I stick with 16KW or try to save a grand or so with a smaller capacity. Obviously the original supplier didn't provide any heat loss calculations to justify the choice of 16KW - I think he just put in the same system as he'd put in at a local school (!). We'll see - at least we have some breathing space to get the calcs done properly.

So that's where we are. Hopefully we can now get through Christmas "celebrations" in reasonable comfort, or at least with hot water... 

I also had two 16 kw Daikin installed in 2008 and one has died - no real diagnostics - just replace all the circuit boards and see whether it works -  First attempt with a 600 GBP comms board- nothing - then quote for two further boards at 1200GBP with no guarantees.   I think the original outside unit was 2k back in 2008.

This is in the unit that did not have all its boards replaced several years ago under warranty ( twice as engineer dropped and broke one and was only spotted when second set were installed).

New system due to be installed in early January.

As heat load is 20kw we will go with a single larger unit.

Another quick update. As mentioned over the Christmas period I asked for a few quotes. 

I had some good calls with Heat Pump Installers and provided all the information requested. They have not provided a quote. I also had a good conversation with the Daikin installer provided by the Daikin website and detailed follow up information via email. They also have not provided a quote. 

My impression is that heat pumps are a sellers market. I guess this is due to there being a low volume in the market (IIRC <10% of the boiler market) and a small number of qualified installers. Hence, if you want to buy a heat pump, one should probably be prepared to do a lot of chasing, because otherwise you won't get to the top of an installer's to do list. I suspect - but cannot prove - that installers would rather go for a new install over a replacement because there's more work and higher revenue involved for each sales contact. Fair enough. 

Anyway, fortunately, I had an existing relationship with Peter, who is a Daikin engineer, has done maintenance visits here, and did some work on the system a few years ago to tune it up (which had an excellent impact on system efficiency). He did do a quote: £7.5K all in. Affordable.

Long story short: We have a new heat pump and it works brilliantly.

Tuesday last week Peter did the heavy lifting while leaving the old heat pump running off the immersion - getting the old pump drained of gas and off the roof, getting the new pump hung off a wall in the light well, and drilling holes for pipes. He brought a specialist AC engineer to drain the system. Amusingly, the AC engineer had an innovative approach to getting the extremely heavy compressor off the roof, which other installers had said would require scaffolding: dismantle the pump, and take an angle grinder to the compressor, so they could easily take the compressor away in bits.

Then on Thursday a return visit to plumb in the new unit and get it going. This mostly worked, but the upstairs UFH didn't work because of a failed air vent upstairs - having drained the system this stopped warm water flowing through the pipes. He came back on Monday to fix this.

We now have an amazingly warm house.

There are a couple of things left to do which he will sort out in the next few weeks, once the system's had a chance to bed in. Final commissioning and set up - we haven't gone through the myriad options to tune the system yet. Plus, we don't yet have the wifi adapter for the controller so I can't use the Onecta app yet. But it works great. Plus we need to do warranty and get it in the MyDaikin service so I can get a support contract going. 

 Look at this magnificent beast - we are so happy the pump is no longer on the roof. 

And here's the new controller where the old internal unit used to be - now at eye-height so I don't need to stoop to fiddle with the settings. I was wondering if I could reclaim the space from the internal unit for a battery at some point but there's too much plumbing gubbins to do that, so still not sure where I can fit a Give Energy All In One. 

Most noise is less - but there's a bit more when it's working hard, which it was at first when bringing the UFH up to temperature. It's possible there's more vibration since it's on a wall. This may be a slight issue in future, we'll see. Most of the time it's silent. 

I think the pump is a lot more efficient but I can't tell for sure yet - the house ticks over at about 1.6kw then boosts to 2.6 or 4kw depending on how cold it is in the morning. 

I'm pretty happy right now.