Go for new rego box. It’s true they are hard to get but we’ve replaced a lot of them and no issues. 

if you do replace the heat pump then it’s madness to put in an Air to water when you have a geo collector. 

geothemal heat pumps last much longer and are generally more reliable than air to waters. This is from 25 years of fixing both. 

@greenlight I actually called you and spoke to you to ask if you had a work instruction or could give me an idea of how much it should cost to replace these. You said you would call me back, but I guess you have been busy.

Just leaving an update to my issue.

The pump completely shut down on the 26th Jan. I had ordered the internal flexible hoses from Alto Energy and they turned up in 2 days, (see below), brilliant service. With nothing to lose, together with a friendly plumber, who was willing to help and had the right tools, we shut off the heating circuit at the filter and the pumps, and began to drain the system at the bottom connection to the electrical cassette. (see below also). I could not believe how much water was in this circuit, it is obviously a large water heating loop around the tank.

After a fiddly few hours (due to the fact that we could only access the pump from the front, see photo) we removed the hoses x3 and replaced them. We then refilled the loop, which also took a long time. With anticipation, after checking there was no air in the system, we opened up the heating loop and turned the heat pump on. It immediately gave a GT3 alarm, same as before, but then sprang into life. Continually checking GT8 vs GT9 temp delta, which remain within 5 degrees for the first time in a while, the pump remained heating the water to the set temp, still set at 35 degrees, and then switched to rad heat. Everything seemed find. My friendly plumber left me to clear up, and I was feeling rather pleased, especially as I was about to leave my wife and kids for a week on business in Orlando. 

I then thought I would try out the electrical cassette. Switched on 'add heat' and BANG! All our electrics tripped. I reset the master trip and switched the pump back on and BANG! Main trip went again. I was not in the best frame of mind at this point and thought I had jumped the gun. However, I waited for 10 minutes and tried again. The pump came back to life, and continued in Rad heat mode. 

Reflecting at this point I thought we must had got moisture into the electrical cassette controller which sits below the cassette, just to the left in the photo attached. I put a dehumidifier next to the pump and left for the US, with fingers cross that the following Sunday (5 days away), when the pump tried to go into legionnaires mode, the control box would be dry. 

My wife complained that the water was not hot enough, still set at 35, so she discovered the 'add heat' function 2 days later. and NO bang, the pump heated the water to 60 degrees. 

So in summary, now after 7 weeks and some really cold weather, the pump is still operating (touch-wood) and in fact using less than a 1/3 of the electric it did when in HTF alarm mode. So @greenlight it worked!!

Sweetest of all my friendly pumper only charged me 1/2 a days labour at £150. So why do so called renewable heating experts expect you to pay over a £1,000 plus VAT? The extortionate costs and lack of knowledge of heat pump maintenance are the reason I still believe heat pumps are not yet a viable option in the UK. 

I am still looking at putting in a secondary gas heating system. I just need to work out how I can switch between the 2 depending on kWh prices and very cold weather. 

So a stay of execution for the time being for the heat pump.

I hope this post may help others with an IVT heat pump, as I gather that these flexible hoses are an issue on all of their models.

Posted by: @abbote

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Sweetest of all my friendly pumper only charged me 1/2 a days labour at £150. So why do so called renewable heating experts expect you to pay over a £1,000 plus VAT?

Somebody has to pay for their ignorance!

In fairness there are some very good ones out there, as well as some poor ones.  That's true of much of the building trade, it's not special to heat pumps at least based on my own experience.  Don't forget that many, possibly most, of us have been paying about 10% more for our heating than we needed to for about the past 20 years, and 'enjoying' a reduced level of comfort, courtesy of the (gas) heating industry.

@abbote good to see you've fixed the problem.    

I've also managed to get mine fixed too.    A heat pump engineer came out and isolated the issue to the control box and put me in contact with Alto Energy who seem to have bought up a large stock of IVT parts. 

An Alto Engineer came out and it's the first time I've spoken to anyone with specific IVT in depth knowledge rather than a general heat pump background and it's made me more confident in keeping the GSHP in and working now I know there is expertise and parts available. 

He also mentioned the issue with the flexible hoses and as @greenlight mentioned in his video it's important to add inhibitor as part of a regular maintenance routine which I wasn't aware of before.     

I had a quick look at costs for replacing with a new GSHP or 9KW Air Source and both extremely expensive even though the ground work has already been done.  the cost of buying the kit alone comes to around 10K or 6k including water tank so hoping to keep this running for a good few years longer.    

@abbote great stuff. We’ve replaced hundreds of those hoses. Be no harm to clean out the immersion casing if you ever have to do it again, it fills with sludge. Also very prone to leak through the temp limiter probe hole. Ivt Greenline is a great heat pump. Keep fixing geothermal and go on 3-5 holidays with the money you’d spend on replacing it. 

@pike005 Mines a Greenline 6 KW fitted in 2008 and is failing various errors, alarms, cassette failed end of last year, limping along now just has hot water to do.
Having same issue with lack of knowledge and few willing to look at it. Not helped by IVT not being available in UK.

Had a couple of quotes for a replacement £16-18k.

Considering having it removed and going oil, unfortunately gas not an option.

Posted by: @abbote

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We designed and built our own house around a GSHP in 2011, because we wanted to do the right thing, even though we had mains gas. This year it has developed many issues and alarms and has finally now stopped working. With sub-zero outside weather I'm rather desperate!

No one seems to know anything about it, I'm over £500 down just having 3 separate 'expert' heating engineers stand there and let me shown them how it works and them to scratch their heads and walk away and send me a bill. On top of this it took me a while just to get someone to come and look at it, we had no heating in November.

Is there anyone out there that can help?

The main issue seems to be a HTF alarm (GT8/GT9) and then a HTF max which trips the unit out. I'm told there should be a particulate filter but cannot find it, I know it's not in the inside of this model, so it might never have been fitted.

I increased the alarm threshold and lowered the water temperature to force the pump to drop into rad heat in order to get heating into the house. This was in November, and it's limped through to now, but the GT8 temp has increased to over 70 with a GT9 at sub 30, and with water temperature of only 40. Now cannot get it to jump to rad heat. If I try add heat to get it to cycle the water temp to over 60, then a electrical cassette alarm triggers.

Alto Energy have been quite helpful and have told me to drain the system and check the flexible hoses below the electrical cassette, but this is beyond my abilities and when I have suggested this to the heating engineers, then don't seem keen either?

I have been given a quote to install a Worcester Bosch gas boiler and HW tank, it's quite eye watering after spending £25k on a system I thought we would get 20-30 years out of, however, it's a lot cheaper than a replacement GSHP.

Its a fact that there are more engineers out their that understand gas boilers, and very few that are either interested or have knowledge of heat pumps. 

On top of this the increase in electricity/kWhr has really also enforced my belief that we are just not ready to heat our homes with this technology.

Hi, I have retrofit IVT GL C11 fitted in 2011 (Badly). We had to immediately rip out and replace all the pipework with much bigger diameter to up the flow and fitted a Magnaclean. The GSHP then functioned efficiently for 13 years before throwing up an extraordinary number of alarms. We engaged an "engineer" to acid power flush the whole system, but when he arrived he said "I do these all the time and yours doesn't need flushing". I might add we did clean the clogged flexies a few years before this cascade of alarms. To cut a long story short, after many "Engineers" and diagnoses involving almost every component, replacement of some parts (Unnecessarilly), re-gassing twice (to no avail) it was fixed by a full system acid power flush. Also I fitted a washable 10" pleated filter on the return before the GSHP which has captured loads of muck.  One year on and still running well.

Posted by: @watkins247

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@pike005 Mines a Greenline 6 KW fitted in 2008 and is failing various errors, alarms, cassette failed end of last year, limping along now just has hot water to do.
Having same issue with lack of knowledge and few willing to look at it. Not helped by IVT not being available in UK.

Had a couple of quotes for a replacement £16-18k.

Considering having it removed and going oil, unfortunately gas not an option.

What's to stop you simply replacing the heating bit with an ashp.  Presumably all the emutters etc are fine so it's just a straight swap of heat source which shouldn't cost anything like 16k and is more maintainable.  

It's a bit disappointing that gshps haven't really caught on, but I guess that the upfront cost for the coil makes them less attractive and thus reduced production quantity leading to higher cost.

Should be a minimum sentence of 3 years behind bars for anyone who replaces a geothermal (assuming a good collector) with an air to water 🤣. 
I’ve 6,000 plus customers with both geo and air to water on my service books and hands down geothermal is more reliable.

@jamespa No good location to put ASHP would need considerable  building work. Meaning cost very similiar.