Replacement for Genvex 400

[Judith]

Hi all. Our old Genvex 400 MVHR with heat pump has almost certainly given up the ghost. A capacitor was obviously no longer working, we replaced it (took ages to get it imported from Germany), but a fuse blows every time the machine is switched on. We understand that probably means the condenser is faulty, and it cannot be worked on because the CFC in it is no longer legal. So we are resigned to buying a new MVHR with heat pump for our space heating, this time I think with the "comfort cooling" option. All the ducting is still in place to re-use. What brands are on the market that we should consider? I see that Genvex is still available, but perhaps there are more choices now? Many thanks. 

[Nickfromwales]

5 hours ago, Judith said:

Hi all. Our old Genvex 400 MVHR with heat pump has almost certainly given up the ghost. A capacitor was obviously no longer working, we replaced it (took ages to get it imported from Germany), but a fuse blows every time the machine is switched on. We understand that probably means the condenser is faulty, and it cannot be worked on because the CFC in it is no longer legal. So we are resigned to buying a new MVHR with heat pump for our space heating, this time I think with the "comfort cooling" option. All the ducting is still in place to re-use. What brands are on the market that we should consider? I see that Genvex is still available, but perhaps there are more choices now? Many thanks. 

Hi.

How long had the system been in and running for, before it gave up the ghost? I think it would be prudent to rule out poor system design (overworking the unit(s)) before suggesting you replace like for like with a modern / alternate product.

[Judith]

15 hours ago, Nickfromwales said:

Hi.

How long had the system been in and running for, before it gave up the ghost? I think it would be prudent to rule out poor system design (overworking the unit(s)) before suggesting you replace like for like with a modern / alternate product.

Installed 1999. 

[Nickfromwales]

10 minutes ago, Judith said:

Installed 1999. 

Ouch. 4 years is a bloody short lifespan!! I'd review what you ask this to do, and reconsider some auxiliary space heating, maybe from A2A so you have some A/C too? At least you'll still have the benefits of a heat pump, but something is either wrong with the design and execution or the equipment was crap.

I take it this is a passive house and there is no wet UFH?

[Judith]

12 minutes ago, Nickfromwales said:

Ouch. 4 years is a bloody short lifespan!! I'd review what you ask this to do, and reconsider some auxiliary space heating, maybe from A2A so you have some A/C too? At least you'll still have the benefits of a heat pump, but something is either wrong with the design and execution or the equipment was crap.

I take it this is a passive house and there is no wet UFH?

So that's 24 years, not 4. We have electric duct heaters in the ducts. No wet heating. 

[Judith]

Just now, Judith said:

So that's 24 years, not 4. We have electric duct heaters in the ducts. No wet heating. 

 

1 minute ago, Judith said:

So that's 24 years, not 4. We have electric duct heaters in the ducts. No wet heating. It was before the passive house concept was really in place but we were aiming for something similar. 

 

[Nickfromwales]

3 minutes ago, Judith said:

So that's 24 years, not 4. 

Lol. I must stop reading whilst on the phone  

4 minutes ago, Judith said:

We have electric duct heaters in the ducts. No wet heating. 

Ah, ok. Are the duct heaters only upstairs?

[Judith]

15 minutes ago, Nickfromwales said:

Lol. I must stop reading whilst on the phone  

Ah, ok. Are the duct heaters only upstairs?

There are three duct heaters. One does the basement lounge, and that's 2 kW. with a grid at floor level. Another at 1 kW does the kitchen-diner and the other at 1 kW the bedrooms, those all into the ceiling MVHR. They're on 3 programmable thermostatic controllers. We might replace them as well, as they are prone to cutting out unnecessarily and hard to reset. We could DIY that replacement or get a local sparks to do it. We are very upset about the Genvex failing BTW as it would have been repairable were it not that the CFC refrigerant is no longer legal (for good reason of course but we like to keep stuff running). 

[sharpener]

55 minutes ago, Judith said:

we like to keep stuff running

 

Yes. I had a capacitor fail too, on my Villavent MVHR heat exchanger drive motor (rotary wheel type). Was in a hurry to get it fixed ahead of visitors coming so cost me £150 for a new motor. But for under £10 I got a new capacitor (well tbf three capacitors in parallel to make up the right value) from Farnell so now I have a spare motor if it happens again.

 

If that is all that is keeping your Genvex from the scrapheap it is a feasible DIY job. When you say it blows a fuse do you literally mean that or is it tripping a breaker and if so is it on overcurrent or earth leakage?

 

Of course now the unit exists, the ozone layer and global warming threats only really come into play when the thing reaches the end of its life.

[Judith]

4 minutes ago, sharpener said:

 

Yes. I had a capacitor fail too, on my Villavent MVHR heat exchanger drive motor (rotary wheel type). Was in a hurry to get it fixed ahead of visitors coming so cost me £150 for a new motor. But for under £10 I got a new capacitor (well tbf three capacitors in parallel to make up the right value) from Farnell so now I have a spare motor if it happens again.

 

If that is all that is keeping your Genvex from the scrapheap it is a feasible DIY job. When you say it blows a fuse do you literally mean that or is it tripping a breaker and if so is it on overcurrent or earth leakage?

 

Of course now the unit exists, the ozone layer and global warming threats only really come into play when the thing reaches the end of its life.

The capacitor cost about £30 to import from Germany. But despite the brand new capacitor, the same thing is happening again. The instant the machine is switched on, a fuse blows, a real one inside. They are very cheap but fiddly to put in. A sparks told us that it probably means the condenser itself is gone. We could have it degassed and removed, but then we would need a new condenser, which would be a different kind and wouldn't fit in the box. Maybe someone could do it, but not a DiY job. 

[JamesPa]

54 minutes ago, Judith said:

The capacitor cost about £30 to import from Germany. But despite the brand new capacitor, the same thing is happening again. The instant the machine is switched on, a fuse blows, a real one inside. They are very cheap but fiddly to put in. A sparks told us that it probably means the condenser itself is gone. We could have it degassed and removed, but then we would need a new condenser, which would be a different kind and wouldn't fit in the box. Maybe someone could do it, but not a DiY job. 

There are such things as slow blow fuses, designed to deal with start up spikes, is there any chance you need one of these?

[Judith]

19 minutes ago, JamesPa said:

There are such things as slow blow fuses, designed to deal with start up spikes, is there any chance you need one of these?

Thanks, but I don't think so. It functioned for years, no fuse ever went. Then last autumn we tried switching it on and it just wouldn't come on. I think it probably has reached the end of its life after about 24 years, and we need a new machine. I wonder what brands are on the market. 

[dpmiller]

I'm guessing the spark meant compressor, not condenser.

[Judith]

46 minutes ago, dpmiller said:

I'm guessing the spark meant compressor, not condenser.

Yes, yes he did, definitely. My mistake. 

[Nickfromwales]

1 hour ago, Judith said:

Thanks, but I don't think so. It functioned for years, no fuse ever went. Then last autumn we tried switching it on and it just wouldn't come on. I think it probably has reached the end of its life after about 24 years, and we need a new machine. I wonder what brands are on the market. 

I'm just wondering if you could have these units split, so the MVHR stand alone, and then the heat cool unit as a bolt-on. Would give better results I think, plus much better redundancy.

[Judith]

1 hour ago, Nickfromwales said:

I'm just wondering if you could have these units split, so the MVHR stand alone, and then the heat cool unit as a bolt-on. Would give better results I think, plus much better redundancy.

Well that's interesting. It would take someone who knew what they were doing to decommission the heat pump in the Genvex, then hopefully it would no longer blow fuses. Do you know of any make of heating-cooling heat pump that could run inline with it?

[Nickfromwales]

1 hour ago, Judith said:

Well that's interesting. It would take someone who knew what they were doing to decommission the heat pump in the Genvex, then hopefully it would no longer blow fuses. Do you know of any make of heating-cooling heat pump that could run inline with it?

Oh. BPC used to list one, but it's disappeared from their website. Maybe ominous...  

 

You'll probably have to sell a kidney, but:-

https://products.zehnder.co.uk/en/product/zehnder-comfoclime-36 I think you'd be looking at a complete swap out, but this may allow you to do away with the duct heaters. I'm not sure of your heat demand, so that would need close examination.

[Judith]

13 hours ago, Nickfromwales said:

Oh. BPC used to list one, but it's disappeared from their website. Maybe ominous...  

 

You'll probably have to sell a kidney, but:-

https://products.zehnder.co.uk/en/product/zehnder-comfoclime-36 I think you'd be looking at a complete swap out, but this may allow you to do away with the duct heaters. I'm not sure of your heat demand, so that would need close examination.

Heat calcs are 6kW (don't forget we were building in the 1990s), so the 4kW in the duct heaters was a deliberate undersizing. We don't need to heat all the rooms in the winter, and we have a lot of solar gain in the south. 

[Nickfromwales]

1 hour ago, Judith said:

Heat calcs are 6kW (don't forget we were building in the 1990s), so the 4kW in the duct heaters was a deliberate undersizing. We don't need to heat all the rooms in the winter, and we have a lot of solar gain in the south. 

Do you defo need the cooling effect?

[Judith]

5 hours ago, Judith said:

Heat calcs are 6kW (don't forget we were building in the 1990s), so the 4kW in the duct heaters was a deliberate undersizing. We don't need to heat all the rooms in the winter, and we have a lot of solar gain in the south. 

 

5 hours ago, Judith said:

Heat calcs are 6kW (don't forget we were building in the 1990s), so the 4kW in the duct heaters was a deliberate undersizing. We don't need to heat all the rooms in the winter, and we have a lot of solar gain in the south. 

My short list of companies is so far: Genvex, Zehnder, BPC, Daikin, Vaillant, but still at a very early stage of research. 

[Judith]

4 hours ago, Nickfromwales said:

Do you defo need the cooling effect?

No, not definitely. It wouldn't have cost much extra if we'd had it with the Genvex though. Not much extra to install, maybe much extra to run. 

[Steve k]

Hello I seam to be coming to this thread a bit late but have been running a genvex  heat recovery unit for 24 years in a well insulated 4bed barn conversion to great effect. The only additional heating in the building is a heated towel radiator heated from the  main buildings oil boiler. Over the years we have had to change the motor capacitors, only one was faulty but we changed both of them. We bought the capacitors from the now closed Maplins and the cost a couple of quid each. About 3 years ago the machine popped a fuse and after replacing the fuse I realised that one of the motors did not sound too healthy, thinking I was facing a disaster I took out the motor, the bearings were very rough. It took me about 10 minutes to remove the bearings finding that they were a standard off the shelf bearing. I had a new set of bearings within an hour and the machine was back together within 3 hours of the fuse popping. As the motor is the first thing that starts on start up and it is several minutes before the compressor starts this might be a good place to start. The machine has run faultlessly ever since. I suspect that both the replacement capacitors and bearings were of better quality than the originals but will not be able to confirm for another 17 years. On another note does anyone know where I can purchase another machine in the UK, possibly I would consider a second hand one  even if it needed repair.    

[sharpener]

On 04/01/2024 at 14:53, Steve k said:

I took out the motor, the bearings were very rough. It took me about 10 minutes to remove the bearings finding that they were a standard off the shelf bearing. I had a new set of bearings within an hour and the machine was back together within 3 hours of the fuse popping.

 

Tagging on I have done the same with the bearings in a lawn scarifier that was under 8 ins of floodwater and an oil boiler with a very noisy motor, from simplybearings.co.uk in both cases but I am sure there are plenty of others.

[joe90]

I too have replaced bearings in various stuff with generic bearings when told they were “sealed for life” 🤣

[Bancroft]

On 12/06/2023 at 17:38, Judith said:

Hi all. Our old Genvex 400 MVHR with heat pump has almost certainly given up the ghost. A capacitor was obviously no longer working, we replaced it (took ages to get it imported from Germany), but a fuse blows every time the machine is switched on. We understand that probably means the condenser is faulty, and it cannot be worked on because the CFC in it is no longer legal. So we are resigned to buying a new MVHR with heat pump for our space heating, this time I think with the "comfort cooling" option. All the ducting is still in place to re-use. What brands are on the market that we should consider? I see that Genvex is still available, but perhaps there are more choices now? Many thanks. 

Hi Judith,  do you have an update on this post?

I'm presently looking at A2A heat/MVHR systems and the more modern Genvex systems are on my list of possibilities.

Would be interested in knowing what you ended up with and why.