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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorJeff B
    • CommentTimeFeb 9th 2019
     
    I have a 21 panel PV solar set up. Each panel has an Enecsys microinverter installed underneath it. Of the 21 microinverters 6 have died at various intervals since they were installed back in 2011. The Enecsys company went bust after about 3 years but the system was insured (and is until 2021) and I was lucky to find a supplier of Enecsys microinverters in the USA so I have been able to replace the faulty units.

    Most of the failures were due to rain and salt ingress into the casings (we live about 1 mile from the sea). I have a plan to take all the microinverters off the roof, install them in a weatherproof enclosure at ground level and run the necessary cables up to the panels on the roof. We are in a bungalow so the distances are not huge - probably the longest run would be about 6 metres. It's a long shot but I wonder if anyone on the forum has ever tried to do this and if they have any comments? You may have comments even if you have never done this - I'd be grateful to receive them as well. Basically can anyone see any flaws in this approach?

    The big advantages would be that all the inverters would be in a dry enclosure and also would be accessible from the ground - I could change them myself rather than have to hire access equipment and pay a solar PV electrician to get up on my roof!
    • CommentAuthorphiledge
    • CommentTimeFeb 9th 2019
     
    If your roof void is accessible putting them in there would save having to route the cables to the ground
    • CommentAuthorbxman
    • CommentTimeFeb 9th 2019
     
    Hi

    Are the panels subject to shadeing ?

    Remember if you will be only getting panel voltage on the wires down to the micro-inverters.

    How long will those wires be ?

    I might well be wrong but will there be 42 wires from roof to floor.

    I would be inclined to make up 2 strings and get a s/h regular dual mppt inverter .

    cheers Patrick
    •  
      CommentAuthordjh
    • CommentTimeFeb 9th 2019
     
    I don't suppose the microinverters are designed to work with long cables between them and the panels. I don't know what effect the change might have on performance or reliability. It seems likely that the reconfiguration would void any warranty and probably insurance. So I would check that the change is technically allowed/sensible and also that your insurance remains valid before making any changes.

    Personally I would follow a different strategy. I would continue to replace the units as you have been doing as long as the insurance is paying. If any failed after that time, I would replace them with an alternate brand since there's no necessity for them all to be the same (their interface is just a mains cable after all). Myself, I'd probably choose Enphase microinverters since they have a twenty-five year warranty and none of mine have failed yet.
    •  
      CommentAuthorDamonHD
    • CommentTimeFeb 9th 2019
     
    If you are being paid FiTs or any other kind of government support then in principle you should be seeking the administrator's agreement (and providing justification) before making any changes whatsoever to avoid violating terms of that support. Echoing djh, like-for-like replacement because of equipment failure is likely to be the most successful in terms of that as well as operation.

    Rgds

    Damon
    • CommentAuthorJeff B
    • CommentTimeFeb 9th 2019
     
    <blockquote><cite>Posted By: philedge</cite>If your roof void is accessible putting them in there would save having to route the cables to the ground</blockquote>

    There is a void space but as we are in a dormer bungalow we have that classic small right-angled triangle shaped space behind the dwarf walls. I would not like to bring the inverters inside the roof space there in the event of overheating and the potential for fire.
    • CommentAuthorJeff B
    • CommentTimeFeb 9th 2019
     
    <blockquote><cite>Posted By: bxman</cite>Hi

    Are the panels subject to shadeing ?

    Remember if you will be only getting panel voltage on the wires down to the micro-inverters.

    How long will those wires be ?

    I might well be wrong but will there be 42 wires from roof to floor.

    I would be inclined to make up 2 strings and get a s/h regular dual mppt inverter .

    cheers Patrick</blockquote>

    Yes there would be 42 cables. Currently the panels are not subject to shading but my neighbour has trees on the boundary and these are still growing, albeit slowly, hence I would not be happy to go to a dual inverter system. Also I like the idea of being able to monitor the output from each panel.
    • CommentAuthorJeff B
    • CommentTimeFeb 9th 2019
     
    <blockquote><cite>Posted By: djh</cite>I don't suppose the microinverters are designed to work with long cables between them and the panels. I don't know what effect the change might have on performance or reliability. It seems likely that the reconfiguration would void any warranty and probably insurance. So I would check that the change is technically allowed/sensible and also that your insurance remains valid before making any changes.

    Personally I would follow a different strategy. I would continue to replace the units as you have been doing as long as the insurance is paying. If any failed after that time, I would replace them with an alternate brand since there's no necessity for them all to be the same (their interface is just a mains cable after all). Myself, I'd probably choose Enphase microinverters since they have a twenty-five year warranty and none of mine have failed yet.</blockquote>

    Unfortunately there is no technical person at Enecsys that I can talk to as the company went bust several years ago. I have spoken to an electrician who specialises in PV and he can't see any objections provided we use reasonably fat copper cables to minimise resistance. My plan is initially to move just one microinverter to a new position as a trial, using the maximum length of cable that I anticipate would be needed - approx 6 metres. Two have gone pop recently so I have to change them anyway so now seemed a good time to try the experiment.

    Would there be a compatibility issue if just a few of the inverters were changed to Enphase? Also I am sceptical of 25 year warranties after the Enecsys experience!
    • CommentAuthorJeff B
    • CommentTimeFeb 9th 2019
     
    <blockquote><cite>Posted By: DamonHD</cite>If you are being paid FiTs or any other kind of government support then in principle you should be seeking the administrator's agreement (and providing justification) before making any changes whatsoever to avoid violating terms of that support. Echoing djh, like-for-like replacement because of equipment failure is likely to be the most successful in terms of that as well as operation.

    Rgds

    Damon</blockquote>

    Thanks for the comments. Yes, something to consider there.
    • CommentAuthorJeff B
    • CommentTimeFeb 9th 2019
     
    To all responders: thanks for all the comments thus far. I'm thinking maybe I should put the whole project on hold until the insurance policy expires in February 2021 as this covers any breakdown costs until then. I also have found a good supply of Enecsys microinverters from the USA and any new ones I fit will be given extra protection before installation. I am advised to apply silicone grease around the nitrile gasket (the electronics are encased in a two-part, very heavy duty, finned, aluminium case) and also where the cables pass through the seals into the case to enhance the weather proofing.
    • CommentAuthorJeff B
    • CommentTimeFeb 9th 2019
     
    I should have added that another option I have considered is to take down the microinverters one by one, clean them up, do the silicone greasing and put them back. A very long job though I'm thinking, and very costly of an electrician's time. I can do the cleaning/greasing but there could be a lot of hanging about in the process!
    •  
      CommentAuthordjh
    • CommentTimeFeb 9th 2019
     
    Posted By: Jeff BWould there be a compatibility issue if just a few of the inverters were changed to Enphase?

    What issue could there be?

    Also I am sceptical of 25 year warranties after the Enecsys experience!

    I would have thought that your present experience of still being able to claim after the company went under would encourage rather than discourage you.
    • CommentAuthorJeff B
    • CommentTimeFeb 9th 2019
     
    djh - Re compatibility: I am not technically qualified, that's why I asked the question. The only sure way to know would be for me to ask the technical support guys at Enphase I suppose?

    Re 25 year warranty: the insurance policy is only for 10 years. I suppose I was lucky to get this actually - it was a bolt-on extra, separate from the manufacturer's guarantee. After 2021 I'm on my own!
    •  
      CommentAuthordjh
    • CommentTimeFeb 10th 2019
     
    Yep, I guess Enphase could answer. 25 years is one of their features; I appreciate most other manufacturers are 10 years.
    • CommentAuthorJeff B
    • CommentTimeFeb 10th 2019
     
    djh - can I ask please: how long have you had your Enphase microinverters? Do you live near the sea? Thanks.
    • CommentAuthorJeff B
    • CommentTime7 days ago
     
    djh - can I ask please: how long have you had your Enphase microinverters? Do you live near the sea? Thanks.
    • CommentAuthorsam_cat
    • CommentTime7 days ago
     
    Is it worth talking to the insurance company, get them to look at your file and explain the risk/cost of ongoing failures... See if you can get them to 'buy your out' of the policy by doing a complete removal of all microinverters, convert to string and single inverter?

    Is there a reason you are on microinverters? Got a complex shading issue?
    • CommentAuthorJeff B
    • CommentTime7 days ago
     
    sam-cat: I don't think they'd be too interested as the policy only has 2 more years to run or they'd make a derisory offer. I have only claimed for two replacement inverters in the previous 8 years as the earlier failures I paid for myself. This was because I had some spare inverters here and one of the guys who used to work for the original installation company (who went bust in the interim) was still around and did the work cheaply. I have an excess of £50 to pay each time so I am conscious of that too! The present claim is to install two new inverters which I have had to pay for up front.

    I am learning more and more about the Enecsys inverters and it seems there is a lot I could do in the way of protecting the units either by re-siting them as I've described (which IMO is favourite) or by using silicone grease to seal the various entry points in the casing.

    I don't have a shading issue at the moment but my neighbour has planted more trees along her boundary and these might cause issues in the future. I still like the underlying idea of microinverters because I can monitor the output of each panel and I could detect if there was a problem.
    •  
      CommentAuthordjh
    • CommentTime7 days ago
     
    Posted By: Jeff Bdjh - can I ask please: how long have you had your Enphase microinverters? Do you live near the sea? Thanks.

    Sorry, I answered thiswhen you first posted. I don't know how my answer got lost. I've had them about four years and no we're not especially near the sea, so not an ideal reference for you.
    • CommentAuthorJeff B
    • CommentTime6 days ago
     
    djh - ok thanks.

    I have been in email contact with Enphase and Segen (who sell Enphase stuff) and they both seem confident that the units will be ok in a salty atmosphere. I'm told that the units can be submerged under a metre of water with no ill effect. Segen are a bit cagey about giving advice about relocating the inverters as although apparently they know of other people who have done this, due to data protection rules they are not willing to disclose details.

    Enphase say that I could relocate their microinverters into one place as long as the connecting leads are not too long (how long not specified). They say the idea is to keep the DC leads as short as possible to prevent high DC voltages across the roof but isn't one of the advantages of using microinverters is that you don't have high DC voltages that you would have using a single inverter system?

    There are several solar PV installers in my county so I intend to seek advice from them, if they are willing to talk to me of course!

    P.S. We get fairly frequent power cuts where we live and Enecsys microinverters are apparently very sensitive to these which doesn't help the situation either. Don't know about Enphase inverters - I haven't asked the question.
    •  
      CommentAuthordjh
    • CommentTime6 days ago
     
    Posted By: Jeff BThey say the idea is to keep the DC leads as short as possible to prevent high DC voltages across the roof but isn't one of the advantages of using microinverters is that you don't have high DC voltages that you would have using a single inverter system?

    Yes, but that's because the microinverters convert the DC to mains AC at the panel, so there's no DC on the roof at all (apart from about a foot of cable under each panel). And there's no mains on the roof if the mains is turned off, so it's business as usual for the fire brigade. Long DC cables negate all that.

    We get frequent power cuts (many more than our previous location - I don't know why) and I haven't noticed any problems with our solar system. The only effect I've seen is that the energy display on our diverter resets in a power cut, but that's nothing to do with Enphase. The mains voltage here sometimes gets up to the legal limit and the system seems to cope without any problem.
    • CommentAuthorJeff B
    • CommentTime6 days ago
     
    djh - re DC voltage. Sorry I don't follow that. I can understand that having all my PV panels on a single string would mean a high DC voltage as it would be like having a line of batteries wired in series. Let me compare a single PV panel to a battery, and the microinverter to a light bulb. I could connect a light bulb to a 12v battery a foot away or 20 feet away, the voltage delivered to the lamp is still 12v surely? The resistance of the cable would affect the current but if a "fat enough" cable is used, then this would not be significant.
    •  
      CommentAuthorDamonHD
    • CommentTime5 days ago edited
     
    You'd be astonished about the voltage drop in practice at any reasonable power. You REALLY don't want to spend enough on copper or aluminium to make that go away. Or embed all that energy if you are trying to save the planet. That is why we tend to run higher voltages over longer pieces of wire. (Losses are I^2.R)

    Look at the difference between the red (near battery) and pink (near my RPi that its is powering) lines in this graph, for low power (~1W) and quite expensive chunky cable.

    http://www.earth.org.uk/_off-grid-stats.html

    Rgds

    Damon
    • CommentAuthorJeff B
    • CommentTime5 days ago
     
    DamonHD - my reply to you earlier seems to have disappeared off the forum!

    Thank you for the info. I went on to say that I was intending to just modify one microinverter by making extension cables to simulate the worst case scenario. I was thinking of using the one in the bottom RH corner of the array (i.e. the most accessible) for this purpose. Although this is only a few feet above the wall of the house I would use about 5 metres of extension cable (the maximum distance needed) and locate the inverter on the wall below the soffit board. At least this way I could generate some actual data which would either support the idea or cause its total abandonment. I presume that the experiment would not have any detrimental effect on the rest of the system? However I am minded to take your's and djh's advice that I do not attempt this until after the insurance policy expires in Feb 2021 so as not to invalidate the guarantee.

    It is quite expensive to replace the faulty microinverters: there is the cost of the electrician, the hire of access equipment and the inverters themselves plus a £50 excess imposed by the insurers, so buying chunky cable may actually be quite cost effective over the remaining 17 years that the FIT payments are made. Moving the inverters down to chest height means I could do the job myself whilst standing on the ground.

    Alternatively I could save the next two years worth of FIT payments and replace all the inverters with Enphase units if they truly prove to be as reliable as claimed!

    BTW - what is the Rpi?

    Jeff
    •  
      CommentAuthorDamonHD
    • CommentTime5 days ago
     
    • CommentAuthorJeff B
    • CommentTime4 days ago
     
    Ah, ok, I've heard of that, but have no idea what it did! The guy who supplies me the Enecsys inverters has developed a kind of mini-PC using this I believe and he plans to send me one to monitor my PV panels. This is so I wouldn't have to rely on my desktop PC for this purpose and it will use a lot less energy. However it seems a bit pointless as my PC is on all day anyway and I turn it off through the night.
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