Circuit protection against corrosion

[colinf]

System is 2x Growatt SPF 3000TL LVM in parallel, with single Narada 48NPFC100 and approx 6kW of panels.

I recently installed a system within 50m of the sea. It's in the Caribbean so we knew that overheating is also a challenge as temperature is consistently 30°C+, as a result we installed the system in a box within a room which had some airflow but netting on all windows to attempt to stop salt fog. The client understood the system would have a shorter lifespan due to corrosion but not quite that short, in hindsight I designed poorly for the conditions. The Growatt inverters started to show overtemperature alarms (corrosion on the thermistor terminals) and fan operation warnings (corrosion on fan connections to the control board?) after about a month and one of them had an internal short after 2 months due to salt water ingress internally.

We are in the process of building an entire sealed cement structure with an air filtration system to house the inverters. I am beginning to research other brands of inverter that may have better protection in harsh environments. It appears the Growatts are very poor in this respect, because I have 4 smaller EPEver inverters on the site in even less protected environments and they show zero signs of corrosion on the PCBs after an internal inspection. I suppose the Growatts don't have a clear coat on the boards while EPEver does?

I have also researched into circuit protection spray but they are very hard to get a hold of due to my remote location. Troubles of living in paradise!! I'm also not sure if the circuit protection spray would help with the corrosion at the connection of the thermistors to the control board.

I'm looking for any info on the following:
- Brands of inverter/controllers which are reputed to have better protection in adverse environments
- Circuit protection techniques ESPECIALLY for pin type PCB connectors (which don't cause additional resistance which will alter the temp readings)

Thankyou for any help!!

 

[BiduleOhm]

The clear coat for PCB is called conformal coating. But the problem is that unless you do a full immersion under vacuum you'll not cover 100 % of the PCB and components and so you'll have corrosion on anything left unprotected.

For connectors the only solution I know is to coat both parts of the connector with dielectric grease (silicone grease), don't be afraid to use too much.

I have a radical solution which will work 100 % but will void the warranty and will require a few changes (mainly the fan): put the whole thing under mineral oil.

 

[colinf]

The clear coat for PCB is called conformal coating. But the problem is that unless you do a full immersion under vacuum you'll not cover 100 % of the PCB and components and so you'll have corrosion on anything left unprotected.

For connectors the only solution I know is to coat both parts of the connector with dielectric grease (silicone grease), don't be afraid to use too much.

I have a radical solution which will work 100 % but will void the warranty and will require a few changes (mainly the fan): put the whole thing under mineral oil.

Thanks!

I think I can assume there are some parts which are much more susceptible to corrosion based on looking at what went bad in the current inverters (just based on the heat and airflow within the inverter). And something is better than nothing. It definitely seems like a big task to try and coat the PCBs just using a brush. I might have to spend a full day completely disassembling the units.

Mineral oil is an interesting one and looks like it would solve the problem absolutely! But looks like out here in Colombia it will cost almost 3x the cost of the inverters themselves. I'll pitch that one to the clients and see what they think.

 

[robby]

I see that Outback makes some Marine Grade models for boats, but for home use I am not sure if it has all the features.
Outback Mobile Marine
Sol-Ark Inverters are sealed inverters that if you wire them right they will let no air in but the external fans will need replacing probably every year so the 12K model would be the best choice.
Sol-Ark
Fortress Power eFlex batteries are completely sealed air tight batteries with a thick 3mm Aluminum case.
Fortress eFlex

I have done what your going through. Outdoor AC units that disintegrate in 2 years as the case rusts away.
Even Door hings and locks that have to be replaced almost every year. Living near to the Ocean is not something for poor people,
it costs a lot of money to maintain a house.

 

[colinf]

I see that Outback makes some Marine Grade models for boats, but for home use I am not sure if it has all the features.
Outback Mobile Marine
Sol-Ark Inverters are sealed inverters that if you wire them right they will let no air in but the external fans will need replacing probably every year so the 12K model would be the best choice.
Sol-Ark
Fortress Power eFlex batteries are completely sealed air tight batteries with a thick 3mm Aluminum case.
Fortress eFlex

I have done what your going through. Outdoor AC units that disintegrate in 2 years as the case rusts away.
Even Door hings and locks that have to be replaced almost every year. Living near to the Ocean is not something for poor people,
it costs a lot of money to maintain a house.

These are exactly what I was after, but I'm curious about your recommendation for the 12K model regarding the fans? It seems like the 5K suits the needs of the project - does the 12K have more accessible fans?

Absolutely beginning to realize how pervasive salt is through absolutely every corner of the place!!

 

[BiduleOhm]

I think I can assume there are some parts which are much more susceptible to corrosion based on looking at what went bad in the current inverters (just based on the heat and airflow within the inverter). And something is better than nothing. It definitely seems like a big task to try and coat the PCBs just using a brush. I might have to spend a full day completely disassembling the units.

Yep. But salty spray is basically the worst case for electronics (it's actually how corrosion tests are made... salt spray is what eats stuff the quickest...).

My recommendation would be to filter the air real good (furnace filters or car air filters are probably the cheapest way to get high flow air filters with high availability) and conformal coat at least what you see failed first in the current inverter, plus grease in the connectors of course. That should buy you a few years if I had to guess.

Mineral oil is an interesting one and looks like it would solve the problem absolutely! But looks like out here in Colombia it will cost almost 3x the cost of the inverters themselves. I'll pitch that one to the clients and see what they think.

If it can be useful: here the cheapest way to get mineral oil is actually to get baby mineral oil (be sure there's no additives like perfum, etc...).

 

[robby]

These are exactly what I was after, but I'm curious about your recommendation for the 12K model regarding the fans? It seems like the 5K suits the needs of the project - does the 12K have more accessible fans?

Absolutely beginning to realize how pervasive salt is through absolutely every corner of the place!!

I was so focused on the corrosion issue and I forgot that you only needed 120V and 5-6K of power.
Yes the 5K would be a better fit for your application.
The fans are the only major component that is exposed to the air and I have a lot (I mean a lot) of experience with Fans near salt air.
I have a salt water Aquarium that uses 2 muffin fans for cooling the lighting system in the Tank and Sump.
I had to abandon the Sump one and Instead rely on passive cooling. The Tank Fan had to be changed from drawing out hot air from the Lights to blowing air in over the lights using Dryer Ducting so as to keep the Fan far enough from the salt air so they last.

Before I did these modifications the Fans would die almost every 6 months just from being in the vicinity of the Salt Air.
I even tried Hazardous chemical Muffin Fans that cost $89 a pop. These worked for a year and then crapped out.

So if your going to use a Sol-Ark you want to have some spare fans on hand and know how to change them.
Being 50M from the sea you will probably get two years out the fans.