VFDs out in the cold

S

soundmind

KNIFE MAKER
I realized VFDs are probably susceptible to failure by developing condensation with outside temp fluctuation. I'm looking into a solution like either a heater for it or cable connectors so I can keep it inside when I'm not using it.

Is anyone else keeping their VFDs in unheated shops in temps below 15 degrees F? Any problems or solutions you've found?
 
WOW! Good point and timely email. I haven't thought about this but I should have. We had a very cold snap in NC a couple of years ago and the computer on my exercise bike went out (it was in my unheated building at the time.) Maybe something I should look into for really cold spells. Is 15 degrees the breaking point for concern on the VFD's?
 
I read that but I'm not sure yet.
opaul said:
Is 15 degrees the breaking point for concern on the VFD's?
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I believe I found that on an engineering forum last night. I need to stop reading before bed. Actually 10 celcius which is about -20F. I'll let you know if I have more solid info. The issue on the engineering forum was on a hoist subjected to wind and ice. Different application entirely. I'm worried about condensation again.
 
I have an attached garage that's mostly insulated, but unheated. It often gets cold enough in the winter to freeze my water bucket solid, but I've never had trouble with any of my VFDs. There were a few times that my old PID for my heat treat oven wouldn't turn on if it was super cold, but as soon as it warmed up a few more degrees, it was fine... at least, until it wasn't. ;) Hard to say if condensation was a factor at all. I don't think it was.
 
Drew Riley said:
I have an attached garage that's mostly insulated, but unheated. It often gets cold enough in the winter to freeze my water bucket solid, but I've never had trouble with any of my VFDs. There were a few times that my old PID for my heat treat oven wouldn't turn on if it was super cold, but as soon as it warmed up a few more degrees, it was fine... at least, until it wasn't. ;) Hard to say if condensation was a factor at all. I don't think it was.
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I put one of those cheap 7500W electric heaters in my attached garage (had to because I had a high efficiency furnace installed out there) but it has no issues keeping it pretty decent in there.
 
All this talk about how cold it gets and problems of condensation if temps drop below zero, or any really cold temp is missing the point. Condensation happens anytime the temp falls below the dew point, and that could be 70°F, all depends on the % humidity. Right now here on Gulf Coast the temp is 42°F with a dewpoint of 39F with a humidity of 89%. Even a NEMA 4X enclosure will have condensation inside if the temp of the air inside drops below the dewpoint.

The chemical plants and refineries all use NEMA 4X (or explosion proof depending on area) enclosures outside in the weather and they still have corrosion issues after several years. Some companies will purge the enclosures with N2 to help prevent this problem.

The enclosure for a VFD is so small there just isn't enough moisture inside to worry about. Also the circuit boards usually are coated after assembly to help prevent corrosion, and help with arcing from metal grinding. Note, I said "help", not prevent.
 
On the subject at hand, I agree with Ken. Could it be a problem? Of course, anything is possible. Is it likely? I suspect not.

Reading this thread reminded me of my days working in unheated shops...having to haul anything freezable into the house at the end of each day, and all the problems not having heat in a knife shop brings. Preheating anvils, hammers, etc..... and freezing my behind off.

I simply can't image every gong back to that. Yeah, I'm, way spoiled! :) I actually have two overhead heaters in my finish shop, fully insulated, and weatherproofed. The forging shop has "hot water" heat in the concrete floor, and an auxiliary electric heater in case the temps dips past -30F (that's the point where the in floor hot water heat can't keep up....and yep, those temps are not as rare in Montana as you'd think) :)
 
Cold in and of itself is not harmful to VFDs. Heat is the enemy. As Ken says, condensation will happen based on dew point but I also agree it won’t be enough to hurt anything. I’ve worked on machinery that lived in pretty horrific conditions. VFDs are about the toughest electronic devices I’ve seen. If a little condensation was an issue, those of us living in the sweltering swamps of the South would see it first. I have seen VFDs fail from severe heat. (A factory had them in a non-vented stainless enclosure, on the roof, in the sun, in Texas...)

Case in point- I used to work on machines that were inside industrial cold rooms. (Orange juice plants). You had to dress in severe cold weather gear to work in there. My laptop screen would freeze every few hours. I thought the computer was acting up, but it was only the screen- literally- freezing and not updating.

The problem with those machines was the air valves freezing up. Even though they were supplied with dry air, the dehydrators were outside of the coldroom. The dew point of the compressed air would change as the warm air came into the cold pipes and when the pneumatic valves would cycle the pressure change would form ice crystals in the valves and plug the ports. I had to fight the plant engineer to let me put light bulbs under the valve manifolds to keep them from freezing. (He didn’t want a heat source in the cold room. Legit point, but the valves have to work for the machine to cycle so he had to concede.)

The whole point of my rambling story is to say that those machines had ten to twelve VFDs on them. They were never a concern. Once turned on, a VFD makes enough heat in a few seconds that it’s a moot point.
 
EdCaffreyMS said:
On the subject at hand, I agree with Ken
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Folks who know Ed 'n my history of epoxy discussions will understand Ed's statement above. I think I agree with Ed 99+% of the time. I'm still following his advice on the blown burner and forge, and it's getting closer now. I have learned so much from Ed on this forum and the times we've talked at Blade - when we had time to talk much because of all the folks wanting to talk with their Hero Ed - and count me in that bunch {g} Allow me to say THANK YOU for sharing and teaching so much on this forum.

Ken H>
 
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In real life I'm a computer server admin and work in large data centers. Electronics don't mind the cold and will last longer when kept cool rather than hot. Condensation and moisture are killers for electronics. As we all know liquid water will cause shorts and a freezing/thawing (read in expanding and contracting) cycle isn't going to do microscopic electronic connections any good. All it takes is one little break on a board and it's done.
 
My grinder is in my workshop and last night it was -3 C outside and so it certainly got cold.

I think where knife makers are concerned the main worry with VFDs are concerned is dust, the dust from grinding in particular.

I think the rating here in the UK is IP66, that dust and moisture protected, there are certainly ratings that are lower ratings which are covered here.

Good VFDs of a high protection rating aren't cheap but they are pretty bomb proof.

 
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