Help Calculating time to recharge air tanks

[Richard Wallace]

Originally Posted by Jon Stratis

I'm no expert, but I've been repeating the "conventional wisdom" for years as an inspector and making teams replace their spike fuse with a breaker for the compressor. I had heard that the fuse will wear out over time due to the start up surge until it eventually pops...

Can anyone with a better understanding correlate the readings posted in this thread with the compressor breaker rule we've all been following for years?

I am not an expert, but my team has made some tests which may shed some light. See attached summary of our set up and results for recharging a 48 cubic inch system using three FRC-legal compressors.

When recharging from ~100 to ~120 PSI, the compressor must start against load. As Mr. V pointed out above, this case is much more pertinent to actual FRC operation than the tests I reported earlier.

The initial peak surge current observed using Viair compressors is relatively short duration (<0.1 sec), but the Thomas compressor's initial peak surge current is much longer duration (~0.5 sec). Comparing the Thomas surge against typical automotive fuse curves suggests an explanation for the "conventional wisdom" Jon mentioned above. The Thomas compressor has much less margin against blowing a 20A fuse during surge, and historically that is the compressor on which our FRC "conventional wisdom" is based.