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.

[Mr V]

Originally Posted by Richard Wallace

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.

Excelent and very useful data, thanks very much.

What people need to keep in mind is that a fuse and the type of circuit breakers that we use are thermal devices. When they reach a certain temp they will open. With a large overload it will open almost instantaneously. With a slight overload it will open but in a longer period. With intermittent medium overloads it can eventual heat to the point where it opens.

So the old Thomas compressor if it starts multiple times during a match could certainly eventually heat up the fuse to the point it opens. I'm not sure why they choose the ATM form factor instead of the ATO/ATC form factor as used for the 20/30 amp circuits on the PDP, PDB and Spike. The ATM is not that much smaller than the ATO/ATC.

[yara92]

Originally Posted by Richard Wallace

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.

Richard HI
I try the test. noting move may be because of the spike, I use defrent spike , nothing move.

[Richard Wallace]

Originally Posted by yara92

Richard HI
I try the test. noting move may be because of the spike, I use defrent spike , nothing move.

I saw your questions in the other thread. Have you been able to determine if your Thomas compressor is still functioning normally? Do you have another compressor to try?

[yara92]

Originally Posted by Richard Wallace

I saw your questions in the other thread. Have you been able to determine if your Thomas compressor is still functioning normally? Do you have another compressor to try?

YesI have ,
for testing Iconnect dirict itis working.
My quation i you knowhow to use the spike as relay. I use Jumber, the output 0 [V]

[Richard Wallace]

Originally Posted by yara92

YesI have ,
for testing Iconnect dirict itis working.
My quation i you knowhow to use the spike as relay. I use Jumber, the output 0 [V]

Ok, now I understand your question. I caused confusion by showing the control connection between the pressure switch and the Spike incorrectly in the diagram attached in my earlier post. The connection used on my team's bench test board is shown in the attached (revA) version of that diagram.