My boss planned the job and then I was asked to execute it. Place a UPS in front of the controls for a small gas fired boiler. Seemed simple enough. Once everything was in place I did a test and watched the UPS shutdown on overload. Then I started doing what I should have done in the first place - check the details of the installation. The UPS output was insufficient. The inrush for the fan motor was 31A and the UPS output is 12.5A. The default overload setting is >102% with a max setting of >150% (for 100ms). Right on the boiler controls itself it states that a minimum circuit ampacity of 13.25A is required. Red flags all over the place if I had only taken a few minutes to double check the details. My boss is an experienced electrician who seldom makes these types of mistakes. Looks like I'll have some bad news for him on Monday morning. Gotta love Mondays.
How about the factory's work? Good one was, I wired in a large electric fan. Sounded like a C-130 taking off but everything checked out. A few weeks later, I got called backed because the motor flamed out. It was properly protected but the end users were resetting the tripped over loads thinking it was a timer controller.
Get a new motor, sounds like a C130 taking off and I put my amp clamp on it. This time it's over loading. Get my bosses amp clamp and it reads the same. When I originally installed the fan, my amp clamp read good. I put the old battery back in my meter which was weak and was getting bad readings. Needless to say, I deep sixed that meter
Back to the new motor. I tried everything, triple checked my wiring, sizing of wires, adjusted the motor to try to minimize the air captured by the fan. No dice. Told my boss that the only thing I could figure the motor for was the wrong size for the fan. He wigged out yelling, "you telling me the factory is churning out hundreds of theses with the wrong motor!?! Bull puckey!"
A few days later, my boss calls me in and says, "remember that fan motor? They put the wrong motor in it. They are sending the proper one.".....
I've run into this with furnace blowers a lot. One nameless manufacturer produced hundreds of them in my area as heat pump system sections that were equipped with 1/2 HP motors instead of the proper 1/3 HP ones. We chased our tails for months, eventually changing the taps to the lowest speed so that they would at least run continuously.
Another contractor in the area finally figured out the issue and contacted the manufacturer's local rep. Fortunately, they provided replacement blower assemblies free of charge and paid us about $100.00 each to replace them.
Yes, the factory does make mistakes. Sometimes, they can be very costly ones.