Power Transfer Switch Adventure
Well on this last holiday weekend I had an unexpected detour which seems par for the course with my bus.
As part of my home automation system; I wanted sensors for shore power/RV camping lots where it could detect the difference between a 120V and 240V external feed. I.E. on 120V it would need a user input over-ride to know that the external feed was 30 amps verse's a simple extension cord in someone's driveway; to know the maximum power that it could draw for air conditioners or hydronic tank heating.
So anyway I removed the cover from the power transfer switch to add wires for a 120V shore/eternal power presence sensor and discovered the following:
https://www.crystalpoint.com/cpdownl...itchBypass.jpg
Some previous owner had totally bypassed the entire transfer switch functionality; which seems to a major theme on my bus. I.E. If you don't understand it, just bypass it!!!
My buses transfer switch is an Todd Engineering PS2-245S which has the following power input modes:
1. Inverter power input
2. Shore/external power input
3. Generator input
I can see from the physical damage evidence what more and likely lead them down this path:
https://www.crystalpoint.com/cpdownl...tchBurnout.jpg
It looks like the switch had been used extensively in shore power mode and had a loose connection for the neutral wire, which heated it up to the point that it melted away the connection from the plastic mount on the external power input bus bar. Look at the orange box in the picture, for where the neutral connection should be.
It seems that whoever tried to fix it, couldn't read the electrical diagram that was inside of the cover.
https://www.crystalpoint.com/cpdownl...tchDiagram.jpg
Future note, be sure to use the cell phone to take pictures before you muck with things!!!!
Anyway what was expected to be a 20 minute task; turned out be a full day of figuring things out, but hey I fixed it and didn't have to spend $600.00+ to replace the power transfer switch.
It turns out in attempting to fix the melted neutral connection problem; they had rewired the generator input connection and shorted out the HOT2 to the neutral connection.
Which might explain why I also found both air conditioners in the bus wired to the HOT1 connection which had previously puzzled me as to why someone would do that!!!
They had probably ran for sometime with a blown generator fuse on HOT2 input lead, before taking a second pass at the problem.
Anyway functionally in this transfer switch is as follows:
1. The default connection is for inverter power input. Which initially confused me in decoding the circuit diagram; as I had thought that the power cord/shore power input would be the default.
2. When in power cord/shore power input mode; two relays are energized with one light showing on the top time delay board, after a 30 second delay.
3. When in generator input; all the relays are energized with both timer delay boards showing lights. The first timer delay light comes on after a 30 second delay and then the second after an additional three minute delay; before generator power is passed through to the house systems.
So anyway on to the next problem....