Replace Transfer Switch

[Old Scout]

I replaced the LYGHT transfer switch on our 2003 this week. The old LPT50CA was buzzing loudly the last few months and finally quit--shore power failed to connect/stay connected and one leg of genset power eventually failed as well. Our 2003 has a stand-alone x-fer switch with an after-market Progressive Industries surge guard to protect shore power.

I selected the LPT50BRD to reduce the buzzing caused by the LPT50CA AC-current contactors [BRD uses DC current to activate contactors]. During install, I noticed one of the terminals on the old X-fer switch was loose and had melted the terminal block and some of the wire covering. In retrospect, this may have contributed to my front A/C acting up [eg, frequent stop/starts--A/C compressors dont like low current]. This wire was loose despite having inspected and tightened these terminals within the last two years. Note--the CA model has a set of secondary terminal screws underneath the primary terminal lugs on one contactor bank [cross-ties the two contactor banks].

This LPT50CA lasted some 6-7 years but I have to wonder whether leaving the shore power connected while in storage contributed to the failure [contactors stay activated while on shore power].

[Luv2go]

Contactors (with either AC or DC coils) for transfer switches are designed for continuous duty, having the coach plugged in during storage should not have contributed to the failure.

I do think it is a good choice to replace the transfer switch with a DC model as you have done, usually they have better transfer characteristics (less contact bounce and less chance for chatter as the plug is plugged in).

Stewart

[mrschwarz]

Typically, the default position of the transfer switch is for shore power. The coil is not energized and the contacts can handle the current.

[Old Scout]

Pretty sure the design of the LYGHT requires the contactor to be closed [energized] to conduct shore power--thus the constant humming. With the Cutler-Hammer contactors, gravity opens the contacts, the coil lifts/closes them.

[Luv2go]

You both are right.

I've personally used both designs, one with two DPDT contactors and one with two 3PST contactors. The DPDT are used in my current Iota transfer switch, the 3PST was used on a Progressive Industries model (both these were 50A and both use DC coils on the contactors).

Both contactors on the Iota are de-energized on shore power and energized when on generator. The Progressive had one relay that was energized on shore power, the other energized when on generator.

Stewart

[Old Scout]

After being on my back in the basement and looking up at the ceiling [floor] for awhile during the install, I am no longer sure which way is up??????. Energized or not, I am betting on the LPT50BRD's DC-contactors not buzzing so much--hope I am right....

[iron mike]

Where are you getting the DC voltage from? The rectified AC coming from the park or from one of the batteries on the coach? Iron Mike

2003 38' Alpine

[Old Scout]

Can't tell you the technology involved but according to the specs, the LPT50BRD converts incoming AC power to DC current to activate the contactors. No outside/secondary DC wiring is required.....