Preventive Maintenance Auto Transfer Switch

[2chiefsRus]

Is there any preventive maintenance we should be doing on our Auto Transfer Switch? Heres why I ask - We just had an odd situation. Plugged into shore power a couple days ago as normal, then flipped the pedestal breaker on, watched the numbers come up on the hard wired Progressive Industries unit. All good so far. Waited to hear the clunk of the auto transfer switch over from inverter to shore power, and waited, and waited, and waited. Finally flipped the breaker off on the pedestal and then flipped it back on again. Finally after about what seemed like 5 minutes, heard the clunk and all was fine.

[MEXICOWANDERER]

Kudos to Generator Jim!

There are special electrical cleaner lubricants just itching to be sprayed into a DISCONNECTED relay or contactor, after following Generator Jim's excellent advice.

The light lube keeps pivot points lubricated.

I would UNSCREW and VISUALLY CHECK each wire, one-at-a-time, plus look inside the screw clamp, reattach, tighten the screw then DOUBLE CHECK the tightness of all screws. One more check a month later unless the manufacturer decided to hide the transfer switch atop the black water tank.

[time2roll]

Posts of failures seem to be poor connections in the transfer switch box more than burning up the contacts.
+1 for opening the box and tightening the connections while inspecting for heat issues or corrosion.
And of course if you carry a spare the original will never fail. 😉

[dougrainer]

Chris Bryant wrote:
I'll play devil's advocate for a moment and ask what is different between a relay in the air conditioner switching the load and a relay in the transfer switch- other than the transfer relay is the size of your fist, and the a/c relay is the size of your thumb.

🙂

Fpr the rare transfer switch with open contacts, I do clean the contacts with Caig deoxit and treat them with progold.

I hope you are just messing with us. There is a BIG difference transferring 30/40/50 amps of load on spring loaded Contac point relays and transferring an AC unit. Remember, the AC comp relay is transferring NO real load, just closing the compressor contac relay, and THEN a few seconds later the Start Capacitor starts the LARGE load required to start and run the compressor. MOST AC units also have a time delay (2.5 to 3.0 minutes) between compressor starts if you try to short start. In other words, you are comparing apples and oranges, not the same thing at all. Doug

[wa8yxm]

If you are simply turning the A/C on or off, not much difference, but if you are "Hot Switching" it, that, in this context, is switching from one power source to another, Some very strange things can happen that will cause the contacts to arc over on the transfer switch and damage the contactors (Relay, Solenoid, Contactor, three names depending on the size of the contacts, at 50 amps, Contactor applies if the coil is AC)

THe relay in the A/C, never does this, EVER, it can not, since it is on/off only, not on/on

[Chris_Bryant]

I'll play devil's advocate for a moment and ask what is different between a relay in the air conditioner switching the load and a relay in the transfer switch- other than the transfer relay is the size of your fist, and the a/c relay is the size of your thumb.

🙂

Fpr the rare transfer switch with open contacts, I do clean the contacts with Caig deoxit and treat them with progold.

[wolfe10]

Agree with Doug (as usual). Torquing connections in ATS and in 120 VAC breaker box is on the annual check list (and has been for many years).

[dougrainer]

The REASON for the recall was because the OEM's did NOT correctly torque the mount screws for the heavy 120 wiring. When I do a replacement on a Transfer switch and it has screws, I torque down the first time and let sit for 10 minutes to allow the individual wires to collapse and then retorque. You would be amazed at how much extra the 2nd torque will allow the screws to turn. ALL burnt/fire related damage I have ALWAYS seen was NOT on the transfer relay's but on the Connection screws on the buss. They were loose after a period of time because they were not torqued correctly at build. AND, TRANSFERRING POWER WITH LOADS WILL CAUSE THOSE LOOSE CONNECTIONS TO HEAT UP AND BURN THRU FASTER. THAT IS WHY YOU NEVER TRANSFER UNDER LOAD, TO HELP PROTECT YOUR SYSTEM. Maintenance would mean you retorque the wire mount screws a few times and check for tight connections. Doug

[2chiefsRus]

Original poster here - never did find anything. We've been at several different sites since then without it happening again. Starting to believe it was something at that particular campsite.

[wolfe10]

Yup, switch with NO LOAD. That means all big loads off. Plug in and unplug from shore power with CG breaker OFF as well for longer shore power cord life.

Other annual maintenance includes tightening all connections in the ATS as well as 120 VAC breaker box.

[2chiefsRus]

Original Poster here - thanks for all the feedback. When we left our campsite today, we flipped the pedestal breaker off and back on a couple times and the transfer switch worked fine each time. We will be opening it up and taking a closer look at our next stop just to see what we see.

[Corkey05]

MrWizard wrote:

The transfer switch is rated to function with heavy loads (such as air conditioner) being active when engaged if you have auto temp start for the generator. Many of us have animals and keep the temp start active when there's a chance of hot weather driving up inside temps.

i disagree with the way you 'think' it functions

the stat clicks on calling for power
the ems auto starts the genset
after the warmup delay the transfer switch closes
then the ems allows power to the A/C

the power surge goes thru 'closed contacts' of the transfer switch

IF the A/C was pre-engaged and the contacts closed, there would be a tremendous arc from the compressor 'star up spike load' up to 10x what the run current is, that could be 120amps or more arc on the contacts

True, .. I was attempting to describe why the IOTA transfer switches have been recalled without getting into the detailed mechanics of how the switch works for loads such as air conditioners. Other loads such as Hot water, sound systems, space heaters, etc are present when the switch makes contact. It's those loads that are heavy enough to drive the EMS nuts if the connection is loose in the transfer switch. Bottom line, .. with the delay they are designed to work with AC's in the 'ON' position at startup. Virtually every Monaco coach wired for 50 amp - built from 2004 - 2009 has the recalled IOTA transfer switch installed as OEM.

IOTA closed it's doors after the recall, and of course Monaco is not held accountable under the (then) new ownership of Navistar for those build years. So the followup is at the discretion of the coach owner, ... I have never been notified of the recall, but found out instead through publications such as Motorhome magazine. Pretty sad really ...

I fought the same problem as the OP until I read the recall notice and looked inside the transfer switch ... not a pretty sight and burned badly. The relay contacts where fine, but the feed wire connection was badly burned.

His may be another situation, but there's no harm in looking, especially if his is one of the faulty, fire prone recalled units.

[MEXICOWANDERER]

Corkey05 wrote:
If your 07 is like my 08, the IOTA transfer switch has been recalled by NTSA. The terminals loosen up over time and act just as you describe plus they can overheat to the point of causing a fire.

Info ....

The transfer switch is rated to function with heavy loads (such as air conditioner) being active when engaged if you have auto temp start for the generator. Many of us have animals and keep the temp start active when there's a chance of hot weather driving up inside temps.

When my transfer switch first acted up, the control panel lights would come on one at a time as you say, then shut off and restart. It was the transfer switch kicking out from a damaged (loose and overheated) terminal on L2.

You can tighten the terminals inside the transfer switch and it will work again for a while, if it's not already damaged like mine was. But the condition usually returns, ... best to replace it.

Don't these idiot manufacturers know what a SEMS SCREW IS?

With really critical tab connections I use a longer SEMS screw to bind the wire terminal to the threaded tab then use a KEPS NUT on the other side, I freakin' guarantee you that termination will not "loosen up" EVER.

[Generator_Jim]

Any six year old mechanical transfer switch should have its load contacts visually checked about every 2 or 3 years. If pitted, use a very fine file or fine sandpaper (NOT emery paper) to smooth the contact points. Other than that, tighten wiring connections and enjoy.

The 70 amp switch in my coach is twice oversize for the 30 amp generator so I don't worry too much about overload on the contacts. The 200 amp switch on my whole house generator is a bit oversize for the 83 amp generator. No trouble from either switch since new.

(Another chief, 54200, 57-87)

JimL

[MrWizard]

The transfer switch is rated to function with heavy loads (such as air conditioner) being active when engaged if you have auto temp start for the generator. Many of us have animals and keep the temp start active when there's a chance of hot weather driving up inside temps.

i disagree with the way you 'think' it functions

the stat clicks on calling for power
the ems auto starts the genset
after the warmup delay the transfer switch closes
then the ems allows power to the A/C

the power surge goes thru 'closed contacts' of the transfer switch

IF the A/C was pre-engaged and the contacts closed, there would be a tremendous arc from the compressor 'star up spike load' up to 10x what the run current is, that could be 120amps or more arc on the contacts