30 AMP fuse blowing

[RickW]

The Load Carrying Capacities table at http://www.powerstream.com/Wire_Size.htm claims that a 10AWG wire is 55 Amps for Maximum Amps for chassis wiring and 15 Amps Max for power transmission. I am not a electrician but it does sound as if the wire can handle the larger fuse/circuit breaker but what about the motor and the circuit board? I would hate to have to replace the circuit board because of too much current being allowed. I am sure it is not cheap.

Has anybody actually talked to Lipart to find out what that fuse is really suppose to be? It would suck to burn something up and think it is under warranty and then to have the claim denied because you had too big of a fuse. I know mine came with a 30amp mini. I blew it 4 or 5 times before replacing with a 30amp circuit breaker. I have not blown it since placing the circuit breaker in but we have only moved the trailer a few times since then. We are headed out for 3 weeks later this week with several stops.

[HamRad]

If I remember correctly it was an employee from Lippert that first suggested that it was OK to use the larger fuses. I know many folks who use the larger fuses and to date I've not heard of one of them having any fire trouble or any trouble blowing out motors or control boards. But regardless of what someone suggest you need to be happy with whatever decision it is you end up making.

Good luck.

HamRad

[sreigle]

I would think if Keystone puts 30a in some and 40a in others of the same weight range then the wiring should be able to handle 40 amps. What I don't know is why 30 in some and 40 in others of the same weight range. Maybe the 30's are intended for the lighter rigs and the 40's for the heavy rigs and someone on the production line this fact is getting lost?

[firetrucker]

Current carrying capacity (ampacity) depends on a lot of variables, not the least of which are air temperature, type of insulation, whether the wire is bundled, and accceptable voltage drop (related to the length of the wire).

The NEC limits 10 awg wire to 30 to 40 amps, based on 60 to 90 degree C insulation. Other guidelines go as high as 70 amps for a 125 degree C insulation and 75 amps for 200 degree C insulation.

A round trip of 10 feet (motor 5 feet from the battery) would only generate a voltage drop (or loss) of about 1/2 volt at 50 amps (providing that all the connections were secure), a very acceptable number.

Bottom line: a 40 amp fuse will work just fine as far as the wiring for the landing gear is concerned.

BTW: a bad ground cannot increase the amount of current the dc motor will draw. It will only decrease it because of the increased resistance. The ground connection will get warm, and the motor will not have as much power. Maybe an intermittently bad ground could affect the fuse, but chances are low.

Bob

[NCFischers]

Upon examining the wire for the motor, I amend my answer. The wire is rated for 105 degrees and will handle a 40 amp fuse. If I don't bind the motor when I raise the jacks, I won't blow the 30 amp fuse so I lowered the jacks 1/4 inch from full up and marked the drivers side leg with tape. When I can't see leg above the tape, I stop raising. Problem solved as long as there isn't another problem causing the fuse to blow. I still won't use a 40 amp fuse.

[richfaa]

We marked our landing legs day one so they can not bind long ago upon advise on this forum. We have the 30amp fuse We have never blown a single one..

[exav8tr]

Same here as Rich and Helen.

[SlickWillie]

Very good discussion. I had done a little research when I recently pulled battery cable through the hull of my boat for my trolling motor.

Bob, (Firetrucker), thanks for your informative post. I didn't go into any detail in my previous post.

I'm curious about one thing. Are the rear electric stabilizers fused separately? I noticed in the Lippert sheets, the add on stabilizers show to have their own 6 amp fuse. We don't have them, don't want them as we don't need anything else to rust. BTW, we've never blown the landing gear fuse either, but I have replacement fuses on hand, just in case. I like the idea of the tape on the leg. I used a Marks a Lot, and it has faded out.

[Desert RVer]

Our 30AMP fuse blew on our 2006 Montana 3400RL front landing gears on our third outing. No documentation anywhere in Keystone/Montana supplied materials that there is a fuse much less where it is located. Replaced it with a new 30 AMP fuse and hasn't failed again. Would not recommend using a 40 Amp fuse.

[azleflyer]

Never had a problem with the fuse on the landing gear. However in addition to the wire size, lenght of wire run, etc. that others have mentioned you also have to take into account the amperage rating of the motor or "load" before increasing the fuse size.

[sreigle]

We blew our first fuse while setting up in this park earlier this month. I have no idea why. We were not at the limit. In fact, the switch had been pressed to raise the rig for only a few seconds. I know we had some spares but we couldn't find them. And we were not yet unhitched. Thankfully we had the car with us this trip so we were able to get to an auto parts store to get some fuses.

[Redrover98]

I was having the same fuse blowing problem with my 2007 3475Rl. I noticed that the wires from the motor to the feed were crimp connectors. I cut them out, soldered them and used heat shrink to seal the connection. Problem went away.

[8e3k0]

Never had a problem with our Monty but eliminted the mini fuse and its holder, then installed a 40 amp circuit breaker as of last Wednesday, put it to the test last nigth of raising and lower unit a number of times in a continuous operation. No problems and the drive motor was still very cool to the hand throughout the test and at the end of the test. Evidentally we are receiving the full voltage to the motor with no spike in amperage and /or no binding in the drive mechanism. Ellis

[db_engineer]

Thank you MOC! Brought the Monty home from storage last week to load up for the weekend. Went to run out the bedroom slide -- nothing, tried landing gear -- nothing , check battery - good. Into stick house, log on to MOC, quick search and AH-HA - everything I needed to know. Off to the parts store the next morning for a 5-pack of fuses, pop one in and all is well. The rest of the fuses are now in the toolbox that stays in the rig.

[sreigle]

Ours came from the factory with the landing gear legs blackened below the point where they can be retracted to. No need to mark that end. What I need to do yet is mark the other end, extending to max and then marking them.