| Author | Message | ||
| Jim Wilkerson (Wagwar)
Registered Member Username: Wagwar Post Number: 63 Registered: 12-2009 Posted From: 99.109.187.242 Rating: N/A |
We just completed our first 2-week trip in our 'new' bus - 1981 MC 9 and it was a big success! I even fixed a couple of electrical problems on the road. All systems worked well-enough, but of course I've also added to the 'fix it' list. One problem that I'm not sure how to proceed on is: Bus has an older PowerTech PTS 6.6KW AA diesel gen. It seems to run fine and has two 30 Amp switches on it. So, I assume that it is supplying two 120 VAC 30 Amp hot leads to a small breaker panel (panel has a double 50 Amp breaker). The problem is that it does not seem to be able to run my two rooftop A/C units at the same time. Turning them both on throws one of the 30 amp breakers on the gen. THe rooftop units are Carrier V units and work fine if I'm on a 30 Amp shore power. Another factor is - I have a Trace 4024 MC2 inverter that was also trying to bulk charge a 24V bank of 4 Type 31 batteries. What could be causing the gen to throw a breaker? Thanks, | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 548 Registered: 10-2003 Posted From: 66.165.176.62  Rating: N/A |
If only one of the breakers is blowing I would assume they are both installed ont he same circuit where it would be better balanced if one was on each leg. Check out the panel to make sure everything is wired correctly. | ||
| Jim Wilkerson (Wagwar)
Registered Member Username: Wagwar Post Number: 64 Registered: 12-2009 Posted From: 99.109.187.242 Rating: N/A |
Thanks Tim, I would not be surprised to find something wired incorrectly. BTW, for those of you who might be interested in our blog: http://mightybus.wordpress.com/ Regards | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1926 Registered: 10-2003 Posted From: 71.58.71.157  Rating: |
does it make any difference if the Trace is turned off? | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1073 Registered: 8-2006 Posted From: 99.62.7.26 Rating: N/A |
Jim, You have given us the answer in your post. When connected to 30 Amp shore power, you are only using one "120 Volt leg" of power. That is why your 50 Amp shore power connection has a double pole breaker. (It has two 50 Amp 120 Volt legs.) It sounds like your generator is wired for 30 Amp 120/240 power, where it puts 30 Amps of 120 Volt on each leg, and both of your A/C units are connected to one leg. There is enough difference in the tripping amperage of circuit breakers to allow the 30 Amp shore breaker to hold at 26 or 27 Amps, while the generator breaker trips. The generator may not be putting out exactly 120 Volts either. If it is putting out less than 120 Volts, the Amperage draw of your A/Cs will rise. So, look at the connections, and your generator manual will tell you how to reconnect for nearly 50 Amps of 120 Volt, or move one A/C to the other leg, depending upon the way the 30 Amp shore cord is connected. As suggested above, a 30 Amp shore cord or gen will usually run two roof airs, but NOTHING else! HTH, George | ||
| Bill Gerrie (Bill_gerrie)
Registered Member Username: Bill_gerrie Post Number: 370 Registered: 3-2006 Posted From: 216.198.139.38  Rating: N/A |
Jim I had the same problem as you do with my 7.5kw Onan diesel gen set. I did as George suggested. Reconnect the gen set to provide 120 volts only. No more problems with running 2 A/C units as all the amperage is available on one line. Bill | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 525 Registered: 2-2001 Posted From: 184.0.3.170 Rating: N/A |
That's what I was going to suggest. Two 15,500 BTU ACs should run fine on a 6.5 kw. Most gensets have two output winding coils. Normally one is attached to each breaker. If your power load is not balanced you could, (for instance) have 40 amps on one leg but only 15 on the other. Hence the one breaker trips. But if you don't have any 240 volt equipment on board then I'd connect the genset for 120 only. That way the load is added together as "55 amps" but shared equally by the two coils and breakers so 27 each. To do this you will need a real "shore power switch" because your shore cord will still be connected as 120/240 but the genset as 120 only. With a proper switch or interlocked main breaker setup this is easy to do. | ||
| Jim Wilkerson (Wagwar)
Registered Member Username: Wagwar Post Number: 66 Registered: 12-2009 Posted From: 99.109.187.242 Rating: N/A |
Thanks Jim Bob, The genset is currently connected as two 120 Volt legs to a 50 amp double breaker. The output from the double breaker goes to an ES 350 Automatic transfer switch (ESCO) that has two lugs on the input and output side of the generator relay and a common neutral: one for each of the two 120 Volt legs from the genset. One lug feeds one side of the house panel and one lug feeds the other side of the house 120 volt panel. Each A/C unit is on a separate side of the house panel. I have no 240 volt equipment. The way it is set up now, if I have NO shore or gen power I can run one A/C unit (front) off inverter power from one side of house panel and the other side has no power. If I have shore or gen power I have power on both sides of the house panel. Side two of the house panel handles the rear A/C unit, microwave and some AC outlets. Side one of the house panel handles some AC outlets, refrig (if on 120V) and one A/C unit (front). | ||
| Len Silva (Lsilva)
Registered Member Username: Lsilva Post Number: 384 Registered: 12-2000 Posted From: 72.187.35.208  Rating: N/A |
It could be as simple as a bad breaker on the generator. I would replace it before going and further. You might troubleshoot by swapping the two hot leads from the generator and see if the trouble follows the swap or stays the same. |
