Roottop AC

[SkyCop4U]

2008 Discovery.

I have two AC units, the front is at 1500, and the back 1350.The back has begun to spike during startup. If I am on 50 amp service I cannot see this and nothing goes wrong. On 30 amp service I see a 40-50 amp spike. It still starts as it is only momentary. However it is bad enough to shut down the GenSet as it sees the spike and shuts down to protect itself.

So, what do I need to replace?

[SkyCop4U]

Final Report.

I got on the roof and opened up the electrical area. The starter solenoid was burned up. The plastic attachment on top was melted and gone. It also burned the side of the run solenoid. I replaced both the starter and run solenoid. Did a test on both 30 amp service and the gen set. Both run perfectly without any spikes.

[jyrostng]

be sure and check the connections at the generator and the ac panel where it connects.

[time_to_go_now]

SkyCop4U wrote:
The generator does not like the spike. It is a 8 KW BTW. lots of power.

I am still watching with great interest. I have put an ammeter on the main line. I can see the 29 amp momentary spike when the AC first starts. It never used to be an issue. My 6KW genny started and ran both A/C units just fine. But, something has changed. I just spent a week in a 50 amp service campground. Both A/Cs came on as needed. That would kill my genny and give me an over limit code.

I replaced the capacitor and replaced the hard start kit in both A/C's (both A/C units already had the hard start kit installed by Tiffin). Made no difference on mine. I hope it helps the OP.

[SkyCop4U]

dougrainer wrote:

Bill.Satellite wrote:
How large (small) is your genset? A 50 amp system would need at least a 6000K genset but since there is also a "surge" factor it might take 7-8K to simply break even. I have a 15K genset on board and have never encountered a similar issue but I certainly can see where this could be an issue.

A Genset 5.5 or larger has more than enough power to start and run 2 AC units. Doug

Doug,

I have run both ACs on 30 amp service as my unit can shed power if needed. I bought it new in 08 and always ran both units on 30 amp. Total draw with fridge on too is about 28 amps. Never popped a breaker.

[SkyCop4U]

dougrainer wrote:

Bill.Satellite wrote:
How large (small) is your genset? A 50 amp system would need at least a 6000K genset but since there is also a "surge" factor it might take 7-8K to simply break even. I have a 15K genset on board and have never encountered a similar issue but I certainly can see where this could be an issue.

A Genset 5.5 or larger has more than enough power to start and run 2 AC units. Doug

I have not made it to the roof yet and will check the capacitor. To answer your question on why I don't notice it on 50 amp service is because my coach does not register amps when using 50 amp service. On the generator or 30 amp it gives me the load. On 30 amp service I see the 55 amp spike, but it is short and starts. The generator does not like the spike. It is a 8 KW BTW. lots of power.

[dougrainer]

Bill.Satellite wrote:
How large (small) is your genset? A 50 amp system would need at least a 6000K genset but since there is also a "surge" factor it might take 7-8K to simply break even. I have a 15K genset on board and have never encountered a similar issue but I certainly can see where this could be an issue.

A Genset 5.5 or larger has more than enough power to start and run 2 AC units. Doug

[dougrainer]

There are a lot of smart people on these forums. How come NOBODY on this thread noticed one thing???? He stated on 50 amp service he did not notice a spike or problems. But on 30 amp he did. HOW DOES THE "BAD" AC KNOW HE IS ON 30 AMP SERVICE?????????????? Appliances do NOT know what the total amperage is available. They only "see" current(voltage). Which may mean his available voltage is NOT steady at 115 or higher. Also, you cannot expect to run 2 AC units on 30 amp service as the breakers are going to trip. His tell is when he is on Genset. THAT points to he DOES need either a new compressor start capacitor or just spend a few extra dollars and install a Hard Start kit. The compressor is aged and the extra jolt from a hard start capacitor will probably fix his problem. He also needs to install a Hard Start on the other AC as it does not cost that much and will probably help him out down the line. Doug

[pulsar]

wolfe10 wrote:
Sounds like a bad capacitor (at least you hope so). With all power off, go up on the roof, remove the cover and then access the "electrical area". Check capacitors for swelling, discoloration or leakage. Be sure to discharge by shorting terminals before removing. Any HVAC store should have capacitors to match.

Could it be the compressor-- yes, but check the cheap stuff first!

This was the problem on one of our coaches. And the dealer wanted to replace the compressor! And I fixed it for a couple of dollars.

Tom

[Bill_Satellite]

How large (small) is your genset? A 50 amp system would need at least a 6000K genset but since there is also a "surge" factor it might take 7-8K to simply break even. I have a 15K genset on board and have never encountered a similar issue but I certainly can see where this could be an issue.

[jyrostng]

There are many hard start kits available to reduce the amps at startup

A 6.5kw should run both ac units

[time_to_go_now]

Boy, Am I watching this with interest!!!! I have spent more than $1,500 with 6 different shops to try and solve the EXACT same problem. Nobody can figure it out!

It happens with BOTH my A/C units. So, I think it is the generator misreading the spike and shutting itself off. But, two Onan repair facilities give my genny a clean bill of health.

[jyrostng]

How long does the back unit compressor stay off before restarting, as thermostats age sometimes they lose their differential settings. Another possibility is the area where the air blows out isn't sealed well from the air inlet where the filters are and the cold air is blowing on the thermostat capillary tube causing it to short cycle.

and great answer Wolfe

[wolfe10]

Sounds like a bad capacitor (at least you hope so). With all power off, go up on the roof, remove the cover and then access the "electrical area". Check capacitors for swelling, discoloration or leakage. Be sure to discharge by shorting terminals before removing. Any HVAC store should have capacitors to match.

Could it be the compressor-- yes, but check the cheap stuff first!