Jon Wehrenberg
09-10-2007, 02:43 PM
On another thread Paul has posted some descriptions about issues he is having with his "new" coach. The issues as we all know never happen during business hours, Monday thru Friday, so the potential for a minor issue to turn serious is fairly high.
In Paul's case his house batteries were losing their charge.
His woes bring up a point for every owner to consider and address. How should the coach be set up for the use the owner wants to employ? For example, an owner that is going to do some primitive camping and attempt to get along on a 30 amp service is going to need to set up and use his coach completely different than an owner that is going to be parked outside the stadium on football Saturday with the generator runnning full time.
Shore power is limited and if a coach is going to rely on available shore power the owner has to limit what items are going to be used and when they are going to be used. For example, with 30 amps, it is probable the shore power can handle one AC unit, and the refrigerator, and possibly the TVs. If the inverters are set for charging, however they need to charge at a low rate so the current draw does not pop the shore power circuit with the other stuff mentioned above working.
On the other hand, the owner using the coach with the generator running continuously, can run almost anything whenever he chooses and also set up the inverter to charge at the highest setting so he can have all his sexy coach lighting going full blast and still maintain a battery charge. This and any type of dry camping probably is a justification for a high charge rate setting. This way the owner can rely on auto-start and the high charge rate will get the batteries charged quickly.
The 50 amp shore power service falls somewhere in between.
The key to understanding how to set up the coach and the switches is knowing limitations. As a practical matter a 30 amp shore power supply is capable of handling on a continuous basis about 80% of its rated capacity or 24 amps. Any greater and the risk of tripping exists.
A 50 amp service is actually 2 50 amps supplies or a 100 amp rating with 50 per leg. That means it can handle 40 amps per leg continuously or 80 amps equally divided between the two legs.
The typical generator is 17.5 KW or 20.0 KW. These can supply a rated load of 141.6 (roughly 70 amps per leg or 56 amps continuous) or 166.6 (roughly 83 amps per leg or 66 amps continuous).
Boring stuff until you start tripping breakers. At that point owners tend to learn what they can get away with and what they cannot.
The manner in which we use our coach is simple. We do everything from dry camping to 30 amp service to 50 amp service to extended use of the generator. So we choose to set our up for the lowest possible current draw. We have limited our inverter / chargers to their lowest possible battery charging rate. That way we have minimal current draw to maintain our 24V house circuit. The theory is that no matter how we use the power during the day and evening, we are still going to have about 8 hours for our batteries to get charged up while we sleep. We are not energy pigs because we know that excessive use of the power will deplete the batteries over time.
When we are on 50 amp service we can load up the devices we turn on at a given time. Instead of just a few circuits that we may have to juggle on the 30 amp service, on the 50 amp service we can plan on using two or more AC units, pluc the TVs, plus the refrig, plus the HW tank, etc. As long as the current draw on the AC panel does not exceed 40 amps per side we are OK because the battery charger current draw is minimal.
We always turn on the generator when we park overnight in a rest area or Wal-Mart. It keeps the battery charging, and allows us to run a lot of AC to get the bedroom temps down, and we can enjoy all the stuff we have on board. By keeping the house batteries charged we rarely have the chargers pulling a big load and even extended stays with only 30 amp are not problems. To make our set up work we keep the house batteries as fully charged as possible. And that actually is beneficial to the batteries.
As owners we have gotten to know that a multimeter is essential because when we do use our coach a lot, something may emerge as a problem, and then we need to know what we are dealing with. With a multimeter it is easy to verify the presense of shore, generator, inverter, or bus DC power. We can check for open circuit breakers, or for power going to a specific device.
The buses are complex, but rarely are there problems encountered. The buses are very reliable and it is usually the owner who had created the problem or issue that has to be resolved.
In Paul's case his house batteries were losing their charge.
His woes bring up a point for every owner to consider and address. How should the coach be set up for the use the owner wants to employ? For example, an owner that is going to do some primitive camping and attempt to get along on a 30 amp service is going to need to set up and use his coach completely different than an owner that is going to be parked outside the stadium on football Saturday with the generator runnning full time.
Shore power is limited and if a coach is going to rely on available shore power the owner has to limit what items are going to be used and when they are going to be used. For example, with 30 amps, it is probable the shore power can handle one AC unit, and the refrigerator, and possibly the TVs. If the inverters are set for charging, however they need to charge at a low rate so the current draw does not pop the shore power circuit with the other stuff mentioned above working.
On the other hand, the owner using the coach with the generator running continuously, can run almost anything whenever he chooses and also set up the inverter to charge at the highest setting so he can have all his sexy coach lighting going full blast and still maintain a battery charge. This and any type of dry camping probably is a justification for a high charge rate setting. This way the owner can rely on auto-start and the high charge rate will get the batteries charged quickly.
The 50 amp shore power service falls somewhere in between.
The key to understanding how to set up the coach and the switches is knowing limitations. As a practical matter a 30 amp shore power supply is capable of handling on a continuous basis about 80% of its rated capacity or 24 amps. Any greater and the risk of tripping exists.
A 50 amp service is actually 2 50 amps supplies or a 100 amp rating with 50 per leg. That means it can handle 40 amps per leg continuously or 80 amps equally divided between the two legs.
The typical generator is 17.5 KW or 20.0 KW. These can supply a rated load of 141.6 (roughly 70 amps per leg or 56 amps continuous) or 166.6 (roughly 83 amps per leg or 66 amps continuous).
Boring stuff until you start tripping breakers. At that point owners tend to learn what they can get away with and what they cannot.
The manner in which we use our coach is simple. We do everything from dry camping to 30 amp service to 50 amp service to extended use of the generator. So we choose to set our up for the lowest possible current draw. We have limited our inverter / chargers to their lowest possible battery charging rate. That way we have minimal current draw to maintain our 24V house circuit. The theory is that no matter how we use the power during the day and evening, we are still going to have about 8 hours for our batteries to get charged up while we sleep. We are not energy pigs because we know that excessive use of the power will deplete the batteries over time.
When we are on 50 amp service we can load up the devices we turn on at a given time. Instead of just a few circuits that we may have to juggle on the 30 amp service, on the 50 amp service we can plan on using two or more AC units, pluc the TVs, plus the refrig, plus the HW tank, etc. As long as the current draw on the AC panel does not exceed 40 amps per side we are OK because the battery charger current draw is minimal.
We always turn on the generator when we park overnight in a rest area or Wal-Mart. It keeps the battery charging, and allows us to run a lot of AC to get the bedroom temps down, and we can enjoy all the stuff we have on board. By keeping the house batteries charged we rarely have the chargers pulling a big load and even extended stays with only 30 amp are not problems. To make our set up work we keep the house batteries as fully charged as possible. And that actually is beneficial to the batteries.
As owners we have gotten to know that a multimeter is essential because when we do use our coach a lot, something may emerge as a problem, and then we need to know what we are dealing with. With a multimeter it is easy to verify the presense of shore, generator, inverter, or bus DC power. We can check for open circuit breakers, or for power going to a specific device.
The buses are complex, but rarely are there problems encountered. The buses are very reliable and it is usually the owner who had created the problem or issue that has to be resolved.