Need Help Setting TRACE Inverter

[wagwar]

I just installed 6 new DEKA 8D AGM deep cycles in my battery compartment. The bank is connected parallel-series for a 24VDC bank with a 12 volt center tap. I want to take very good care of these and I could really use some help programming my TRACE SW4024 inverter for proper charging and auto generator start. I have some of the settings figured out, but several I am clueless. 

Using the 20 hr rate and other mfg specs, I calculate 735 AH battery bank capacity.:

Here are the settings I'm unsure about:
Absorption Time: ?
Equaliz. time
Low Battery Cutin: ?
Low battery cutoff delay: ?
Set Gen Amps  (AC2): This is the amps the generator can provide to the inverter as input. I think this should be set to 50A OR the shore power amps whichever is less, but I'm not sure.  * 

*AC2 will be the AC input to the inverter. No input on AC1 since I want the inverter to auto-start the genset and input must be on AC2 for this to work. Shore AC input will also be on AC2 because I have an automatic transfer switch. My genset is a 6.6kw diesel with two 30 amp. 120 vac legs. I don't have any 240VAC loads. I hope that makes sense.

Gen Auto Start Settings:
Load Start Amps: ?
Load Start Delay Minutes: ?
Load Stop Dela Min.: ?
Set 24 hr. start volts: 24.3
Set 2 hr. start volts: ?
Set 15 min. start volts: ?
Read 30 second LBCO start volts: ?

These are the settings I think I've figured out:
Charging parameters
Bulk charge: 29vdc
Float charge: 27vdc

Max Charge Amps: 36.75A AC
Equaliz. charge (not recommended): 29.6 vdc

LBCO: 24.3 vdc
Hi Batt Cutoff: 28.6

Other TRACE Settings:
Set Input Lower Limit VAC: 108
Set Input Upper Limit VAC: 132
Set Grid (AC1) Amps: NA or default

Sorry this is such a long post. Your help and advice is greatly appreciated.

[Cary and Don]

Can't help with the inverter, but maybe with the batteries.  We have found that if your inverter has an option to turn off the charger use it when the bus is in storage.  We have found that running a charge cycle once a week or twice a month has made our batteries last a lot longer.  Our batteries are six years old and still going.  Our first set lasted two.  We thought that the float would be good for them.  Didn't work that way.

Don and Cary
1973 05 Eagle
GM 4107
Neoplan AN340

[pvcces]

I agree with Don. I have seen many situations of increased internal resistance and poor cranking in batteries that were left on a float charger.

Our storage routine is to recharge once every month or two with an unfiltered regulated ten amp charger for a day. They hold up for years.

I try to hook up a desulfator at least once per year using a one amp charger. Observing the voltage once a day will tell you when desulfating is done. The voltage will rise slightly each day; when it drops instead of rising, it is done.

Good luck.

Tom Caffrey

[Bill B /bus]

Verify battery charging voltage with the manufacturer. Bulk appears high.

As to the rest no comment.

Bill

[Sean]

...Your help and advice is greatly appreciated.

Sorry, I have been away from the board for a few days.  My recommendations below.

Using the 20 hr rate and other mfg specs, I calculate 735 AH battery bank capacity.:

That is correct.

Here are the settings I'm unsure about:

Absorption Time: ?  This is a complicated subject, but for an initial program setting I would suggest 2 hours.  The ideal absorption time setting can be determined by setting a much longer time, say 4 hours, and carefully monitoring the charge current while NO loads (DC) are presented to the batteries.  When charge current drops below about 2-3% of AH capacity, so in your case about 15-22 amps DC (about 3-5 amps AC), that is the correct time to switch to float.  If that happens, on your system, in, say, 1:40, then that's what you should set for absorption time.

Equaliz. time  None.  Do not equalize VRLA batteries.  On your Trace, set the equalize voltage to the same value as the bulk voltage.

Low Battery Cutin: ?  This is another complicated subject and depends on what other charge sources are available besides the charger in the SW4024.  It also depends on what you are risking by having the AC power off-line -- for example, do you have an AC fridge?  Usually 1-2 volts above LBCO is sufficient, but choosing numbers that are too close can induce what I like to call "yo-yo mode," wherein the LBCO cuts off power under heavy load, then when the load is removed voltage immediately rises above the LBCI threshold.  The only way to get this right is to experiment with your real-world loads.

Low battery cutoff delay: ?  Depends on your chosen LBCO voltage and what sort of intermittent loads you might have.  For instance, we have an air compressor that comes on every half hour or so, but only for 20-40 seconds.  We are happy to let the voltage drop below LBCO for this short time, knowing it will come back up as soon as the compressor stops.  Again, only experimentation can tell you for sure.  If you have no transient loads, use the lowest setting.

Set Gen Amps  (AC2): This is the amps the generator can provide to the inverter as input. I think this should be set to 50A OR the shore power amps whichever is less, but I'm not sure.  * 

*AC2 will be the AC input to the inverter. No input on AC1 since I want the inverter to auto-start the genset and input must be on AC2 for this to work. Shore AC input will also be on AC2 because I have an automatic transfer switch. My genset is a 6.6kw diesel with two 30 amp. 120 vac legs. ...


Set AC2 Amps to 27, which is what one leg of your generator can provide.  (On a separate note, with a 6.6 kW generator, I would suggest re-strapping it for straight 120 instead of 120/240 split phase.  That would let you feed a full 55 amps to the SW4024.).  You are correct in surmising that you will need to re-set AC2 Amps to whatever the shore power can provide when using shore power.  That would be 24 amps for a 30-amp shore service, and 40 amps for a 50-amp shore service.  Remember to set the value back to 27 when disconnecting from shore power, especially if you have enabled generator auto start.

Gen Auto Start Settings:
Load Start Amps: ?  This depends on what sort of heavy AC loads you intend to run from the inverter, and whether you want the inverter to control generator starting based on load or only voltage.
Load Start Delay Minutes: ?  Same comment as above, but I also suggest this be long enough to cover any transient or start-up loads, such as the air compressor example I gave earlier.

Load Stop Dela Min.: ?  This parameter keeps the generator from going into yo-yo mode when a device cycles off only briefly.  For example, if you set the load start to run the generator when, say, your air conditioner comes on, you don't want the generator to stop every time the thermostat cycles the compressor off for a few minutes.  Set this to be just a bit longer than the longest off-cycle time of whatever thermostatically-controlled device you are using the load start system for.

Set 24 hr. start volts: 24.3
Set 2 hr. start volts: ?
Set 15 min. start volts: ?
  All three of these are, again, fairly complicated to set.  The only way to know for sure is to experiment.  The issue is that you really want the generator to start based on battery state-of-charge (SOC), and voltage is a poor substitute for this important information.  While you can reliably tell SOC from "resting" battery voltage, that requires the batteries to be disconnected from all loads for an hour.  The voltage the SW4024 sees is, instead, a "loaded" voltage, and the relationship of SOC to loaded voltage depends heavily on the load presented at the time.  The correct settings for start voltages depend so much on your own load situation that it can only be reliably determined by careful monitoring of your system over time.

Read 30 second LBCO start volts: ?  You can't set this, only read it.  The LBCO is set on a different menu and controls, as the name implies, the complete shutdown of the inverter in the event of a low battery condition, not just the generator auto-start.  Note that generator auto-start based on LBCO is subject neither to quiet hours settings nor to temperature compensation.  I recommend choosing an LBCO much higher than you think you want until you have the load-based experience to make a better choice.  The factory default is, IMO, way too low.  I would start no lower than 23.0.

These are the settings I think I've figured out:
Charging parameters
Bulk charge: 29vdc  This is too high.  Per the East Penn/Deka documentation, this setting at "normal" temperature (77°F) should be 28.6v, dropping to 28.0v above 90°, and 27.8v above 100°.  If you have the temperature sender for your 4024 hooked up, use the normal settings and the charger will automatically compensate for battery temperature.

Float charge: 27vdc  This is also too high.  Manual says 26.8v at normal temperature.

Max Charge Amps: 36.75A AC  I'm not sure where you got this number.  The 4024 has a maximum of 33 amps, so that's all you can set.  Your 735ah bank could easily accept 300+ DC amps of charge, which would translate to an AC setting of over 60 amps.

Equaliz. charge (not recommended): 29.6 vdc  Here again, I recommend you set this value to the same as the bulk setting, 28.6v.  It is all too easy with the clunky control system on this unit to accidentally command an equalize cycle.

LBCO: 24.3 vdc  See my earlier comments.  I think you will find that 24.3 is too high; you will very likely drop to this voltage while still at 75% or so SOC.

Hi Batt Cutoff: 28.6 OK.

Other TRACE Settings:
Set Input Lower Limit VAC: 108
Set Input Upper Limit VAC: 132
Set Grid (AC1) Amps: NA or default


Those are all fine.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com

[wagwar]

Thank you, Sean.

some more questions, below.

At this point, I want to be sure I have the TRACE set up properly for charging. The bus is sitting in my driveway plugged into 30A service and we are not using it for living purposes. So, I think with your advice I can now set the inverter to keep the batt bank properly maintained until we hit the road fulltime in October, so some of the other settings will have to wait until we have some time to live with the system.

I also appreciate the other responses I have rec'd and will not leave the inverter in Float all the time, but rather set it to charge a couple of times per month.

Sean wrote: "Set AC2 Amps to 27, which is what one leg of your generator can provide.  (On a separate note, with a 6.6 kW generator, I would suggest re-strapping it for straight 120 instead of 120/240 split phase.  That would let you feed a full 55 amps to the SW4024.)."

JDW: Since I have no 240 volt loads, that makes great sense. How do I 're-strap' it for straight 120? How would I check to see if it is already set for straight 120? It may be and I just don't know what I'm looking at. If it is set up for straight 120, then the Set AC2 amps would be set to 40A or 50A?   

JDW: Bulk charge: 29vdc  - I calculated this from the DEKA tech manual, but I did not know what the 'normal' temp was for the TRACE inverter. Thanks for the 77 degrees info.

Sean wrote: "Low Battery Cutin: ?  This is another complicated subject and depends on what other charge sources are available besides the charger in the SW4024.  It also depends on what you are risking by having the AC power off-line -- for example, do you have an AC fridge?"

JDW: I have four solar panels on top, but the PO did not provide any info regarding watts/amps, etc and there are no labels with this information on the panels. So I am still working on figuring out what these are as an additional charge source. I don't have any other AC power requirements like an AC fridge. My AC power needs are: a few lights, two rooftop A/C units, microwave and refrigerator (in AC mode). The other AC loads such as microwave I only use with shore or genset. The refrig will run on AC or propane and so only requires a 12 vdc load.

Sean wrote:
"Equaliz. time  None.  Do not equalize VRLA batteries.  On your Trace, set the equalize voltage to the same value as the bulk voltage."

JDW: I read that equalizing was not recommended. I may have misunderstood a posting on the Odyssey blog when you were having problems with your batteries and did an equalization. I was just trying to think ahead.

Sean wrote:
"Gen Auto Start Settings:
Load Start Amps: ?  This depends on what sort of heavy AC loads you intend to run from the inverter, and whether you want the inverter to control generator starting based on load or only voltage."

JDW: I do anticipate running from the inverter one of the rooftop A/C units  at night if we are dry camping. So, I was thinking that the inverter should start the genset if the battery bank is getting more than 80% discharged. Is there a better way to set it up?

Your help is much appreciated.

[wagwar]

I also should mention that I have a Trimetric 2025 Battery Monitor and I'm setting it up for these new AGM's. I also have the TRACE BTS installed.

A couple of questions regarding the Trimetric instructions that are not clear. The installation requires setting the P1 parameter "charged setpoint volts" to 1%-2% below the "absorption Charging Voltage". The instructions imply but do not definitively say if this is the same as bulk VDC although it is specified for 77 degrees. Is the "absorption charging voltage" the same as the bulk vdc?

The Trimetric instructions say to calculate the P2 parameter "charged setpoint amps" as follows: (Battery Bank AH * 2)/100). So, 735*2/100 = 14.7. Is this correct?  What is the charged setpoint amps"?

[Oonrahnjay]

(snip)   JDW: I do anticipate running from the inverter one of the rooftop A/C units  at night if we are dry camping. So, I was thinking that the inverter should start the genset if the battery bank is getting more than 80% discharged. Is there a better way to set it up?

     I'm looking forward to a discussion on this.  I'm very inexperienced with this and I know little about AGM's, but my understanding was that if you're pulling a fair bit of power off the batteries, it would be more practical to go ahead and pull them down to a reasonably low SOC (maybe AGM's can safely go down a bit further than wet-cells ??).  Otherwise, the result in practice would be that the generator would be cutting in often, bringing the batteries up, then shutting off, only to see the batteries go down to the gen-start setpoint and then restart the whole sequence again (and again).  Of course, you're going to be "cycling" your charge over time, but it just seems to me that longer legs on the cycle would be more practical.  The overriding principle would have to be the health of the batteries but if you're within the battery parameters, it seems to me that an 80% SOC is too high.

     Can someone who knows and has experience with this discuss?  Thanks,  BH

[Sean]

...
Sean wrote: "Set AC2 Amps to 27, which is what one leg of your generator can provide.  (On a separate note, with a 6.6 kW generator, I would suggest re-strapping it for straight 120 instead of 120/240 split phase.  That would let you feed a full 55 amps to the SW4024.)."

JDW: Since I have no 240 volt loads, that makes great sense. How do I 're-strap' it for straight 120?

Changing the generator from 120/240 split-phase to 120-only is usually a simple process, but it varies by manufacturer.  See if you can find instructions in your generator manual or on-line.  If you post your make and model I might be able to tell you if all else fails.

How would I check to see if it is already set for straight 120? It may be and I just don't know what I'm looking at.

Simple: measure the voltage between the two "hot" leads.  If it reads 240, you have split-phase, if it reads zero, you have single phase.

If it is set up for straight 120, then the Set AC2 amps would be set to 40A or 50A?    

In order for this to work right, you need to have a single output from the generator, not two separate outputs on separate breakers.  Again, consult the generator documentation to find out.  If you have a single hot lead coming from the generator, then you can set the input amps on the inverter to 55.

Sean wrote: "Low Battery Cutin: ?  This is another complicated subject and depends on what other charge sources are available besides the charger in the SW4024.  It also depends on what you are risking by having the AC power off-line -- for example, do you have an AC fridge?"

JDW: I have four solar panels on top, but the PO did not provide any info regarding watts/amps, etc and there are no labels with this information on the panels. So I am still working on figuring out what these are as an additional charge source.

You'll need to work this out.  The reason being that if you set the cut-in lower than the system voltage with depleted batteries under photovoltaic charging, what will happen is the inverter will see this value as a higher SOC, cut back in, present load to the batteries, overwhelm the solar equipment, and immediately bring the voltage back down under LBCO, leading to yo-yo behavior.

I don't have any other AC power requirements like an AC fridge. My AC power needs are: a few lights, two rooftop A/C units, microwave and refrigerator (in AC mode). The other AC loads such as microwave I only use with shore or genset. The refrig will run on AC or propane and so only requires a 12 vdc load.

If your fridge runs on LP, you should not tie the AC input to the inverter.  Absorption fridges are very inefficient on AC, so with no shore power, you should run on LP.  If you are not depending on the inverter for your fridge or any medical devices or the like, then setting a higher cut-in will add a margin of safety for the batteries.

Sean wrote:
"Equaliz. time  None.  Do not equalize VRLA batteries.  On your Trace, set the equalize voltage to the same value as the bulk voltage."

JDW: I read that equalizing was not recommended. I may have misunderstood a posting on the Odyssey blog when you were having problems with your batteries and did an equalization. I was just trying to think ahead.

Yes, I have equalized AGM batteries in the past, but only under careful observation and using parameters provided by the battery manufacturer.  Since this is an exceedingly rare situation (only done when the batteries are suspected of being near end-of-life for various reasons) and requires supervision, it is best to disable the equalize mode (using the method I described) during normal operation, to minimize the chance of accidentally equalizing perfectly good VRLA batteries.

Sean wrote:
"Gen Auto Start Settings:
Load Start Amps: ?  This depends on what sort of heavy AC loads you intend to run from the inverter, and whether you want the inverter to control generator starting based on load or only voltage."

JDW: I do anticipate running from the inverter one of the rooftop A/C units  at night if we are dry camping. So, I was thinking that the inverter should start the genset if the battery bank is getting more than 80% discharged. Is there a better way to set it up?

No, that is the way to go.  This does not utilize "Load Start" but rather is based on battery voltage, which is a proxy for SOC.  Load Start would be for a case where you wanted to make sure the generator was running any time a load such as an air conditioner was running.

I also should mention that I have a Trimetric 2025 Battery Monitor and I'm setting it up for these new AGM's. I also have the TRACE BTS installed.

A couple of questions regarding the Trimetric instructions that are not clear. The installation requires setting the P1 parameter "charged setpoint volts" to 1%-2% below the "absorption Charging Voltage". The instructions imply but do not definitively say if this is the same as bulk VDC although it is specified for 77 degrees. Is the "absorption charging voltage" the same as the bulk vdc?

The Trace SW series performs the absorption cycle at the Set Bulk VDC voltage.  I am not a Tri-Metric user so I am not completely familiar with their settings.  My own Link-10 meter wants me to set the  voltage at which the charging is "finished," which is actually the float voltage.  Perhaps someone more familiar with Tri-Metric can chime in here.

The Trimetric instructions say to calculate the P2 parameter "charged setpoint amps" as follows: (Battery Bank AH * 2)/100). So, 735*2/100 = 14.7. Is this correct?  What is the charged setpoint amps"?

Again, I don't have a Tri-Metric, but all these meters need to have some way to know when the charging is "finished" and the charger is in float mode.  Usually the way this happens is the meter is looking for a voltage (which you set in P1) that indicates the charger is still working but finished with bulk, and a current going into the batteries that indicates the batteries have absorbed as much charge as they can.  That is typically around 2% of the bank's capacity in aH at the 20-hr rate.  Usually, when the system meets both conditions (voltage and current indicating charging complete), the meter "resets" the SOC to 100% at this point.  Otherwise the meter tends to accumulate an error in one direction or the other, because it is only estimating charge efficiency and Peukert exponent.

...  I'm very inexperienced with this and I know little about AGM's, but my understanding was that if you're pulling a fair bit of power off the batteries, it would be more practical to go ahead and pull them down to a reasonably low SOC ...  Otherwise, the result in practice would be that the generator would be cutting in often, bringing the batteries up, then shutting off, only to see the batteries go down to the gen-start setpoint and then restart the whole sequence again (and again).  Of course, you're going to be "cycling" your charge over time, but it just seems to me that longer legs on the cycle would be more practical.  The overriding principle would have to be the health of the batteries but if you're within the battery parameters, it seems to me that an 80% SOC is too high.

So, this is another one of those complicated subjects that requires a good deal of math, and some experimentation.  That's because batteries have a limited life span measured in cycles, but the number of cycles they will last depends on the DoD of those cycles.  Making matters worse, it is not linear.  You need to get the DoD vs. cycle life curve from your battery manufacturer.

Next you need to compute the operating cost of your generator per-hour by load.  Again, this is not linear, it is a curve.

With these two curves, it becomes possible to do a multi-variable optimization that will yield the optimal DoD and generator cycle time to minimize the overall cost of the derived power.  BTW, that power is very expensive indeed -- I once calculated that it costs us $0.25 per kWh stored and retrieved from batteries, and that's on top of the cost to generate or purchase the power in the first place.  (You can read my essay and analysis on this topic here: http://ourodyssey.blogspot.com/2011/07/about-those-batteries.html).  For us, that's another $0.50 for each kWh stored in the batteries (when using the generator), for a total cost of about $0.75/kWh.  Compare that to $0.10-$0.20 per kWh for grid power to your home, for example.

Because the multi-variable optimization is mathematically complex, it is easier and nearly as effective to do it with a spreadsheet, with DoD across one axis and generator cost down the other.

Another dimension to the problem has to do with how much absorption you allow the batteries.  The cost per kWh going into the batteries goes up as the current drops during the absorption phase.  However, the lifetime of the batteries also drops as the number of "incomplete" charge cycles goes up.  Factoring this last variable into the problem space adds another layer of complexity.  I take the approach that, at least in my case, generating the power is far more expensive than storing it, so I optimize for run time at the expense of battery life.  On my system, that means setting absorption down to 20 minutes.  When we are on shore power, we set it back up to three hours to "top up" the battery plant.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com

[rv_safetyman]

Wow, what a great thread. 

I wish I could contribute something meaningful.  The closest I can come is the wiring of the generator.  Dick Wright is adamant that any generator under 12KW should be wired as 120V.  His concern is the impact of an unbalanced load on the windings of the generator (his explanation is much better than mine).  I have questioned him on that subject several times and he does not budge ***unless*** you have ammeters on both legs and watch/control the loads.  I have a 10KW (turns out the head is a 12KW per Dick) and I watch my ammeters like a hawk when I add some big load.  I generally use the ACs to balance the load.  I have to keep the generator wired for 240 since we have an electric dryer (not one of my better decisions). 

Earlier in the thread, it was mentioned that you should not leave batteries on float.  I would like to have a bit more discussion on this, as I leave our bus on float quite a bit (more so now that we don't use the bus as much as we used to).  I am sure that one of the factors is the quality of the inverter/charger.  We have a Trace SW2512MC full sine inverter and I have never had a problem leaving in on float for months on end.  I just checked the water level in my golf carts (new last fall) and it was just fine after 6 months of full time float.

Jim

[wagwar]

First, I want to Thank Sean and Jim and all of you for your help! Thanks!

I'll call Bogart on the Trimetric settings.

My genset is an older Power Tech PTS 6.6 AA Kubota diesel. It is listed as a 55 Amp model. The manual is no longer available from the mfg and the PO could not find his copy. So, I'm using the manual for an 8KW Power Tech that Power Tech sent. I would love to have the right manual, but so far, no luck finding one.
There are two 30 A breakers on the genset control panel and a double breaker on the panel the genset output goes into. I believe that each 120Volt leg goes feeds one side of the main house AC panel. I will confirm this.

Sean wrote:
"If your fridge runs on LP, you should not tie the AC input to the inverter.  Absorption fridges are very inefficient on AC, so with no shore power, you should run on LP.  "

JDW: I do have the AC input for the fridge tied to the inverter. The reason is that when we are running the bus engine rolling down the road, I can tie the house and coach banks together with the solenoid and run the refrigerator on AC instead of LP. I like to keep the LP shut off while we are moving. Do you recommend that we run the fridge on LP - at all times? 

I've run into an Error condition on the TRACE after I (thought) I set it up to properly charge my new batts. The charger is shutting down after a minute or so and setting the High Battery voltage error condition. The manual indicates this is set when the battery voltahge exceeds the High Battery Cut Out VDC. Does the High Batt cut out need to set higher than the bulk rate?  I've set the Trace to the following settings:
Bulk: 28.6
Float: 26.4
LBCO: 24
Low Batt cut in: 26
Absorp. Time: 2 hr.
High Batt. cut out: 28.6

[Sean]

... Dick Wright is adamant that any generator under 12KW should be wired as 120V.  His concern is the impact of an unbalanced load on the windings of the generator (his explanation is much better than mine). ...

This is one of those areas where Dick and I differ.  My own recommendation is that all generators below 6k should be wired for straight 120, and all generators above 12k should be wired for 120/240 split phase, and in between those values, "it depends."  Generally speaking, from 6k-9k, most folks will do better with single-phase.  9k is 75 amps, which is the most you can safely put through a 50-amp transfer switch by "ganging" two poles (the normal way of handling a straight 120 generator and a 120/240 50-amp shore service).  Once you start going above 50 amps, transfer switches get large and expensive quickly -- there is an industry cut-off at this size because it is so commonly used in RVs and boats.

From 10k-12k, most folks will be better off going with split phase.  That lets them stick with standard 50-amp transfer gear, and usually does not pose too many challenges in assigning loads to each leg.

The issue, BTW, of "unbalanced" legs has nothing to do with the dynamic balance of the generator set (for most 120 or 120/240 split-phase units) -- split phase power is fully balanced by nature (the voltage peaks and valleys of each half of the waveform match exactly), unlike, for example, three-phase power, where an imbalance among phases can actually cause an asymmetric dynamic load on the generator set.

A possible exception to this is a 12-wire set wired in "zig-zag", which is how you get 120/240 split-phase out of a generator head made for three-phase power.  While there are some 12-wire heads out there in common use for 120/240 applications, sets commonly sold for RV use are generally NOT 12-wire units, but rather 4-wire units.  I believe the heads on Dick's units are also 4-wire, so I am not sure why he is so adamant about this.

It is true, however, that chronic load imbalance on even a 4-wire set will have the effect of uneven "electrical wear" of the windings, meaning that one set will constantly be hotter than the other, with all that implies.

"Evening out" this kind of wear is simple: do your best to load the legs evenly, and then swap the two hot legs periodically, perhaps once a year or so.  No need, IMO, to watch ammeters like a hawk on a 4-wire generator set.

Earlier in the thread, it was mentioned that you should not leave batteries on float.  I would like to have a bit more discussion on this, as I leave our bus on float quite a bit (more so now that we don't use the bus as much as we used to).  I am sure that one of the factors is the quality of the inverter/charger.  We have a Trace SW2512MC full sine inverter and I have never had a problem leaving in on float for months on end.  I just checked the water level in my golf carts (new last fall) and it was just fine after 6 months of full time float.

Jim, with flooded batteries that are periodically checked for water, there should be no problem leaving them on the float stage of a high-quality charger, so long as the float voltage was set per the battery manufacturer's instructions.

AGM batteries, OTOH, have been known to develop "thermal runaway" when left unattended on a charger.  Also, folks with flooded batteries tend to forget to check and replenish water levels.  Since so many things, including the ambient temperature in the battery compartment, can impact proper float voltage and push things just a bit over the edge, I err on the side of safety by recommending against leaving batteries on float indefinitely.

For the record, telecom and other backup-type installations leave the batteries floating forever between grid outages, so it's possible to do it.  But Sprint and Verizon have more money for replacing batteries than most bus nuts...

...
There are two 30 A breakers on the genset control panel and a double breaker on the panel the genset output goes into. I believe that each 120Volt leg goes feeds one side of the main house AC panel. I will confirm this.

The two 30-amp breaker setup is typical of a generator that can be wired either way.  Usually, if the generator is wired for 120/240 split phase, the breakers will be "handle-tied" so they trip together, a safety requirement when there are any 240-volt loads.

The problem with separate 30-amp breakers is that you can't simply tie the outputs together to get the full 55 amps, even if the generator has been strapped internally to straight 120.  You need to get the correct procedure for this from the manufacturer.  It is possible that the procedure is to remove the two 30s and replace them with one 50 or 60, but it is also possible that the 30s should be handle-tied and the outputs paralleled.

...
JDW: I do have the AC input for the fridge tied to the inverter. The reason is that when we are running the bus engine rolling down the road, I can tie the house and coach banks together with the solenoid and run the refrigerator on AC instead of LP. I like to keep the LP shut off while we are moving. Do you recommend that we run the fridge on LP - at all times?  

OK, so this is a religious debate and I don't want to argue it with anyone, but I will say that when I owned an S&S rig with an LP fridge, I left it running on LP while driving.  That said, if this makes you nervous, then it is fine to run it on AC when the alternator is supplying power.

The risk is that you will forget to switch it back.  For this reason I recommend you get a double-throw relay rated for 20A@120VAC (contacts) and with a coil voltage matching your chassis system.  Connect it so that the fridge is connected to an inverter circuit only when the alternator is charging (use the relay signal or oil pressure), and it is connected to a shore circuit at all other times.

I've run into an Error condition on the TRACE after I (thought) I set it up to properly charge my new batts. The charger is shutting down after a minute or so and setting the High Battery voltage error condition. The manual indicates this is set when the battery voltahge exceeds the High Battery Cut Out VDC. Does the High Batt cut out need to set higher than the bulk rate?...

Yes, MUCH higher.  The factor default is 32 volts, and there are few reasons to make it lower.

Remember, this is to protect the inverter, not the batteries.  It shuts the inverter down completely if the battery voltage spikes for some reason, such as overvoltage from another charge source like solar or wind.

-Sean
http://OurOdyssey.BlogSpot.com

(edited to correct typo in relay rating; correction shown in Red)

[wagwar]

Sean wrote:
"The risk is that you will forget to switch it back.  For this reason I recommend you get a double-throw relay rated for 20A@120VAC (contacts) and with a coil voltage matching your chassis system.  Connect it so that the fridge is connected to an inverter circuit only when the alternator is charging (use the relay signal or oil pressure), and it is connected to a shore circuit at all other times."

JDW: That sounds like exactly what I did (per your help and recommendation) with one of my rooftop A/C units. It is wired to run from the inverter only if the engine is running. I used a timer that is tied to a switch on the dash. The relay signal depends on this switch being 'on' AND the engine is running (alternator signal).  Could I use the same 'signal' to another 20A/120VAC relay to accomplish the same objective w/ the refrigerator?

[Sean]

Sean wrote:
... wired to run from the inverter only if the engine is running. I used a timer that is tied to a switch on the dash. The relay signal depends on this switch being 'on' AND the engine is running (alternator signal).  Could I use the same 'signal' to another 20A/120VAC relay to accomplish the same objective w/ the refrigerator?

Yes.

[wagwar]

Thank you!

There is one small issue that I've wanted to ask you about this setup. My concern is that if we are running the A/C unit (or the fridge) from the inverter while the engine is running, is it important to remember when we shut the engine down to switch them off using their own controls rather than simply cut the engine and have the power be dropped suddenly to the device? Will that damage the A/C unit or the fridge.

Jim

www.mightybus.wordpress.com