INput on Replacement Alternators

[KenEhresman]

With dual 4000 watt inverters, and 4 rooftops, and basement heaters and such, 270A isn't gonna get it done.... and it has developed the dreaded oil leak on front of the shaft... so I guess it gets a replacement.... I see Delco remade the 50DN+ at 450A and there are about 4-5 Air Cooled 450A-550A units available that can replace... Any input form owners with any choices they made, and the longevity and outcome of the upgrade? Oil leaks on 50DN+ or can 450+ Amps really be air cooled efficiently enough to run for 12 hours under heavy loads of 2-3 air units?
The stock 270 AmP screams help with 2 Rooftop airs on with a few other items, and winter, well all the electric heat in the basement, with the rooftop heat strips, it chokes and isn't worth a crap.... winter driving is almost mandatory GENSET hours..

thx

[Gil_J]

Ken,

Let me answer the subsets of your questions and concerns.

The easy one first. Surely, a 2000 Vantare' has a Webasto or AquaHot. Either one should have an engine supplied coolant loop and floor heat exchanges. While driving you should have ample engine heat to heat the interior without the Webasto or Aqua Hot firing their diesel burner. You should also have the Prevost dash heat. This should be more than enough heat while driving to preclude the need to use AC powered heaters. As for the bays, they shouldn't need supplemental heat while driving. Your hot water heaters or Aqua Hot should radiate enough heat to prevent freezing. The extend to which you are loading your inverters should also produce a lot of heat; although using inverters as heaters shouldn't be our goal.

Each of your 4KW inverters tops out at about 165amps@24V. So, your maximum inverter load is around 320A@24V. Of course you have direct 12V loads that could add to that. I would be surprised if you are loading both inverters near peak current for any length of time. You also have 500-1,000 AH our battery capacity. So, even if you exceed your alternator's capacity, your batteries should bridge the current gap between what your alternator can supply and your loads require until your batteries are discharged. Can you really have that high of current demands? I guess that's yes if you are using 4 heat strips and other resistive heating in the bays.

At some point Vantare used load shedding motorized AC circuit breakers that limited what could be energized when your solely on inverter power. If you have this setup you shouldn't be able to run all rooftop airs. In any case, a 15K BTU rooftop has a constant load of about 14A. That's about 70A@24V. I don't have the heat strip specs, so that might be more. BTW, is it so cold that your heat pumps are ineffective or your rooftops don't have heat pumps? If you run 3 rooftops you're drawing about 210A@24V. Keep in mind that after you achieve your set temperature the rooftops will cycle on and off. This will reduce your average load to something less than 200A@24V; maybe, far less depending on the delta between outside temperature and your desired inside temperature. I have to believe your alternator's stated output and the capacity of your battery bank is enough to satisfy your needs.

It's possible your alternator is not producing the output it should either due to an alternator or regulator problem. You may have rooftops that are nearing their end of life. Although this isn't the case when using the heat strips, as air conditioner compressors age they will draw more current while running and especially at startup. I recently clamped a CruiseAir pulling 62A@120V at startup. This extreme is pretty easy to find without meters. The inverter will likely go into over current condition. If the generator is supplying power you can hear the generator load change as it tries to maintain its fixed RPM.

There are other alternator choices other than the oil cooled 50DN. Many are good units. When you look at alternators with much greater outputs you need to look at wiring requirements. 4/0 cable is the largest you'll buy and it can be limited to less than 300A depending on temperature, distance, and acceptable voltage drop. This cable limitation is one of many factors that drives a coaches from a 12V to a 24V house battery system. Does your coach have an amp meter of the alternator feed? If so, are you seeing its output come close to its rated output?

[KenEhresman]

HI Gil, Finally someone who sounds more like an engineer and not a shadetree mechanic... I'll try to describe more in detail...

The 4 roof units are definitely heat strip units, and not any type of reverse heat pump. I have not monitored the current pull on these but I can tell you that running more than 2 will send the genset into operation within 15 minutes of cruising speed assuming the aqua hot heaters are running, and maybe some supplemental heat in the bays... We recently were in Wyoming, and it dropped to 10 below and we were running heavy AC current to keep up with the heat loss. One issue we identified as a problem is the location of the lines routed from the bays to the forward sink... they are under the bathroom closets, and actually started to freeze at about 2 degrees going down the road due to the heat loss and cold air under the closets... although there is a single Aqua heat exchanger in the bathroom to I suspect keep the flooring and heat under the cabinets at or close to above freezing, it wasn't keeping up... hence turning on the additional "Mid Heat" baseboard unit in the bathroom to help keep up.

The aquahot never seems to get to full temp just from engine, hot water gets decently hot, but with extended runtime it seems to bleed off alot of the heat... but does work. FWIW, the Webasto Fired Aquahot system in my humble opinion is a total piece of junk. I have repaired my webasto head unit 4 times in the last year, including most recently almost a full rebuild including bearing, only to have it die again on the last winter trip... All this to the end, we need at least in our coach to run some supplemental heat in the winter or it gets cold and quick...

So back to the Alternator(s). Most curves I read say that their power curves are not reaching above 70-80 percent of rated capacity during normal driving. If I were going down the road at 70, my alternator is probably only producing about 70-80 percent of its rated capacity based on the RPM speed of the Alternator pulley (which I have not calculated but will shortly) Although it will see burst above that at higher RPM shift points, when it settles back in to normal cruise its back in that range. Having said that, a standard 50DN unit rated at 270A is probably only putting out 190-215A at cruising speed. (if anyone has calculated the curve for the Series 60 with the stock pulley ratio please post to save me some time :-) then there is heat loss....

So my thought process is to realize a true boost in mid rpm power output by going to a higher output unit. I can't see any 450A unit ever delivering above 375A continuously based on input shaft RPM. So 375A max of Inverted power plus some additional 12V needs, and that would tell me I need to be generating about 350-400A continuous at cruising speeds to provide ample power for all potential systems... (even then I couldn't run all 4 Roof AC's in summer) as that would be tripping the invert-er outputs every time a compressor kicks on while another is running...

So wishing it had a DC amp meter... I have clamp on units, I will get on it and work it and see what I get for amp's under low, mid and high loads.... Understood I might need to upgrade the power cable....

Assuming my Battery Isolator right at the engine compartment will limit the AMP pull as well? or will it just pull until it blows up?

[Gil_J]

Ken,

I have to laugh, your use reminds me of a friend. His converter calls him an extreme user. You really should head south, at least to a latitude that's above freezing.

Few converters put in an amp meter on the alternator. It really would be a good idea.

If you are trying to satisfy a temporary power need, you might just rely on your generator. It could probably benefit from running in those temps anyway. Unless your Aqua Hot has temperature activated solenoids on the engine loop or the engine loop valves are partially closed you should be circulating almost engine coolant temperature fluid through your AH interior heat exchangers. I would expect 3 interior heat exchangers.

I just looked at the 50DN and 50DN+ output curves. If the alternator is spinning at a ratio of 2.6 times engine speed it will not over rev and will have 90% of full output at 1,600 engine RPM. Delco's 275A @24V air cooled alternator has a similar somewhat flat output over our 60's operational RPM although at a higher alternator RPM. If you want a lot of current try the C800 series alternators from Niehoff. Before jumping on a single high current alternator, you might want to consider 2 smaller units. The big plus to this solution is you're not dead in the water if one fails. Yes, you will lose a little engine efficiency driving two devices, but not enough to matter. BTW, Prevost installs 4 alternators on new coaches, so you certainly won't be paving new ground if you choose this path.

You should also check your regulator and sense voltage. You may not be getting everything your 50DN has to offer. Did you say isolator? I hope you have a dedicated alternator for the house side of the coach. You sure don't want to steal power from the coach. BTW, if you do have one alternator and an isolator, the isolator should be on the chassis side as the chassis demands are far less and you want to excite your alternator from the house batteries and not the chassis batteries.

[KenEhresman]

Negative 10 with 50MPH winds isn't acceptable lol? I bought this baby to use, and I'm gonna push it to its limits and then some.... then re-engineer the weak points, and keep upgrading using lessons learned lol...

Sounds like a safe choice is 300-350A since mine is leaking oil anyway, then deal with another unit for additional power should I need to go that route. i'll crunch the numbers but I think 350A would be safe to operate in the existing config with little to no additional changes, except maybe some cable, I will have to take a look at the entire runs on those....

It is a 99 chassis built and titled in 2000 (Vantare)with 2 slides. there indeed are 3 heat ex-changers, one up front ( I think every converter gets that one right) one in the kitchen area sorta, under the couch and one in the bathroom... that is the weak point for freezing.... I think this particular coach was actually built up in Oklahoma. Have tried to get support a number of times using a concierge type of premium service I pay for, and although very helpful, I get a lot of the, hmmmm... that sounds different, then the ....I think that coach was built up in Oklahoma during a transitional time. With the older XL chassis and 2 slides, I think it is the best of both worlds.... love the stainless (hate the shining it part lol) Getting prices now.... not sure I want to tackle the whole Air Cooled route, although it is popular, I have to believe the 50DN PLUS would hold up better, as a tried and true solution