Remote Mounted Generator Fan CFM?

[Kevin]

Hello All,

I have an Isuzu-powered 11.5 KW generator that I am installing into my Gm 4104 in original A/C compartment. Due to the size of the thing, I will be remotely mounting the radiator.

From doing a search, I see that many (including Wrico) recommend using a 110V squirrel cage type blower fan for radiator cooling, though I did not see specific CFMs mentioned. Based on the engine (1.4 L Diesel) and generator sizes, will anyone recommend an aptly sized blower fan, please?

Thanks,
Kevin

[luvrbus]

The only reason people use the 110v cage fans Dick included is for the convenience factor the fans starts when 110v is detected the 12 v Flexlites do a better job and are lot easier to set up IMO but you need a separate system for the generator like a charging system.

The Eagle Matt owns has a 110v 3 speed 1200 cfm cage fan I never ran it on anything but low all the years we owned it but if I had it to do over it would have been a 12v Flexlite the full size of the radiator with a thermostatic control that only came on when it was needed for cooling 

What I did not like about 110v fan if the generator was running so was the fan and being vented out the bottom like it was what a mess on a dusty road like the road up to Yellowpine and it was to much trouble to install a switch inside the bus after the fact lol

[john9861]

Do you think the electric fan makes less noise than the standard mechanical radiator fan?
  Also does anyone have any recommendations for a fan that can be used to remove heat from the compartment when the generator is off? Can the flexlite be wired to do this?

[Oonrahnjay]

Do you think the electric fan makes less noise than the standard mechanical radiator fan?       Also does anyone have any recommendations for a fan that can be used to remove heat from the compartment when the generator is off? Can the flexlite be wired to do this?   

       John, as I read the original question, Kevin must set up a "remote radiator" for the generator because of the layout of his bus, the space available, etc.  Once he's been forced into that, he will have to arrange for coolant to be circulated between the generator and the remote radiator as well as air flow for that radiator.  (I gather he's not trying to tie his generator cooling into the engine cooling system and radiator but instead is keeping a separate, discrete system for the generator alone.)

       Once he's made up his mind that he needs to do this, he has group of factors to consider; first, he's got to have *some* kind of fan so he's got to figure out a fan that fits in the area that he's got.  That fan also has to move enough air to provide adequate cooling (heat removal) under all conditions.  I'm not really familiiar with his generator, but I'm guessing that since it's a generator with a water-cooled engine, it has been designed to be quiet and and I'd want the fan to be as quiet as possible.  And, as Clifford points out, it would be an advantage to have the hot air blow out in a way that doesn't blow up dust and debris as you're moving your bus around near other people.

       Working on the KISS principle, it's apparent that if you're making 120V AC with the generator and you mostly only need the fan to run while the generator is running and making heat, you can do a simple system that when the generator is making 120, some of that power is pulled off to run a 120V fan.  (Of course, if you need to have a thermostat system so that the fan runs a bit after the generator is shut down to remove excess heat, you'd be forced to a more complicated control system.)  I don't see how you could arrange for a simple, effective system (for this kind of layout) with a "standard mechanical radiator fan" -- he's pretty much forced to use an electric fan.

       Concerning cooling the generator compartment,  I don't know if Kevin has to mount the radiator away from the generator compartment.  It might be practical to pull air from the generator compartment with the fan and then blow that air across the radiator, but such a system might get complicated (controls, air piping, etc.).  If you really need to ventilate the generator compartment to keep the mechanical components cools (separately from the radiator cooling air), it seems to me that a system with a separate fan, air pick up, and air outlet might be the best way to go.  Another factor is that if you're using hot air from the generator compartment to be blown across the radiator to cool the radiator coolant, you're already reducing your efficiency; it seems to me that you'd probably be better off to pick up cool air from some place, have one fan blow the cool air across the radiator and then exhaust it and another fan to pick up cool air, blow it across the mechanical parts of the generator (or at least through the generator compartment) and then exhaust that heated air separately.

        Is it's necessary to go to that level of complexity, it would be pretty easy to set up a system with two fans.  You could have one fan that's controlled by simple relay so that any time you're generating power, you're blowing air across the generator radiator; on the other hand, you might choose to have a more sophisticated control system that only blows air (and uses the power to do so) when it's needed -- you could base this upon a thermostatically controlled relay or somehow off the thermostat in the system (assuming that there is a thermostat in the engine for Kevin's generator).  Especially if you already have an inverter/charger system, you could arrange a separate vent fan for the generator compartment with a 12V fan; if the generator compartment is hot (and assuming the generator has been shut down), you could pull battery power to run the compartment fan with separate controls (probably an ambient temperature sensor) to regulate it.  But that assumes that Kevin already has an inverter/charger system, and a sufficiently big battery bank.

       So, it seems to me that Kevin has three choices:

1)  "Super simple" system - when the generator is running, take 120V output to run a radiator fan; have grilles and air openings in the generator compartment to passively cool the compartment, or,

2)  The "complicated" system - when the generator is running and the radiator coolant is warm enough, you run a fan with control system to assure that the fan is removing heat from the radiator when you need for it too; you also have another separate fan with appropriate controls to ventilate the generator compartment -- you'd probably need battery power for this and it would probably be more efficient to use a 12V fan for the ventilation fan.  Once you're at this level of complication and you have the 12V power available, you may choose to use 12V for the radiator fan and arrange "aftercooling" of the radiator (i.e. air blowing across the generator radiator after the generator has been shut down to draw off residual excess heat).  But you'd have to consider current draw, size of cables, availability of a 12V fan with sufficient air flow, etc.)

3)  Something in between - perhaps run a 120V fan for the radiator when the generator is running and relays to also run a compartment ventilation fan at the same time.  This might be suffcient, but you'd need to consider if you may be "over cooling" the radiator when the generator has just been started up and if you're providing sufficient aftercooling to prevent heat-baking from damaging components and spreading excess heat to the living compartment of your bus.

      So, in my opinion, the answer that Kevin is looking for here is "it depends".  And I'm thinking that he's thinking that way since he was asking the best way to adequately size the radiator fan and provide power to it.  He has a number of variables to consider and a variety of configurations of cooling to meet the needs that those variables will impose.  Oh, yeah, and also consider noise levels and the best way to exhaust the hot air.

[luvrbus]

I gave him the CFM I used for my remote mount he could probably get by will 800 CFM but I would have a off and on for a 110v and 3 speeds I ran into problems with the 110v not being able to shut in down of all places it was in Idaho -13 the Kubota did not like all the cold air

FWIW I saw a Prevost with a 20kw with a remote radiator that had a 2500 cfm 12 volt setup pretty neat the fans were variable speed it was quite I guess about all are going the 12v route now for cooling and the cage 110v for compartment cooling I don't care for 2 different types of system myself 

You do not go to Auto Zone and pay 50 bucks for a 12v fan and except a good system not going to happen

[TomC]

I have a 10kw genset in my bus with remote radiator.  I used a 10" squirrel cage belt driven blower with 1/2hp two spd totally enclosed fan cooled 120v electric motor.  120vac will always be quieter then using the 12vdc radiator fans.  Usually the 12vdc radiator fans create a high pitched whinning sound that to me is irritating.  I also used an 8" inline bathroom ventilator for cooling the genset compartment with variable speed controller. Has worked well.

Now with my truck conversion and the Wrico 12kw genset, Dick Wright set me up with a European 120vac bladed fan that is low in amperage and is powerful enough to push you back if you're holding it while running.  With a electronic speed controller, you can have the hurricane force during the day (with some noise) or dial it back to nearly silent for night time use.  I will use the 8" inline ventilator again (from Graingers) to ventilate the sealed genset compartment.  My goal is to have a genset as quiet as the studio gensets-to be able to run the genset at night without bothering my neighbor. Call Dick Wright at Wrico International and ask him about the bladed fan from Europe he is using. Good Luck, TomC

[Kevin]

Thanks Fellas,

I appreciate all the good information. I'm thinking now (mainly due to space constrictions) that I may opt for the 12v-electric-w/thermostat-fan mounted directly to radiator approach.

This will be simpler, and as the generator will be used primarily to power the two roof airs while underway rather than when parked, noise is less of a concern at this time.

I will have to see how hot things get in the generator compartment area to determine whether or not I will need supplemental cooling fans. I've read that it is best to not allow the generator head to exceed 140* F.

Generator is not an enclosed type. The previous owner did do a good bit of lead-lined/foil-faced foam insulation throughout generator compartment, though the floor is completely open. I will have to see about sealing up this compartment a bit better in future for sound deadening.

Thank you again,
Kevin

[Sean]

Kevin,

I got your PM on this subject; sorry, I've been away from the computer.  I see you got lots of good information already.  What I can add is that a good guesstimate for automotive radiators is to figure moving air toward the radiator at 9-10mph which is 800-900 FPM.  So if you multiply that by the area of the radiator, in square feet, you will get a good estimate of the CFM required.  If your radiator was 12"x12", that would be 800-900 CFM.  18"x18" would be 1800-2000 CFM, and so on.  A lot depends on ambient temperature and other factors.  Also:

...
the generator will be used primarily to power the two roof airs while underway rather than when parked ...

Be careful here.  Whatever CFM fan you will need while the coach is parked might not be sufficient when it if moving.  Or it might be overkill.  Very few places on the skin or underbelly of the coach will be at neutral dynamic pressure when the coach is moving.  So you might find that a fan which is more than adequate when parked is fighting dynamic air pressure under way and is not sufficient.

The best way to deal with this is to rough in your ventilation openings before designing the system, and measure the air flow.  Setting up the fan and cooling system to work with, rather than against, the natural air flow around the coach will allow you to use a smaller fan.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com

[luvrbus]

I looked at the Prevost generator fan setup at Desert West again it has Flex-A-Lite Syclone S bade fans has 2 but the driver says very seldom do both run at the same time .A 104 today and he is out in the sun running 3 AC's  on the generator only 1 fan was running the other came on for a minute or so while I was looking very quite fans the shop guy tells me around 100 bucks each

[Kevin]

Thanks Guys,

Generator has overheat/low oil pressure safeties to stop engine, worst case scenario. I will give things a whirl with thermostatically-controlled 12v fan and see how it goes.

Very appreciate everyones' contribution! Still working to install 0000 wiring from alternator to house battery bank to inverter so I can run (1) roof air while underway too.

Hoping to keep my cool one way or the other!

Kevin