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Sean Welsh (Sean)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 12, 2005 - 2:23 pm: | |
OK, in the interests of not overwhelming the emergency road service thread further with an orthogonal topic, I'm starting a new thread here.
At the tail end of the road service discussion was the following exchange:
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By Sean Welsh (Sean) (69.35.62.223) on Saturday, March 12, 2005 - 5:05 am:
"...the question of having a gen set that is independent of the main mill..."
I know, Henry, that you're being tongue-in-cheek, but we actually considered this.
By which I mean we looked at the possibility, for example, of cooling the genny through the main engine radiator, or eliminating a separate starting battery for the genny. We decided against this principally so that, if a main engine failure stranded us someplace, we could still make electricity for however long it took to get help.
We do carry many tools and spares to make common repairs ourselves, but we drew the line at carrying spare tires and wheels, 1" impact guns, and cribbing. We simply could not afford the space for such big items that are readily available virtually anywhere.
Interestingly, I do carry a 1" drive 30mm socket, which is the size of my lug nuts, because many service trucks do not carry this size. When I change lug nuts to 33mm, a more common size, I can do away with this.
-Sean
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By TWODOGS (Twodogs) (4.226.237.13) on Saturday, March 12, 2005 - 12:00 pm:
I know we butt heads sean,,but how would you cool the gen. with the bus radiator if the bus radiator fan wasn't moveing...or...maybe I don't understand the theory...
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By Sean Welsh (Sean) (69.35.62.223) on Saturday, March 12, 2005 - 12:14 pm:
2D,
As I said, we chose not to do this, so it became a non-issue. (We did not want the possibility that a coolant leak, for example, could take out both our power sources at once.)
That being said, if we had chosen to go that route, we would have installed an auxilliary electric fan to move air over part of the main radiator for cooling while the main engine was not running. Not a big deal, since we are using an electric fan to move air over the dedicated genny radiator anyway. We pulled the shaft-driven fan off the genny motor, and moved the radiator into a sound box for noise control.
Great care must be taken, if going the combined route, to engineer the coolant flows correctly. Otherwise, it is possible for the water pumps on the two engines to be trying to work against each other when both are running at the same time. This is another reason we decided against combining them.
There has been a great deal of discussion on this subject in the past -- you might search the archive for more information.
-Sean
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By Richard Bowyer (Drivingmisslazy) (66.168.168.57) on Saturday, March 12, 2005 - 12:59 pm:
My genny was plumbed into the top and the bottom of the main engine radiator. The two waterpumps never saw each other. They were completely independent.
I had two 16 inch, 12 volt electric fans installed on the main radiator, thermostatically controlled at 190 degrees. These fans served two purposes. Helping cool the main radiator during mountain driving (and yes, they really helped) and they would also come on occasionally while boondocking and running the genset. Generally about five minutes every thirty minutes or so. It was a great system and I loved it. The hot water created by the genset while boondocking in cold weather provided enough heat the keep the bus warm. The Webasto was tied into the same system and it would supplement the genset heat if needed. One big cooling system and no problems during 15 years of use.
I really suspect that many converters worry so much about any of the possible things that can potentially go wrong that they end up with so much redundancy that they never get finished.
Richard
Richard
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So, responding to Richard's last post:
Richard,
When you said your "...genny was plumbed into the top and the bottom of the main engine radiator. The two waterpumps never saw each other. They were completely independent" I have to suggest (for the benefit of anyone thinking of doing this) that you were either clever in how you routed the plumbing, or lucky, or both.
The reason is that, while the water pumps are indeed "independent," flow restrictions in the radiator itself and then further downstream in the cooling system provide a certain amount of back-pressure.
Whenever only one pump is running, that backpressure will cause the coolant to take two paths at the junction before the radiator -- some of it will proceed through the radiator, and some will flow "backwards" through the cooling system and pump impeller of the non-running engine.
In the case of the main engine running, this will likely have little impact, because the cooling passages of the generator will not admit too much coolant, especially backwards, and most will flow through the radiator as intended. In the case of the generator running, it's not so clear-cut. Large pathways in both directions at the tee may cause significant amounts of coolant to run backwards through the main engine.
Neither of these cases is likely too much of a problem, because the non-running engine will usually act as a sink for some of the heat from the running engine.
It is the case where both engines are running that can be problematic. In this case, if one pump is significantly stronger than the other (very likely, given the size discrepancy between engines), the backpressure at the junction can cause coolant from the larger system to literally overwhelm the pump on the smaller system, thus stalling coolant flow out of the smaller engine altogether.
When designing a joint cooling system such as this, there are several ways to deal with this potential problem. One is to ensure that coolant flow through the radiator and beyond generates minimal backpressure. Another is to design the piping in such a way that the dynamic pressures cooperate instead of compete -- using "Y" fittings (properly oriented) instead of "T" fittings, for example. Yet another possibility is high-flow check valves to ensure that back-pressure can not enter the other system in the wrong direction.
To be clear: I am not criticizing your installation or saying there was anything wrong with it. Clearly, it worked as you implemented it. I'm just trying to lay out some cautions for anyone else contemplating sharing one radiator between two engines.
-Sean |
jimmci9 #2
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 12, 2005 - 5:35 pm: | |
after reading this thread, i would like to add.... the thermostat in the generator keeps the generator engine coolant from circulating in it....however a little will circulate because of the bypass built in the system... and if the main engine overheats, the small one's thermostats may eventually open and allow circulation.... |
R. Steve Nichol (N4rsn)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 12, 2005 - 7:25 pm: | |
Why not just add a fitting in the top tank, and the bottom tank for the radiator,for the small engine, and than each engine is totally independant.
Just a thought
Steve |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 12, 2005 - 7:57 pm: | |
Steve, Individual top and bottom fittings would be ideal, but space is really at a premium in that area.
As Sean suggests, the use of "Y" 's properly orientated for the genset assures the water from the genset flows easily to the top of the tank, and coming from the radiator a “T” pointed toward the genset helps the water flow to it. Due to the immense size of the main radiator hoses and the 1” size of the genset hose I do not think the genset was ever starved for water. If it had had a lack of water the OT thermostat would have shut it down. With a properly flowing radiator, there is very little, if any, back pressure at the top of the tank. In fact there is generally a void at the top of the tank I believe.
I was never really concerned about the genset ever pushing water thru the main engine when it was non operational. I suspect the engine thermostats would have prevented this, but I really do not know.
Dick Wright at Wrico actually designed the system when it was initially installed and my understanding is that he had done dozens or more of these with no apparent problems. The nice thing was that I only had one coolant system to worry about, no separate expansion tank for the Webasto, supplemental heat in the coach from three different sources, always lots of hot water and excellent pre-heat for the main engine from the genset.
Richard |
Jim Wilke
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 13, 2005 - 7:24 am: | |
Richard, did you ever have a problem with overheating while running the genset while driving (climbing big hills}? That's the only possible issue I see.
You are correct, each engine's thermostat/s will prevent all but a little of the coolant from circulating through the non running engine. This is actually nice because I do not want the genset to be heating my dormant main engine up to 180 degrees under the bed while we are camped.
Which of Miss Lazy's bays was the genset mounted in? (How long was the piping run to the genset?) How many KW was your genset?
Jim-Bob |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 13, 2005 - 8:48 am: | |
Jim, When I first got the bus, the 16 inch fans had not been mounted on the radiator and that caused problems with the genset running when parked. After installing the fans, and an indicator light on the dash, I never had problems with the genset overheating anymore.
Even if I was not running the genset, the fans would come on during a hard pull. I had put in an 8V92 and the largest radiator I could cram in, but I still had occasional overheating problems.
Once the 190 degree temp light came on, I would just back out of the throttle some and try and keep it below 200-210.
The 10 kw genset was mounted on the curb side where the original A/C unit was I believe. The Webasto was mounted directly behind it in the engine compartment. 1" hoses ran from the genset directly to the radiator. I would estimate the hoses were 8 feet long. There was an inline circulating pump in the return line, but I never had to use it once I installed the auxiliary fans.
I really do not recall how the Webasto was plumbed into the engine and the heating system and hot water heater (or is it a cold water heater?).
Once I found out what the genset overheating problem was and installed the auxiliary fans, it was a great system and I would recommend it to anyone.
Richard |
Jim Wilke
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 14, 2005 - 8:35 am: | |
Hmm, not sure that will work for me. I will be installing the gen in either the #1 (front) left or #2 bay. I want to keep it as far away from under the bed as possible. I don't think the engine circulating pump could move the water that far.
Jim Bob |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 14, 2005 - 5:02 pm: | |
For that distance, I suggest you check with Dick Wright. A 120 volt circulation pump would be gobs cheaper than a 12 volt pump. Either should solve the distance problem.
BTW, I found the installation beneath the bed great. A little bit of white noise and a very small, almost indetectable, amount of vibration shure helps you sleep good.
Richard |
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