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A.K. Boomer
06-16-2012, 11:19 AM
I service a wide variety of generators scattered all over the place,
from massive cummins,perkins,cats to smaller generacs and such,

This topic is more to due with the smaller gen sets as the big diesels usually have the air expansion built right into the radiator and therefor there is no need for a purge tank, (most of them anyways)

This is like old school automotive ---

but the smaller gensets have adopted the newer type of "purge" system that can be found under the hood of your typical car nowadays.

This is basically a total fill cooling system that does not allow for any air - and each time the engine is heated the extra fluid expansion is purged into an aux. tank - then when the engine cools the duel acting radiator cap allows for vacuum to draw fluid back into the pressure system by means of a one way check valve in the cap,,,

so all is fine right?

No - I don't think so, My concerns are this;

many of these smaller gensets that are used in cold climate either have a factory installed coolant heater or have them as an option that you put on if needed, this not only aids in starting but also reduced engine wear because going from 0 to 3,600 (or whatever) RPM's with a cold engine is a little tough on them, and many of these engines fire up once a week needed or not just as a maintenance cycle, These coolant heaters work by circulating hot engine coolant through the entire block and most are thermostatically controlled --- but here in lies the problem.

These engine's never actually cool down, many are kept at 120 degree's or so --- so the vacuum to the purge tank never get's "actuated"

the system remains under constant positive pressure...

You cannot have a functioning purge tank if this occurs

Iv seen this on more than one occasion and seen it again just yesterday,
a slight seepage leak that normally would show up as a low purge tank level is never realized, air builds in the system and the internal fluid level goes down, A slight "lazy" positive pressure remains - the coolant heater may start percolating and create an isolated steam effect keeping positive pressure regardless of fluid loss - luckily the sets have a low coolant shut off BUT this does not help if they are gensets installed for critical applications...

So, im somewhat questioning coolant heaters on these type of systems as once again Im thinking its just another brain fart by engineers who call themselves that but actually don't know how the real world works,,, (there's plenty of them)

Im thinking the magnetic oil pan heaters might be a better way to go (not to mention keeping it simple for less plumbing connections so less chance of leaks)

But in the meantime --- If any of you guys have these type of systems this may be a heads up for you,
Never take the purge tank for granted esp. if you have a coolant heater installed, and with genset totally cool check your rad level... your purge tank could show perfect, yet your radiator level might just be down to the cores... in these type of systems you should pop the cap and the coolant should be right there at the top with no room for air...

Purge tanks are a nice "buffer" when operating properly -- they can supply the engine what it needs when smaller issues develop - till either a maintenance schedule arrives (genset) or a nosy mechanic (like me) pops the hood of a car to check out a few things...

KIMFAB
06-16-2012, 11:46 AM
+1 on this.
Before I retired I was responsible for 6 Generac 35 kw generators, all with purge tanks and heaters.

Many times when I checked the fluid in the radiator was low with plenty of fluid in the purge tank.

Another problem here in the desert was the purge tank itself, made out of HDPE it would shatter and self destruct because of the heat.

A.K. Boomer
06-16-2012, 02:14 PM
Thanks on that Kimfab,

The old heat unit is pulled and we will be checking for a sticky thermostat that does not shut the unit off too...
That could create the issue as well, also --- it's seems to be a "one size fits all" heater, so the wattage is the same for bigger units and smaller ones alike - well,
this is the smallest water cooled genset they make - and even though the heat unit is therm. controlled they make be counting on a certain amount of dissipation just in the mass and this unit remains warmer and does not get rid of enough heat to create a vacuum -

anyways - will keep you posted to what we come up with, thanks for the confirmation.

michigan doug
06-16-2012, 04:35 PM
In warm weather, you could defeat the coolant heater. In cold weather, you could put it on a timer so the engine never gets stone cold, but it does get once a week cool off to cycle the purge tank.

Are these residential units with clueless owners, or people with some sense that could think outside the box?

Finest regards,

troy

A.K. Boomer
06-16-2012, 05:27 PM
Good suggestions Troy - kicking around allot of options because some of these units are all on their own, and way far away from typical "civilization".

I hate heaping systems on top of systems as it's an increased failure rate, Im thinking the oil pan heater might just be the way to go as it will allow the upper end to cool enough but not get frigid - also thick oil is one of your biggest concerns as you can blow a filter right off the block due to the pressure relief not being able to shed enough volume when the oil is dead cold and the engine has to immediately rap out at max rpm.

The magnetic pan heater would eliminate allot of potential plumbing leaks also...

but, im listening to all options so thanks for your input.

Willy
06-16-2012, 09:03 PM
You bring up some very interesting points about the surge tank issues A.K.
I'm sure this is an issue that is often overlooked by many.

I am a little surprised that the 70 or so swing in engine temperature from a 120 'cold' engine to one fully warmed up at about 190 is not enough of a temperature variation to allow the surge tank to 'cycle'.
However I have no reason to doubt your observations as you have obviously witnessed the effects associated to this condition.

Other than a very thorough preventive maintenance schedule, paying particular attention to all cooling system components, I don't have any suggestions.

The block heaters as you noted do an excellent job of keeping the engine toasty and do lessen the thermodynamic stress and wear associated with starting a cold engine and bringing it up to full operational speed (1800 or 3600 rpm). This can add up in the course of the unit's lifetime when you take into account this is probably once a week.
When the unit is actually started in the event of a power system failure it is under full load instantly making the use of these devices almost mandatory if a decent service life is to be expected.

One point that I would like to bring up is that during extreme cold winter temperatures the magnetic oil pan heaters by themselves are not capable of providing sufficient heat to reliably start engines. Used in conjunction with block heaters they do provide the benefits that you spoke of earlier, but by themselves they do not heat the engine itself enough if at all.

Of course this is all very much dependent on the observed ambient temperatures that are expected. I'm not sure what your lows are in the locations of these units, but as I'm sure you already know, battery capacity and engine startablity rapidly diminish when the temperatures get into the minus category.

The Artful Bodger
06-16-2012, 10:08 PM
There is a similar, at least related, challenge when engines are fitted at the rear of a car with the radiator up front.

We had a Suzuki LC10W coupe with a 358 motor in the rear and the radiator hoses running under the floor. Obviously in such a system air would accumulate in the engine and never make it way to the radiator and expansion tank up front. The Suzuki solution was a seperate purge tube, including a purge valve, that ran from the highest part of the engine up under the cabin roof and down to the radiator.

If air is accumulating in these generator engines perhaps an equally simple solution could be found.

A.K. Boomer
06-16-2012, 10:14 PM
You bring up some good stuff also like the following;



I am a little surprised that the 70 or so swing in engine temperature from a 120 'cold' engine to one fully warmed up at about 190 is not enough of a temperature variation to allow the surge tank to 'cycle'.
However I have no reason to doubt your observations as you have obviously witnessed the effects associated to this condition.

I would have thought it would be enough also but were definitely having problems - I'll tell you one area where this system also differs from typical conventional modern purge --- because it's a genset they want the highest possible dependability and are not quite as concerned with fuel efficiency --- so this Rad. fan is not only massive, it's direct drive to eliminate the possibility of fan clutch failure --- so what this means is it's only the engine that is experiencing these lesser temp shifts too, this could be just another factor that keeps the purge from working as the radiator is always in super cool mode unless the weather gets real warm...

We still have not checked this block heater out for control and that's going to be a biggie in the decision,

Like you also stated I am worried about the pan heater not getting it done even though all these units also have a therm. controlled battery heater.

Also --- what's your take on viscosity and thermal break down of the oil from these types of heaters, not the little 100 watters but something much more serious ---- it's a concentrated heating area so the initial temps must be pretty high to heat the entire oil capacity in such a small space... You ever heard of anything bad when it comes to this? say something like 600 watts or more...

That being said I have to say this --- I notice that some of the heater hoses that are used for the block heater's have a pretty tough life due to all the thermal they have to handle, and some of these are actually the good stuff hi temp (goodyear blue hi-miller) and they still degrade fast.

Not an easy decision as there seems to be allot of pro's and con's with anything I can come up with at the moment... maybe a milder block heater as these ones were using are the recommended dealer unit's but the thing that puzzles me is like I stated - they are a one size fits all and its allot of watts for the smaller units.

A.K. Boomer
06-16-2012, 10:21 PM
There is a similar, at least related, challenge when engines are fitted at the rear of a car with the radiator up front.

We had a Suzuki LC10W coupe with a 358 motor in the rear and the radiator hoses running under the floor. Obviously in such a system air would accumulate in the engine and never make it way to the radiator and expansion tank up front. The Suzuki solution was a seperate purge tube, including a purge valve, that ran from the highest part of the engine up under the cabin roof and down to the radiator.

If air is accumulating in these generator engines perhaps an equally simple solution could be found.



I knew a guy who did the opposite and moved his cooling system to the back of the vehicle of a front engine care for drag racing and more traction.

he could have benefited from your advice... he had big troubles - some of it may just have been the fact that water pumps are designed to get over a pre-determined amount of drag and he changed all that also...

Willy
06-18-2012, 12:56 AM
what's your take on viscosity and thermal break down of the oil from these types of heaters, not the little 100 watters but something much more serious ---- it's a concentrated heating area so the initial temps must be pretty high to heat the entire oil capacity in such a small space... You ever heard of anything bad when it comes to this? say something like 600 watts or more...



I can't see this being an issue as the ability of the magnetic type oil pan heaters to conduct heat is somewhat compromised to begin with. The path of heat conduction is not direct, unlike a direct in the pan oil heater where the oil is in direct contact with the element itself. Although I have seen some light coking on these elements, oil sample analysis showed that this level of heat was not detrimental to the oil.

Modern oils have come a very long way in their ability to cope with temperature extremes. The newer oil formulations deal with some very high temps when in contact with certain engine components, but I do appreciate your concern.

The engine heaters your clients are using, although effective, do carry with them the price of an extremely hot outlet.
This of course shortens hose life and causes leaks. This being one of the reasons I suggested an extremely vigilant preventive maintenance regime for the cooling system.
You may occasionally have to toss the hose on this portion of the cooling system more often due to the localized heat.

Also, and this is important as it's quite often misdiagnosed as a minor cooling system leak that can't quite be pinpointed at any one particular location, is the fact that silicone hose, while very much capable of withstanding high heat, is 10 to 15 times more permeable to water than standard hose.
This can often be one of your biggest sources for having to continually add make up coolant. In effect you have a very slight leak that is undetectable. Not a problem on a piece of equipment that is checked routinely but could explain why you may be experiencing a lose of coolant in some of these units and why they should be routinely monitored.

As far as engine heaters go I prefer the block heaters that are installed directly into the engine's water jacket through frost plugs holes. Very even and well distributed heat and no maintenance issues due to short hose life or the possibility to create steam or air pockets.

A.K. Boomer
06-18-2012, 09:15 AM
Not a problem on a piece of equipment that is checked routinely but could explain why you may be experiencing a lose of coolant in some of these units and why they should be routinely monitored.

They had been warned 3 times they were past due, Now however I think they get the hint as they want all their other ones inspected immediately,

Most people and even companies think your just trying to get into their wallet when you bring up generator maintenance - I don't know if they think there's a dilithium crystal under there that will run forever or what, well now at least they know...


As far as engine heaters go I prefer the block heaters that are installed directly into the engine's water jacket through frost plugs holes. Very even and well distributed heat and no maintenance issues due to short hose life or the possibility to create steam or air pockets.


Iv thought about those - might be a way to go - they are not infallible either however as it's a localized hot spot and the units seems to crystalize their sealing O-rings after time -- I have seen those units leak right from the block, BUT,
I could see replacing the standard O-ring with a silicone one or searching for a unit that's built with that to begin with if they make them... If you get that kicked then they are the most minimum invasion for block heating.

If it's those shoddy units with the big rubber plug that you tighten up to make fit im definitely not interested.

I also don't believe most are thermostatically controlled so that means elements burn out prematurely - at the same time there is an added dependability factor due to not having the thermostat ------ everything with gensets has to be considered and when you can eliminate unneeded systems that can fail it can be a long term bonus --- still - there design is such that they have to pack allot of heating into a very small area,
So what this can equate to is a scaling build up on the element, esp. when it's not thermostatically controlled, that's where you can get even the mildest percolating action going and then scaling snowballs --- once this occurs the element cannot properly dissipate its heat so it starts internally cooking itself and its days are numbered --- Iv seen them go for years and years on the work trucks but that's being used only overnight in the winter months... It's easier on the element when it's surroundings are cool.

Some of these gensets are high altitude mountain settings --- even in the spring and fall the temps can get way below freezing overnight, yet hit 80 or 90 f easy during the day...

and last but not least is it will not solve the purge tank problem...

What im considering doing with that is mounting the tank as high as possible - right now the tank is mounted way below the rad. inlet - so it's a literal siphon to get coolant back up - this along with the small spring loaded check valve in the rad. cap may be enough to deter coolant drawback...

most all the car's that have purge tanks I work on have the tank close to level with the rad. cap...

jdunmyer
06-18-2012, 03:50 PM
My VW-powered genset has a 400-watt block heater that I need to run if the thing is to start when it gets cold. However, I found that operating the heater at half voltage gives me 1/4 the wattage, and that's plenty to give me reliable starting. The 400-watt heater will warm it up enough to start given less than an hour's running time. If it's on 24/7, the 1/4 wattage is fine.

See: http://www.oldengine.org/members/jdunmyer/genset/