Cooling fan direction

simonsrplant · Nov 1, 2019

I have an enclosed 8KW Kubota 3cylinder powered generator running heaters to take the chill off my sea can through winter.
I'm finding it doesn't hold hear or even get warm.
Points to add at this point.
The cooling fan currently pulls air through the gen set and out through the rad housing.
There are vent holes in both side doors and the front door and radiator end.
I'm yet to cover the side doors but figure since it's pulling unrestricted cold air through its not going to make much of a difference.
I know fans are designed to run in a specific direction, but is it as simple as turning it around to reverse the air flow, making a winter front more effective at restricting air flow through the rad.
I'd also do the same for my Miller trailblazer... It too doesn't get warm

Delmer · Nov 1, 2019

No, it will still push or pull the same direction because the engine is turning the same direction. It will be less efficient installed the wrong way, significantly less efficient if you're overheating, not enough if it won't warm up in the cold.

Is this gen inside the can, or outside? I can think of all sorts of changes you could make to get more heat inside, but easiest would be to put the generator inside with an exhaust going outside.

funwithfuel · Nov 1, 2019

How bout replacing the thermostat?

kshansen · Nov 1, 2019

simonsrplant said:
is it as simple as turning it around to reverse the air flow,

This is one of those things that seem to come up every so often and it always gets me that so many people don't have a grasp on why it will not work.

I always try to explain that a fan blade is nothing more than a very short piece of threaded rod. Anyone see why many boat people refer to the propeller(another version of a fan)as the screw?

Picture clamping a nut in a vice and take a section of threaded rod turn it clock wise and it will thread into the nut(assuming it and the nut have right hand threads). Now take the piece of threaded rod and turn end for end and guess what turning it clockwise it still will thread in to that nut!

Now with most fans the blades are designed in a way that they are more efficient when facing the right way but even if installed backwards they will still move the air in the same direction but with a bit less efficiency!

Tinkerer · Nov 1, 2019

Figure out a way to enclose (a shroud) the exhaust system to preheat the cooling air ?

DIYDAVE · Nov 1, 2019

Put a piece of card board fronta the radiator...

funwithfuel · Nov 1, 2019

Am I missing something, I took it as he was concerned about NOT retaining heat.

simonsrplant · Nov 1, 2019

DIYDAVE said:
Put a piece of card board fronta the radiator...

None likes a scabby piece of card in the rad...
I'll start by insulating and filling the door vents and getting a partial cover for the radiator.
Would have been nice to change the direction of airflow but no big deal

repowerguy · Nov 2, 2019

Keep in mind that the air flow is designed that way to keep the generator section cool, if you put a suction fan on you will be putting hot air on the generator.

kshansen · Nov 2, 2019

repowerguy said:
Keep in mind that the air flow is designed that way to keep the generator section cool, if you put a suction fan on you will be putting hot air on the generator.

Agree, and I might not be really understanding the problem.

Is there a problem with the cooling system of this engine like a bad thermostat? Or are we talking of a application in sub-zero temps for long periods of time. Or is the load on the unit way too low?

Not sure what the minimum load that a genset like this should be working under.

Years ago we had a 3-53 Detroit genset that they used to just run a block heater in a 3412 Cat genset overnight and weekends and a few lights. Anyone who knows Detroit's can imagine the wet stacking that caused.

Nige · Nov 2, 2019

What is the kVa rating of the generator and approximately how much load do you have on it.?

simonsrplant · Nov 2, 2019

Problem is the unit doesn't hold heat.
Ambient air temp through winter will average minus 20.
Much colder at times but not always.
The unit is 8Kw. It runs two electric heaters at 4800w each (peak) and x4 60 watt incandescent bulbs.
My thoughts would be it is under close to full load consistently. Seen these things fail due to lack of load before.
The cooling system does not have a problem. I don't like that the unit doesn't get warm... Efficient running should be at running temp not at warm up temp.

simonsrplant · Nov 2, 2019

repowerguy said:
Keep in mind that the air flow is designed that way to keep the generator section cool, if you put a suction fan on you will be putting hot air on the generator.

Noted.
That would be my only real concern in reversing the fan. Not sure if it would have an adverse effect on the generator. But with the cold ambient temperature would it make a difference?

Nige · Nov 2, 2019

Seems like you have plenty of load on the set so that's one box ticked.

The problem is that you can't just "reverse the fan" unless you can find a "left-hand threaded" (puller versus pusher) fan spider for this particular application. See KSH's post #4 above.

Thinking about it you could reverse the air flow direction IF you could turn the fan round as per your OP, but THEN you would need to also reverse its direction of rotation as well. I would imagine that's not practical.

Here's a thought. If the engine is staying so cold why not try removing the fan completely just for a test and see what temperature it runs at..? It may be that your ambient is so cold that radiated heat would be sufficient to keep the set at an acceptable operating temperature.

simonsrplant · Nov 2, 2019

I'm tooled up with some plywood to block off the door vents as a test.
Will post the results

Birken Vogt · Nov 2, 2019

You can definitely find the opposite direction fan for that engine. You just have to find the part number off a puller fan the same size that went in a piece of equipment with that same engine. I have seen a lot of those engines for sale on ebay as a puller so maybe borrow the serial number off one of them.

That being said, if it was me I would never ever restrict the air flow so bad that if it got warm the engine could not cool. Overheating is far worse than running cool I am sure you know. I assume this unit stays cool because the block is losing all its heat to the air flow. I wonder if you might remove the radiator air flow from the equation entirely somehow. Or wrap the block with insulation or something.

Don't allow the generator head to overheat whatever you do.

Welder Dave · Nov 2, 2019

I agree there should be a reverse fan available. I have one for my skid steer with a Kubota but don't use it anymore. While it helps keep the cab warmer, if the entire machine isn't spotlessly clean it stinks up the cab from even slightest bit of oil or dirt in the belly pan. For more heat I'd see if a higher thermostat is available. I run a 190 in my tractor with a Perkins and never have any problems in the hot summer. Another thought is put a small electric heater with a thermostat in or around the engine on the generator.

kshansen · Nov 2, 2019

Okay how about this idea? Can you locate a set of shutters off an old over the road truck? Not sure if anyone uses them nowadays.

Of course that would require a source of air to actuate them with a shutterstat mounted on the engine. Maybe a small electric air compressor?

Welder Dave · Nov 2, 2019

I used to have a welder with manually adjusted rad shutters. It was part of an Arctic modification.

Tinkerer · Nov 2, 2019

Hhhow about removing the fan and install thermostatically controlled electric one in front of the radiator. They are readily available. It could be mounted to push or pull the air.

Cooling fan direction

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