Fast warm up ideas: oil pan immersion heater

[oil pan 4]

I have done this before so I know it works. Last time I did it was before I joined here.

All you do is take a 1'NPT pipe coupler, weld it to a plate with a hole cut in it, making a flange then stick the highest voltage hot water heater element that you can get that isn't too long. I think I had to use a 1500 watt 120 volt heating element last time.

I have the oil pump, oil pan and the engine block all I am waiting on is the oil pump pickup to finalize oil heating element placement.

There are some requirements to selecting and placing the heating element in the oil pan.
1 it needs to be less than the width of the oil pan.
2 you need to make sure the heating element does not interfere with the oil pump or pickup.
3 the heating element needs to be below well below the minimum recommended operational oil level.
4 put the longest heating element you can fit in there.

Then once you know all those requirements are met, cut a hole in the oil pan and attach the flange. Last time I tack welded bolts to the inside of the oil pan and bolted the flange on with a gasket. This time I am just going to weld it all.

The heating element needs to have a lot of surface area. Because you don't want to run it anywhere near its rated wattage. 300 to 400 watts should be plenty. You don't want to install a small 300 or 400 watt element because they get way too hot. As the engine runs junk settles out of the oil and lands on the heating element if the heating element is ran at full power this stuff gets cooked on to the heating element, will build up layer after layer each time you use the heater and will eventually over heat and burn out the heating element.

[Daox]

How do you run your heating element at partial power?

[Piwoslaw]

^^ Good question.

Also, insulate the oil pan!!

[oil pan 4]

Originally Posted by Daox

How do you run your heating element at partial power?

I was thinking I would use one of my varracs or get some kind of high voltage PWM, to regulate power going to the heater. I have not thought that far ahead.

Normally you really don't want to insulate the pan because during the summer some where like here where it can get over 100'F during the summer. But this 7.4L engine has the heavy duty towing package with a big oil cooler. So I might be able to do something like that.
Then I can reduce the oil heater wattage even further.

I recall 50 volts being ideal on this heating element for this application last time I did it. Of course I will test it to make sure I am not thinking of something else.

[oil pan 4]

I took a stainless steel pipe coupler and cut it in half and welded it to a 1/8 inch thick 2 inch wide flat bar.
I used stainless be cause it welds up a lot better than the iron pipe fittings they sell at the hard ware store.



Iron tends to crack when you weld it.

[Daox]

Looks purdy.

[oil pan 4]

I thought the oil pump pickup would be in today and that I could fit it.
Nope, it had not even been ordered.

[oil pan 4]

We know the best way to warm up something like a tank of fluid is an immersion heater. That way the heat from the heating element only has one place to go. The stick on heaters need to be insulated on one side or the heat will conduct and radiate to the cool air instead of the fluid to be warmed.
To quickly warm up the oil in a vehicle I am going to use a stock GE 1500 watt heater element. These elements are about an inch longer than hardware store replacemens.
Also remember that hot water heater elements are designed to heat water and water plus glycol mixtures.
Engine block heaters and hot water heater elements are almost identical in construction, since they do the same thing.

This hot water heater element is almost too long to fit in the oil pan of my big block chevy with out touching the other side. But you want ad much surface area as possible, more about that later.

So you have major physical and chemical differences of the oil in the oil pan versus coolant in a metal engine block.
Which means you can't just run these hot water heater elements at full power in oil like with an engine block heater. If the oil comes in contact with a surface hotter than 200°C to 300°C it will scorch, produce acids and sludge and that's bad.
Will a hot water heater element in oil produce surface temperatures in excess of what it takes to scorch oil?
I'm not 100% convinced it will but let's not find out.

So to be safe I will need to more than cut the power in half.
Then you are only heating 5 or 6 quarts of oil, compared to the cooing system where you have few gallons of coolant and at least a few hundred pounds of iron or aluminum with a big surface area. So with a block heater you are not going to over heat anything.
In the oil pan you can fry the oil easy.
And and don't forget oil has about half the specific heat of the coolant, so it warms up twice as fast.

Then you have thermal shock, you could accidently send very hot oil into a cold engine block. Bad.

That means the oil temperature will need to be limited.

The standard 1500w heater element has about 9.5 ohms of resistance. I was thinking about rigging up 2 heating elements in series but that would make almost 400 watts come off each heating element. That would heat the oil up really fasted compared to the engine block heaters warming the coolant. It could work but I don't want to do it that way.

So the oil will need to be heated slowly compared to the coolant and have its maximum temperature limited.
If my oil pan holds 5 quarts of oil that would weigh about 8 pounds. 1btu will heat the oil 2°F. So let's say I want to bring the oil temperature up to a maximum temperature of 120°F, let's say the oil is starting at 0°F. We will just round it and say it 500btus to heat the 5 quarts of oil. For every 1,000w of heat put off by a heating element you get around 3,600btu/hr.
Let's say I turned down the power some and the heating element put off 1,000 watts, it would heat the oil in like 8 minutes and scorch the crap out of it.
Let's make the target temperature 1 hour.
So we want to get 500btu per hour out like a 5,400btu/hr heating element. To do that we want to turn down the power to about 140 watts. With a 9.5 ohm heating element, well the rest of the math isn't too hard to figure out.

But in the real world with real losses I have a feeling the oil will never get up to temperature when it's 0°F with the wind blowing. I'm trying to think what a 150 light bulb feels like in the blowing cold if the light bulbs surface area was the size of an oil pan. I just don't see it working real well, or coming up to temperature any time soon. I actually did this once, I painted an oil pan one winters night when it was about 20°F out side then to get the paint to dry I set the oil pan over top a 150 watt light bulb.

So I think my target wattage should be at least 150 watts to no more than 250 watts.
Which means I need to send between 36 and 48 volts to the heating element. My transformer tig puts off exactly between 36 and 48 volts and my varrac makes any voltage I want. So I have temporary power.
I'm thinking I gut and rewarp a microwave oven transformer for the desired voltage.

Then I need a thermostat to cut off the power at the desired temperature level. I have a whole collection of screw in and surface mount thermostats in that temperature range all I have to do is pick 1 or 2. Two if I want a backup.

Now all I have to do is cut a hole in the oil pan weld it up so it doesn't leak, where it is well below the oil level when down a quart or 2 and positioned so the heater element doesn't hit the oil pump or pickup or dip stick.

At the very least I think I found several very good reasons why oil pan heaters are very uncommon.

[Stubby79]

One of these kind of things should suffice for your control:
2000W AC 50-220V 25A Adjustable Motor Speed Controller Voltage Regulator PWM | eBay

[oil pan 4]

I think I am going to rewarp a microwave oven transformer.
The PWM controllers may fail shorted, providing full power to the load.
The microwave oven transformer is fixed voltage and would only fail open.