Is it really bad to leave the engine heater plugged in 24/7?

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JasonM

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I just purchased an airplane and it has an E-Z Heater for the Cessna 182. I am hearing mixed reviews from people. Some say to leave it plugged in and some say using a heater without running the motor within a few hours will cause condensation and rust. This heater is internally thermostatically controlled at I believe 165 deg.
 
How would it cause condensation? Heat drives water off.

Constant heat will age seals and hoses faster, and probably the oil, too.

Dan
 
If the engine is left for weeks or months that way, yes, leaving a sump heater pad on is a bad idea. Part of the reason for that is that it does not get to 165F inside, more like 75-80F, so the moisture just condenses at the top of the crankcase, which means on the camshaft in a Lycoming -- very bad juju. If you fly it every few days or a week, then you probably burn out the condensation before it does significant harm, but better to put the heater on a cell-phone controlled relay and turn it on 3-4 hours before flight.
 
Dan Thomas said:
How would it cause condensation? Heat drives water off.

Constant heat will age seals and hoses faster, and probably the oil, too.

Dan
Click to expand...

The theory is that the higher internal temps will cause the oil film to drip off of the steel bits faster. Whether the trade-off of leaving the heater on all the time (lower crankcase humidity BUT less oil film too) is better or worse, I dunno.

I use mine on an as-needed basis - visiting the airport as a side-trip on my commute only costs me 10 minutes, so it is pretty convenient. But a GSM switch would be even better.
 
with the heater plugged in the oil is the warmest part, the camshaft (in the case of a lycoming) the coldest. water is driven out of the oil as you heat it. That means you have a saturated water vapor solution in the air immediately above the oil. That water will condense out somewhere else. Since the solution is saturated at the bottom and there is some non-zero temperature gradient throughout the engine, condensation somewhere is 100% guaranteed.

For people unable to accept basic thermodynamics it is easy anough to prove. Plug in the heater for a couple days and then take off a rocker shaft cover. You will find the inside of the metal cover covered with a fine mist of water. That is what most of the inside of your engine looks like.
 
All right, turn it off when the weather gets warm. But otherwise, if it isn't hot enough to cook the oil any problems are mitigated by the fact the plane will be ready to fly when you are.
 
JHW said:
with the heater plugged in the oil is the warmest part, the camshaft (in the case of a lycoming) the coldest. water is driven out of the oil as you heat it. That means you have a saturated water vapor solution in the air immediately above the oil. That water will condense out somewhere else. Since the solution is saturated at the bottom and there is some non-zero temperature gradient throughout the engine, condensation somewhere is 100% guaranteed.

For people unable to accept basic thermodynamics it is easy anough to prove. Plug in the heater for a couple days and then take off a rocker shaft cover. You will find the inside of the metal cover covered with a fine mist of water. That is what most of the inside of your engine looks like.
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I disagree with your thermodynamics from both a theoretical (BS Physics, San Diego State, '67) and a practical sense (A&P, IA).

Yes, as the water is driven off, the saturated vapor WILL condense out unless the vapor is given an easy method of evacuation. The crankcase vent is one easy method of getting rid of the vapor; leakages through the rings and out the exhaust/intake valves are another.

The whole engine will come to thermal equilibrium given a relatively short time. The warm oil will tend to warm the entire engine. What the thermal resistance between individual engine components and the environment is cannot be easily stated but we have empirical data that shows that the whole engine comes to some striated temperature relative to the ambient temperature.

It is this variable, ambient temperature, that we cannot control. Therefore, just like carburetor temperature relative to carb ice, we have to postulate some range of temperatures that will have a positive versus a detrimental effect on the engine.

To simply say, "It is always bad to leave it plugged in" shows a lack of understanding of the variables involved.

THanks,

Jim
 
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I know a few guys that leave theirs plugged in during the winter. I met one that told me to plug it into a thermostat so it only comes on if the hanger gets below 50 deg or so. I also know a few that are telling me not too. Is this another one of those "who the hell really knows" deals?

I have always left the engine heaters on farm tractors during the winter and they always start easier with them on.

Is there any real proof of this causing damage to the engine? Is this something that would make flight risky if there was condensation?
 
This is often debated, but never definitively resolved. The folks at Tanis had a Cherokee they left plugged in December through February for years. It usually flew at least weekly, but sometimes sat for a few weeks during the winter doldrums. At 2,400 hours they rebuilt the engine and said it disassembled with normal wrenching...no sign of corroded components.

I think the key is a good engine blanket to keep the temp stable. The Bo I'm currently flying stays plugged in 24/7 with blankets, but it flys at least twice a week (2-3 hr. flights), often 3-4 times when weather is cooperative. We need it ready to go when we're ready to fly, so leaving it plugged in is the only option.
 
In everything we're talking about here, it's important to make the distinction between sump-only heaters such as the EZ-Heat and heaters that heat both the sump and the cylinders (Tanis/Reiff are the only two mfr.'s of these AFAIK). In addition, the presence or absence of cowl plugs, engine blankets, etc. will have an affect. And, of course, ambient temperature.

Personally, I have the full Reiff system with both sump and cylinder heaters, custom-fit cowl plugs and an engine blanket. I also leave the engine plugged in 24/7, and I leave the oil filler open. Here's my reasoning:

1) Heating the cylinders in addition to the sump should provide a much lower temperature gradient between the hottest and coolest parts of the engine. The engine blanket and cowl plugs assist in that as well.

2) Lower gradient and higher overall temperature greatly reduces the chances of condensation inside the engine.

3) Opening the oil filler allows the high-humidity warm air to escape, drawing in fresh, very dry air through the breather.

4) Leaving the heater on 24/7 keeps the parts warm, and ensures the engine is always warm and ready to go - I often don't know 8 hours in advance that I'm going flying, so it's better to keep it ready all the time. It also means that the engine never cools down to the point of allowing internal condensation.


With a sump-only heater, I'd probably only plug it in a few hours before departure.

Thermostats are the worst - They heat the engine up and get the water into vapor form, shut off to let it condense, and then heat it back up to speed up the corrosion reaction! Okay, maybe they're not QUITE that bad, but it seems like an exceedingly bad idea for engine longevity.
 
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weirdjim said:
I disagree with your thermodynamics from both a theoretical (BS Physics, San Diego State, '67) and a practical sense (A&P, IA).

Yes, as the water is driven off, the saturated vapor WILL condense out unless the vapor is given an easy method of evacuation. The crankcase vent is one easy method of getting rid of the vapor; leakages through the rings and out the exhaust/intake valves are another.

The whole engine will come to thermal equilibrium given a relatively short time. The warm oil will tend to warm the entire engine. What the thermal resistance between individual engine components and the environment is cannot be easily stated but we have empirical data that shows that the whole engine comes to some striated temperature relative to the ambient temperature.

It is this variable, ambient temperature, that we cannot control. Therefore, just like carburetor temperature relative to carb ice, we have to postulate some range of temperatures that will have a positive versus a detrimental effect on the engine.

To simply say, "It is always bad to leave it plugged in" shows a lack of understanding of the variables involved.

THanks,

Jim
Click to expand...
It's obvious your background is electronics and not engines. Yes the engine reaches thermal equilibrium. That equilibrium is not a constant temperature throughout. It is a temperature gradient. Engines with oil sumps heated continuously condense water out somewhere else. It's something that is easy to understand and something I have observed in every vehicle cold test chamber I have worked in.
 
JHW said:
It's obvious your background is electronics and not engines. Yes the engine reaches thermal equilibrium. That equilibrium is not a constant temperature throughout. It is a temperature gradient. Engines with oil sumps heated continuously condense water out somewhere else. It's something that is easy to understand and something I have observed in every vehicle cold test chamber I have worked in.
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^^^ This.

For an easy example, think of the propeller, which is bolted to the crankshaft.

At equilibrium, the oil is warm (and likely damp), and the propeller blade is a large, cold heat sink; perhaps as cold as the outside air.

There is a temperature gradient along the propeller / crank / case "system."

Where is the transition line, where some part of that system may below the dew point of the crankcase environment? Do you know enough for any given day to determine if that transition point is inside or outside the engine?

Now, how about that Lycoming camshaft?
 
I plug the heater in the day before I go flying.

That works very well. It's what I'd do. I go over this some in my "Engineer Ted..." threads.

Do not leave it on a thermostat or a timer. Just plug it in the day before you fly.
 
Corrosion rates are a function of temperature. The warmer it is, the faster corrosion proceeds.

Now, what was the advantage of leaving it plugged in so it can stay warm?
 
Capt. Geoffrey Thorpe said:
Now, what was the advantage of leaving it plugged in so it can stay warm?
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If it is cold and the hangar is far away from home and you are planning on flying later in the week.

Tanis says you can leave it plugged in continuously for at least a week with no issues.
 
JHW said:
It's obvious your background is electronics and not engines. Yes the engine reaches thermal equilibrium. That equilibrium is not a constant temperature throughout. It is a temperature gradient. Engines with oil sumps heated continuously condense water out somewhere else. It's something that is easy to understand and something I have observed in every vehicle cold test chamber I have worked in.
Click to expand...

What may NOT be obvious is that I earned that A&P IA starting in high school working on aircraft frame & engine and continued through college as a greasy mech for the airlines ... and in the 50+ years since. I think I've paid my dues several times over to be able to discuss what happens inside a crankcase.

Having said that, do you understand the meaning of the word "striated"? Perhaps I should have used the term thermocline. That is, the temperature inside the engine if only the oil is heated is not constant throughout. There will be pockets of warm and pockets of cold. Can water condense out if the conditions are right? Of course. What fool would argue otherwise?

My point is that if the OP chooses to configure his engine for this always-on mode of operation he can do so. As one person noted, opening the oil filler cap is one way of venting warm moist air out of the engine. As another noted, using a thermal blanket is another. To say that it will ALWAYS condense out on the cam lobes, or in the rocker covers is to show ignorance of the conditions under which the organism exists.

To the fellow who pointed out that the prop is a huge heat sink, I offer the following analogy. Go out in a snowstorm naked and you are likely to have frostbite in a short period of time. Go out triple-wrapped with heavy boots and thermal socks and you will be comfy warm. To take the analogy a step further, provide a little auxiliary heat to that human thermal chamber by shoveling said snow or pushing a snowblower around and you will in fact create an environment where very little of that thermal blanket will be necessary in a short period of time.

Yeah, most of my current work is in electronics. That doesn't mean that I left the real world of the last 60 years behind me when I took that profession.

Jim
 
weirdjim said:
To the fellow who pointed out that the prop is a huge heat sink, I offer the following analogy. Go out in a snowstorm naked and you are likely to have frostbite in a short period of time. Go out triple-wrapped with heavy boots and thermal socks and you will be comfy warm.
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If you go out bundled up but nothing on your head, you will not be comfy warm for long.
 
Any comments from the experts on using a warm air blower like this with a piece of aluminum ducting into the bottom of the cowl blowing relatively dry 75F air into the engine compartment all the time?
5d4c40aa-7838-488f-9443-628a0d8c3452_300.jpg
 
Ron Levy said:
Any comments from the experts on using a warm air blower like this with a piece of aluminum ducting into the bottom of the cowl blowing relatively dry 75F air into the engine compartment all the time?
5d4c40aa-7838-488f-9443-628a0d8c3452_300.jpg
Click to expand...


1500 watts for the blower vs 100/200 w for the Reiff or Tanis solution. Do you pay the electric bill or is it included in the cost of the hangar?
 
weirdjim said:
My point is that if the OP chooses to configure his engine for this always-on mode of operation he can do so.
Click to expand...

That would be correct, however I would hazard to guess that the (vast?) majority of those using some kind of engine heat have no idea on how to do successfully do this to prevent condensation, other than through old wives tales they heard from someone else.


weirdjim said:
As one person noted, opening the oil filler cap is one way of venting warm moist air out of the engine.
Click to expand...

Hmmm... not sure how this by itself would ensure that there is not metal within the case that is below the dew point of the case environment.

weirdjim said:
As another noted, using a thermal blanket is another.
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I like that better, assuming is is appropriately designed and applied ... who can verify that?

weirdjim said:
To say that it will ALWAYS condense out on the cam lobes, or in the rocker covers is to show ignorance of the conditions under which the organism exists.
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I'm not sure that was the point, but there are plenty who think that it will NEVER condense, or have no understanding on how or why it might occur.

weirdjim said:
To the fellow who pointed out that the prop is a huge heat sink, I offer the following analogy. Go out in a snowstorm naked and you are likely to have frostbite in a short period of time. Go out triple-wrapped with heavy boots and thermal socks and you will be comfy warm. To take the analogy a step further, provide a little auxiliary heat to that human thermal chamber by shoveling said snow or pushing a snowblower around and you will in fact create an environment where very little of that thermal blanket will be necessary in a short period of time.
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OK, I'll bite. Now modify that analogy to change "eliminating frostbite" to "eliminating condensation" on any surface inside that triple wrapped container.

I'll politely challenge that its easier to succeed with the first than the second, particularly if one notes that the oil and case (and that naked body) start out as damp, and both generate water vapor as they heat up.

weirdjim said:
Yeah, most of my current work is in electronics. That doesn't mean that I left the real world of the last 60 years behind me when I took that profession.
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Ah, so you are in the EE club too? :)


By the way, I just ordered a dehydrator with an automatic recycle feature to supplement my thermal blanket, prop blanket, and sparingly applied heater after replacing a Lycoming cam that only had 550 hours.

Apparently, I couldn't successfully keep condensation off the cam, either.
 
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Ron Levy said:
Any comments from the experts on using a warm air blower like this with a piece of aluminum ducting into the bottom of the cowl blowing relatively dry 75F air into the engine compartment all the time?
5d4c40aa-7838-488f-9443-628a0d8c3452_300.jpg
Click to expand...

I think it's rather silly to do vs. a Tanis heater and won't get the engine as warm, but ought to work.

On a side note, while the electric is included in the hangar rent, if they see electric usage going up, expect hangar rates to eventually go up with it. Just because it's included I don't think is a good excuse to be wasteful with it and ultimately is bad for you and the rest of the tenants if the hangar rates go up. I leave the battery tender plugged in all the time in the winter, but that's virtually zero draw. Heaters only when needed.

Fearless Tower said:
If it is cold and the hangar is far away from home and you are planning on flying later in the week.

Tanis says you can leave it plugged in continuously for at least a week with no issues.
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These days there are lots of ways around that. I can even call the airport and they'll plug the plane in for me. I leave it ready so they just have to plug in the cable. Plus remote activation, etc.

Now, what happens when power goes out? Then you're getting the heat cycled, which is definitely bad for the engine.
 
Is there an ambient room/hanger temperature that keeping it plugged in would make sense. I live in an area that gets relatively cold during the winter. Could some of these problems be more conducive to occurring in climates that are not really as cold?

Well, I plugged it in yesterday and the weather looks like crap until next week now. I was hoping to go up this afternoon, but its not going to happen. Am I safer to unplug it now or keep it plugged in until I get her up in the air again next week?
 
Keep it plugged in until you fly next.

40F or below if you plan to fly, plug it in. Pay attention to overnight lows the night before.
 
Ron Levy said:
Any comments from the experts on using a warm air blower like this with a piece of aluminum ducting into the bottom of the cowl blowing relatively dry 75F air into the engine compartment all the time?
Click to expand...

The problem with blowers like that is they are generally not designed to move their rated volume of air through ducting. Of course as air volume is decreased the heating element runs hotter than spec. They do generally have a thermal protection circuit to prevent overheating. All that said, a short, oversize duct should not be a problem.

Other than the mis-application noted above, and the excess energy usage noted by Ted, they should be fine.

OTOH, for $3 or 4 thousand a month you can rent a fine diesel fired heater that will warm the engine...and the entire hangar...just gotta buy the fuel at ~3.50/gal in addition to the rent.
 
ElPaso Pilot said:
Ah, so you are in the EE club too? :)
Click to expand...


Well, sort of. One of my friends defines the difference between EE and EEE as a division above one amp and below one amp. I'm a little on the high side of one amp but most of my stuff is 10 mils and below (RF, ya know).


Jim
 
murphey said:
1500 watts for the blower vs 100/200 w for the Reiff or Tanis solution. Do you pay the electric bill or is it included in the cost of the hangar?
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Reiff and Tanis use more than that. My Reiff uses 400W total, they go up from there - Except if you have sump-only heaters, in which case I wouldn't recommend leaving 'em on all the time.
 
Capt. Geoffrey Thorpe said:
Corrosion rates are a function of temperature. The warmer it is, the faster corrosion proceeds.

Now, what was the advantage of leaving it plugged in so it can stay warm?
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Well, you'd better not ever fly then, as the temperatures rise so much that your engine will rust out before you land! ;)

Of course, what you say is true, all else being equal - But all else is not equal. Which is better, an engine at 0ºC with moisture on all the internal surfaces, or an engine at 20ºC with no moisture?
 
ElPaso Pilot said:
There are commercial versions available, too, but why would a fish tank aerator and a box of desiccant scare you?
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Just that I have no idea about that stuff really. Looks like something that could actually expose your engine to something harmful by accident. I could see my homemade version pumping that silica gel into the motor. :idea:
 
flyingcheesehead said:
Of course, what you say is true, all else being equal - But all else is not equal. Which is better, an engine at 0ºC with moisture on all the internal surfaces, or an engine at 20ºC with no moisture?
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How many days/ weeks/ months does it take to evaporate and diffuse all of the moisture out a skinny little tube that is several feet long? There is a lot of water inside the engine.
 
Ted DuPuis said:
I think it's rather silly to do vs. a Tanis heater and won't get the engine as warm, but ought to work.
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Gets it warmer, according to the JPI in my current non-Tanis Tiger versus the JPI in my former Tanis-equipped Cheetah. If I set it right, the oil and CH temps will be up in the 70's at even about a 4/10 heat setting on the blower. Also, purchase and installation of a Tanis or Reiff pad/cylinder system costs about eight times what this baby did.
 
Ron Levy said:
Any comments from the experts on using a warm air blower like this with a piece of aluminum ducting into the bottom of the cowl blowing relatively dry 75F air into the engine compartment all the time?
Click to expand...
you are essentially heating the room as far as the engine is concerned. That is a best case scenario for the engine given enough time. HOWEVER I would struggle to find a place to make that work with the heater high enough off the floor for my comfort level. I refuse to place an electrical appliance closer than a 5-gallon bucket height to the floor in a building containing gasoline.
 
I plug mine in about the middle of Oct and unplug it in June.. During that time the hangar is always below 50f... Oil stays at 140f using one of these
http://archeat.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=A&Category_Code=FAAAIR


and water stays at 120f using a 100 watt light bulb sitting under the radiator....

Costs about 30 cents a day....

Been doing it for 12 years and absolutely NO sign of corrosion anywhere in the motor..

Ps. The blanket over the cowling helps a TON...:yes:
 

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N801BH said:
Ps. The blanket over the cowling helps a TON...:yes:
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blankets with characters from warm climates work better. The Dora the explorer blanket is the best you can get.
 

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