Electric A/C


IHC in the early to mid-fifties.

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Golden Jubilee
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Post Wed Apr 28, 2021 7:24 am

Electric A/C

After stumbling on to a solution to an overheating problem, I’ve begun contemplating changing the source of energy powering my A/C compressor. I found that I had been losing radiator coolant gradually due to a leaky cap. The cap was replaced and the engine now runs consistently at a reasonable temperature. However, this being Florida, A/C is a vital component of motoring down the highway and when I turn it on the temp gauge rises to a level that concerns me. Being one to wonder how things could be better, the light bulb over my head turned on when I thought about hybrid and all electric cars (and trucks) have A/C and they’re electric operated. What if I utilized one of those, my engine should run at its reasonable temperature, and not rise higher when the A/C is turned on. I am just beginning to research this idea, so I decided to present the topic here and see what kind of response I got from you guys. As far as the compressor is concerned, it’s mechanical and shouldn’t matter what powers it. My questions are more oriented toward the electrical side and wire sizes and wiring in general. Also will this extra load on the battery cause problems? Do you think my Vintage Air system controls will be adaptable to operate this new configuration? I’m open to input from you guys and what am I overlooking?
L110 owner since 1974, finally rebuilt 2014.

Golden Jubilee
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Post Wed Apr 28, 2021 10:15 am

Re: Electric A/C

The energy source is the engine. The AC compressor will require the same amount of energy, mechanical or electric.
Your heating problem is from the AC condenser. This is where the heat absorbed in the evaporator by the refrigerant is transferred to the outside air. The now heated air passes through the radiator. The radiator cannot cool the engine adequately with the addition of hot air.
Your solution is a remote fan cooled condenser, possibly under the box
I had a cooling problem with my V8 Diesel powered R120. I moved the transmission oil cooler and AC condenser under the box. Both were electric fan cooled.
Problem 100% solved.
I would rather have tools I do not need than to need tools I do not have
Opportunity is missed by most people because it is dressed in overalls and looks like work.
Thomas A. Edison
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Golden Jubilee
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Post Wed Apr 28, 2021 12:36 pm

Re: Electric A/C

Nikki spelled it out clearly. The only thing I would add is that the additional fan may require you to upsize your alternator depending on how close the total load is to it's capacity

Dean
Lifelong Kansan
Grew up with red paint
Moved off the farm 30 years ago.

Golden Jubilee
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Post Wed Apr 28, 2021 1:17 pm

Re: Electric A/C

I built some air deflectors to help move the road blast air through the under-box coolers. I thought it was important to have the scoops/deflectors force the air up rather than fighting the natural tendency of heated air to rise. The deflectors added an additional protection from rocks and debris.
The cooling fans ran only when they were needed. The transmission oil cooler was controlled by KAISER in-line sensor. The Ford C6 automatic behind the 6.9 Diesel produced lots of heat when working hard. I remember the fan running continuously on the Coquahalla, AKA, Highway through hell, on my way to Merritt, BC from Hope.
The standard VINTAGE AIR fan controls were used for the additional fan on the AC condensor. I bought and used two computer 12 volt cooling fans at an electronics shop.
Alternator performance and longevity depend on good cooling. I had a good air supply at the front of the "R" to help cool the alternator. Tis is a situation where size matters as much as cooling.
Attachments
ATF oil cooler.jpg
ATF cooler with a Bosch/Mercedes fan
ATF oil cooler 2.jpg
ATF cooler
R120 6.9.jpg
Big engine small space. A cooling challenge
I would rather have tools I do not need than to need tools I do not have
Opportunity is missed by most people because it is dressed in overalls and looks like work.
Thomas A. Edison

Golden Jubilee
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Post Wed Apr 28, 2021 2:37 pm

Re: Electric A/C

Does your system use a Sanderson unit?
I saw this on the road once.
Attachments
HOT OUT.jpg

Golden Jubilee
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Post Wed Apr 28, 2021 2:45 pm

Re: Electric A/C

That picture has no information. What is it? The compressor should not make any difference.
I would rather have tools I do not need than to need tools I do not have
Opportunity is missed by most people because it is dressed in overalls and looks like work.
Thomas A. Edison

Golden Jubilee
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Post Wed Apr 28, 2021 3:54 pm

Re: Electric A/C

I believe the electric's like the Nissan Leaf, use the traction battery and a VFD inverter to run the sealed compressor on 3 phase power, the compressor speed can then be matched to the heat load. No excess compressing of the gas an no storing as high pressure liquid. It reduces the power required to the minimum.
All of this make adapting to an old truck a non-starter.
I think what Kevin was refering to was a window A/C unit cut into the rear of the truck cab. May be he ment "Sanford and Son"
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Golden Jubilee
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Post Thu Apr 29, 2021 7:11 am

Re: Electric A/C

Well, that went in a direction I wasn’t expecting. But, there are some very valuable suggestions given. My condenser is in fact mounted in front of the radiator and certainly could be contributing to the problem. Running the compressor by an electric motor wouldn’t change that and the heating condition would still be present. I will look into relocating the condenser and adding another fan. There already is a cooling fan mounted on the engine side of the radiator. I have long believed that the engine bay of these trucks was designed with the heat load from the inline 6. Therefor, when a hotter, bigger engine is installed, there is less available cooling air moving through the compartment unless other provisions for ventilation are made. I now know I should have added louvers in the inner fender panels during the rebuild to help alleviate this deficiency. To do that now would make a mess of the panels and the paint unless I do a major disassembly and some paint matching. But, back to the issue at hand. Thanks for the suggestions and advice. When I have completed the relocation, I’ll report back on the findings.
(....and the window unit mounted to the rear windows is for sure not an option. No matter how effective it is! But I have seen that solution before.)
L110 owner since 1974, finally rebuilt 2014.

Golden Jubilee
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Post Thu Apr 29, 2021 7:48 am

Re: Electric A/C

An engine at full load only needs to drop the coolant temp 10-15 degs across the radiator to keep the engine cool. If it can't do that, it will overheat. Sounds hard to believe but I have found that figure from more than one source.
Cooling consist of air flow, coolant flow and surface area of the radiator. Assuming the block is clean of rust build up, you can increase coolant flow by changing the drive pulley on the waterpump. This is not generally required as the engine designer sets this. So the next area of flow coolant is the radiator, you can increase the number of passages (tubes) and dimple them to keep the flow rate to where there is enough time to transfer heat.
Radiators need a good thermal bond between fin and tube to transfer heat to the air.
If you have a stuffed full engine bay, it can be hard to get enough air out to bring more in, you end up with somethin akin to pushing a slab of plywood thru the air and cooling suffers. If all the air is contained by inner fenders, and has to be forced under the cab, it not only makes the cab hot, but can limit the air flow. Cutting "vents" in the inner fenders can help.
electric fans:
Vehicles that use electric fans generally have larger radiators than the same engine used with an engine driven fan. Electrics usually have one speed, and can't move more air as the heatload increases with engine speed. They also can't be ducted like a large engine driven fan to draw air over the whole core, they can work well for condenser cooling.
I've found in my heavy trucks, there is no replacement for surface area when it comes to cooling. If the radiator is margial at best in size it will continue to have cooling problems
There is nothing like pulling over the Big Horn Mts in summer with a full load, 45 min of full throttle operation at speeds under 25 mph, to show you if you have cooling problems! BTDT!

Rookie
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Post Thu Apr 29, 2021 9:47 am

Re: Electric A/C

Seems like most of the important stuff has been covered, but I'll throw a few tidbits in from my personal experience . .

First, the electric A/C compressor on hybrid vehicles is part of the High Voltage system, and requires the presence of the HV battery and charging components to operate successfully. So while a good thought, is an impractical upfit. Obviously there are 120v compressors, and ways to operate them in a 12v environment, but as explained the heat load at the condenser doesn't change in any event.

Second, electric cooling fans can be a black hole of their own. In my experience none of the aftermarket fans can generate airflow approaching that of OEM units. Numerous times I have solved overheating problems on modified vehicles by discarding aftermarket "high capacity" electric fans and replacing them with 1 or 2 OEM type units. I have found 2 fans sourced from front wheel dive applications usually do the trick, and allow flexibility on installation configuration, while obtaining the required near 100% coverage of the cooling package (radiator, condenser, and other coolers in the stack) with the shrouds. Having the correct available voltage and current at the fan is also vital.

And last - airflow through the cooling package without the fans is also vital. Baffling around the cooling package to insure that air is not by-passing the coolers is important, especially with high capacity (dense) heat exchangers. As mentioned, once you get the air through the cooling package it has to be able to exit the engine compartment. Cutting the inner fenders shouldn't be necessary - a quick look at any modern vehicle will demonstrate that - but something often overlooked is the main purpose of the "spoilers" that hang down below the front bumper. Most people think these are there to aide vehicle handling by reducing airflow under the car and subsequent lift - which they may - but the main reason they have become so ubiquitous is that by diverting airflow from under the car they allow the airflow through the cooling package to exit out the bottom of the engine compartment. If you take a look under your modern pickup truck you'll find that the spoiler is typically mounted pretty close to right under the cooling package - this creates a low pressure area behind and below the cooling package for the hot air to flow into. I know you thought it was there so your F250 could track like NASCAR, but sadly not . . .

Gregg
Professional automotive tech, Volunteer firefighter.

1956 S-120 4wd pick-up
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