AC Condensors (r134a) and Radiators - Who is better? DMCH or Hervey?

[stevedmc]

In a few days 16510 will be getting some insurance work done and I suspect it will need a new AC condensor, radiator, and probably some other things.

Hervey likes to brag about his stuff being better. His website says his condensors are able to handle the higher pressure of r134a. I believe the DMCH unit is just new old stock. I used a DMCH condensor last year and I was able to get ~43 degrees with r134a at highway speeds and about 60 degrees when idling. Does anyone have any experience with Hervey's condensor?

The raditor I currently have is an aluminum from DMCH. If you have been following my $500 repair thread you will see I have had all sorts of problems getting this aluminum radiator repaired after an accident. Hervey brags about his radiators being copper/brass. I think this would be easier to get repaired should I ever have problems down the road. Does anyone have an opinion on this?

Also, in addition to needing a radiator, there are some parts on the fan mount that are cracked and I noticed a hairline crack on one of the fan fins. I am going to try getting my insurance company to replace the radiator along with fans and the mount. Hervey has this available as one unit for $499. I believe his fans are low amerage and the fan shroud is made of metal instead of the fiberglass/plastic stuff DMCH is using.


I really do prefer dealing with DMCMW because I know they can get me stuff fast, and they are super professional, but in this instance I think I want to see if the repair shop will get the parts from Hervey. Does anyone have any thoughts on this?

These components from him look really good. I guess my biggest fear is it might take him a week just to ship the stuff.

[jawn101]

I have Hervey's fans and am very happy with them. The mount is metal, the fit is excellent. They are quiet, very low draw and move a lot of air. I have heard excellent things about DPNW's fans as well but in the end I got Hervey's.

My two complaints would be:
- The blades are white, not black But you cannot see them unless you're under the car.
- The fans do not have electrical connectors on them when they arrive. Bare wires. You have to either cut the connector off your stock fans or cut and splice into the harness. I chose to cut the connectors off the stock fans and reuse them after a good cleaning to avoid modifying or hardwiring into the harness.

No experience with the rad or condenser though, sorry.

[dmc6960]

There is nothing wrong with a NOS condenser. It will handle the pressures just fine. If I knew what I know now about AC condensers when I replaced mine, and the only options were Hervey or DMC, I would have done the DMC NOS one.

Yes, I do have Hervey's condenser, and yes it works good for me. My experience with him during my AC rebuild was less than ideal and I've never done business with him since.

Also, from a thermal physics standpoint, the "Serpentine" NOS condenser has a higher efficiency than the "Tube and Fin" condenser Hervey sells. Only issue I have with the NOS condensers is that they are painted black. The black paint acts as an insulation barrier to the heat transfer between the aluminum and air. Hervey's tube and fin condenser is not painted. Without a scientific study though there is no way to determine what the total affect of the paint is compared to the bare aluminum tube and fin.

For ultimate r134a performance, a "Parallel Flow" condenser is required. To my knowledge no DeLorean vender sells one. I have yet to size up the largest one which will fit and perform the necessary modifications to mount on the radiator. So from your current situation, this will not work for you.

When it comes to fans, get Toby's at DMCNW. He's just as good as Dave S, so no worries there. What I think many people done realize, is that AIRFLOW is MORE IMPORTANT than having less current draw. While any modern replacement fan will draw less current than the originals (and Toby's are still a good deal less), your goal should NOT be the lowest current. Physics also dictates you need power to move air. Reduce that power too much and no matter what your motor or blade design is, it will not move as much air. Toby's fans are black, and have a shroud or fit in the original one (my 2006 versions have no shroud, another upgrade I will be doing if I switch out my condenser for a parallel flow).

With regards to radiators, the brass/copper ones are more thermally efficient, but the aluminum ones have more surface area. This results in both models being about equally capable.

[Bitsyncmaster]

For ultimate r134a performance, a "Parallel Flow" condenser is required. To my knowledge no DeLorean vender sells one. I have yet to size up the largest one which will fit and perform the necessary modifications to mount on the radiator. So from your current situation, this will not work for you.

That's what I have read also. But you can not flush the parallel flow type if that matters.

[stevedmc]

I wonder if Dave at DMCMW stocks Toby's fans. I really would like to just get everything from one place.

[LEVY]

Actually, it is the other way around, black paint will help to dissipate heat better than bare metal.

LEVY





There is nothing wrong with a NOS condenser. ............

...........Also, from a thermal physics standpoint, the "Serpentine" NOS condenser has a higher efficiency than the "Tube and Fin" condenser Hervey sells. Only issue I have with the NOS condensers is that they are painted black. The black paint acts as an insulation barrier to the heat transfer between the aluminum and air.............

With regards to radiators, the brass/copper ones are more thermally efficient, but the aluminum ones have more surface area. This results in both models being about equally capable.

[dmc6960]

Are you sure about that? In this application we are looking to most effectively transfer heat from the condenser to the air. I still believe the paint would act as a small insulator in this situation. I would be happy to change my opinion with some scientific data though!

[Bitsyncmaster]

Are you sure about that? In this application we are looking to most effectively transfer heat from the condenser to the air. I still believe the paint would act as a small insulator in this situation. I would be happy to change my opinion with some scientific data though!

I think a very thin black coat of paint would improve the heat transfer. The best way would be to anodize the metal black. It use to be all heat sinks were black anodized for that reason.

[rddmc]

I have been running John's radiator/fans combo for several years and I am very pleased with it. The heat gauge stays on the first line or just slightly above it. I find that it does take the gauge longer to get there than it did before. I bought John's combo before Toby's current system was available. From all that I have heard Toby's system works fine also.

Rod
10921

[LEVY]

Yes, I'm sure.

As long as there is not direct sunlight, black will dissipate better than any other color.

I believe you can even buy special radiator black paint!

LEVY



Are you sure about that? In this application we are looking to most effectively transfer heat from the condenser to the air. I still believe the paint would act as a small insulator in this situation. I would be happy to change my opinion with some scientific data though!

[justlooking]

I had bought John's condenser. It didn't look anything like the one on the website, and I would have had to drill holes in it to mount it on the radiator. It was returned thereafter.

I bought a DMCMW unit and haven't looked back.

[dmc6960]

Well I just spent the whole evening reading up on black bodies. Seems to be a lot of arguments over how well black paint will increase the emmisivity of a radiator/condenser VS acting as an insulator.

In a nutshell, black anodizing is probably best. Alternatively the specialized paints will work, but there are many primers which must be avoided as they will reverse the affects. Finally the paint must be as thin as possible to fully coat the metal, as anything too thick will start acting as an insulator.

I take back my statements about the painted condenser, assuming the factory painted it propery for emission in the first place.

I wouldn't trust a generic shop who just up and painted a bare unit. And when I get my own parallel flow condenser, I may consider getting a bare aluminum one and having it anodized.

Oh, and in addition... Everything I've read also makes me want to have my oil pan anodized. Other stage II or turbo users would think the same. Our oil pan is already a great heatsink with its design, we should make it conduct like one as well.

Well I wasn't done reading yet, and now I don't know what to think. In my initial reading I noted one comment about the difference between a forced-air radiator (like automotive ones) and free standing radiators (like passive room heating). I found this gem of information on a pretty definitive source....


There are two ways heat is transferred from the radiator to you and the room: radiation and convection. Convection is due to air flowing over the radiator surface, heating up the air as it does. Radiation is heat transferred directly from the surface of the radiator to you and other surfaces of the room, without heating the air.

Color and surface finish affect the performance of radiators by affecting how well heat is transferred by radiation. Convection is not affected by color, provided the surface temperature is unchanged, which should be the case. How well a surface radiates is quantified by its emissivity. The higher the emissivity, the greater the heat transfer by radiation.

Undoubtedly automotive radiators work off of convection, not radiation. Kinda makes their name a misnomer eh?

At this point the only definitive answer may be a controlled test between two identical radiators. I may just obtain two small units myself, paint one of them, and conduct the test myself. I wouldn't do this until later this year though. Not anytime soon.

[stevedmc]

Thanks for the advice everyone. I guess I'm just going to tell the guy at the shop to call up Dave at DMCMW. I'll try to figure out how to get upgraded fans if Dave doesn't stock them.

[David T]

Paint is a coating and it will act as an insulator reducing heat transfer. Anodizing is basically an oxidized coating to prevent further corrosion. Paint does the same thing, preventing corrosion, it just insulates more. The goal here is to reduce or prevent corrosion which can greatly reduce heat transfer. You really don't need to paint a brass/copper radiator but an aluminum one needs to be anodized. You cannot "improve" heat transfer by painting. you do not get a lot of heat transfer by emissivity. Do not confuse a radiator with a "black body". You are trying to transfer the heat of the coolant to the metal of the radiator and then to the air forced between the parts of the radiator. Anything that "gets in the way" like paint or corrosion, will only reduce the efficiency of the process. That goes for corrosion deposits inside the radiator as well. Repairing an aluminum radiator is difficult-to-impossible. Repairing a brass/copper radiator is done all the time. BTW, the fans only are important at low speeds or when standing still. Over around 30 MPH and they are not very important.
David Teitelbaum

[Henrik]

Not to change the topic too much, but when I converted to R134a five years ago (and I had just purchased the car) I was amazed to find that it didn't have a High Pressure Cut-Out Switch or a Pressure Releif Valve. The HPCOS of course is the first line of defense - turns off the compressor in case of an over-charge, a fan failure, etc - whereas the PRV blows a portion of the charge if all else fails. Both were relatively simple additions and are a must on every A/C application.

[jawn101]

Not to change the topic too much, but when I converted to R134a five years ago (and I had just purchased the car) I was amazed to find that it didn't have a High Pressure Cut-Out Switch or a Pressure Releif Valve. The HPCOS of course is the first line of defense - turns off the compressor in case of an over-charge, a fan failure, etc - whereas the PRV blows a portion of the charge if all else fails. Both were relatively simple additions and are a must on every A/C application.

Yeah, early VINs didn't have a relief valve at the accumulator. Mine didn't and still doesn't because I didn't realize it was a consideration when I put the system together. I frequently worry about that oversight.

[David T]

The early cars have a high side cut off. The low side cut off will also act if the pressure gets too high. It opens if the pressure is too low (low refrigerant or frozen evap coil) OR too high, high head pressures from a blockage, air or an overcharge. (It's called a binary switch). I agree there should have been a high pressure relief AND a HP cut-off on all cars. As is done with many car manufacturers, they cheat and "cheap out" by skimping on things. There could also be service valves so you can lock the refrigerant into the condenser and accumulator for service. There could have been valving so they didn't have to cycle the compressor to prevent the evap coil from freezing. Point is there are many things DMC could have done. But each additional thing would have made the car cost more. The car was designed and built to a certain price-point and that dictated many engineering compromises.
David Teitelbaum

[LEVY]

I would disagree on this one but, you are the expert.

Note: If done properly!

LEVY



Paint is a coating and it will act as an insulator reducing heat transfer. Anodizing is basically an oxidized coating to prevent further corrosion. Paint does the same thing, preventing corrosion, it just insulates more. The goal here is to reduce or prevent corrosion which can greatly reduce heat transfer. You really don't need to paint a brass/copper radiator but an aluminum one needs to be anodized. You cannot "improve" heat transfer by painting. you do not get a lot of heat transfer by emissivity. Do not confuse a radiator with a "black body". You are trying to transfer the heat of the coolant to the metal of the radiator and then to the air forced between the parts of the radiator. Anything that "gets in the way" like paint or corrosion, will only reduce the efficiency of the process. That goes for corrosion deposits inside the radiator as well. Repairing an aluminum radiator is difficult-to-impossible. Repairing a brass/copper radiator is done all the time. BTW, the fans only are important at low speeds or when standing still. Over around 30 MPH and they are not very important.
David Teitelbaum

[Henrik]

The early cars have a high side cut off.

Mine didn't.


The low side cut off will also act if the pressure gets too high. It opens if the pressure is too low (low refrigerant or frozen evap coil) OR too high, high head pressures from a blockage, air or an overcharge. (It's called a binary switch).David Teitelbaum

I have never seen a binary pressure switch on the low side. The binary ones I have seen and worked with over the years were on the high side: High side, high pressure cut-out due to high head pressures and high side, low pressure cut-out to keep the compressor from turning on in cold ambient temperatures (if it did, it would be fast-cycling on the low side, low pressure switch; this would be bad for the clutch and the compressor (poor oil return)) and of course low charge.

All switches have an open/close setting but that does not make it a binary switch.

[Henrik]

The low side cut off will also act if the pressure gets too high. It opens if the pressure is too low (low refrigerant or frozen evap coil) OR too high, high head pressures from a blockage, air or an overcharge. (It's called a binary switch).
David Teitelbaum

Look at this way: Let's say your low side binary switch is set to cut out at 80 psig high pressure (believe me, no A/C system ever runs at this high of a suction pressure, but still) because of a high pressure situation on the high side. But, with the A/C system at rest it is already at 100-150 psig under normal conditions, so this means that the compressor would never even turn on.

If you set the low side binary switch to cut out at a higher pressure, the high side would have already exploded before it triggered. If you set it at a lower pressure the A/C would never, ever turn on.

Binary switches only work on the high pressure side of the A/C system.

[Farrar]

The early cars have a high side cut off.

Mine did not, and I got a blown hose as proof.

[sean]

Mine did not, and I got a blown hose as proof.

POs are great :D

[Henrik]

POs are great :D

Did Farrar buy his D from Sean, by any chance....:shhh:

[sean]

Did Farrar buy his D from Sean, by any chance....:shhh:

Oh no, I've just had to deal with many of the PO issues. I was just assuming Farrar had a PO issue.

[Morpheus]

Getting this thread back on topic....

I'm faced with having to purchase a new radiator, condenser, and all new A/C hoses for my rebuild project. I have decided to switch over to 134A since im swapping out the whole system anyway...

Obviously, i will be going with JH's newer barrier hoses (one piece) in this situation.

My question is this: Which radiator/condenser combination would be the best choice?

[stevedmc]

Obviously, i will be going with JH's newer barrier hoses (one piece) in this situation.

My question is this: Which radiator/condenser combination would be the best choice?

If I ever change out my hoses I am going to go with Hervey's split hose.

But based on what everyone has said in this thread, and my previous experience, I am planning to go with a DMCH radiator/condensor ordered from DMCMW. Dave and Julie are the best, I just wasn't sure the Houston parts would be the best. From what I gathered on this thread (and the fact that the parts worked for me before) it sounds like the Houston stuff will be fine or maybe even better than what Hervey is selling.

[Cory W]

I converted over two seasons ago. After my compressor seized, and the amount of black gunk I found in the system, I chose to replace everything.

As I've mentioned elsewhere, in Canada R12 is guarded by Unicorns, so R134A was the way to go.

My compressor is some generic Chinese R134A unit, bought off eBay when I was still figuring out how far I was going to go.
My hoses (all three) and evaporator are from JH.
My condenser is from DMCH (Midwest)...at the same time I replaced my original radiator with a brass unit (the last one Dave and Julee had, apparently)

As an aside, my fans are from Toby and Misty, done after the fact. I cannot say enough GOOD about them and their product. I can say plenty about changing the fans at the same time as you do all of this if you have any thought of doing so (why dismantle some of it just to change your fans when you can do it all at once?)

My car stays cool to the point I rarely turn the fan speed above 2, and never seems to have a problem keeping up.

That's my experience. YMMV, but I suspect you'll have no issues following that path.

[Morpheus]

I converted over two seasons ago. After my compressor seized, and the amount of black gunk I found in the system, I chose to replace everything.

As I've mentioned elsewhere, in Canada R12 is guarded by Unicorns, so R134A was the way to go.

My compressor is some generic Chinese R134A unit, bought off eBay when I was still figuring out how far I was going to go.
My hoses (all three) and evaporator are from JH.
My condenser is from DMCH (Midwest)...at the same time I replaced my original radiator with a brass unit (the last one Dave and Julee had, apparently)

As an aside, my fans are from Toby and Misty, done after the fact. I cannot say enough GOOD about them and their product. I can say plenty about changing the fans at the same time as you do all of this if you have any thought of doing so (why dismantle some of it just to change your fans when you can do it all at once?)

My car stays cool to the point I rarely turn the fan speed above 2, and never seems to have a problem keeping up.

That's my experience. YMMV, but I suspect you'll have no issues following that path.

I completely agree on the fans, I had an earlier version of their "wings be cool" fans and loved them. I will definitely be going that route again.

Do you think it makes a difference to have either an aluminum versus a brass radiator?

[Farrar]

An interesting read on the subject (http://www.hotrodhotline.com/md/html/aluminum_vs_copper.php) contains this info:


While all radiator cores might look the same they perform differently based on tube spacing and fins per inch. Heat transfer points where temperature is actually allowed to leave the radiator are where the fin is bonded to the tube. The more transfer points, the greater the temperature drop. A 60’s core for example had a 1/2” tube spacing (ie, 1/2” fin between the tubes) and by going from a two row radiator to a four row core design they were able to double the heat transfer points which resulted in a 15-20% increase in temperature drop without changing the other variables (air flow, coolant flow). ... By changing the tube spacing to 3/8", a design referred to as High Efficiency in the industry, more tubes or water passages and fins were allowed across the face of a core with a specific width in inches. The design was simple enough but proved to be very efficient in that more heat transfer points created greater temperature drop inlet to outlet. At this point the move to aluminum construction was purely financial in that raw materials are purchased “by the pound” and a finished aluminum radiator weighs about 25% of a copper/brass unit ..."

I'd pick aluminum just because it's lighter. But that's just me.

[jawn101]

An interesting read on the subject (http://www.hotrodhotline.com/md/html/aluminum_vs_copper.php) contains this info:



I'd pick aluminum just because it's lighter. But that's just me.

I have no dog in this fight - not right now anyway. But this thread will be important to all owners at some point so I thought I'd bring up the troubles that Steve has had recently with his aluminum radiator being repaired. It might be worth finding out if the problem with the leaks coming back time and time again was due to the increased difficulty of welding aluminum vs copper/brass?

[DMCMW Dave]

Interesting discussion.

All radiators were brass for the longest time. Brass is a good heat conductor, can be easily soldered, but is expensive. And relatively heavy, not really an issue until the 80s when fuel economy got to be a big deal.

The first "enhancement" which start making repairs difficult were the plastic side tanks. The plastic tanks can be removed and replaced with brass tanks, but that costs about as much as the whole radiator, then you have a used radiator with new tanks.

Most modern cars are now using aluminum radiators with plastic tanks. Light, cheap, and disposable. Aluminum is difficult to weld, especially this thin, so you don't often see them repaired. And you still have the plastic tank issue. Look around your town, you rarely see a radiator shop any more. This is why.

The radiator we sell is all aluminum, no plastic tanks. This is most likely due to the low volume production compared to other cars, it is a custom radiator and making a plastic mold for the side tanks would not have worked out well. The competitive brass radiator is a bit heavier and thicker so the fit is a bit tighter. Price is about the same.

I believe the cooling capacity is the same, I don't think "2-row" vs "3-row" means anything, what is important is surface area and fin tube density. One wide row can have as much or more area as two skinny rows, so without knowing the measurements it's a pretty irrelevant factor.

[stevedmc]

Aluminum is difficult to weld, especially this thin, so you don't often see them repaired.

Amen.

[rddmc]

Speaking of weight, when I replaced the OEM radiator, the OEM Smith(I think) fans and OEM fan cowling, with John's radiator/fans combo unit, John's system weighed one pound more.

Rod
10921

[Cory W]

I completely agree on the fans, I had an earlier version of their "wings be cool" fans and loved them. I will definitely be going that route again.

Do you think it makes a difference to have either an aluminum versus a brass radiator?

I honestly don't know which one would be "better". We're not running drag racers or anything, and I suspect they are both similar enough in heat dissipation to make performance differences irrelevant in this application. You live in a warmer climate than I do; if the original radiator worked well enough on your previous car, I can't see a new brass rad letting you down.

I like my radiator, as well as the idea of not having to order a replacement simply because of an impact. I still have a local rad shop that could repair or recore my rad if it ever became necessary.

Since you'll be ordering from both vendors from the looks of it for this project, I'd go with whomever you choose, using whatever criteria you wish.

[David T]

The car manufacturers switched to aluminum for several reasons. Since the radiator isn't repairable anymore they will sell more replacement radiators. With the price of copper and brass going way up, aluminum is cheaper. With the plastic tanks the aluminum radiator is lighter and reducing weight is the easiest and cheapest way to improve performance and gas mileage.
David Teitelbaum

[stevedmc]

TWith the plastic tanks the aluminum radiator is lighter and reducing weight is the easiest and cheapest way to improve performance and gas mileage.

I always laugh about people reducing vehicle weight in order to increase performance. The easiest way to reduce the weight of the vehicle is to simply quit visiting the McDonalds drive through.

[David T]

Hot-Rodders used to use as a rule-of-thumb, for every 10 lbs you can remove you add 1 HP. The great news is, it is one of the cheapest ways to improve performance. I agree but reducing driver weight is a lot harder though and can take a while. At least empty your pockets! This is one reason why I say you have to be careful about going overboard on using Dynamat or any such product. Yes, they do make the car quieter but there is a cost. The other low cost way to improve performance and gas mileage is to regularly check the air pressure in the tires. Finally, go through the car and remove any junk that you do not need.
David Teitelbaum

[Farrar]

hot-rodders used to use as a rule-of-thumb, for every 10 lbs you can remove you add 1 hp.



9188

[stevedmc]

9188

Thats just awesome.

[David T]

I remember "Back in the Day" we would pull the heater (and the A/C if it had it) the radio, the back seat, the interior trim, glass, and anything else that wasn't essential (like the hood, bumpers, spare tire). Barely street legal! Headers, small battery, no power steering (maybe just take the belt off) no air cleaner. Anything to lighten the car.
David Teitelbaum

[stevedmc]

Wasn't there a silly movie called called "Need for Speed" where they removed radiators from Honda Civics to save weight.

I never saw the movie and might even have the title wrong, but I believe there was some sort of movie that caused a Honda Civic fad about 10 years ago.

[DMCMW Dave]

I sort of recall a certain splotchy green/black DeLorean where the owner removed those nasty heavy cooling fans to save weight.

[stevedmc]

I sort of recall a certain splotchy green/black DeLorean where the owner removed those nasty heavy cooling fans to save weight.

What did he do about sitting in traffic? The fans don't always work on my Geo Metro and usually I have to shut my engine off when sitting in traffic. I'm too cheap to replace them on the Metro.

[dmc6960]

What did he do about sitting in traffic? The fans don't always work on my Geo Metro and usually I have to shut my engine off when sitting in traffic. I'm too cheap to replace them on the Metro.

He only street-raced the car at night so of course they weren't necessary!

Duh!!!!!