# EV200 questions



## pYr0rAGE (Feb 21, 2012)

Hello all

I am new to designing high power circuits, and recently ordered an EV200 contactor without an economizer. Now, after attempting to install it, I managed to blow it up. I figure it was a combination of the following factors:

1) Not having any kind of economizer circuitry in place
2) Running the coil off of 18.5V instead of 12V

Now, touching the coil terminals reads an open circuit. I figure that by running it at too high of a power, the coil drew too much power and fried itself (although, right after the incident, the case didn't feel particularly warm...)

So, here's my question to the board: I am going to try again with this relay. It is the same as the one I was using before, but it has an economizer built in. Now, in order to prevent me from blowing it up again, here are some precautions I am going to take:

1) Set up a voltage divider circuit to reduce the voltage at the + side of the coil to 12V
2) Measure the resistance of the wires through the coil and find out how much power the wires will draw at inrush. It if looks too high, reduce the voltage further.

My questions to the board are...

1) Did the relay blow up for the reason I think it did (too much power dropped across the coils)?
2) Are the steps I'm taking above necessary?
3) Is there something I'm leaving out that would cause the coil to blow up again?

Thanks for your time!

-pYr0


----------



## Guest (Feb 21, 2012)

Why aren't you running 12 volts? Or more like 13.5 volts to power the relay coil? Why 18 volts? That is pretty high but I think they can do like 18 but that is the upper limits. Why run electronics at the upper limits? You are asking for trouble. I would not want to give it more than like 15 volts max. Do you have it fused?

Get a good DC to DC converter and one that will output like 13.6 or 13.8 volts and just use that. I have a bunch of those and never have put more than 15 volts to them. 

Pete


----------



## pYr0rAGE (Feb 21, 2012)

Well, here is the thing: the module that this part is being used on runs off of an 18.5V lipo battery (which really gives off around 21V when fully charged), so there isn't really a 12V or 13V rail. (Note: sorry about being extremely vague about the application, but I can't quite tell *what* this part is being used in just yet)

The linked datasheet for the EV200AAANA says that a part with this code, specifically the "A" in the 2nd slot, has a coil that can handle 9-36V. If that's true, then 20V is nowhere near the upper limit. I'm honestly not sure where Digikey got the 12v from. In any case, wouldn't creating a voltage divider circuit with power resistors create a virtually identical case as with the 12v rail? 

Technically, we have the coil fused, but it's connected to a 150amp circuit breaker, so effectively no. What size fuse would you recommend?


Oh, and thanks for the quick response!


----------



## piotrsko (Dec 9, 2007)

some rip-offs of these are chinese and if purchased really cheap aren't worth the price. they look the same but won't handle specs.

instead of resistors, 12vdc shunt regulators come in a 3 pin TO-72 case and stack for currents.


----------



## pYr0rAGE (Feb 21, 2012)

I purchased from digikey both times. Usually they don't sell rip-offs? How would I tell the difference between a rip-off and a genuine part?

I still don't quite understand why the digikey specs page rates the coil for 12V but the data sheet rates it for 36, or which one to believe.

Thanks for the quick responses, guys. 
-pYr0


----------



## frodus (Apr 12, 2008)

Why did the first EV200 NOT have an economizer? Are you sure it wasn't a 12V LEV200? That is the same style, but without economizer. I've never heard of an EV200 without economizer option.

The EV200 indeed does work 9-36VDC, so using it in that range is just fine, but the economizer SHOULD REMAIN CONNECTED, DO NOT REMOVE IT.

It sounds like you ordered one thing, got something else, and ran it over it's ratings. That or you ordered the wrong one and ran it over it's ratings. A real EV200 with economizer will work in your range without doing some voltage divider or some other crap.

It you did indeed get an EV200 with 9-36VDC economizer, use it with the economizer.

here's the PDF
http://relays.te.com/datasheets/ev200.pdf

Digikey should list it as 9-36VDC


----------



## pYr0rAGE (Feb 21, 2012)

Digikey did have an option that was exactly the same as the solenoid linked, but without the economizer. It's part number had "A1" in the "A" slot. At the time, we figured that it was $50 cheaper, and couldn't figure out what exactly the economizer did, so we went cheap. Obviously, that wasn't the best idea 

But this one should work without any additional coil protection circuitry?


----------



## frodus (Apr 12, 2008)

They sell it without, but it still requires an external economizer. These are so that the customer (usually an OEM) can design and build their own circuit. There are some application notes at Tyco. It still requires one and the Close volts is 9V and the hold is 7.5V. You were giving it twice the voltage. 

your EV200AAANA will work from 9-36VDC, as it has the economizer built in.


----------



## JRP3 (Mar 7, 2008)

I'm having an issue with my EV200AAANA economizer circuit. Hooked up to 12 volts, either directly to a battery, or in the vehicle with a DC/DC at 13.4V, the economizer gets really hot, specifically one little chip gets hot and starts smoking the coating if I leave it on for a minute or so. No other wiring is getting warm, I had it wired to the same circuit as my 12V water pump for the heater so they come on at the same time.
Waazzup?

Chip on the upper right is the smoker:


----------



## JRP3 (Mar 7, 2008)

Another data point, might be relevant, at one time I tried to use this contactor with my HEPV's system which PWMs the contactor voltage. It didn't work so I took it out, but could that have damaged the economizer? Can I get another economizer to fix it?


----------



## frodus (Apr 12, 2008)

That's the problem, I think PWM'ing these damages them. Not sure what needs to be replaced. Maybe contact Tyco directly and see if they have replacement boards.


----------



## swoozle (Nov 13, 2011)

I see mention of non-genuine knockoffs of these on occasion. I bought a couple off of ebay. Are there telltale signs to look for to know if one has the real thing?


----------



## JRP3 (Mar 7, 2008)

In case anyone is interested I'm running it without the economizer and it's drawing about 3.5 amps to hold, as opposed to the supposed 1.7 watts the specs claim with the economizer. That little economizer does make a big difference, though even 3.5 amps at 12V won't really impact my pack.


----------



## major (Apr 4, 2008)

JRP3 said:


> In case anyone is interested I'm running it without the economizer and it's drawing about 3.5 amps to hold, as opposed to the supposed 1.7 watts the specs claim with the economizer. That little economizer does make a big difference, though even 3.5 amps at 12V won't really impact my pack.


Hi JR,

Will the coil overheat at that 3.5A? Have you run it for a long period?

major


----------



## frodus (Apr 12, 2008)

JRP3 said:


> In case anyone is interested I'm running it without the economizer and it's drawing about 3.5 amps to hold, as opposed to the supposed 1.7 watts the specs claim with the economizer. That little economizer does make a big difference, though even 3.5 amps at 12V won't really impact my pack.


What voltage?


----------



## JRP3 (Mar 7, 2008)

major said:


> Hi JR,
> 
> Will the coil overheat at that 3.5A? Have you run it for a long period?
> 
> major


Yes it will   I wouldn't think so at 3.5A but after running it for about 10 minutes it's warmer to the touch than I would expect, while my main pack contactor running much higher current is cooler. So that economizer is a necessity for this contactor.


----------



## JRP3 (Mar 7, 2008)

frodus said:


> What voltage?


My pack voltage is 115V, the heater pulls about 13.5 amps from the pack.


----------



## major (Apr 4, 2008)

JRP3 said:


> Yes it will   I wouldn't think so at 3.5A but after running it for about 10 minutes it's warmer to the touch than I would expect, while my main pack contactor running much higher current is cooler. So that economizer is a necessity for this contactor.


I thought that might be the case. So it will probably hold at lower coil current. Lee Hart had posted some interesting circuits to reduce coil voltage after pulling it in. Maybe a simple 2 or 3 component circuit could make it useful.


----------



## frodus (Apr 12, 2008)

I meant what voltage are you running to the coil, not contact voltage.

I see you're using 12V, but that's above the non-economizer pull in voltage of 9V and hold voltage of 6V.


----------



## JRP3 (Mar 7, 2008)

OK why is the higher voltage, which I would think would take lower current, causing more heating?  It's actually getting 13.4V from the DC/DC.


----------



## major (Apr 4, 2008)

JRP3 said:


> OK why is the higher voltage, which I would think would take lower current, causing more heating?  It's actually getting 13.4V from the DC/DC.


The coil is a fixed resistance. P = V²/R


----------



## frodus (Apr 12, 2008)

Exactly. You're using 13.4V and 3.5A or 46.9W, so since P = V^2/R, 46.9W = 179.56/R, R = 3.8ohm.

So at 9V, current would be I = V/R = 9V/3.8ohm and I = 2.37A and use 21.33W
And at 7.5V, current would be 1.97A and use only 14.8W.

The coil itself isn't rated for 13.4V continuous (that's only with the Economizer).


----------



## JRP3 (Mar 7, 2008)

This guy used a resistor and capacitor to make a simple economizer, about two thirds down the page: http://www.neon-john.com/EV/EV_home.htm
He used a 50 ohm resistor and a 2200 uf capacitor wired in parallel and then wired in series with the coil. I might have a 2200 uf cap lying around somewhere, if that's a reasonable value, not sure about a resistor. Of course I could always buy both


----------



## major (Apr 4, 2008)

JRP3 said:


> This guy used a resistor and capacitor to make a simple economizer, about two thirds down the page: http://www.neon-john.com/EV/EV_home.htm
> He used a 50 ohm resistor and a 2200 uf capacitor wired in parallel and then wired in series with the coil. I might have a 2200 uf cap lying around somewhere, if that's a reasonable value, not sure about a resistor. Of course I could always buy both


Hi JR,

That might work. The resistor value needs to be set to the coil resistance and holding voltage. Get out your Ohm's Law app  From memory, your source voltage was 13.4V. The hold voltage for the coil was 6V. You need to drop 7.4V in the resistor. Call it 7V. The coil resistance is 3.8Ω. At 6V, the coil current is 1.58A. I=V/R. Resistor needs to drop 7V at 1.58A or needs to be 4.4Ω. R=V/I. Double check. Circuit resistance = 3.8Ω + 4.4Ω = 8.2Ω. 13.4V / 8.2Ω = 1.63A. A little above the 1.58A, so is good.

Resistor Wattage is I²R = 1.63A² * 4.4Ω = 11.7W minimum rated.

The capacitor in parallel with the resistor will block DC or look like an open circuit once the initial surge is timed out. So it does not enter into the holding current calculation. BUT, the cap looks like a short circuit when the voltage is first applied to the circuit. So the cap will divert the initial current flow around the 4.4Ω resistor to the coil. That current will be the source voltage / coil resistance, or the 3.5A. This will bring in the contactor.

As the cap charges up it will reduce the current flowing through it until it completely blocks it. The Farad value will determine how long this takes. I'd just start with Neon's cap value and see if it works. Or get out your RC time constant app 

Regards,

major


----------



## JRP3 (Mar 7, 2008)

Thanks, that helps a lot. What I don't get is if I'm looking at a 4.4 ohm resistor how did his circuit work with a 50 ohm resistor?


----------



## major (Apr 4, 2008)

JRP3 said:


> Thanks, that helps a lot. What I don't get is if I'm looking at a 4.4 ohm resistor how did his circuit work with a 50 ohm resistor?


I didn't see where Neon said what contactor he was using. I assume different contactor parameters and maybe different supply voltage.

And using a cap may cause an arc on closing your control switch. Probably tolerable, but don't overly do the Farads.


----------



## EVfun (Mar 14, 2010)

JRP3 said:


> In case anyone is interested I'm running it without the economizer and it's drawing about 3.5 amps to hold, as opposed to the supposed 1.7 watts the specs claim with the economizer. That little economizer does make a big difference, though even 3.5 amps at 12V won't really impact my pack.


That got my attention. So the coil inside it has 3.8 ohms of resistance (from reading further down the replies) and the contactor is supposed to require 1.7 watts to hold. That would be about 2.6 volts at the coil to hold, but likely more to initially pull it in. 

2.6 volts / 3.8 ohms = 0.684 amps
0.684 amps * 2.6 volts = 1.779 watts

So the coil can see full voltage briefly to pull in but then should back off to about what it is expecting to have applied. A 12 ohm resistor in series with its power would provide 2.6 volts to the coil until the vehicles 12 volt system was pulled down to about 10.5 volts. You would need a substantial size electrolytic capacitor in parallel with the resistor to provide the slug of current to initially pull in the contactor. The resistor will be dissipating more heat than the contactor coil. I would likely choose about a 10 ohm 20 watt resistor.


----------



## major (Apr 4, 2008)

EVfun said:


> That got my attention. So the coil inside it has 3.8 ohms of resistance (from reading further down the replies) and the contactor is supposed to require 1.7 watts to hold. That would be about 2.6 volts at the coil to hold, but likely more to initially pull it in.


I was working with these numbers from Travis.



frodus said:


> I see you're using 12V, but that's above the non-economizer pull in voltage of 9V and hold voltage of 6V.


----------



## frodus (Apr 12, 2008)

Evfun, 
The contactor uses 1.7w with the economizer. jrp said it uses 3.5A at 13.4V without. The coils need 7v to hold and 9v to pull in. Its in the datasheet.


----------



## EVfun (Mar 14, 2010)

Is the coil in the units with the economizer the same as the coil in the units without the economizer? I ask because the contactor supposedly needs only 1.7 watts to hold and we know the coil resistance is 3.8 ohms. There is no way to apply 7 volts to a 3.8 ohm resistance and only consume 1.7 watts -- something isn't adding up here.


----------



## major (Apr 4, 2008)

EVfun said:


> Is the coil in the units with the economizer the same as the coil in the units without the economizer? I ask because the contactor supposedly needs only 1.7 watts to hold and we know the coil resistance is 3.8 ohms. There is no way to apply 7 volts to a 3.8 ohm resistance and only consume 1.7 watts -- something isn't adding up here.


I agree but would rather use a couple extra watts and not have it unintentionally open upon hitting a bump in the road  10 watts isn't bad if the coil doesn't overheat. I have a couple of these with the economizers off. I'll stick them on the power supply tomorrow and see.


----------



## EVfun (Mar 14, 2010)

If they are really only designed to dissipate a couple watts 10 watts might overheat the coil. Think about how hot a resistor gets killing 10 watts and then imagine it in a plastic box. The coil doesn't get any cooling from the traction pack cables (well it better not or isolation is compromised!) 

I look forward to your test results.


----------



## major (Apr 4, 2008)

EVfun said:


> If they are really only designed to dissipate a couple watts 10 watts might overheat the coil. Think about how hot a resistor gets killing 10 watts and then imagine it in a plastic box. The coil doesn't get any cooling from the traction pack cables (well it better not or isolation is compromised!)
> 
> I look forward to your test results.


Been on 6 volts for about 45 minutes. Started at 1.77 Amps and down to 1.44 A since it heated up. It is warm to touch. Hard to tell temp. I'll shoot it with IR thermometer. You can calculate copper temperature from resistance change. Gives me 77ºC, IMMIC (If My Math Is Correct).

I took it down to about 2 volts. Banged it on the bench and it held in. Pull in seems to be about 6 volts. Will hold down to less than 2 volts, maybe about 1.5V.


----------



## major (Apr 4, 2008)

major said:


> Been on 6 volts for about 45 minutes. Started at 1.77 Amps and down to 1.44 A since it heated up. It is warm to touch. Hard to tell temp. I'll shoot it with IR thermometer. You can calculate copper temperature from resistance change. Gives me 77ºC, IMMIC (If My Math Is Correct).
> 
> I took it down to about 2 volts. Banged it on the bench and it held in. Pull in seems to be about 6 volts. Will hold down to less than 2 volts, maybe about 1.5V.


At 1.5 hours, still 1.44 A, 6.0 V. IR thermometer reads hottest spot on bottom of Kilovac at 166ºF. Had been sitting upright on wooden bench. Bench top reads 75ºF.


----------



## JRP3 (Mar 7, 2008)

That seems excessively warm and might lead to premature failure. I guess 6V hold is too high. Since this is on my heater circuit it's not a disaster if the contactor doesn't hold going over a bump, so maybe I should be aiming for even lower power consumption? Did you try to keep it at 2V for a while and measure the temp?


----------



## major (Apr 4, 2008)

JRP3 said:


> That seems excessively warm and might lead to premature failure. I guess 6V hold is too high. Since this is on my heater circuit it's not a disaster if the contactor doesn't hold going over a bump, so maybe I should be aiming for even lower power consumption? Did you try to keep it at 2V for a while and measure the temp?


At 6V it appeared to stabilize at about 170ºF. I turned down the voltage. 2V results in less than the 1.7W I saw as spec for holding power. So I dialed in 2.8V. Went down to 0.73A, or about 2 watts. After about 20 or 30 minutes, it is at 2.8V, 0.75A and 135ºF. Likely will cool some more. I'll check before I leave and shut it down.* I think 3 volts would be a good number to shoot for 

Especially with you JR. You're just making heat anyway 

*edit: Looked like it settled to about 110/113ºF.


----------



## frodus (Apr 12, 2008)

Nice! Thanks for doing this Major!

I know a few people took the economizer off and tried using them with controllers like the Curtis 1238 that PWM the contactor..... which is set up for 24V (but adjustable) and at 24V avg PWM voltage, the contactor doesn't work for very long.


----------



## JRP3 (Mar 7, 2008)

major said:


> At 6V it appeared to stabilize at about 170ºF. I turned down the voltage. 2V results in less than the 1.7W I saw as spec for holding power. So I dialed in 2.8V. Went down to 0.73A, or about 2 watts. After about 20 or 30 minutes, it is at 2.8V, 0.75A and 135ºF. Likely will cool some more. I'll check before I leave and shut it down.* I think 3 volts would be a good number to shoot for
> 
> Especially with you JR. You're just making heat anyway
> 
> *edit: Looked like it settled to about 110/113ºF.


Thanks for all the work. Still seems a little on the warm side but probably acceptable since it will only see limited use, in cold weather. I did a little experimenting of my own, I had a 2200 uf 16v cap and a 47 Ω 5 watt resistor lying around so I thought I'd see what happened. It took the voltage below 1V. The contactor would close but not hold, no surprise there.


----------



## JRP3 (Mar 7, 2008)

frodus said:


> Nice! Thanks for doing this Major!
> 
> I know a few people took the economizer off and tried using them with controllers like the Curtis 1238 that PWM the contactor..... which is set up for 24V (but adjustable) and at 24V avg PWM voltage, the contactor doesn't work for very long.


Yup, I tried that too, with and without the economizer, and the 1238 didn't like either and wouldn't work. This little contactor has taken a lot of abuse in a very short amount of actual use time, pwm'd with and without the economizer, run at 13.4V with a damaged economizer that smoked, run at 13.4V without the economizer and getting warm, and now my most recent attempt at less than 1V. It's something of a contest to see if I can get this working properly before I kill it


----------



## JRP3 (Mar 7, 2008)

major said:


> That might work. The resistor value needs to be set to the coil resistance and holding voltage. Get out your Ohm's Law app  From memory, your source voltage was 13.4V. The hold voltage for the coil was 6V. You need to drop 7.4V in the resistor. Call it 7V. The coil resistance is 3.8Ω. At 6V, the coil current is 1.58A. I=V/R. Resistor needs to drop 7V at 1.58A or needs to be 4.4Ω. R=V/I. Double check. Circuit resistance = 3.8Ω + 4.4Ω = 8.2Ω. 13.4V / 8.2Ω = 1.63A. A little above the 1.58A, so is good.
> 
> Resistor Wattage is I²R = 1.63A² * 4.4Ω = 11.7W minimum rated.


Is there something possibly wrong with the math? I just tried a 10 ohm 10 watt resistor and a 1000 uf 50V cap, which gave me about 3.3 V and about .8 amps, adding another 10 ohm resistor in parallel gave me about 5.3 V and about 1.5 amps. (I don't have my exact numbers in front of me). The resistors were getting really hot, above 180F so I stopped. Contactor held fine with both setups.


----------



## major (Apr 4, 2008)

JRP3 said:


> Is there something possibly wrong with the math? I just tried a 10 ohm 10 watt resistor and a 1000 uf 50V cap, which gave me about 3.3 V and about .8 amps, adding another 10 ohm resistor in parallel gave me about 5.3 V and about 1.5 amps. (I don't have my exact numbers in front of me). The resistors were getting really hot, above 180F so I stopped. Contactor held fine with both setups.


I think the 10Ω resistor, 3.3V and 0.8A, is good. Yep, I²R for 10Ω and 0.8A is 6.4W in the resistor and it will get hot. If it is rated at 10W, it's o.k.

BTW, the kilovac with economizer hooked up to 13.4V draws 0.15A and heats up to about 98ºF* on the bottom sitting on a wooden bench which is at 78ºF today. Warm day in Ohio 

And I didn't use IMMIC. But the Ohm's Law equations are right there. Check me 

major

*edit: Settled at about 101ºF


----------



## JRP3 (Mar 7, 2008)

I guess the only thing "wrong" with the math was I had the wrong number for current  I got my notes and the actual numbers are a bit different and explain the excessive heat. Using the single resistor current was actually 1.05 amps at 3.3 V, so I²R for 10Ω and 1.05 amps is 11.025 watts, a bit over the resistor rating. Maybe I should mount the resistor in the cabin for extra heating


----------



## TigerNut (Dec 18, 2009)

JRP3 said:


> I guess the only thing "wrong" with the math was I had the wrong number for current  I got my notes and the actual numbers are a bit different and explain the excessive heat. Using the single resistor current was actually 1.05 amps at 3.3 V, so I²R for 10Ω and 1.05 amps is 11.025 watts, a bit over the resistor rating. Maybe I should mount the resistor in the cabin for extra heating


Most manufacturers derate the power handling of components at higher ambient temperatures... and it's a good idea to not stress a part beyond about 80% of its (derated) power rating under any conditions including situations where other components have failed (eg. assume that the coil shorts so you have 13.4V across the 10 ohm resistor). (13.4^2) /10 is about 18, so you should probably be looking for a 20 to 25W resistor.


----------



## JRP3 (Mar 7, 2008)

Yes I wasn't intending to continue using the 10 watt resistor, thinking 20-25 would be good, which your post confirms.


----------



## JRP3 (Mar 7, 2008)

Tried an 8 ohm 20 watt resistor and it got to 236 F before I turned it off. WTF? It's looking like I'd need close to a 50+ watt finned resistor to get anywhere near acceptable temps at this rate.


----------



## TigerNut (Dec 18, 2009)

Did that resistor have a temperature-rise-per-W spec? I would expect that a high-wattage resistor is going to have either a heatsink body or else it will be wirewound on a ceramic core so that it can survive being really hot.

Is it possible that the resistance was not 8 ohms, but less? Did you measure the voltage drop across the resistor?


----------



## JRP3 (Mar 7, 2008)

No temperature spec, it's a ceramic type, but even if it's within specs I don't want something that hot in my vehicle. Voltage dropped to 3.7 from 13.4, though measured current was still at 1.05 amps, the same as with the 10 ohm 10 watt resistor.


----------



## EVfun (Mar 14, 2010)

Since this is a heater contactor perhaps you can put the resistor into the heater airflow. Many vehicles that use a resistor for the different fan speeds put it in the heater intake airflow. 

The amount of heat the resistor will have to dissipate will get larger as the resistor value gets lower, down to the point where the resistor value is the same as the contactor resistance.


----------



## TigerNut (Dec 18, 2009)

JRP3 said:


> No temperature spec, it's a ceramic type, but even if it's within specs I don't want something that hot in my vehicle. Voltage dropped to 3.7 from 13.4, though measured current was still at 1.05 amps, the same as with the 10 ohm 10 watt resistor.


I don't know if this is at all similar:
http://documents.tycoelectronics.co...et1773285LpdfEnglishENG_DS_1773285_L.pdf

But if it is, there is a 'load against temperature' plot on the second page. For a 20W resistor at 50% of rated load, it gives a surface temperature of 200 degrees C. Yeow!

These ones
http://documents.tycoelectronics.co...et1773035BpdfEnglishENG_DS_1773035_B.pdf
look like they have a much more reasonable surface temperature. If I read the graph correctly, a 25W resistor (presumably mounted on a suitable heatsink) should have a surface temperature rise of about 40C when dissipating 10 watts.


----------



## EVfun (Mar 14, 2010)

Thanks TigerNut. I've always used the theory of using a resistor for 1/2 its rated wattage, max. That reinforces my view. I also tend toward using long leads and silver bearing solder for putting power resistors in place. Resistors can unsolder themselves!


----------



## JRP3 (Mar 7, 2008)

EVfun said:


> Since this is a heater contactor perhaps you can put the resistor into the heater airflow.


Might be a possibility.


----------



## Guest (Mar 9, 2012)

Seems like an awful lot of wasted energy for an economizer solution. Not very economizing now is it?


----------



## JRP3 (Mar 7, 2008)

Well it's wasting less than 15 watts, it's just concentrating a lot of heat in a very small area. In a 1500 watt heater application that's less than 1% of the system energy being wasted. If I can stick the resistor in the air flow then it's not being wasted at all


----------



## major (Apr 4, 2008)

gottdi said:


> Seems like an awful lot of wasted energy for an economizer solution. Not very economizing now is it?


It is a solution to use an existing part as opposed to buying a new one at $100.

It is an electric heater control so it is converting 100s if not 1000s of watts to heat anyway. What difference does it make if it is the heater element or the control resistor for like 10 of those watts?

Where is the wasted energy? What is uneconomical about this solution?


----------

