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Old 10-04-2013, 05:54 PM   #1
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Circuit Board on Tankless Water Heater Issue?


There is an EEMAX Model EX280T2T Tankless Water Heater in the home we bought. Unfortunately, I have read reviews that the circuit boards seem to go bad regularly as I recently found out I have 2 of 3 bad boards which is the cause of my luke warm water issue.
The company sells boards for $70 each, but if this is a regular issue - I figured there had to be a way to fix the board for much less. I took it to a local electronics guy and he said the light blue part I have pictured is bad. He said he did not have the part, but that I could buy it online for about $1. He said he could not tell what ohm it was due to it already being bad, but he said it was probably around 1 ohm. The electronics guy said if I take out the good board and put a meter on it I can get the reading I need to buy the right part. I have a picture of the good board with the volt/ohm meter on it, but I'm not sure what the measurement is telling me to buy???




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Old 10-04-2013, 06:42 PM   #2
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Circuit Board on Tankless Water Heater Issue?


It's a resistor.

You may not be able to measure it "in-circuit." Depending upon the board other devices can change the reading but, what are the colors? I can't make them out from the picture. All resistors are color coded, follow the link:

http://en.wikipedia.org/wiki/Electro...r_color-coding

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Old 10-04-2013, 06:57 PM   #3
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Circuit Board on Tankless Water Heater Issue?


On this larger resistor on all 3 boards, it looks like 4 black bands with light blue up to about the second band on the left, then white between the 2nd and 4th band, lastly light blue after the 4th band.

The other smaller resistors on the board all look like the examples in the link you posted being tan with colored bands, but all 3 board's larger resistor look to have only blacks bands with the baby blue and whit in-between.

On the 2 boards that are not working the meter reads nothing in-circuit on the larger resistor, where the good board gives the reading in the pic on the larger resistor - if that helps any?



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Originally Posted by AandPDan View Post
It's a resistor.

You may not be able to measure it "in-circuit." Depending upon the board other devices can change the reading but, what are the colors? I can't make them out from the picture. All resistors are color coded, follow the link:

http://en.wikipedia.org/wiki/Electro...r_color-coding
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Old 10-04-2013, 07:27 PM   #4
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Circuit Board on Tankless Water Heater Issue?


I make the meter out to read 8k ohms. Follow the top scale. You have the range set at X1K or times ONE thousand. Did you calibrate the meter first?

The colors should be grey (8), black (0), red (x100) the last color is the tolerance.

This is a case where you'd be better off with a digital meter for a more accurate answer.

Last edited by AandPDan; 10-04-2013 at 08:30 PM. Reason: correct color
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Old 10-04-2013, 08:02 PM   #5
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Circuit Board on Tankless Water Heater Issue?


Thanks for your help.
I took the meter-reading picture at an angle to keep the flash from glaring on the meter, so it looks like 8. It actually reads just a hair over 7 straight on. I do not have a digital meter though.
I took another picture zoomed even closer and hopefully clearer of one of the other resistors that is not as worn looking. The first band looks more gray now that I look closer, and maybe the 2nd band is brown? The 3rd band definitely looks black.



Last edited by jason586; 10-04-2013 at 08:09 PM.
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Old 10-04-2013, 08:11 PM   #6
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Circuit Board on Tankless Water Heater Issue?


I have the 36kw model wonder if the boards are the same will check them out I have not even had a chance to install it yet. May be able to tell better.
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Old 10-04-2013, 08:30 PM   #7
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Circuit Board on Tankless Water Heater Issue?


Its a resistor !
More specifically it's a flame proof / fusable resistor !
That one's been getting quite warm in the middle,
this will cook the paint in the color codes,
Making it hard to read.

So it's most likely an 8.2K ohm,
Which is - GREY-RED-RED.
Size is 2 watt.

the reds would be hard to see properly if there burnt.
The fourth band is the tolerance

Make sure you use the correct type of resistor,
Do not use standard carbon type resistors.
Use only flame proof/fusable resistors.


Circuit Board on Tankless Water Heater Issue?-resistor-color-chart.jpg
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Old 10-04-2013, 08:38 PM   #8
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Circuit Board on Tankless Water Heater Issue?


I actually have the 38kw model with four elements and it has a completely different board. Maybe call the company up and ask them about the resistor. They seem like decent people I sold them my web page url when I decided to get out of the electric tankless water heater sales.
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Old 10-04-2013, 09:08 PM   #9
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Circuit Board on Tankless Water Heater Issue?


The resistor on the good board already looks overheated. Not sure what function this resistor serves in the circuit, but overheating a 2W 8.2k resistor is not easy to do - it requires that the resistor have full line voltage across it. At 120V, that resistor would produce 1.75W of heat. That's enough to toast it if it is in a warm environment without airflow. There is a high probability that this resistor is being used as a voltage dropping device in a crude regulator circuit to provide low voltage power to the control circuitry. If that is the case, then failure of the resistor probably causes destruction of the control parts, too. Simply replacing the failed resistor may not fix the board. However, replacing the resistor on the NEW board with a 5W version might be a good idea!
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Old 10-04-2013, 09:42 PM   #10
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Circuit Board on Tankless Water Heater Issue?


The resistors do look similar on all 3 boards, so it probably is a matter of time before it goes too. I hate to spend almost $225 shipped for 3 boards especially if I have any chance of fixing them for minimal cost. Also, it is definitely in a warmer climate with minimal airflow.

I took a better picture (straight on) of the meter reading the resistor. I don't think it is 8.2 - maybe 7.2 if that is a common size?

Are there some other pieces on the board that I should check with the volt/ohm meter that would be likely to go bad due to the resistor going bad from overheating. I checked each piece on either side on the 3 boards and they all read the same as the other except for the flame proof fuse which reads nothing on the 2 bad boards. I will check everything again to make sure I did not miss anything.




Last edited by jason586; 10-04-2013 at 10:02 PM.
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Old 10-05-2013, 12:56 AM   #11
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Circuit Board on Tankless Water Heater Issue?


In the first picture it looks like the resistor has gotten so hot that the solder connection on the end next to the LED has become bad too.

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Old 10-05-2013, 06:16 AM   #12
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Circuit Board on Tankless Water Heater Issue?


Are metal oxide resistors the same as flame proof resistors - just a different name? They seem to have the same chaulky light blue color.

Will resistors like these work? If not, where to buy flameproof?

http://www.newark.com/nte-electronic...ors/dp/06H0652

http://www.ebay.com/itm/25pcs-8-2K-o...item3a7b3e57ce





Quote:
Originally Posted by dmxtothemax View Post
Its a resistor !
More specifically it's a flame proof / fusable resistor !
That one's been getting quite warm in the middle,
this will cook the paint in the color codes,
Making it hard to read.

So it's most likely an 8.2K ohm,
Which is - GREY-RED-RED.
Size is 2 watt.

the reds would be hard to see properly if there burnt.
The fourth band is the tolerance

Make sure you use the correct type of resistor,
Do not use standard carbon type resistors.
Use only flame proof/fusable resistors.


Attachment 76439

Last edited by jason586; 10-05-2013 at 06:46 AM.
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Old 10-06-2013, 02:37 PM   #13
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Circuit Board on Tankless Water Heater Issue?


Quote:
Originally Posted by jason586 View Post
Are metal oxide resistors the same as flame proof resistors - just a different name? They seem to have the same chaulky light blue color.

Will resistors like these work? If not, where to buy flameproof?
Flameproof is a general description, not a specific type of resistor. There are many different types of resistors that would work - metal oxide thin film, thick film, carbon composition, or wirewound. Don't replace it with another 2W resistor though - that defeats the purpose, since 2W is obviously inadequate here. Try this:

http://www.digikey.com/product-detai...8.0K-ND/257457

And you will probably have to get a new board, and install the new resistor on it unless you can find and replace all the other components that failed as a result of the resistor failure.
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Old 10-06-2013, 04:16 PM   #14
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Circuit Board on Tankless Water Heater Issue?


i dunno, sure looks like brown,black, brown to me. Which would be a 10 Ohm resitor with a +/- 1% tolerance.

I'm reading that meter at around 7.2 Ohms. Not 8K..it looks like that thing tops out at 1k.

Unless im totally reading it wrong.
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Old 10-06-2013, 05:16 PM   #15
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Circuit Board on Tankless Water Heater Issue?


Quote:
Originally Posted by tfo411 View Post
i dunno, sure looks like brown,black, brown to me. Which would be a 10 Ohm resitor with a +/- 1% tolerance.

I'm reading that meter at around 7.2 Ohms. Not 8K..it looks like that thing tops out at 1k.

Unless im totally reading it wrong.
Yes your reading the scale wrongly !

In the first post there is a picture of the meter and it's setting,
It is on x 1K ohm, so the reading on the meter is around 7,
so this becomes 7K ohms.

The closest standard value to this is 6.8 K ohm.
The heating would easily cause the value to rise from 6.8 to 7.2.
Using a larger wattage rating won't hurt.
But I would not use a wirewound resistor in place of resistor,
that was not wirewound.
As this can introduce an inductive component to the circuit.
Use only what the manufacturer has used.
Which is a fusible type.
They do make 3w fusible
You could use 2 x 3.9k ohms is series
This would give 4w or 6w depending on the resistors you use 2w or 3w.


Last edited by dmxtothemax; 10-06-2013 at 05:26 PM.
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