Hello, everybody,

I have a UPS with two identical fans connected in parallel. Because they are loud, I would like to replace them.

The UPS is an old online Riello Dialog Plus Rack 150.

The nominal voltage of all fans is 12V.

Each of the old fans draws max 2.5W.
Each of the new fans draws max 0.96W.

Old fan type: Sunon KDE1208PTB1
New fan type: be quiet Silent Wings 2 (BL060)

If I only connect the new fans, the UPS reports a serious error (beeps unhappily).
If I add one of the old fans in parallel to the two new fans, the error goes away.

I think this is because the UPS recognizes a power consumption of only about 2W instead of 5W.

It doesn't look like a temperature sensor triggers the error, because the UPS works fine with two new fans and one old fan (all connected in parallel), even if the old fan is physically outside of the case and not cooling anything.

Without load the fan voltage is about 8V. The fans accelerate as the load on the UPS increases (while operating on batteries). Hence I am assuming that fan speed is regulated in an analog way only by voltage, since there are only two wires (hence we can't talk about PWM).

I am thinking about connecting a resistor in parallel to the new fans.

• If this is a good idea, the question is how big this resistor should be.
• If not, how can I get the new fans to run wihtout triggering errors?

An old fan has a measured resistance of 650 Ohm or 1320 Ohm, depending on the polarity.

Thank you very much.

 

Without load the fan voltage is about 8V. The fans accelerate as the load on the UPS increases (while operating on batteries). Hence I am assuming that fan speed is regulated in an analog way only by voltage, since there are only two wires (hence we can't talk about PWM).

They can be applying PWM on a two wire fan based on temperature rise.The protection mentioned in the user manual mentions, Overload - short-circuit - overvoltage - undervoltage - temperature - low battery. The only way to know would be look at the fan power using a scope.

The smarter UPS units I have seen using a three wire fan only looked at fan speed as a more of it's there or not. I have never seen a UPS which actually looked at fan current draw to know if a fan is running or not but I have no clue if such a system exist. Measuring the 8 VDC is not unusual if the fans are running on a PWM source because with 12 VDC PWM you are going to measure the average. Anyway a scope will show you exactly what is going to the fans.

I see no reason why placing a resistor in parallel with the fans would not work assuming the unit does in fact look at fan current draw. Nothing ventured and nothing gained. Crunch the numbers and give it a try.

Ron

 

KDE1208PTB1 (80x80x25), Datasheet: 12VDC @ 2.3W; 3000RPM; 39.5CFM; 33dBA
Silent Wings 2 (BL060), Mfg Spec: 12VDC @ ???W; 2000RPM; 44.2CFM; 14.5dBA

Based on your description and the KDE datasheet, it makes me think they are obtaining additional information from the fan, and what they are getting from the new fan is different. You're sure, the old KDE fans only have 2 wires?

 

You're sure, the old KDE fans only have 2 wires?

Yeah, I also wondered but looked at the data sheet. Only two lead wires, red and black.

Ron

 

They can be applying PWM on a two wire fan based on temperature rise.The protection mentioned in the user manual mentions, Overload - short-circuit - overvoltage - undervoltage - temperature - low battery. The only way to know would be look at the fan power using a scope.

The smarter UPS units I have seen using a three wire fan only looked at fan speed as a more of it's there or not. I have never seen a UPS which actually looked at fan current draw to know if a fan is running or not but I have no clue if such a system exist. Measuring the 8 VDC is not unusual if the fans are running on a PWM source because with 12 VDC PWM you are going to measure the average. Anyway a scope will show you exactly what is going to the fans.

I see no reason why placing a resistor in parallel with the fans would not work assuming the unit does in fact look at fan current draw. Nothing ventured and nothing gained. Crunch the numbers and give it a try.

Ron

Thank you, dear Ron. That already helps. Nevertheless, precisely the number crunching is the thing I am asking here for help. I have no idea how to calculate the size of this resistor. I know other things. This one I have yet to learn.

 

If you want to place an additional 3 watt load on the controllers @ 12 volts you will need a 48Ω 5 watt resistor.

 

N.B that resistor will get hot, so keep it away from wiring insulation etc.

 

If you want to place an additional 3 watt load on the controllers @ 12 volts you will need a 48Ω 5 watt resistor.

Thank you. Meanwhile, I researched the matter a bit further and found the following formula:

P x R = U^2

where P = electrical power, R = electrical resistance and U = Voltage

In my case U is a constant (12V).

For a target load of, for instance, 3W, the equation becomes 3R = 12^2 <=> 3R = 144 <=> R = 48. Apparently you suggested 5W instead of 3W to account for the heat.

At any rate, I just ordered the following resistors for now:
[ ] 150Ω @ 1W (draws 0.96W)
[ ] 75Ω @ 2W (draws 1.92W)
[ ] 56Ω @ 3W (draws 2.57W)
intending to use the first one one first, then, if that doesn't take care of the error, the second one, then, if that doesn't work, the third one, leaving the temperature issue at the very last.

Is what I wrote here correct?

Would you know if AAC posts can you write Latex (or similar) formatting?

 

N.B that resistor will get hot, so keep it away from wiring insulation etc.

Thank you.

By the way, is it true, then, that the error gets triggered only by the fact that the total power drawn by the fans is below a certain preset limit?

 

At any rate, I just ordered the following resistors for now:

You will be running them very close to their maximum power rating, so they could be VERY hot. Note that Ron suggested a 5W-rated resistor for dissipating only 3W, to allow a good working margin.

 

You will be running them very close to their maximum power rating, so they could be VERY hot. Note that Ron suggested a 5W-rated resistor for dissipating only 3W, to allow a good working margin.

Thank you.

So is it true, then, that the error gets triggered only by the fact that the total power drawn by the fans is below a certain preset limit?

 

I was thinking you could test if it worked or not by using a 12V 5(ish) watt bulb. Most people have some in their glove boxes from replacing auto lights.
https://www.homedepot.com/p/Sea-Gul...8_iNI6fhvXGyjk1of_YaAuoBEALw_wcB&gclsrc=aw.ds

 

I was thinking you could test if it worked or not by using a 12V 5(ish) watt bulb. Most people have some in their glove boxes from replacing auto lights.
https://www.homedepot.com/p/Sea-Gull-Lighting-0-3-in-W-12-Volt-5-Watt-Clear-Incandescent-Wedge-Lamp-9728/204773472?cm_mmc=Shopping|G|Base|D27L|27-16_INTERIOR_LIGHTING|NA|PLA|GeneralInteriorLighting|71700000038836110|58700004241533705|92700044088232250&gclid=Cj0KCQjwj_XpBRCCARIsAItJiuQsKu9RBDJLvePnyzxtC9qaFIf0BUwDmlNp8_iNI6fhvXGyjk1of_YaAuoBEALw_wcB&gclsrc=aw.ds

It's the same idea as with the resistors, which I already ordered.

My main question at this point is if it is true, that the error gets triggered only by the fact that the total power drawn by the fans is below a certain preset limit.

 

Hello,

When I look at the data of the fand the KDE has a flow of 42.5 CFM and the Silent Wing only 26 CFM.
https://elcodis.com/parts/452891/KDE1208PTB1-6AR.html
https://www.bequiet.com/en/casefans/258

The cooling witrh the Silent Wing will be to low.
Better look for a fan with more flow.

Bertus

 

Hello,

When I look at the data of the fand the KDE has a flow of 42.5 CFM and the Silent Wing only 26 CFM.
https://elcodis.com/parts/452891/KDE1208PTB1-6AR.html
https://www.bequiet.com/en/casefans/258

The cooling witrh the Silent Wing will be to low.
Better look for a fan with more flow.

Bertus

KDE1208PTB1 (80x80x25), Datasheet: 12VDC @ 2.3W; 3000RPM; 39.5CFM; 33dBA
Silent Wings 2 (BL060), Mfg Spec: 12VDC @ ???W; 2000RPM; 44.2CFM; 14.5dBA

Based on your description and the KDE datasheet, it makes me think they are obtaining additional information from the fan, and what they are getting from the new fan is different. You're sure, the old KDE fans only have 2 wires?

Valid point. Nevertheless, the technical sheet behind your URL points to the wrong variant of Sunon fan (its code has the 6AR suffix and 3 wires). If anybody finds the technical sheet for my fan, please share. I couldn't find it anywhere.

 

There appears to be a version with tach out: http://datasheetz.com/data/Fans/DC/KDE1208PTB1-6AF-datasheetz.html

Power consumption doesn't make sense.

 

There appears to be a version with tach out: http://datasheetz.com/data/Fans/DC/KDE1208PTB1-6AF-datasheetz.html

Power consumption doesn't make sense.

What is causing the error, then?

 

It's the same idea as with the resistors, which I already ordered.

My main question at this point is if it is true, that the error gets triggered only by the fact that the total power drawn by the fans is below a certain preset limit.

I offered it as a easy way to test while you wait since the bulb is probably easily found in a junk drawer. If it works I think it's safe to assume something is looking for x amount of load to be happy. I know nothing about running fans but from what you describe it sounds like an error code to alert if one of the fans is dead.

 

My main question at this point is if it is true, that the error gets triggered only by the fact that the total power drawn by the fans is below a certain preset limit.

Without knowledge of the UPS how can we tell? Have you asked the manufacturer?

 

I offered it as a easy way to test while you wait since the bulb is probably easily found in a junk drawer. If it works I think it's safe to assume something is looking for x amount of load to be happy. I know nothing about running fans but from what you describe it sounds like an error code to alert if one of the fans is dead.

Thank you.