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HVAC shutoff periodically knocking out PC & modem


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#1 drinabar

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Posted 18 June 2015 - 01:17 PM

First, I'm not even sure this is a computer problem. I have an HP laptop with Verizon fios as carrier; I do not use wireless, only connected. For about the last 6 months or so (spanning winter thru summer), I've noticed that when my HVAC does a periodic "hard" (makes a clunk noise) shutoff, it immedicately knocks out my PC and my modem...shuts down the laptop completely. I have the PC/modem connected to a UPS (uninterrupted power supply) with 625 volts/surge protection/power backup. I have my HVAC serviced 2 times/year, and just had it serviced last week. I have not noticed any other problems with any other appliance/lights/TV's affected by this...only my computer/modem. I know this cannot be good for my laptop, and am at a loss as to how to proceed. I thought the UPS would resolve the problem but that is not the case. Any one else experience this problem? Any thoughts? My printer is also connected to the UPS, but does not seem to be affected when this problem occurs. I live in a 2 level townhouse, with the HVAC on the first level (in the laundry room), and my office (most living space) on the second level. When this happens, it does not trip a circuit breaker. I aplolgize in advance if this is not an appropriate question for this forum.      



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#2 JohnC_21

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Posted 18 June 2015 - 04:58 PM

Hello, and Welcome

 

There are UPS's and then there are UPS's with AVR (Automatic Voltage Regulation). A UPS with AVR is the one you want. I think when the HVAC turns on you may be getting a voltage drop and then your Modem and Computer turn off. 

 

It's possible your UPS is defective or your battery in the UPS is on the week side. You could try changing the battery first. 

 

Do you have a make and model of the UPS.



#3 drinabar

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Posted 18 June 2015 - 07:42 PM

Thank you for responding. My UPS is brand new (only had for 2 days). It is a CyberPower battery backup with surge protection, 625 va, 375 watts, with building wiring fault indicator. I verified that the PC & modem are plugged into the side/outlets (4) that are labeled "surge & battery", not the side/outlets (4) labeled "surge". I have lived in my home for 3 years, and this started happening about 6 months ago. My HVAC is checked/tuned every six months, and my HVAC guy was just here last week. This is not a reproducable problem, because it only occurs when the HVAC does a "hard" shutoff (like a clanking sound via the register/vent); most of the time the shutdown is a soft shutdown and there is no problem. So far, this has happened twice today. If I understand your post, am I correct that my UPS does not have AVR? 



#4 JohnC_21

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Posted 18 June 2015 - 08:15 PM

Do you have a model number of the Cyberpower UPS?



#5 drinabar

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Posted 18 June 2015 - 11:11 PM

UPS model #: SX625G



#6 JohnC_21

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Posted 19 June 2015 - 09:31 AM

According to the specs here the UPS does not have AVR. That is my best guess on why the computer and modem shut down but I would contact Cyberpower customer service and tell them your situation and if using a UPS with AVR is the solution.

 

Here is the AVR series which is more expensive.



#7 drinabar

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Posted 19 June 2015 - 02:36 PM

Thank you for the information. I had gone to Best Buy, and the model I picked up was the one that had the highest volt listing (625)...I did not realize there was a difference between a UPS and a UPS with AVR; thanks to you, I do now and will look to pick one up. Best Buy did not have a wide array of choices in the store. The price is not an issue...It is less expensive than replacing my laptop. I have also spoken with my HVAC guy, and he has never heard of this happening; he is also doing some research for me as to why the furnace is periodically doing a hard shutdown and what is happening when this is occurring. My getting UPS/AVR is a reactive measure; finding the possible problem with the furnace and/or electrical would be proactive. I'm going to address this problem from both perspectives. Thank you again for pointing me in the right direction...I am so very appreciative of your time/information/help.    



#8 JohnC_21

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Posted 19 June 2015 - 03:13 PM

I can't guarantee that the problem will be fixed by using a UPS with AVR but it should work. It all depends on how much of a voltage drop occurs as the UPS can only compensate for so much. Even with an AVR the hard shutdown of the HVAC may even cause the computer to shut down. Can you return the UPS back to Best Buy? For good deals on a UPS take a look at ebay or newegg but you would need to take a look at the shipping costs too.

 

AVR = Automatic Voltage Regulation.
What it does is to regulate the mains voltage within a limited range. In the case of your UPS, it boost +12% when the incoming voltage is too low. Let’s say the incoming voltage is at 200 volts, the output then goes to 224Volts, +12% of 200 volts, which is still acceptable for most UPSs. When the UPS output reaches let’s say, 230V with the boost mode on, then the UPS sends a command to a component called relay so that the +12% compensation is turned off.
Basically the voltage regulation is a series of power transformers, it can either be step-up transformers or a step-down transformers  They basically do the same thing a 220V to 110V step-down transformer does, or a step-up transformer does, when it gets 110V and transforms to 220V. The UPS senses the incoming voltage and commands a series of relays  to select a different transformer output or “tap”, as they call it.
An automatic voltage regulator can only work within a limited range. 
A voltage regulator transformer can have a much higher range as its developer wants, but it makes the unit much heavier, it wastes more energy and generates more heat. It doesn’t matter what range the AVR has, it is still slow for suppressing voltage surges

 

 

http://www.thaivisa.com/forum/topic/736721-ups-inverters-avr-and-mov-explained/

 

Edit: I am not sure why the laptop would get knocked out as it has a battery that should have kept the laptop functioning.

 

Edit: Another good link on UPS/AVR

 

http://johnnyromano.me/tech/upsbattery-backup-explained.html


Edited by JohnC_21, 19 June 2015 - 03:17 PM.


#9 drinabar

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Posted 29 June 2015 - 11:07 PM

Sorry I have't getten back here sooner. I've looked high and low for a UPS/with AVR, but cannot find one in any box store (target/walmart/office max/best buy/hr gregg)...*sigh* In the intermim, I called my HVAC guy, and he has never heard of this happening....he is as flummoxed as I am. He is checking with some of this suppliers, but hasn't gotten back to me yet. He did say we may have to place some kind of tester in the outlet to determine what is happening. He says he thinks the voltage would drop, not spike, when the furnace shuts sown. Unfortunately, this problem cannot be reproduced "on demand"; most times when the HVAC shuts down, it is fine. Thanks for all of the information you have posted...it is very informative. I moved my current UPS to a different outlet on the opposite side of the room, but the problem still occurs. Yes, I still have a week or two left to return the current UPS, since it really didn't resolve my problem....and, based on the info you supplied, a UPS/AVR may not do the trick either...but I'm going to try anyway. Again, I thank you.    



#10 YeahBleeping

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Posted 30 June 2015 - 08:06 AM

What you need is your local power company to come out and bring a AC circuit analyzer.  It sounds to me like the hvac unit may not be properly grounded.  or may be something wrong with that HVAC compressor drawing way too much during shut down.  Either way this should be a service your electrical company can provide and may be included as a service no charge to you.






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