Multiple Alarm Zone Surge Suppression?

[kurtmccaslin]

I am having the same problem with my Omni.   My data bus has been blown twice by lightning.   I have a Ditek surge suppressor at both ends, but I think one side is too far from the earth ground to be effective.   There is a very good video on the Ditek site covering installation and grounding.   It is found under the tab "webinars"
 
I am planning to try this opto isolator next:
 
http://www.serialcomm.com/serial_rs232_converters/rs232_rs485_rs422_data_repeaters/rs485_rs422_repeater/rs485_rs422_repeater.product_general_info.aspx
 
Have you considered going wireless on the 6 outdoor zones?   

 

[Del91574]

You can isolate the bus but the issue is always going to be the ground reference the bus requires to work properly.

 

[pete_c]

Been lucky here.
 
Here reviewed my outdoor sensors / cams connectivity to the OP2 panel.  The sensors (2 wires) all connect directly to the OP2 panel.  (3 + 4 + 5 + 2 = 14  outdoor sensors).  I also have a 1-wire lightning sensor on the roof which is a metal bar in PVC.  This going to to the Leviton media can which is next to the OP2 can with it's own power supply.  (total cans are 4)
 
All of the powered outdoor sensors are using an autonomous power supply in another housing about 8 feet from the main OP2 panel.
 
(IE: mentioned early one sub panel; it's really three + Leviton 42" can = 4).
 
Grounding is the same for all four sub panels as they are within a few feet of each other.
 
No outbuildings today or externally placed sub panels.
 
Going back to the 80's I recall wiring up the detached garage with alarm keypad and sensors directly connected to the main alarm panel in house.  In the 90's only lightning issue that happened took out a computer / serial connections / network hub.

 

[kurtmccaslin]

Pete, it does sound like you have been lucky.   I had 2 lightning strikes in less than a month, with thousands of dollars worth of damage.   It may have something to do with my house being on a hill.
 
Del, you have a good point.   I don't know if the optoisolator has a ground pass-thru, or if it is also isolated.   I will check it with my ohm meter when I get it.   However, it seems to me that the input and output on the isolator don't necessarily have to use the same reference ground.   The RS 485 circuits look for a positive or negative voltage relative to ground.   Even if the ground is at a different voltage on the input and output, the circuit is only looking for a voltage difference to  ground on the A and B data wires on each side of the isolator.   Each side would have a different ground level, but the relative A-B-Ground voltage difference on each side would be within RS 485 specs.

 

[Del91574]

As you alluded to, depends on how the omni supervises the bus and the ground reference.
 
I just had to replace a few old repeaters at a site that got hit by lightning. These worked exceptionally well.
 
http://gridconnect.com/atc-109n-industrial-rs422-485-data-repeater-with-isolation.html  (FYI, the connection instructions are wrong on this unit but the schematic is correct).

 

[pete_c]

Yeah thinking about this I did lose my outdoor HVAC compressor to lightning damage - it happening one night in the beginning of a thunderstorm.  Temps were in the 90's that night.  We were watching a movie and the whole house buzzed when it happened. We did hear a loud pop coming from the side of the house where the AC compressor was.   I went outside in the rain and noticed that my AC compressor was smoldering and I didn't see any flames then.  Didn't look much though with a flashlight until the next day.  Neighborhood is flat here and only about 15 years old.
 
The whole endeavor was really low on the WAF.
 
Looked like the contactor fused the two 120VAC legs.  Everything was black and charred as a small fire had started and that melted the freon lines and the fire did burn or melt most of the HVAC unit.  The 240VAC back to the house did trip most of the breakers in the panel.  But before it tripped the breakers it took out every (literally) Insteon switch.  Still today cannot figure out exactly what happened.  I did have a large surge suppressor in the panel.
 
It was hot that summer and I did have the HVAC compressor replaced in a matter of about a week.  Over the next few months also replaced every automated switch in the house (the UPB switches still worked though).  Outside I put another surge suppressor where the outside fuse box is at.
 
Only damage that time was the AC compressor and automated switches.  Nothing else got damaged.  It was replaced by a friend who owned an HVAC company and he personally removed the charred device and replaced the unit with a new one.  I did go to a windows AC unit in the bedroom for sleeping only for about a week.  It worked fine.

 

[mikefamig]

As you alluded to, depends on how the omni supervises the bus and the ground reference.
 
I just had to replace a few old repeaters at a site that got hit by lightning. These worked exceptionally well.
 
http://gridconnect.com/atc-109n-industrial-rs422-485-data-repeater-with-isolation.html  (FYI, the connection instructions are wrong on this unit but the schematic is correct).

 
The ATC-109N looks ideal for a situation like mine with rs-485 buried in-ground between buildings but does it continue to protect your equipment in a power failure? 
 
Mike.

 

[cobra]

Del, you have a good point.   I don't know if the optoisolator has a ground pass-thru, or if it is also isolated. 

There must not be a ground pass through for proper isolation.  It would completely defeat the lightning protection of your opto-isolation.
 
Think of opt-isolation setups like air gaps (which they basically are, wrapped in insulating plastic.)  They are a way to completely electrically disconnect two sides of a circuit while still passing a signal.  If a ground is connected between the two sides, it will give you a lightning path across the isolation.  That would be very bad practice.

 

[Del91574]

I'm guessing you got hit with EMP Pete.
 
Mike- I asked the guys at Elk a bunch about extending the 485 bus for a job and I don't recall the answers being cut and dry or promising. I've been too busy to really pursue it further. I don't think it'll help you though, I want to say Elk requires the common ground reference, so that's still going to be the weak point and unable to really be isolated. It's not going to work without power, so it'd need to be powered from the host system.
 
I've had one installed for over a year at the site I told you about after an old B&B unit failed (of course, obsolete) and then replaced the one on their second data branch after a failure this year. With the known hits that have already happened and blown up other things, I haven't had an issue. That said, I'm purely 4 wire 422 out there, no common system grounds.

 

[cobra]

Yeah thinking about this I did lose my outdoor HVAC compressor to lightning damage - it happening one night in the beginning of a thunderstorm.  Temps were in the 90's that night.  We were watching a movie and the whole house buzzed when it happened. We did hear a loud pop coming from the side of the house where the AC compressor was.   I went outside in the rain and noticed that my AC compressor was smoldering and I didn't see any flames then.  Didn't look much though with a flashlight until the next day.  Neighborhood is flat here and only about 15 years old.
 
The whole endeavor was really low on the WAF.
 
Looked like the contactor fused the two 120VAC legs.  Everything was black and charred as a small fire had started and that melted the freon lines and the fire did burn or melt most of the HVAC unit.  The 240VAC back to the house did trip most of the breakers in the panel.  But before it tripped the breakers it took out every (literally) Insteon switch.  Still today cannot figure out exactly what happened.  I did have a large surge suppressor in the panel.

It sounds like you had a strike near the AC unit, or to it directly.  That means the voltage jump occurred inside your surge suppression.  Unfortunately, the surge suppressor in the panel is mainly designed to stop high voltage coming in to your house from the supply lines.  If the strike is on your side, it doesn't buy you much, although it should have some effect in protecting your neighbors...
 
I once came home to half of my circuit breakers blown in the panel (was at work during the day, no major thunderstorms that day.)  Older house with glass fuses still.  After looking around and determining nothing major had happened to the house, called PECO (Philly area power company.)  Was told no issues occurred that day.  Called a neighbor, and he says "Yeah, this morning I was shaving, and a 1 foot flame shot out of my bathroom GFI.  I called PECO and they came out to check my house.  Later, found out they dropped a high tension (high voltage line) on to one of the local lower voltage supply lines while working on it."
 
Fried a couple towns worth of electric equipment around here.   Hahaha.  At least they paid for damaged items in the house and were pretty accommodating about claims for replacement. 

 

[kurtmccaslin]

The ATC-109N looks ideal for a situation like mine with rs-485 buried in-ground between buildings but does it continue to protect your equipment in a power failure? 
 
Mike.

Good question.
 
RS-485 does not have a pair carrying power like other protocols.  Therefore this device will require an external power supply to work.   If the power goes out, you will lose data transmission, but you will still be optically isolated.   Losing communication on your data bus may generate a loss of monitoring, or potentially a false alarm, depending on your security panel.   Therefore, it would be better to have a power supply with backup power.   More complexity, unfortunately.

 

[Del91574]

Not truly.....assuming the isolation is being used on a host system with expansion, there would be some sort of aux power supply or connection to the host panel, depending on the location of the repeater. Also assuming the power supply is isolated from the system or surge protected in itself so as to not feed power into the copper.