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#1
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Periodic transformer failure
I have a 120v to 24vac transformer for a lawn sprinkler system that has
failed about 3 times since I purchased the house. This time I took the windings apart and found the break in the 120v winding. I live in a lightening prone area. Is this failure most likely from power surges or is there some other possible cause. Thanks. Mike |
#2
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Periodic transformer failure
vMike wrote:
I have a 120v to 24vac transformer for a lawn sprinkler system that has failed about 3 times since I purchased the house. This time I took the windings apart and found the break in the 120v winding. I live in a lightening prone area. Is this failure most likely from power surges or is there some other possible cause. Thanks. Mike What do you mean it failed about 3 times? Do you mean you replaced it? What happened the other times? How do you know it failed? All that info is necessary. -tg |
#3
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Periodic transformer failure
On Wed, 4 Oct 2006 22:58:26 -0400, "vMike"
wrote: I have a 120v to 24vac transformer for a lawn sprinkler system that has failed about 3 times since I purchased the house. This time I took the windings apart and found the break in the 120v winding. I live in a lightening prone area. Is this failure most likely from power surges or is there some other possible cause. Thanks. Mike It helps to ask a clear question... g Let's say lightning. Then a surge strip might be a good idea. Let's say 'bad engineering'. THen a better transformer might be a good idea. When off how warm/hot does it get? (There should be little or no heat from an unloaded transformer) When on how warm/hot does it get? (the temperature rise should not exceed the point where you cannot put your hand on it without saying: "OUCH" damn, that's hot.) Also check your line voltage adn the specified voltage of the transformer: do they match, or is the transformer rated for a lower line voltage (bad). |
#4
Posted to alt.electronics
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Periodic transformer failure
On Wed, 4 Oct 2006 22:58:26 -0400, "vMike"
wrote: I have a 120v to 24vac transformer for a lawn sprinkler system that has failed about 3 times since I purchased the house. This time I took the windings apart and found the break in the 120v winding. I live in a lightening prone area. Is this failure most likely from power surges or is there some other possible cause. Thanks. Mike Lightening might be a culprit. Lightening may manifest as an open where the connection to the winding is made or an internal short. A surge protector and a good ground will do wonders for lightening problems - You said you took the winding apart? If the transformer were dying due to over current/heat, you's see charred windings. The other good choice is a massive momentary overload that is enough to open the winding but isn't present long enough to char the insulation on the magnet wire. Shorted wire out to a valve - or compromised insulation inside the transformer itself. Most of the lawn timers I've seen have fuses. Check that to see if it is the correct size. ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#5
Posted to alt.electronics
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Periodic transformer failure
wrote in message ps.com... vMike wrote: I have a 120v to 24vac transformer for a lawn sprinkler system that has failed about 3 times since I purchased the house. This time I took the windings apart and found the break in the 120v winding. I live in a lightening prone area. Is this failure most likely from power surges or is there some other possible cause. Thanks. Mike What do you mean it failed about 3 times? Do you mean you replaced it? What happened the other times? How do you know it failed? All that info is necessary. -tg Yes I have replaced it 3 times. I took the last one apart to see where the failure was. I also have now found there is a big voltage drop on one of the zones... from 24 to 15. So the problem appears to be in that zone. Could be the box, the zone solenoid or the wiring to the solenoid. Hoping it isn't the last one!! Mike |
#6
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Periodic transformer failure
"default" wrote in message ... On Wed, 4 Oct 2006 22:58:26 -0400, "vMike" wrote: I have a 120v to 24vac transformer for a lawn sprinkler system that has failed about 3 times since I purchased the house. This time I took the windings apart and found the break in the 120v winding. I live in a lightening prone area. Is this failure most likely from power surges or is there some other possible cause. Thanks. Mike Lightening might be a culprit. Lightening may manifest as an open where the connection to the winding is made or an internal short. A surge protector and a good ground will do wonders for lightening problems - You said you took the winding apart? If the transformer were dying due to over current/heat, you's see charred windings. The other good choice is a massive momentary overload that is enough to open the winding but isn't present long enough to char the insulation on the magnet wire. Shorted wire out to a valve - or compromised insulation inside the transformer itself. Most of the lawn timers I've seen have fuses. Check that to see if it is the correct size. The fuse was over sized. Probably because it was blowing. See my response to previous poster. Mike |
#7
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Periodic transformer failure
Lightning seeks a conductive path to earth. A most common source of
lightning strikes is to AC utility wires. Incoming on AC mains, into house, and out to earth ground via transformer. Transformer provides galvanic isolation. But if that surge is too large, then galvanic isolation will be overwhelmed. Transformer primary (120 volt) and secondary (12 volt) conduct the surge to earth. Do you think a power strip protector will stop what three miles of sky could not? That is what another here has recommended. Real world protection is about earthing that surge before it even enters a house. Same one protector that is sufficiently sized to remain functional after each lightning strike. Same one protector that also protects everything inside a building. All appliances already contain internal protection - just like the transformer. Protection inside any appliance might be overwhelmed if a direct lightning strike is not earthed before entering the building. It is called 'whole house' protector. Effectiveness defined by quality of earthing at the service entrance (where AC electric, telephone, etc enter the building). Effective 'whole house' protectors are sold in Lowes, Home Depot, and electrical supply houses, Responsible manufacturer brand names are Cutler-Hammer, Leviton, Intermatic, Siemens, and Square D. A dedicated earthing wire short to that earth ground rod means lightning need not find earth via that transformer. Building earthing electrode must meet and exceed post 1990 National Electrical Code requirements. Essential is an earthing connection that is less than 10 feet, no splices, no sharp bends, separated from other wires, etc. A protector is nothing more than a connection device to protection - that earth ground electrode. Those AC electric wires - the most common path for surges that would blow through a transformer. vMike wrote: Yes I have replaced it 3 times. I took the last one apart to see where the failure was. I also have now found there is a big voltage drop on one of the zones... from 24 to 15. So the problem appears to be in that zone. Could be the box, the zone solenoid or the wiring to the solenoid. Hoping it isn't the last one!! |
#8
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Periodic transformer failure
On Oct 5, 5:51 pm, "w_tom" wrote: Lightning seeks a conductive path to earth. A most common source of lightning strikes is to AC utility wires. Incoming on AC mains, into house, and out to earth ground via transformer. Transformer provides galvanic isolation. But if that surge is too large, then galvanic isolation will be overwhelmed. Transformer primary (120 volt) and secondary (12 volt) conduct the surge to earth. Do you think a power strip protector will stop what three miles of sky could not? That is what another here has recommended. Real world protection is about earthing that surge before it even enters a house. Same one protector that is sufficiently sized to remain functional after each lightning strike. Same one protector that also protects everything inside a building. The best information I have seen on surge protection is at http://www.mikeholt.com/files/PDF/Li...ion_May051.pdf - w_tom provided the link to this guide - the title is "How to protect your house and its contents from lightning: IEEE guide for surge protection of equipment connected to AC power and communication circuits" - it was published by the IEEE in 2005 - the IEEE is the dominant organization of electrical and electronic engineers in the US A second guide is http://www.nist.gov/public_affairs/p.../surgesfnl.pdf - this is the "NIST recommended practice guide: Surges Happen!: how to protect the appliances in your home" - it is published by the National Institute of Standards and Technology, the US government agency formerly called the National Bureau of Standards - it was published in 2001 Both guides were intended for wide distribution to the general public to explain surges and how to protect against them. The IEEE guide was targeted at people who have some (not much - should be easy for anyone here) technical background. Both say plug-in surge suppressors are effective. For complicated equipment, all interconnected devices, like a computer and printer, need to connect to the same surge protector. If a device, like a computer, has external connections like phone or LAN, all those wires have to run through the surge suppressor for protection. This type of suppressor is called a surge reference equalizer (SRE) by the IEEE (also described by the NIST). The idea is that all wires connected to the device (power, phone, CATV, LAN, ...) are clamped to a common ground at the SRE. The voltage on the wires passing through the SRE are held to a voltage safe to the connected device. The primary action is clamping, not filtering or earthing. --------------------------- Can you substitute a different transformer? bud-- |
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