Periodic transformer failure

V

vMike

Guest
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
 
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
Click to expand...
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
 
On Wed, 4 Oct 2006 22:58:26 -0400, "vMike"
<MicZhaYel.GeoZrgeY@noYandZ.geZwaYrrenZ.com> 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
Click to expand...
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).
 
On Wed, 4 Oct 2006 22:58:26 -0400, "vMike"
<MicZhaYel.GeoZrgeY@noYandZ.geZwaYrrenZ.com> 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
Click to expand...
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.


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<tgdenning@earthlink.net> wrote in message
news:1160046485.116410.95780@m7g2000cwm.googlegroups.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
Click to expand...
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
 
"default" <default@defaulter.net> wrote in message
news:np1ai2h3k2tll08t808jo1sfttbcns6v7d@4ax.com...
On Wed, 4 Oct 2006 22:58:26 -0400, "vMike"
MicZhaYel.GeoZrgeY@noYandZ.geZwaYrrenZ.com> 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
Click to expand...
previous poster.

Mike
 
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!!
Click to expand...
 
On Oct 5, 5:51 pm, "w_tom" <w_t...@usa.net> 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.
Click to expand...
The best information I have seen on surge protection is at
http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_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/practiceguides/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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