Can anyone provide guidance on how large a timer I need for a 400W
metal halide grow lamp? The vendor suggested a 15 amp grounded
outlet, the stated he likes 20 amps ones. However, I recently ran
across some nice, grounded 10 amp, outdoor timers ( Intermatic . On
the side they list capcaity as 1200 amps R Resistive or 1200 amps
Tungsten. I know that Metal halides are different, but do I really
need a 15 amp timer or will these 10 amp ones work?

Years ago, when I had the money to spend on things like this, I had two
400-watt halides over a large sal****er aquarium (the corals LOVED it). I
don't recall the brand, but I bought a timer that was designed for
high-draw inductive loads. A couple of years later, I sold off the
aquarium, and the timer was still working just fine.

steve

Can anyone provide guidance on how large a timer I need for a 400W
metal halide grow lamp? The vendor suggested a 15 amp grounded
outlet, the stated he likes 20 amps ones. However, I recently ran
across some nice, grounded 10 amp, outdoor timers ( Intermatic . On
the side they list capcaity as 1200 amps R Resistive or 1200 amps
Tungsten. I know that Metal halides are different, but do I really
need a 15 amp timer or will these 10 amp ones work?

Years ago, when I had the money to spend on things like this, I had two
400-watt halides over a large sal****er aquarium (the corals LOVED it). I
don't recall the brand, but I bought a timer that was designed for
high-draw inductive loads. A couple of years later, I sold off the
aquarium, and the timer was still working just fine.

steve

Can anyone provide guidance on how large a timer I need for a 400W
metal halide grow lamp? The vendor suggested a 15 amp grounded
outlet, the stated he likes 20 amps ones. However, I recently ran
across some nice, grounded 10 amp, outdoor timers ( Intermatic . On
the side they list capcaity as 1200 amps R Resistive or 1200 amps
Tungsten. I know that Metal halides are different, but do I really
need a 15 amp timer or will these 10 amp ones work?

Years ago, when I had the money to spend on things like this, I had two
400-watt halides over a large sal****er aquarium (the corals LOVED it). I
don't recall the brand, but I bought a timer that was designed for
high-draw inductive loads. A couple of years later, I sold off the
aquarium, and the timer was still working just fine.

steve

(Mike) writes:
outlet, the stated he likes 20 amps ones. However, I recently ran
across some nice, grounded 10 amp, outdoor timers ( Intermatic . On
the side they list capcaity as 1200 amps R Resistive or 1200 amps
Tungsten. I know that Metal halides are different, but do I really

Tungsten lamps are mostly resistive.

A MH light is an inductive load because of the transformer, which is a
hassle. The transformer will give you power surges, which will in turn
provide nice sparks in a mechanical relay or wear and tear on the
oxide layers in a solid-state relay. In time, things will die,
hopefully not in a spectacular way.

The more expensive the timer is, the better the insides will be
protected from these kinds of surges. A higher power rating means more
robust parts, which will take more abuse before the part dies.

I use a mechanical 2500W digital timer. It is mounted on a tile wall
so it can go bang as loud as it wants without burning the house
down. It has lasted 18 months or so now, and it cost me about $20. I
am on 240V, so the parts only need to cope with half the current that
a 2500W part would need to handle in your part of the world. It
controls about 500W of miscellaneous lights.

YMMV.

Geir

I enjoyed reading all the responses to this thread. Everybody had some
good input on this one.
And the simple answer to your question of a 10 amp timer is:...
Yes you can use it.
And the long answer is:....
DON'T DO IT!!
It will work for a while, but it is a timer bomb! (pun)
Might be in a month, might be in 2 years. If you are lucky it will
just stop working. If you are unlucky it will fire up and burn like a
roman candle! (I have seen digital, analog, and mechanical timers all
burn up) Intermatic makes some very good timers, but the one you are
talking about is not top quality for what you want it to do.
Geir is right to mount on tile.
Beecrofter is right, make sure to use a 3 prong timer and if avil a
GFCI outlet.
Salty is right, I think you will find once a 400 watt MH is up to
full inten. it will pull anywhere from 3.6 to about 5 amps (varys from
1 ballist to another , my MHs run 4 to 4.5 for a 400 watt MH fixture)
The start up can pull 8 amps or more for a brief period.
good rule of thumb is 80% of rating. If you have a 100 amp breaker do
not put more than 80 amp load on that circuit.(same applies to the
wire as well as the outlet)
Remember to be aware that the circuit you are putting this light on
may feed other parts of your house. (check it out and total it all up
to make sure)
Also you may want to think about converting to 220 volt. The ballist
should have taps on it for other voltages. 220 volt will save you at
least one third of your operating cost of the fixture.
Then you need to buy those 220 volt timers for window air
conditioners. Or.. invest in 110 volt controled contactors.
Your timer will last a lot longer and the contactors do not burn up
near as easy as a timer with a heavy load on it.
Because of the loads I run in my rooms, I don't evan take chances with
outlets. Most all my lights, fans, heaters, and humidifiers are all
hard wired into power center enclosed steel boxes that contain the
timers and contactors and all hook up points outside of the high
humidity areas.

In short... I would use the 20 amp timer.


HAPPYNESS TO ALL
NOOK




On 14 Mar 2004 11:43:40 -0800, (Mike) wrote:

Can anyone provide guidance on how large a timer I need for a 400W
metal halide grow lamp? The vendor suggested a 15 amp grounded
outlet, the stated he likes 20 amps ones. However, I recently ran
across some nice, grounded 10 amp, outdoor timers ( Intermatic . On
the side they list capcaity as 1200 amps R Resistive or 1200 amps
Tungsten. I know that Metal halides are different, but do I really
need a 15 amp timer or will these 10 amp ones work?

Thanks
Mike

I enjoyed reading all the responses to this thread. Everybody had some
good input on this one.
And the simple answer to your question of a 10 amp timer is:...
Yes you can use it.
And the long answer is:....
DON'T DO IT!!
It will work for a while, but it is a timer bomb! (pun)
Might be in a month, might be in 2 years. If you are lucky it will
just stop working. If you are unlucky it will fire up and burn like a
roman candle! (I have seen digital, analog, and mechanical timers all
burn up) Intermatic makes some very good timers, but the one you are
talking about is not top quality for what you want it to do.
Geir is right to mount on tile.
Beecrofter is right, make sure to use a 3 prong timer and if avil a
GFCI outlet.
Salty is right, I think you will find once a 400 watt MH is up to
full inten. it will pull anywhere from 3.6 to about 5 amps (varys from
1 ballist to another , my MHs run 4 to 4.5 for a 400 watt MH fixture)
The start up can pull 8 amps or more for a brief period.
good rule of thumb is 80% of rating. If you have a 100 amp breaker do
not put more than 80 amp load on that circuit.(same applies to the
wire as well as the outlet)
Remember to be aware that the circuit you are putting this light on
may feed other parts of your house. (check it out and total it all up
to make sure)
Also you may want to think about converting to 220 volt. The ballist
should have taps on it for other voltages. 220 volt will save you at
least one third of your operating cost of the fixture.
Then you need to buy those 220 volt timers for window air
conditioners. Or.. invest in 110 volt controled contactors.
Your timer will last a lot longer and the contactors do not burn up
near as easy as a timer with a heavy load on it.
Because of the loads I run in my rooms, I don't evan take chances with
outlets. Most all my lights, fans, heaters, and humidifiers are all
hard wired into power center enclosed steel boxes that contain the
timers and contactors and all hook up points outside of the high
humidity areas.

In short... I would use the 20 amp timer.


HAPPYNESS TO ALL
NOOK




On 14 Mar 2004 11:43:40 -0800, (Mike) wrote:

Can anyone provide guidance on how large a timer I need for a 400W
metal halide grow lamp? The vendor suggested a 15 amp grounded
outlet, the stated he likes 20 amps ones. However, I recently ran
across some nice, grounded 10 amp, outdoor timers ( Intermatic . On
the side they list capcaity as 1200 amps R Resistive or 1200 amps
Tungsten. I know that Metal halides are different, but do I really
need a 15 amp timer or will these 10 amp ones work?

Thanks
Mike

I've used just a simple 2-prong lamp timer. I'm not recommending it,
just telling you what I did. Worked great. Your mileage may vary.


Mike wrote:
Can anyone provide guidance on how large a timer I need for a 400W
metal halide grow lamp? The vendor suggested a 15 amp grounded
outlet, the stated he likes 20 amps ones. However, I recently ran
across some nice, grounded 10 amp, outdoor timers ( Intermatic . On
the side they list capcaity as 1200 amps R Resistive or 1200 amps
Tungsten. I know that Metal halides are different, but do I really
need a 15 amp timer or will these 10 amp ones work?

Thanks
Mike

(Mike) writes in article dated 14 Mar 2004 11:43:40 -0800:
Can anyone provide guidance on how large a timer I need for a 400W
metal halide grow lamp? The vendor suggested a 15 amp grounded
outlet, the stated he likes 20 amps ones. However, I recently ran
across some nice, grounded 10 amp, outdoor timers ( Intermatic . On
the side they list capcaity as 1200 amps R Resistive or 1200 amps
Tungsten. I know that Metal halides are different, but do I really
need a 15 amp timer or will these 10 amp ones work?

(I think you mean 1200 Watts, not amps.)

The "right" answer to your question should be stamped on the fixture
somewhere, or on the ballast if the components were manufactured separately.

Metal halides are not a purely resistive load because of the inductors in
the ballast, but even if you double the 3.3A current required to sustain
400W it's less than 10A.

-- spud_demon -at- thundermaker.net
The above may not (yet) represent the opinions of my employer.

(Mike) wrote in
m:

Can anyone provide guidance on how large a timer I need for a 400W
metal halide grow lamp? The vendor suggested a 15 amp grounded
outlet, the stated he likes 20 amps ones. However, I recently ran
across some nice, grounded 10 amp, outdoor timers ( Intermatic . On
the side they list capcaity as 1200 amps R Resistive or 1200 amps
Tungsten. I know that Metal halides are different, but do I really
need a 15 amp timer or will these 10 amp ones work?

Thanks
Mike

A 10 amp timer will work for a while but it isn't designed for an
inductive load like a ballast which is basicly a transformer. Every time
the timer switches off the ballast acts something like the spark coil in
you car causing an arc across the contacts which eventually distroys them.
A 20 amp plug in timer will last longer but 95% of plug in timers aren't
designed for incuctive loads.
I couldn't find a web sight that had a good picture of what you shuld use
but I found one on ebay. note this is a dual voltage unit and you'll only
need a single 115/120 volt unit.

I've run my fluoresent lights (36-40 watt tubes or 1440 watts) for over ten
years with no problems.


http://cgi.ebay.com/ws/eBayISAPI.dll...ategory=42 89
7

Hope this helps
dusty

(Mike) wrote in
m:

Can anyone provide guidance on how large a timer I need for a 400W
metal halide grow lamp? The vendor suggested a 15 amp grounded
outlet, the stated he likes 20 amps ones. However, I recently ran
across some nice, grounded 10 amp, outdoor timers ( Intermatic . On
the side they list capcaity as 1200 amps R Resistive or 1200 amps
Tungsten. I know that Metal halides are different, but do I really
need a 15 amp timer or will these 10 amp ones work?

Thanks
Mike

A 10 amp timer will work for a while but it isn't designed for an
inductive load like a ballast which is basicly a transformer. Every time
the timer switches off the ballast acts something like the spark coil in
you car causing an arc across the contacts which eventually distroys them.
A 20 amp plug in timer will last longer but 95% of plug in timers aren't
designed for incuctive loads.
I couldn't find a web sight that had a good picture of what you shuld use
but I found one on ebay. note this is a dual voltage unit and you'll only
need a single 115/120 volt unit.

I've run my fluoresent lights (36-40 watt tubes or 1440 watts) for over ten
years with no problems.


http://cgi.ebay.com/ws/eBayISAPI.dll...ategory=42 89
7

Hope this helps
dusty

Thanks to everyone for all of the feedback.
In short, my take is- Cheap will be O?K for a while- Could be a short
while and could be a bad outcome when it goes. Spend more get the
better timer.

Thanks again.