can i use a 600w hps ballast to run a 400w hps

i have been told by a local shop that is is safe to use a 600w ballast to run 400w hps ?
is this correct? obviously im no sparky but it sounds a bit dodgy

I wouldn't do it

no
you have to have the total of the ballast....so i can run in a 1k ballast a 400 and a 600...but most match the total watts. and yes ive done thins and ran 2 rooms with a relay and saved money on parts

ok cool so you would say its a bad idear

what would happen if this was done ? or would it just not ignite ?

i would say no
u got a 400w bulb and trying to push 600w through it....something bad is bound to happen(kaboom)
u can probably run a 600w bulb on a 400w ballast
but dont do what u r currently speaking of

The ballast must match the bulb - period.

EDIT : Having said that so definitely, maybe it is not quite so clear cut after reading later posts - none of us ever stop learning.

ok sound cheers for advice . do you think a 600w hps bulb in a meter square by two meter high grow tent will be overkill ?

I've heard of special ballasts that can do that. I've never used or seen one, but ive heard of them. Maybe thats what he means? cuz your right, running a normal 400w in a normal 600w is "a bit dodgy"

post#8........nope................

those are cal;led switchable ballast. i have a quantum that does a 250...400 and a 600 with a flick of a swicth......................http://www.quantumhort.com/images/content/ads/greyback_v1.jpg

Medi 1 said:

those are cal;led switchable ballast. i have a quantum that does a 250...400 and a 600 with a flick of a swicth......................http://www.quantumhort.com/images/content/ads/greyback_v1.jpg

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I was gonna say that, lol, but i wasnt sure on the name. I just knew they made ballasts like that.

Dont know for sure on hps but hell yeah in mh you can put a smaller wattage bulb . Everybody posts answer about lighting that dont know shit about electricity .

Lesson for you Moash ! The lamp determines the load . a 600 watt ballast with a 400 watt lamp doest mean 600w is being run to it .The ballast only draws what you load it with based off the wattage of the bulb.
By the way a 400 w ballast will not light a 600w bulb

Medi1 yes you can do that but thats not how it has to be the lamp has to have a lower wattage and it doent work with allof them anyways because of different sized capaciters on differnt wattage ballasts

well i dont get why people want to put extra loads and strain on equipment. but the right shit and be done and safe, so then where does this left over curent go to then,.must build up somehwere and cause where and tear real fast

kingofqueen said:

Lesson for you Moash ! The lamp determines the load . a 600 watt ballast with a 400 watt lamp doest mean 600w is being run to it .The ballast only draws what you load it with based off the wattage of the bulb.
By the way a 400 w ballast will not light a 600w bulb

Medi1 yes you can do that but thats not how it has to be the lamp has to have a lower wattage and it doent work with allof them anyways because of different sized capaciters on differnt wattage ballasts

Click to expand...

thanks for my lesson
i suppose ill just call it human error when my 400w bulb burnt out on a 1000w ballast
also for someone that is so electricly inclined,why dont u know if it will work for a hps
thats is what the o.p. has

moash said:

thanks for my lesson
i suppose ill just call it human error when my 400w bulb burnt out on a 1000w ballast
also for someone that is so electricly inclined,why dont u know if it will work for a hps
thats is what the o.p. has

Click to expand...

Because I,m a stoner and dont remember everything.But about a year ago I had to put a 250 metal halide in a 400 w fixture did have a choice because i was in a rental lift and thats all I had .It,s still working to this day.Most outdoor lighting nowadays is matal halide instead of hps so I just cant recall from experiance trying it with hps but I,d imagine it would work the same.

You have an electrical question I can answer it for you if not I can find the answer I have been doing electrical construction and service for 18 yrs .I,m an hands on guy not a book guy I know stuff from actually doing it .I,m really good at researching answers from running my own jobs and having to research and plan a job out .

This is for Medi1 .It doesn't work that way .For example a 400 w ballast has a potential to put out 400 watts. So if its on and there is no lamp there is not 400w sitting there waiting to be unleashed . So the ballast needs a load and you put say a 250 w in it.Now the lamp which has a resistance load of 250 loaded on it ,the lamp is the load so thats all that is being drawn from the ballast . It doesnt mean that there is now 150 watts scrambling around ! Now put a 400 in it and now you have loaded the ballast to full potential. Try to put a 600 in it it wont light because the starting capaciter is now out of range .Okay change the capacitor and try again now th ballasted is over loaded with 200 w of overload and will begin to burn up or not work at all.

A ballast is a voltage transformer . 2 sets of independent coils of copper wiring wrapped around a core .Ones an input the other an output .With lighting the voltage is stepped up .

All the above is for for example only do not try unless qualified .Everyone things because the can set up a growroom that this makes them an electrical expert.Let the electricians answer the electrical question and everyone will be okay.

No offence to anyone here . Its just frustrating when i see some giving bad wrong advice because they really think they know what they are talking about.

I,m here to try to help people not argue with people who want to challenge my knowlage .

Alright time to wake and bake peace out !

OH while its on my mind don't resort to name calling on here .Its not nessesary and wasnt appreciated.But I am a very forgiving person and think we should all just get along and help each other grow !

dood im not usualy into the name shit. but you threw the fisrt stone at a few here with your arrogant comments., you reap what you sow. you insuklted others with your ...im so good of an electricion comments.. to me and a few others is no diff than a name calling. lets drop it and move on and loose the ego.


id say i see alot of might and maybe stuff there. so for a guy that makes a claim he knows so much and has done it for so long is sure not sure here.



" I just cant recall from experiance trying it with hps but I,d imagine it would work the same."


i called my certified electrition i have and showed this...he fell over laughing..no offence intended but we usualy talk about the self ballast cfl, as this is what 99% of us have in our stores. so why advise on a tube we never even seen nor use. those ones in the link are little toys, not what we use to grow with or without a ballastthe way id see IF it worked would major heat from an inefficient running ballast. is why we use digi now so we create less heat and get more lumens to the bulb and less loss due to heat. you resist anything more than meant to it makes more heatfunny nobody has said anything about Ohn`s law for being elctricions to do the actual math.

Man i,m trying to get off this subject but u wont let it be . Did u totally miss the point or what? I posted that about the cfl not for the guy that posted originally but for the guy who THEY DONOT EXIST ! Is that to hard to understand? He said they dont exist i,m not gonna let someone tell me somthing i know is wrong . What you mad because i proved that guy wrong or what .Seriously whats your beef here man air it out pm me or whatever but dont shoot me down .All electrical calculations use ohms law common knowlage bro but whos gonna try to explain that to people that cant screw in a light bulb .