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question about 315 cmh

zachrockbadenof

zachrockbadenof

Well-known member
Veteran
i have '2' 315's - the hood came with a glass covering the opening- i removed the glass on my last grow figuring it would give a bit more light- my buddy said the glass should not be removed as its a safety issue - any truth to that?? and do u get a few extra lum's with the glass removed??
 
MJPassion

MJPassion

Observer
ICMag Donor
Veteran
I've not used CMH's.


Are they similar in construction to metal hailide bulbs with the quartz plasma chamber inside another glass envelope?


If so I would think that the outer glass envelope is a safety barrier in case the plasma chamber breaks.


Also, If I recall correctly, CMH can be extremely dangerous if the outer envelope breaks and it continues to operate. Pretty sure the outer envelope is UV protected glass.
 
Lost in a SOG

Lost in a SOG

GrassSnakeGenetics
I think he means the glass on the hood not the bulb.

I presume it was an aircooled hood then? Why did they come in a hood with glass? That's a bit confusing..

These are normal 315 CMH bulbs aren't they? Philips?

Anyway the cmh were designed to be bare bulb as far as I know, they use them like that in professional horticulture.. Any further glass beyond the layers comprising the bulb itself will just block a bit of UVB.. UVB is an advantage to CMH..

Having said that I run my CMH air cooled behind extra glass and it doesn't seem a problem to me. Kind of depends on the thickness of the glass as well a bit.
 
zachrockbadenof

zachrockbadenof

Well-known member
Veteran
yep -i mean the glass on the hood, and yes it could be air-cooled- i just questioned my buddy again and he further says that you can remove the hood glass from a 630 cmh, but u should leave it on a 315 for safety- i would think both the 315 and 630 bulbs are made similar , so don't quite understand ... the bulbs that came with the setup are hydro-crunch, not philips...
 
MJPassion

MJPassion

Observer
ICMag Donor
Veteran
Bulb construction is important for safety reasons.


I fully understood the question about the hood.
I was asking for clarification due to my own interest.


If your bulb has a quartz plasma chamber inside of a glass envelope, I would think it would be safe without the glass in the hood.

HOWEVER:
I think it comes down to whether the bulb self extinguishes upon breaking or if it continues to run after breaking. If the bulb does not automatically extinguish itself upon glass envelope failure you could be exposing yourself & your plants to unusually high levels of UV. At least that's the way I understand it. Also, if the bulb does not self extinguish, it is a fire hazard.


Bulb construction is extremely important!
 
Nico Farmer

Nico Farmer

Authentic Strains Farm
Hi,
never remove CMH glass, like MJ said, you risk very serious health issues, high UV levels are dangerous.
In theory, as in manual, the instructions are to always work covered, even the hands, in case of breakage of the bulb.
 
zachrockbadenof

zachrockbadenof

Well-known member
Veteran
i sent an email to the seller- he replied that you will get better penetration with the glass removed -and there is no safety concerns... i think this go-around i'm putting the glass back on the hood- just to be safe...
 
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