This is a quick and cheap way of cooling your lamp down, it sounds daft but my temps are a stable 25 degrees.

What you need is:
1 metre of double sided foam tape or some really sticky and stable tape.
A square of UV stabilised clear pvc flexible sheeting (which you buy from garden centres by the metre)

Thats about all you need

You stick the sheeting across the bottom of a barn style reflector. The springyness of the reflector keeps it tight. Leave the end of the reflector away from the lamp holder open (that is your air in). Push the end of your flexible ducting into the gap next to the lamp holder, this will then suck air from around the lamp. I connected my ducting to my 6" extractor and moved my carbon filter to the other end of the fan system so the fan blows out through it so I didn't need an extra fan.

As I say it sounds daft using plastic sheeting with a 600w HPS but the plastic just doesn't get hot and it works fine. 5 minute fix for a couple of quid and its thinner than toughened glass so won't steal as many lumens.

Word of caution though: work with a cool lamp, make sure the plastic is on tight before you turn on!
If anyone is brave enough to try it with a 1000 watter let me know!!

Here's a piccy: [attachmentid=119862]
Lastly this plastic gets brittle after a few years so changing every other grow would be a sensible precaution

Nice1 Billious,

Good idea, ill try that.
Is it that pvc easy to get hold of? What is it used for if anyone asks?

Cheers

Its used for loads of things. My cheapo greenhouse is covered in the stuff, people make cloches, incubators, shed windows, cheap polytunnels and the like from it. You can buy it on the net I am sure but my local dobbies garden centre sells it. It may be the same as the clear builders sheeting.

I suspect that it will suppress some of the lumens though

Maybe get hold of a light meter and test it with and without

Owd

I am sure you are correct Owd. When I chose this material for my greenhouse I seem to remember it was 95% transmission. So long as memory serves right then I am losing ~ 5000 lumens. For my limited grow space temps are the important factor though and even with the reduced lumens the leaves at the top of my last buds were bleached white which I believe was the light intensity from the restricted height (read something to that effect on here somewhere)

My light meter had the same max reading as soon as I entered the grow space so I guess it just doesn't quite reach the "blinding light" range

I would caution that the material I use is completely clear like a pane of glass, anyone trying this should avoid the milky commercial polytunnel covering as this is too thick & has a diffussing effect and will probably drop the lumens quite a lot. The stuff I used was 75 microns.

I popped down bnq today to find some plastic sheeting. I came across some clear plastic sheeting which used in shed windows, greenhouses etc.
Im not sure if its pvc or perspex, it seemed a bit thin (3-4mm) like it would melt/warp 2" under a HID. It was flexible(like rolf harris's sheet of card instrument thing if you know what i mean)
Il have to check the number of microns and UV stability.

Would this be the same stuff?

Would it have to be replaced every grow?

Would i lose the same amount of lumens if i used glass?


Cheers

quote name='G Bud' date='Jan 10 2007, 04:31 PM' post='820196']
I popped down bnq today to find some plastic sheeting. I came across some clear plastic sheeting which used in shed windows, greenhouses etc.
Im not sure if its pvc or perspex, it seemed a bit thin (3-4mm) like it would melt/warp 2" under a HID. It was flexible(like rolf harris's sheet of card instrument thing if you know what i mean)
Il have to check the number of microns and UV stability.
Would this be the same stuff?
Would it have to be replaced every grow?
Would i lose the same amount of lumens if i used glass?
[/quote]

The stuff I used is thin, rolled-up sheeting rather than flexible but rigid sheet it quite a lot less than a millimetre thick. Its just clear plastic sheet and the same sort of thickness as black n white sheet if you know that stuff. You can get it at garden centres. BnQ sell the builders sheeting but you have to buy loads at a time and its not as clear as the horticultural stuff! Fraid I can't comment on glass lumen loss versus PVC sheet, I just know what I am happy with and what has worked for me

bit risky and why dont you get the silver foil ype duct,be safer

Thanks for the input. By risky are you referring to the risk of melting or combustion? I placed a temp probe on the inner surface of the sheet right below the lamp and its running at 31.5 C, thats cooler than some popular holiday destinations so I can't see that there is much risk there.

I would agree that there is a risk if the sheet detached from the reflector as it may get sucked up onto the lamp. A secure fixing and a wide opening at the end to reduce the suction load is a must.

I don't understand you comments about the foil ducting though. It would reflect better and reduce light transmission both in and out of the room but I don't understand why it would be safer. Please don't misunderstand my questioning, I would love to use the foil stuff but I can't see why I am being unsafe. Is the plastic stuff unstable or something?

i was thinking if the fan packs up that plastic duct might melt how close is it

Its about 3 inches behind the back of the bulb. I may look out for some of the ally ducting in 150mm the plastic stuff let in light last year and hermied some plants anyway!

Cheers

Had a little look at that mate seems like the solution i'd need but there is one problem. I can't seem to see whats going on in the first pic, don't be offended i think it's probably because the sheeting is see threw. , is it just a case of ducting your extraction fan to the light, then the PVC sheeting across the opening of the light. and hey presto bob's your uncle?? i was planning on ducting to the fan so that heat would be taken straight from the light but i am guessing you use the sheeting is really only used to help create a tunnel effect? like a cooltube, plus i also have a problem with the fact my intake fan is simply pulling the hot air back into the grow room

Appreciate your help mate? but a little more help won't go a miss

Peace GA

OK.... lay your reflector on a sheet of the clear plastic and fold up one side of the sheet and stick it to the outside of the reflector. Now press the side of the reflector inwards a half inch and stick the sheet on this side as well (pressing the side of the reflector in puts the sheet under tension so its nice and tight) Trim the sheet that overhangs the end of the reflector furthest from the lamp holder. Now rehang the reflector and push the end of your duct into the open gap next to the lamp holder and tape in place loosely making sure it doesn't tough the ceramic holder itself. Now all you need to do is fold all the loose bit up and over onto the top of the reflector and tape in place. The most important thing though is to make sure you are using really sticky tape that is grow room compatible, duck tape, selotape, packing tape, etc just won't cut it and could be dangerous.

Not sure exactly what you mean about the intake fan.... you have to try and vent the hot air away as it will be depleted in CO2 or pull your air in from somewhere else, plus using this method you have to put the CF on the terminal end of the duct and blow into it

Just posted in your other thread m8, but just in case you don't see it.... you can't use this method unless you have a fan that can shift a decent amount of air, proper inline ducting fans only, anything else is potentially dangerous because they either may not provide enough cooling or they may break under the constant load.... bathroom fans aren't designed for 24/7 operation... they may work but its just not worth the risk

Those sentences have already made me change my mind, I am not going for the sheeting just a better extract fan! i was thinking if at least heat is being taken out at a faster rate then surely it will help cool the drobe? what do you think?

Cheers billious mate!! i am glad you took the time to pop in on my thread and give is a helping hand!

crank up the extract! sensible move m8, play around with other stuff once you've exhausted all other options!

Great idea! Will this work with an rvk 125? it has a maximum airflow capability of 250m3/hr I have a D.I.Y carbon filter about half a meter long ?

Hi m8, 125?, couldn't answer for sure... sorry!... but it sounds like you like to experiment anyway?!

My whole rig from day one has been a crazy experiment! ill be trying this one out as soon as I can its these ideas that set the poor man up for life!!!

it's a god idea until the fan packs up and sets the plastic sheeting on fire

That was something that worried me as well m8...... but PVC combusts without a flame at 390c which is a very unlikely a temp I think a couple of inches from the bulb..... melting though that's a possible problem, it melts at 212c, but air when its not moving is a good insulator so I'm not sure that 212c is likely at that distance but I suppose if it did it would melt down onto the plants as gravity has its way..... I suppose melting would kick in first anyway if the temps where there?.......I use glass now myself

i agree fire is unlikely, but it is a risk all the same, if the fan did pack in, i'd put money on the pvc melting though. still not worth the risk, as you say, high temp glass/pyrex is a better option