Hi all, need a little help and advice last week i got a 4 bulb t5 prop light the right ups say you can get the bulbs as close as a couple of cm's and they are not too hot. Well thats all a load of bull, I built a prop box 5f wide 4f high and 2f deep, within 10 mins of me turning the light on the temps rose to 95 and thats with exstraction , these things are hot very hot, was just wondering if enyone has had any exsperiance with t5's or had the same prob's.

Thanks all..................Scarab

I use 3 24" high output T5s in a clone/mother cupboard and it does get hot. I don't have extraction just a desk fan pulling in air. I get temps of about 28deg. The only way around it is to sort some ventilation but for me this is both expensive and time-consuming.

I like them though. The plants thrive.

Hope you sort it!

thank you for the rep rubbabudbud,
how far from the plants do you keep the bulbs and how big can you get the plants be4 they are no good...?

Hi Scarab

Can't answer your queries as I'm only finding my feet....also bought 4-light T5...nice light but reckon they give off quite a bit of heat...was being told on this site to keep it 2/3 inches away from seedlings...did and some got fried....trial and error at this stage...hopefully someone will get back to you on that query as I'm also interested.

Best of luck m8

KDD

Whatever happens, you MUST have ventilation going on otherwise temps will rise. Any bulb gives off heat (even LEDs) so without adequate air transfer the temps WILL rise. I use a 4" fan on a timer which goes on 15 minutes in the hour. It means I keep the humidity and heat levels higher but it clears every 45 mins. Plants seem to love it.

GN

Hi Ninja,

I have a 5" extract & 4" intake on when lights on. No fan controller so on 'full tilt'. Turn off at lights out as it's gets too cold. Would you recommend having fans 'on and off' during lights on period....Humidity curently around 70/75% when lights on.

RVK's/Ruck fans, as I use that for 1600w of lighting and my temps are lower!

Himidity around 60% lights on, extraction 24/7.

Something doesn't add up, but put a fan between the light and the canopy regardless it's much needed in any grow room IHMO.

Sorry tutu don't quite get ya? Can you explain?

My 144 watt seedling light :-

Click to view attachment

A thumb's width from seedlings.

My 250 watt seedling light :-

Click to view attachment

9 inches from seedlings.

In both cases, inside a PVC tent in a cupboard with only convection to take the heat away. (though it was winter)

Are you using RVK/ruck fans
http://www.greenshorticulture.co.uk/Grow-r...CK-Fans-101.asp

If so you need to look where you intake air from and extract to. I intake from outside and extract into a large room with the tents in them.

The temps of the room stay low 20C's, humidity too high is normally not enough extraction.

Hi CV....how old are you're seedling in the 2nd pic....just want to compare growth against my seedlings....I think mine should be bigger after 10 days?

Thanks KDD

My comment at the time reads "9 inches from a 250 watt HPS - oldest seedlings popped up 5 days ago."

http://www.uk420.com/boards/index.php?show...=70314&st=0

They were very mixed genetics.

I'm fooked....my seedling are about 10/11 days old and some aren't even that size...ah well.

See this morning some have brown tips on ends of leaves....looks like they're burnt but about 10 inches form light so that's unlikely..

I doubt it's light / heat burn then.

What sort of compost are they growing in ?
What size pots ?

What's your watering / feeding schedule ?

Never turn your fans off. Ever. I learned this the hard way and ended up nearly killing my first plants. Plants breathe 24/7, light or dark. They need air transfer and a stable environment to perform best. You'd do well to invest in a fan controller because it means you can set a minimum idling speed that ensures good airflow at lights out when the heat from the lights themselves would ordinarily turn the output fan on.

75% humidity is okay in veg but too high for flower...you risk all kinds of nasties with poorly controlled humidity. However, if you have good airflow humidity is very unlikely to be a problem except in the summer time or when it rains - and even then with good transfer you should be able to handle the higher humidity better (for short periods, eg. really humid summer days).

GN

Sorry Compost....I lose threads and never see them again in the mess of new posts....have to tag them or something.

As regards your query..Replies above...