Too much heat from light?

[wxcrawler]

This is my first year growing tomatoes from seed. I got a 2-foot, 4 bulb T5 fixture for my growing light. After 3 days, I got my first germination from a Super Sweet 100 seed today. Woohoo! I put my small container under the light fixture earlier this evening, with the top of the container about 3-4" from the bulbs. It felt a little warm under there, so I put in a thermometer. It's now reading 91 degrees about 6" below the bulbs. With this fixture, I can turn on 2 or 4 bulbs, and I only have 2 bulbs on. I checked the soil temperature at the top of my container, and it was only 79, which is what it was before germination.

Is this temperature too hot under the lights?

If it is, what can I do to keep it cooler?

Thank you very much.

Lee

[JamesL]

Can you post a picture of your setup?
What's the room temp outside the lights? Same as the soil temp (79)?
A fan would help...

[wxcrawler]

The temperature in the room is 68-71 depending on whether the heater in the house is on. The soil temp of 79 is what it was when the container was on the heating pad. Since it stayed around 79 with no heating pad for a couple of hours, I'd say the light is warming the soil somewhat.

I thought about a fan, but wasn't sure I should do that when they were so small.

Thanks.

Lee

[JamesL]

The fan won't hurt them. Might cause them to dry out a little faster.
Are you sure your thermometer is accurate?
Seems like a big temp jump from 2 fluorescent bulbs.

[Worth1]

With florescent lights you can do everything but touch the plant.

I have never checked the temp but I would do as James said and use a fan and I would also lower the light and use all four of them..

Worth

[wxcrawler]

Thanks for the input JamesL and Worth.

I figured out my thermometer was reading a little high. I had it laid down on the black capillary mat (not wet yet). The mat was absorbing heat. I set the thermometer upright, and the temp went to 85-86. Most of my other varieties germinated today, so I have 8 of those little containers in there. I turned on the 4 lights. I'm going to take Worth's suggestion and lower the fixture a little. If the temp goes back up, I'll try a fan.

Lee

[luigiwu]

I can't imagine that the fluorescent lights are causing those temps. I have a heat mat on and (in a humidity chamber - for figs ) its only measuring 73 degrees. Could it be that location is right over some radiators? Its like Worth said, you can almost put the fluorescent lamps right on your leaves!

[wxcrawler]

No....it's definitely the lights. No heating pad or heating vents near the table. I can feel the heat from the lights when I put my hand under them. That's what made me check the temp with the thermometer to begin with.

Lee

[gregory]

My t8 puts out very little heat and I use daytime lights.

I thought t5 is even cooler

[JamesL]

Lee,
Sounds like you have it figured. As the gang has already said, put the lights down low.
And run the fan anyway if you have one handy.

[Father'sDaughter]

I think I read something once about T5 grow lights running hotter if a particular ballast is used. I never looked into it any further as I abandoned the grow light route and just went with regular lighting fluorescents from Home Depot in a shop light.

[luigiwu]

Oh, I definitely only use cheapo daylight deluxe tubes from home depot...

[Father'sDaughter]

Originally Posted by luigiwu

Oh, I definitely only use cheapo daylight deluxe tubes from home depot...

Yes, I believe a lot of us went the cheapo route! But where the fixture in the picture appears to be a grow light fixture, Lee may not have, and it may explain the higher temps.

[wxcrawler]

The fan is working a little. I lowered the fixture down to 2-3" above the top leaves. The temp went up to 91. I added an oscillating fan, and the temp dropped down to 86 after a few minutes. It seems to have leveled off there.

Lee