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Seeds forum: DIY Heat Mat

Views: 1615, Replies: 10 » Jump to the end
Name: Mary
My little patch of paradise (Zone 7b)
Gardening dilettante, that's me!
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fiwit
Dec 21, 2011 6:59 AM CST
In case y'all hadn't seen this tutorial...

http://www.vegetablegardener.com/item/11658/diy-heat-mat-spe...

The used plywood, 1x2s and rope lights to make a heat mat that comes darn close to the commercial ones. Lots of good photos too

How well does it work?

The heat mat takes approximately 30-45 minutes to fully heat up, and using my hand, felt as warm as the commercial heat mat. Upon taking measurements with both regular and soil thermometers, the numbers were impressive.

Commercial heat mat
Surface temperature
(thermometer placed on top of soil): 73-75 degrees F
Soil temperature: 80-82
Bottom temperature (gap between heat mat and seed trays): 100-102

DIY light heat mat
Surface temperature: 72-74
Soil temperature: 78-80
Bottom temperature: 105-110

Note: To control heating times, use a thermostat or timer.


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Name: Allison
NJ (Zone 6a)
Forum moderator Charter ATP Member I was one of the first 300 contributors to the plant database! Hummingbirder Region: New Jersey Dog Lover
Seed Starter Container Gardener Garden Ideas: Level 1
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Onewish1
Dec 21, 2011 11:47 AM CST

Moderator

now that is totally attainable in this house.. we have spools and spools of the stuff!!!.. thanks!!!!
Name: woofie
NE WA (Zone 5a)
Charter ATP Member Garden Procrastinator Dragonflies Keeps Goats Plays in the sandbox I was one of the first 300 contributors to the plant database!
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woofie
Jan 5, 2012 12:42 PM CST
Does anyone know what the wattage is for those rope lights? As many of those things as I use (and I could use more), the cost of the electricity is a factor for me. My small, single flat, heat mats use 17W.
Confidence is that feeling you have right before you do something really stupid.
Name: Allison
NJ (Zone 6a)
Forum moderator Charter ATP Member I was one of the first 300 contributors to the plant database! Hummingbirder Region: New Jersey Dog Lover
Seed Starter Container Gardener Garden Ideas: Level 1
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Onewish1
Jan 5, 2012 5:11 PM CST

Moderator

it varies but around 6 watts per foot
Name: woofie
NE WA (Zone 5a)
Charter ATP Member Garden Procrastinator Dragonflies Keeps Goats Plays in the sandbox I was one of the first 300 contributors to the plant database!
The WITWIT Badge I helped plan and beta test the plant database. Garden Sages Enjoys or suffers cold winters Container Gardener Seed Starter
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woofie
Jan 5, 2012 5:25 PM CST
Thanks! Hmmm, this might be worth looking into for larger areas. For some reason, my larger heat mats use more wattage than an equivalent number of singles.
Confidence is that feeling you have right before you do something really stupid.
Name: Rick Corey
Everett WA 98204 (Zone 8b)
Sunset Zone 5. Koppen Zone Csb
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RickCorey
Jan 17, 2012 2:05 PM CST
I looked up heat tapes used for protecting water pipes from freezing, but most of them had built-in thermostats set to 38 F.

Bare Nichrome wire is only 17-22 cents per foot, and can be had at 27, 42 or 70 Ohms per foot (36, 38 or 40 AWG).

I think you need 300 - 1,000 Ohms to get 12-50 watts from 120 V

On the other hand, "waterproof" sounds like a highly desirable feature.

And SHORT lengths of 40 AWG are used as "igniters" and "electric matches", so maybe the whole idea is dubious.
Name: Karen
Cincinnati, Oh (Zone 6a)
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kqcrna
Jan 17, 2012 2:21 PM CST

Moderator

I like these little 3" wide heat mats.
http://wormsway.com/detail.aspx?t=prod&sku=FGP301

Even seeds like impatiens and begonias, which notoriously require heat, have worked well for me. I run them 24/7 until they germinate, and keep a humidity dome on the tray to retain the warmth. Cheap and easy- I like them!

Karen
Name: Allison
NJ (Zone 6a)
Forum moderator Charter ATP Member I was one of the first 300 contributors to the plant database! Hummingbirder Region: New Jersey Dog Lover
Seed Starter Container Gardener Garden Ideas: Level 1
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Onewish1
Jan 17, 2012 4:05 PM CST

Moderator

do you just use one 3" under a tray?
Name: Karen
Cincinnati, Oh (Zone 6a)
Forum moderator I was one of the first 300 contributors to the plant database! Cut Flowers Winter Sowing Charter ATP Member Seed Starter
Echinacea Plant and/or Seed Trader Region: Ohio Region: United States of America Butterflies Hummingbirder
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kqcrna
Jan 17, 2012 4:40 PM CST

Moderator

Yes, Allison. I do keep a humidity dome on too, and it holds the warmth in. For $19, it's hard to beat.

Karen
Name: woofie
NE WA (Zone 5a)
Charter ATP Member Garden Procrastinator Dragonflies Keeps Goats Plays in the sandbox I was one of the first 300 contributors to the plant database!
The WITWIT Badge I helped plan and beta test the plant database. Garden Sages Enjoys or suffers cold winters Container Gardener Seed Starter
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woofie
Jan 17, 2012 4:53 PM CST
For waterproof, these are the ones I use. And the manufacturer stands firmly behind their product. Several years ago, I bought 4 or 5 of these that were apparently from a bad run. I contacted the mfr and they acknowledged that there had been a problem with one manufacturing run of this size and they replaced them ALL, no questions asked, no receipt required.
http://www.hydrofarm.com/pb_detail.php?itemid=3347
If you shop around, you can generally beat the suggested retail on these.

Once, when I ran out of space on my heat mats, I put clip on lights with 60 watt bulbs on a shelf below the flats, with the reflectors pointed up. Had to be REALLY careful watering, but it worked pretty well. Heh, heh, I really don't recommend the practice, tho. Whistling
Confidence is that feeling you have right before you do something really stupid.
Name: Allison
NJ (Zone 6a)
Forum moderator Charter ATP Member I was one of the first 300 contributors to the plant database! Hummingbirder Region: New Jersey Dog Lover
Seed Starter Container Gardener Garden Ideas: Level 1
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Onewish1
Jan 17, 2012 6:31 PM CST

Moderator

Karen that is a good deal.. since we have so much rope light.. spools and spools.. I am def. going to try it this year

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