comparisons of heat mat costs and performance

Richard · 11-02-2009, 10:37 PM

I'm building an outdoor propagation box with insulation. I will be rooting cuttings and starting plants from seeds. My coldest overnight temperature in the winter is typically 33 F (1 C), but more typically 40 F (5 C). My goal is to keep the rooting pots in the mid 70's (23 C) in the day and early evening and above 55 F (13 C) at night. I will use heat mats to warm the 45 sq.ft. surface and a thermostat to regulate the mats.

Here are the mats I'm considering:

Hydrofarm 48" x 20" @ 107 Watts, $55 each --> 16 W/sq.ft. and $8 / sq.ft.

Pro-Grow 22" x 60" @ 200 Watts, $155 each --> 22 W/sq.ft. and $17 / sq.ft.

Stanfield 3' x 6' @ 400 Watts, $376 each --> 22 W/sq.ft. and $21 / sq.ft.

Do you have experiences with these or alternative systems I could consider?

sunfish · 11-02-2009, 11:07 PM

Did you see these?

Redi-Heat Propagation Mats - 12"W x 10'L $132.25 /EA

Output for 12"W mats is 20 watts per linear foot. Output for 17"W mats is 30 watts per linear foot. Output for 21"W mats is 40 watts per linear foot. Mats used on GFI outlets must stay under 500 watts to avoid tripping GFI.

Richard · 11-03-2009, 01:52 AM

Thanks, this model is interesting:

Redi-Heat 21"W x 10'L @ 400W, $132 each --> 23 W / sq.ft., $11 / sq.ft.

Dalmatiansoap · 11-03-2009, 05:12 AM

Have U consider electical underfloor heating system. Its much cheeper and better than heating mats and in my opinion its easier to insulate all system.
Grrrrh, my lack of words.....Hope U understand me

Richard · 11-03-2009, 11:03 AM

Quote:

Originally Posted by Dalmatiansoap

Have U consider electical underfloor heating system. Its much cheeper and better than heating mats and in my opinion its easier to insulate all system.
Grrrrh, my lack of words.....Hope U understand me

Yes, heating cables are less expensive to purchase but very expensive to operate. They consume a lot of electricity which is expensive here in the U.S.

Dalmatiansoap · 11-03-2009, 12:22 PM

Think twice about that. If they are used properly with quality ceramic they can save U lot of money.
And U always pay Watts per Hour!
It isnt named "low energy heating sys" for nothing

Richard · 11-03-2009, 12:40 PM

Quote:

Originally Posted by Dalmatiansoap

Think twice about that. If they are used properly with quality ceramic they can save U lot of money.
And U always pay Watts per Hour!
It isnt named "low energy heating sys" for nothing

The cables I've looked at would consume 50 W per square foot. I'm only trying to raise the temperature from 2 C to 15 C. For this I believe 15 W to 20 W per square foot is sufficient.

My area is also small (see first post). For a larger surface, it would be more cost effective to use hot water pipes under the flats of plants, with water heated by a gas boiler.

Dalmatiansoap · 11-03-2009, 12:59 PM

That is what i was reffering with watts/hour. More watts-less time needed, that why u use thermometers. True is that this sys needs more hardwork but in my opinion if U want to do something more proffesional than it is everthing clear. Heat mats are good and simplest solutions for areas that we dont use only for germinations and rooting.

Richard · 11-03-2009, 02:16 PM

Quote:

Originally Posted by Dalmatiansoap

That is what i was reffering with watts/hour. More watts-less time needed, that why u use thermometers. True is that this sys needs more hardwork but in my opinion if U want to do something more proffesional than it is everthing clear. Heat mats are good and simplest solutions for areas that we dont use only for germinations and rooting.

With heating mats and cables, the first 5 minutes of operation uses nearly the same number of Coulombs (~watt x hours) as the first 20 minutes. This is why I am concerned about power density (watts per sq.ft.).

Following your suggestion I have found this efficient cable here in the U.S.: Gro-Quick 140' and 200' foot cables at 700 Watts and 1000 Watts. If I bury one in a shallow bed of horticultural sand it should be able to keep 18 flats (288 4-inch pots) warm enough for propagation. The 700 W system would be affordable to operate at 17 W / sq.ft.

Dalmatiansoap · 11-03-2009, 02:24 PM

The point is to get quality heating media as tile ceramic. Cables in sand are almost useless but whan cabels heat tiles thats completly different story. Agree? And U also get clean work surface.

Richard · 11-03-2009, 02:49 PM

Quote:

Originally Posted by Dalmatiansoap

The point is to get quality heating media as tile ceramic. Cables in sand are almost useless but whan cabels heat tiles thats completly different story. Agree? And U also get clean work surface.

I agree about sand, but horticultural sand is a different material, grain size, and heat capacity. There is an overhead misting system controlled by an electronic leaf. Water that runs off into the cable area will be heated and could provide mass transport of heat. Placing ceramic tiles on top of the cables and sand would reduce this to radiant transport, possibly keeping the pots too dry. This sounds like something to experiment with.

Attached is a worksheet showing the performance and costs of various options I've considered so far ...

Dalmatiansoap · 11-03-2009, 02:58 PM

But if tiles are glued as in pools or bath tubs your pots can allways be well watered by misting only?
Well after all this is just an idea

Richard · 11-03-2009, 03:57 PM

Quote:

Originally Posted by Dalmatiansoap

But if tiles are glued as in pools or bath tubs your pots can allways be well watered by misting only?
Well after all this is just an idea

Yes, these are good ideas!

If a work surface is important, then glued tiles are worth considering. This propagation table has side walls and a hinged top. It is not a work surface.

I will have cuttings in the pots and the electronic leaf is to prevent over-watering. The media in the pots needs to be less than moist but not dry. The "bed" they are sitting on has drainage because it is poor for the pots to sit in water. Having the pots sit directly on tiles without warm humidity rising underneath could cause them to dry out too fast -- I don't know. It is something for me to experiment with. I believe it is a good idea to have the cables in horticulture sand and allow the run-off water to be heated -- thus taking advantage of the heat capacity of water and heat-transfer by evaporation.

Dalmatiansoap · 11-03-2009, 04:03 PM

One way or another this is going to be an interesting project.
Keep us posted about progress and add tons of pix

.
The most important is that U enjoy it.

sandy0225 · 11-09-2009, 08:58 AM

The sand bed idea will be a bad one for sterilization purposes I'm thinking. If you want to do multiple loads of cuttings in this table, it's going to need to be sterilized between batches. How will you get the sand clean?

Richard · 11-09-2009, 11:26 AM

Quote:

Originally Posted by sandy0225

The sand bed idea will be a bad one for sterilization purposes I'm thinking. If you want to do multiple loads of cuttings in this table, it's going to need to be sterilized between batches. How will you get the sand clean?

1 drop of triple-ammonium per 5 gallons of water.

I will not be planting directly in the horticultural sand (1/8 to 1/4 inch silicate). Its only purpose is to distribute heat laterally. Any cuttings or plants will be placed in 4 inch pots, which sit in 4 x 4 ring-flats. For rootings, I will likely use 50% coir + 50% perlite.

Dean W. · 12-21-2009, 06:55 PM

Thanks for bringing this subject up, Richard. I am considering buying a heating mat myself.

Dean W. · 12-28-2009, 05:55 PM

I finally got a 20x20 Hydrofarm heat mat. I'm considering getting another.

wordwiz · 12-28-2009, 08:30 PM

From a different angle: what about cooling, or more specifically, keeping the the temps reasonable? Cincy and SD or different (for one thing, your football team beat mine!), but one major concern I have run across in spring is the wide variety of temps. Overnight, it may well be 35 degrees, but then during the day 60, maybe 70. Inside a grow box, if it isn't open, it could easily get to 135, frying your seeds/seedlings.

Mike

D_&_T · 12-28-2009, 09:20 PM

Wouldn't the sand cause water to go stagnant due to it holding water? The sand and tile would be heated to same temp as tile would be in basically mortar causing direct contact and radiating heat off. What you lining this with to keep the water from destroying the building material due to direct contact with the water and sand, as tile installed properly would make its own seal to water out.

11-02-2009, 10:37 PM	#1 (permalink)
Richard un-Retired Richard's Photo Gallery Location: Vista, CA Find me on the map! Zone: USDA 10b Name: Richard Join Date: Jan 2008 Posts: 9,674 BananaBucks : 571,346 Feedback: 9 / 100% Said "Thanks" 3,636 Times Was Thanked 12,537 Times in 4,719 Posts Said "Welcome to Bananas" 1,685 Times	comparisons of heat mat costs and performance I'm building an outdoor propagation box with insulation. I will be rooting cuttings and starting plants from seeds. My coldest overnight temperature in the winter is typically 33 F (1 C), but more typically 40 F (5 C). My goal is to keep the rooting pots in the mid 70's (23 C) in the day and early evening and above 55 F (13 C) at night. I will use heat mats to warm the 45 sq.ft. surface and a thermostat to regulate the mats. Here are the mats I'm considering: Hydrofarm 48" x 20" @ 107 Watts, $55 each --> 16 W/sq.ft. and $8 / sq.ft. Pro-Grow 22" x 60" @ 200 Watts, $155 each --> 22 W/sq.ft. and $17 / sq.ft. Stanfield 3' x 6' @ 400 Watts, $376 each --> 22 W/sq.ft. and $21 / sq.ft. Do you have experiences with these or alternative systems I could consider? __________________ Back in business at plantsthatproduce.com

11-02-2009, 11:07 PM	#2 (permalink)
sunfish Banned sunfish's Photo Gallery Location: San Diego Find me on the map! Zone: 9-11 Name: Tony Join Date: Apr 2008 Posts: 18,429 BananaBucks : 1,037,782 Feedback: 8 / 100% Said "Thanks" 3,210 Times Was Thanked 20,592 Times in 7,760 Posts Said "Welcome to Bananas" 2,716 Times	Re: comparisons of heat mat costs and performance Did you see these? Redi-Heat Propagation Mats - 12"W x 10'L $132.25 /EA Output for 12"W mats is 20 watts per linear foot. Output for 17"W mats is 30 watts per linear foot. Output for 21"W mats is 40 watts per linear foot. Mats used on GFI outlets must stay under 500 watts to avoid tripping GFI.

11-03-2009, 01:52 AM	#3 (permalink)
Richard un-Retired Richard's Photo Gallery Location: Vista, CA Find me on the map! Zone: USDA 10b Name: Richard Join Date: Jan 2008 Posts: 9,674 BananaBucks : 571,346 Feedback: 9 / 100% Said "Thanks" 3,636 Times Was Thanked 12,537 Times in 4,719 Posts Said "Welcome to Bananas" 1,685 Times	Re: comparisons of heat mat costs and performance Thanks, this model is interesting: Redi-Heat 21"W x 10'L @ 400W, $132 each --> 23 W / sq.ft., $11 / sq.ft. __________________ Back in business at plantsthatproduce.com

11-03-2009, 05:12 AM	#4 (permalink)
Dalmatiansoap Let there be light Dalmatiansoap's Photo Gallery Location: Makarska, Croatia Find me on the map! Zone: 9 Name: Ante Join Date: Dec 2008 Posts: 9,161 BananaBucks : 622,861 Feedback: 10 / 100% Said "Thanks" 6,508 Times Was Thanked 8,384 Times in 3,032 Posts Said "Welcome to Bananas" 720 Times	Re: comparisons of heat mat costs and performance Have U consider electical underfloor heating system. Its much cheeper and better than heating mats and in my opinion its easier to insulate all system. Grrrrh, my lack of words.....Hope U understand me __________________ https://abnb.me/AXJty518xib

11-03-2009, 12:22 PM	#6 (permalink)
Dalmatiansoap Let there be light Dalmatiansoap's Photo Gallery Location: Makarska, Croatia Find me on the map! Zone: 9 Name: Ante Join Date: Dec 2008 Posts: 9,161 BananaBucks : 622,861 Feedback: 10 / 100% Said "Thanks" 6,508 Times Was Thanked 8,384 Times in 3,032 Posts Said "Welcome to Bananas" 720 Times	Re: comparisons of heat mat costs and performance Think twice about that. If they are used properly with quality ceramic they can save U lot of money. And U always pay Watts per Hour! It isnt named "low energy heating sys" for nothing __________________ https://abnb.me/AXJty518xib

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11-03-2009, 12:59 PM	#8 (permalink)
Dalmatiansoap Let there be light Dalmatiansoap's Photo Gallery Location: Makarska, Croatia Find me on the map! Zone: 9 Name: Ante Join Date: Dec 2008 Posts: 9,161 BananaBucks : 622,861 Feedback: 10 / 100% Said "Thanks" 6,508 Times Was Thanked 8,384 Times in 3,032 Posts Said "Welcome to Bananas" 720 Times	Re: comparisons of heat mat costs and performance That is what i was reffering with watts/hour. More watts-less time needed, that why u use thermometers. True is that this sys needs more hardwork but in my opinion if U want to do something more proffesional than it is everthing clear. Heat mats are good and simplest solutions for areas that we dont use only for germinations and rooting. __________________ https://abnb.me/AXJty518xib

11-03-2009, 02:24 PM	#10 (permalink)
Dalmatiansoap Let there be light Dalmatiansoap's Photo Gallery Location: Makarska, Croatia Find me on the map! Zone: 9 Name: Ante Join Date: Dec 2008 Posts: 9,161 BananaBucks : 622,861 Feedback: 10 / 100% Said "Thanks" 6,508 Times Was Thanked 8,384 Times in 3,032 Posts Said "Welcome to Bananas" 720 Times	Re: comparisons of heat mat costs and performance The point is to get quality heating media as tile ceramic. Cables in sand are almost useless but whan cabels heat tiles thats completly different story. Agree? And U also get clean work surface. __________________ https://abnb.me/AXJty518xib

11-03-2009, 02:58 PM	#12 (permalink)
Dalmatiansoap Let there be light Dalmatiansoap's Photo Gallery Location: Makarska, Croatia Find me on the map! Zone: 9 Name: Ante Join Date: Dec 2008 Posts: 9,161 BananaBucks : 622,861 Feedback: 10 / 100% Said "Thanks" 6,508 Times Was Thanked 8,384 Times in 3,032 Posts Said "Welcome to Bananas" 720 Times	Re: comparisons of heat mat costs and performance But if tiles are glued as in pools or bath tubs your pots can allways be well watered by misting only? Well after all this is just an idea __________________ https://abnb.me/AXJty518xib

11-03-2009, 04:03 PM	#14 (permalink)
Dalmatiansoap Let there be light Dalmatiansoap's Photo Gallery Location: Makarska, Croatia Find me on the map! Zone: 9 Name: Ante Join Date: Dec 2008 Posts: 9,161 BananaBucks : 622,861 Feedback: 10 / 100% Said "Thanks" 6,508 Times Was Thanked 8,384 Times in 3,032 Posts Said "Welcome to Bananas" 720 Times	Re: comparisons of heat mat costs and performance One way or another this is going to be an interesting project. Keep us posted about progress and add tons of pix . The most important is that U enjoy it. __________________ https://abnb.me/AXJty518xib

11-09-2009, 08:58 AM	#15 (permalink)
sandy0225 Northern Tropics sandy0225's Photo Gallery Location: Muncie, Indiana zone 5 Find me on the map! Zone: zone 5 Name: Sandy Join Date: Nov 2005 Posts: 1,718 BananaBucks : 366,529 Feedback: 31 / 97% Said "Thanks" 38 Times Was Thanked 1,801 Times in 682 Posts Said "Welcome to Bananas" 9 Times	Re: comparisons of heat mat costs and performance The sand bed idea will be a bad one for sterilization purposes I'm thinking. If you want to do multiple loads of cuttings in this table, it's going to need to be sterilized between batches. How will you get the sand clean? __________________ Sandy Burrell Northern Tropics Greenhouse 1501 East Fuson Road Muncie, IN 47302 www.northerntropics.com specializing in bananas, heirloom tomatoes and water gardening plants~ check out our new online store at our website!

12-21-2009, 06:55 PM	#17 (permalink)
Dean W. Dean W.'s Photo Gallery Location: Cedar Park, TX Zone: 8b Join Date: Sep 2007 Posts: 4,279 BananaBucks : 242,742 Feedback: 13 / 100% Said "Thanks" 6,325 Times Was Thanked 2,130 Times in 972 Posts Said "Welcome to Bananas" 300 Times	Re: comparisons of heat mat costs and performance Thanks for bringing this subject up, Richard. I am considering buying a heating mat myself. __________________

12-28-2009, 05:55 PM	#18 (permalink)
Dean W. Dean W.'s Photo Gallery Location: Cedar Park, TX Zone: 8b Join Date: Sep 2007 Posts: 4,279 BananaBucks : 242,742 Feedback: 13 / 100% Said "Thanks" 6,325 Times Was Thanked 2,130 Times in 972 Posts Said "Welcome to Bananas" 300 Times	Re: comparisons of heat mat costs and performance I finally got a 20x20 Hydrofarm heat mat. I'm considering getting another. __________________

12-28-2009, 08:30 PM	#19 (permalink)
wordwiz Join Date: Nov 2009 Posts: 76 BananaBucks : 24,362 Feedback: 0 / 0% Said "Thanks" 0 Times Was Thanked 60 Times in 34 Posts Said "Welcome to Bananas" 0 Times	Re: comparisons of heat mat costs and performance From a different angle: what about cooling, or more specifically, keeping the the temps reasonable? Cincy and SD or different (for one thing, your football team beat mine!), but one major concern I have run across in spring is the wide variety of temps. Overnight, it may well be 35 degrees, but then during the day 60, maybe 70. Inside a grow box, if it isn't open, it could easily get to 135, frying your seeds/seedlings. Mike

12-28-2009, 09:20 PM	#20 (permalink)
D_&_T 3rd winter growing indoor D_&_T's Photo Gallery Location: Northern Indiana Find me on the map! Zone: 5 Name: Dan Join Date: Jul 2007 Posts: 877 BananaBucks : 31,220 Feedback: 4 / 100% Said "Thanks" 2,437 Times Was Thanked 260 Times in 169 Posts Said "Welcome to Bananas" 342 Times	Re: comparisons of heat mat costs and performance Wouldn't the sand cause water to go stagnant due to it holding water? The sand and tile would be heated to same temp as tile would be in basically mortar causing direct contact and radiating heat off. What you lining this with to keep the water from destroying the building material due to direct contact with the water and sand, as tile installed properly would make its own seal to water out. __________________

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