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Auxin

Cheap, simple, waterproof root warming

27 posts in this topic

Hi all,

I figured as I’ve learned so much from this forum already I’d try and contribute something useful with my 1st topic. Please be gentle

What you’ll find here is a description of what I use to keep my roots warm in an increasingly chilly cellar. The 3 criteria for me were;

Cheap

Water/dirtproof

Something easy to retrofit to an overcrowded scrog(!)

Its really simple. I use a 12 metre 150W soil warming cable laid on 12 inch squares of 50mm polystyrene. I then place a 12inch tile on top of the cable which each pot sits on.

Cheap root warming 1

Cheap root warming 2

Cheap root warming

The IP67 soil cable is branded Parasene (I managed to pick one up with damaged packaging for £18) and is plugged into a generic thermostat identical to the Root It one (£16 from my local hydro shop). The probe sits under the pot and keeps the tiles at 35 degrees. I find that keeps the centre of my rootball at 20 degrees with 15 degree ambient air temps. Its timed to come on an hour before lights out.

Cheap root warming 4

The geek in me used 12 inch squares as I wanted to work out how many watts per square foot I was using for each pot (15W for anyone interested in being as sad as me). By using the same length of cable for each pot I’ve found all the pots stay within a degree of each other. I measure this with an embarrassingly cheap (£1.74 delivered) temperature probe that is scarily accurate for the money.

I have 4 pots in a 1.2 x 2.4 tent and there is plenty of cable spare for anyone needing more pots to be warmed. There are longer lengths of cable available for not much more money too.

Cheap root warming 3

The only watch out is you have to be careful that the cable never touches itself and that you try and evenly space it under each tile.

Total cost for me (including snazzy grey tiles) was under £40. At 150W, it will be considerably cheaper to run, and way more effective than the 800W oil rad I was using. The plants seem to be loving it too.

Hope it helps someone, I was about to waste a load of money on some heated propagation mats before my brain wave… happy to answer any questions or hear any improvements.

eta : my cheap temperature probe

Edited by Auxin
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hi @@Auxin .. i tried a 2kw heater last winter, wasnt efficient enough, then during building my groom, i tried a single heated blanket, wrapped in thermawrap, but that was a waste of time and money as well, not even warm to the touch after being left on all night... but now i have fitted undercarpet heating, over 2.2m x 80cm .. 200w, and with a touchscreen thermostat...

And it seems super efficient... just got to waterproof it now.. heats up in minutes... got it all for under 130 quid..

This is supposed to be hardwired into the mains, but as this is a very small area i am heating, and its only 200w

i fitted a plug and tested it and it works A ok.. heats up to temp in a few mins..

Ps.. hope you dont think im posting this to say "mines better than yours"

Nearly all these methods we make are not intended for purpose!

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Edited by Subliminal Criminal
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@@Subliminal Criminal I saw your thread but wasn't sure on the etiquette of hijacking... yours looks bob on! Its out of the way too. I'm not a big fan of cable everywhere but as it was a retro fit mid-grow I didn't have much choice. Were you able to insulate underneath?

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@@Auxin hi

yeah the kit comprised of three types of insulation, heat mat, wires, thermostat and tape

you can only see the hardboard on the top.. but underneath is white polystyrene type stuff... then the heat mat... then vapour barrier, which looks like cling film.. then the hardboard on the top..

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@@Auxin. I was just wondering why you don't heat the pots during lights on. Have you found that they don't need it (measurement), or do you just think they wont need it?

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well my growroom isnt even finished let alone tested yet! But i may just find the optimal temp and i could leave the underfloor heating on.. my walls surrounding are insulated with acoustic fibreglass insulation.. i suppose people tend not to need heating during lights on (with HID HPS / MH) I will probably just find the best optimal lowest temp.. and let the heating click on if it falls below that

e2a sorry @@Bird i thought that was @@Auxin asking me that!

Edited by Subliminal Criminal
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@@Bird good question... my lights on root temp is around 19 degrees. I was wondering if it would be better to just leave it on but I wasn't sure. I'm a bit concerned about the lack of/positive the night/day root temp differential so if you have any ideas I'd appreciate it. I've tried to do a bit of research but I'm none the wiser tbh. I'm still quids in leaving it on 24/7 so if that's the way to go then so be it... providing I don't cook my ladies!

@@Subliminal Criminal happy days... I'd definitely recommend you google "digital kitchen probe thermometer" when you're all set. That way you can work out the optimum floor/air temp to keep your roots happy.

Edited by Auxin
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Useful information @@Auxin

Nice poor mans James bond effort. A man after my own heart.

Funny enough I was looking at those parasene heating cables on the big river the other day.

Though the method I was planning on using them was nearer there intended purpose than yours.

Fullmarks for ingenuity and kudos for sharing the knowledge with the forum!

Nice1 tc dodge

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Tidy bit o work, proper Mcgyvering fair play :v:...yep loves a bit inginuity and some DIY, top job bud :yep:

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@Dodgee@botanics Far too many episodes of Macgyver as a kid. There may also have been some humming of the A-Team theme tune when I was sawing polystyrene

If anyone can let me know whether it would be better to just keep the pots warm 24/7, it would be much appreciated. From what I've read its better to have roots slighty colder at night, which I can achieve if I just leave it on. At the minute my root temps at night are higher than during the day. Will this cause any issues?

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@@Subliminal Criminal How does the underfloor heating plug in matey, do you just wire a 13 amp plug on the end or does it need to be hardwired in?

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@@Bird good question... my lights on root temp is around 19 degrees. I was wondering if it would be better to just leave it on but I wasn't sure. I'm a bit concerned about the lack of/positive the night/day root temp differential so if you have any ideas I'd appreciate it. I've tried to do a bit of research but I'm none the wiser tbh. I'm still quids in leaving it on 24/7 so if that's the way to go then so be it... providing I don't cook my ladies!

@@Subliminal Criminal happy days... I'd definitely recommend you google "digital kitchen probe thermometer" when you're all set. That way you can work out the optimum floor/air temp to keep your roots happy.

@@Auxin, well I always used to keep the root heating on 24 hours myself but that was on a stone floor.

I would have thought it might be a good idea but I don't have a feel for how much of a boost your heating system gives them. 19 degrees C is bare minimum and temperatures may well drop.

My advice would be to try leaving it on and monitor the daytime temps. Should they climb too high for comfort then you could try using just a few short bursts during the day to raise temps a little to say 21-22 C. I wouldn't have thought you need to go any higher than that.

I am usually trying to get temps warm enough rather than cool them down tbh.

Edited by Bird

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@@Bird brilliant... thanks. If 19C is a minimum then I think 24/7 is the way to go. Its a pretty gentle heat as I was concerned about frying the roots close to the tile. I'll monitor it and see how I get on. I was looking for an excuse to buy more probes... 1 per pot sounds reasonable to me. Rude not to at sub £2 :).

As a side note for anyone using smaller pots and concerned about too much heat, you can always space the cable further apart... or use thicker tiles. Marble would be lovely... ha ha.

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@@Bird brilliant... thanks. If 19C is a minimum then I think 24/7 is the way to go. Its a pretty gentle heat as I was concerned about frying the roots close to the tile. I'll monitor it and see how I get on. I was looking for an excuse to buy more probes... 1 per pot sounds reasonable to me. Rude not to at sub £2 :).

As a side note for anyone using smaller pots and concerned about too much heat, you can always space the cable further apart... or use thicker tiles. Marble would be lovely... ha ha.

You are welcome. They like temperatures above 20 C but I am just a little wary of recommending that you have temperatures too high in case there are any problems with fungus. I am happy with 20 - 24 C myself, but as I say I am usually fighting low temperatures.

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@@GreenVision

Would be no problem putting a plug on a 200 Watt load GV no need to hardwire besides it means you don't have to have a fused spur then as the fusing will be done via the plug fuse...3 A should cover it easy ;)

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