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Old June 3, 2016   #1
murihikukid
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Default Soil Warming Cable

I have read that "soil warming cable" is widely used in the gardening community.... I have limited knowledge of electrical technology but I wonder if anybody with knowledge of these could answer a couple of questions for me...

I know different length cables are available but in my case its important that I get cables that can be joined together by a connector ...I wonder if this is possible...

I presume that one cannot buy a long length of cable and make individual smaller cables from it ...?? Maybe somebody that works with these cables can enlighten me ...Thanks.
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Old June 3, 2016   #2
Worth1
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I worked in an area that everything was named by what the Brits called it.
Everyone there didn't know it by any other name than what the Brits called stiff.
It goes by the name of heat trace, heat tape heat cable heat line and so on.
You can get it for different temperatures and all manner of ways and yes you can get it in big rolls too.
You can even splice and tee it.
As far as getting it to go up to the temperatures you want you will have to do some research on line.
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Old June 5, 2016   #3
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Amazon's got them. So does Alibaba. They come in various lengths. Reviews on Amazon are mixed. One brand is Jump Start which is also sold on at a website called Hydrofarm.com which also sells heat mats and seedling starting kits. Prices for similar equipment seem in line with big box stores, maybe a little cheaper.

Power ratings at hydrofarm.com range from 32 Watts for the 12 foot long to 140 watts for the 50 foot. They have 110 volt, 2-prong USA-style plugs in the picture. You could plug a bunch of them into a power strip but they don't look like they can be daisy-chained. There is a user manual available for download on the hydrofarm.com site.

Amazon has another brand called Gro-Quick that looks similar.

I never tried this kind of cable so I can't recommend one over another. The built-in thermostat doesn't have any way to control the temperature so it is probably just a pre-set thermal cutoff switch to keep it from getting too hot. "Will it get warm enough?" is another question. The answer to that depends on how much soil there is, how cold it is, and other factors.

Resistance heat is used in all kinds of heating applications . These cables are just resistance wire in pre-cut lengths, sometimes with a thermistor to cut off heating at a pre-set limit. A heating mat is the same thing except the resistance wire is pre-attached to a mesh or board to keep the wire at a constant distance for even heating. With the heating cables you need to supply a separate mesh to keep the wire in position and protect the cable from digging implements. The advantage of the heating cable is that you can arrange the wire in any shape, not just the typical rectangle, square, or circle of a heat mat.
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Old June 6, 2016   #4
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Hi..Well I know I am going to upset some people but I have to purchase from China..I have no other choice...Unless I hop on a plane to America and bring it back with me....

So what now..well there are some great You Tube videos by a guy named Robyn Perry...https://www.youtube.com/watch?v=hpF2UL71bMM
and one can find out how to splice the cable etc....I searched Youtube several times and never came across any videos on the subject so I do not know what I was doing wrong..

Having found these videos my attention is now focused on the warmer cable itself ...I have made some enquiries via Alibaba?? and have some emailed replies that I am working through and some have attachments on prices etc....BUT they have so many different types of cable I am all confused ..I wonder if the seller will put me right ? Also on one email is the warning the cable should not be cut ..well thats not much use....I can understand the safety factor but I am sure if one adheres to the information in the videos there will not be a problem.....

There is still a question that I would like to know from somebody who has experience with these cables....Of course I have taken particular notice of the complete cables out in the market place and it has occurred to me that there could be a safe and inexpensive way to join warmer cable.....but not the warmer cable itself..
for example I know the cables have a non warming cable at their start and this has a power plug and thermostat on it and it is then spliced into the warming cable ...shown in one of the videos ...The end is normally sealed off BUT what if one spliced a piece of non warming cable on the end and attached a normal female connector to it...then a second cable could have a non warming cable spliced onto it with a male connector on it and at the end splice another piece of non warming cable with a female connector and repeat the process and seal the final cable end....

Now I will repeat that none of the cable connectors will be in the soil ..only the warming cable and I would ensure that no electricity will be in contact with soil etc......

Tomorrow I will cut a cover for my freezer for a double Ceramic heat bulb experiment ...The cover will keep most of the heat around the drums in the freezer and help heat loss...or will it...I can only try it and see what happens...I have beautiful tomato plants in the other freezer ..better than anything I have grown and its approaching the middle of winter ... ?? But they need transplanting for more space...

Thanks Ron
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Old June 6, 2016   #5
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Hi Ron,. I have used soil warming cable for years never had a problem I use a old vivarium with a plastic cover with 2air vents on the top it is 30 watts 240 volts , I fill 1inch of sand then run the cable rouund leaving a 2inch space between the cable then another 2inch of sand on top and carry on running the cable round till it is all used up, no thermostat is needed as it is only. A soil warming cable, not a 2bar electric fire, will germinate seeds and can lgrow too 4 inch tall, but you only have 8 hours of daylight now so that's another problem
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Old June 6, 2016   #6
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Moneymaker...With a name like that you must be a Tomato grower ...First thanks for your post ...Now did you use your cable on a soil bed/raised bed because I am not....I am using stainless steel tubs for a "final" transplant IE I do not want the warmer cable for seeds etc ..I have the equipment for that....I need the warmer cable for initially an experiment in my living room where I have plans for up to 4 freezer "SHELLS "with 4 X 450mm Diameter Stainless steel in each ...Its the soil in these drums that I want to heat to round 20 degrees celcius or 70 degrees F and hold it there.....My plants are now to the stage that they require transplanting into their final resting place so I have to get this done as soon as possible ...I have lights etc that will compensate nearly for daylight...They go from 2am til 10am every day ....I really have the most beautiful plants grown from cuttings ..better than I have ever had...

Now back to the stainless steel drums ..I resume you can image a 450mm drum full of soil ...They will be pretty heavy so this is my plan ...I am going to get warmer cable and wind a few coils inside the drum ..put soil in the drum so the plant itself will be planted in the middle of the coil......But what if I want to move a drum (for whatever reason) ..If I have one long warming cable across the four drums I could get a problem and to me its not worth the risk ..So my idea is to purchase 100metres of warmer cable that can be cut ...Now hopefully I will find out soon if this is possible.I will Splice a short non warming cable onto the warming cable ..the non warming cable will have the power plug and thermostat on it..I estimate I could need 4 -5 loops inside the drum..(the less the better) this equates to aprox 6 metres so I cut the warming cable (I then have 94 metres) ....but instead of insulating the end of the initial 6 metre cable I splice a small length of non warming cable onto and on the end of that I attach a female socket ........I then cut more 6 metre cables from the 94 metres and I splice a short non warming cable with a male socket on it to the start of these cables and do the same to the other ends except I would put a male socket.....
Doing it this way .. each drum can be disconnected from the "circuit" at any time just by unplugging its warmer cable ....Now I will probably have a circuit for each freezer .....the end cable could be insulated off or I could just have the female socket on it incase I wanted to add another freezer to the "circuit"...

Now the warming cables will be spliced and connected out of the drum in a safe position NO connectors will be in the soil only warming cable and there will be allowances for this on the length used to ensure the warming cable has aprox 20 cm at each end clear of the drum..

Thats my plan but I am not an electrician so I had hoped to see one today but they are still celebrating "Queens Birthday " weekend and is not returning to work til tomorrow .....I will explain my plan to him and see if he sees any flaws or dangers in it....

In the meantime I am going to try a freezer with 2 ceramic heat bulbs under the Drums heating the air...with an aluminium cover (with holes in it for the drums to go through) blocking off any air outlet at the top ...

Down here at the bottom of NZ in my short time at growing Tomatoes one is wasting ones time without some type of soil warming .....Now hopefully by August I will not only have Tomatoes to eat but I will be growing the laterals from my plants to plant out in my greenhouse ....If my warmer cable system has been successful inside I will do something similar in the greenhouse because "whens Summer" ..well going by this year it missed us if you get what i mean ...so one has to have insurance of this...or else tomato growing is just a waste of time and money....

Cheers Ron
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Old June 7, 2016   #7
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Murihiku Kid,

I have confidence you can do this. The Maori paddled hundreds of miles across the ocean to reach New Zealand and they didn't have Google maps to show them the way.
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Old June 7, 2016   #8
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Yes thousands of miles if they came from Tahiti ...I do not think the maori people came from the Cook Islands ....I think they sailed right past those islands and then they saw the long white cloud on the horizon that indicated to them there was land under these..once landed they proceded to eat the true indiginous people ..Fascinating..We will never know..

Anyway I have a snag in my plans ...Apparantly warming cables should be surrounded by sand and seeing sand does not stand uphill I could have a problem...in my mind the sand has to be porous enough to hold water in it or else i will not get conduction from the warming cable via the sand to the soil and I do not know if a binding agent would stop this ... I am not quite sure where to go next ...If i knew the sand would hold its position I could put a sleeve in the drum so as I could pack sand round the warming cable and then pull the soil in and then pull out the sleeve OR if I could think of a material I could use as a sleeve that absorbs water and leave it in the drum ......I wonder if any forum could advise on this?
I actually think there may be a porous gardening material that one could wrap round the outside of the sleeve and would hold the sand round the warming cable after the sleeve is pulled out....Anyway I have to see the electrician tomorrow and discuss the warming cables with him...

Thanks...

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Old June 7, 2016   #9
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Moneymaker..Sorry I got distracted earlier today...(I use a old vivarium) I wonder what that is....Seeing you have had experience with warming cable I value your knowledge ...Would you have an opinion on how many loops one would require inside a stainless steel drum ...I presume that one could keep it to maybe as low as 2 or 3 and use the thermostat to keep the soil up to 70 - 75F... Thanks Ron
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Old June 7, 2016   #10
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You can add some peat or diatomaceous earth to improve water retention. The sand alone will conduct heat, just more slowly. This won't make much difference because eventually the heat will diffuse away. If you are really getting down to 35F (2C) your problem will be that the heat cables may not produce enough heat to keep your soil at 70F. Of course it depends on how many feet of cable you have in a tub too. That is the unknown experimental variable.
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Old June 7, 2016   #11
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Apparantly warmer cable should not be put in soil ....The suppliers say it should be encapsulated for want of a better word in sand ....Its a minefield...and "do not cut the cable"...Well I do not understand that ....they sell thousands of metres of this cable...??It must be able to be cut and spliced....thank goodness I found those videos on You tube.....Later today after a trip to the doctors I have to cut the 440MM holes in the cover for the drums to slip through onto the rails....So I have to ensure I get this done very accurately so I have a cardboard template cut for guidance..Then I can put up a photo...with the cover on top..

I am going to look very stupid if a couple of heat bulbs or a sealed oil heater underneath the rails in the freezer heat the soil up to 70 degrees F simply by air temperature ..but I would be extremely happy if they did...

It seems that I can drill 3 holes in the plastic rim of each drum at 120 degrees apart and simply put a 6 foot bamboo pole in each hole and tie them at the top with a centre pole for a Teepee frame to support dare I say all the tomatoes...each plant...

I have made a document for the electrician to read ..photos etc and what i want to do ..so I am hoping he cannot find any problems.....

Yes there was white frost and ice this morning when I went outside ....Cheers Ron

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Old June 7, 2016   #12
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Hi Ron ,. I read your reply a soil warming cable will never get to 70f. But why do you need such a high temp for the soil ?? 50 F should be plenty,the only way you will get that temperature is with a domestic underfloor heating cable coupled too a thermostat if theory. It could work. But practically it's a big no, the cost of a set up like that plus the electric bill far outweigh the final result,, seeing the first electric bill you would be on VALIUM,, so back too the drawing board??
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Old June 7, 2016   #13
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I have started to reply to this thread and backed off several times as I dont think my advice or thoughts are welcomed anymore.

But I want to ask is the cable going to be spliced parallel or in series?

Then before you even think about spending the time and money to do this just try it with one cable.
Before you do that look at the watts the cable draws this can be converted to BTU's.
By knowing the BTU output the soil temperature and volume and the temperature you are trying to overcome.
You will know if it will work or not before you spend one thin dime.
When you figure out how many watts you need to raise the temperature to what you want as was said you will find out real fast that it is going to cost you a ton of money in electricity.
As in the old saying there is no such thing as a free lunch and you cant make energy you can only change it from one state to the next.

I just looked at one and it is 10 watts.
The watts converted to amps is about .8 amps.
10 watts is about 34 BTU's.
With these simple calculations you aren't going to get anything for enough heat and you wont even have enough power to get where you want.
Think of it this way if you have ten of these things that did put out enough power it would be like having ten burners on a stove on at least low all of the time.

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Old June 7, 2016   #14
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Hi worth,. Soil warming cable is just what it means. No way can you get the temp that Ron is trying to reach. As for the cables there sealed units ,,. So leave well alone especially if it's made in China,. I have used mine for years can fit 4 flats in my vivarium only 20 watts but it warms the sand enough to germinate my seeds both onions and tomatoes
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Old June 7, 2016   #15
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Hi..Hope the photo explains ..At this stage I only have two drums in the freezer... I will be putting heat bulbs in this afternoon then I have to clean four drums and drop them in .. Fill up with soil switch the bulbs on and see what happens to the soil temperature .... I have tryed to research everything I can about the soil temperature and its basicly always 70 - 75 F......in articles ....If its lower than that well it makes it easier...

I also bought a panel heater this morning that could be worth a try in the freezer??
I am afraid I might have no success with the electrician .... I am putting him in a position he does not want to be in if he ok's my plan and then something happens ..he could lose his lively hood ......anyway I will try out the bulbs first and see what temperature I can get in the soil...
Cheers Ron
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