heat mats for plants

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FREEBALL

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york pa usa
I have a question on heat mats. I copied this excerpt from agritape which has me puzzled.


"An Agritape system consists of a control unit to regulate soil temperature, the Agritape Heat Mat, and a grounded screen. The screen serves to protect the tape from physical damage, to safely ground the current if the tape is penetrated, and to draw off static electrons that collect on the surface of the tape. (The tape acts as a capacitor when it is in operation.) The flow of static electricity can trip GFCI outlets if the system is not properly grounded. The screen also holds the tape in position on the bench".
Why would it matter if the system is not properly grounded, The system is properly grounded by the way, but why would static electrons trip a GFI. They placed screws into the metal screen and ran to the control box as stated to do, but all this does if gives any leakage current an alternative path which will trip the GFI. So what are they talking about stray electrons, it seems the heat mats are shorting out to the screen which is grounded and current is leaking to ground thus tripping the GFI. In the paperwork with the mat it says that if the grounding does not work to simply isolate the ground wire to a separate form of grounding instead of the ground that comes connected to the control box.

They started watering the plants on Friday and Saturday the gfis for the mats began tripping. I believe they need better heat mats.

any ideas.
 
So the mats work fine until they get watered. There is some linkage in the mats either when it got installed or when the soil got put in.
 
Dennis, that's what Im figuring these mats are old they reuse each year, they look rough. The metal screen is giving the current an alternative flow of current do you agree ?. Id like to use a fiberglass or even just disconnect the makeshift ground to the screen to see if this changes things. And what about the static electricity claim of tripping the GFI.
 
FREEBALL said:
Im thinking a fiberglass screen instead of the metal, but obviously there must be damage somewhere enough to cause 5ma of leakage.
Click to expand...

If the leakage is in the mat and it must be then c hanging the screen should not make a difference. You can check that our by removing the bond on the screen and see what happens. I doubt it will change anything
 
ok I grasped that I was thinking changing the screen to fiberglass to protect the mats only. So you don't see anything in the static electron theory they spoke of. This is what they are saying that the system must not be grounded. I know it is I installed it. I explained to them that by the metal screen being bonded it gives an alternative path for current which will also trip the gfi. It seems the manufacture built in a somewhat plausible excuse why their unit trips gfis without being responsible in my opinion.
 
So the manufacturer says not to bond the screen? If so, don't bond it and see what happens. If they don't require that bond that I wouldn't do it. I just don't know why bonding it would cause a gfci to trip unless something is leaking anyway.
 
yes they say to bond for electrons, but they say that the flow of stray electrons is what causes the gfi to trip. But if you have a metal screen and leakage that will also cause the gfi to trip that is my dilemma. So if I use a fiberglass screen there will be no static buildup ? and therefore no trip, unless there is significant leakage in the mat itself that would cause the gfi to trip ???
 
FREEBALL said:
yes they say to bond for electrons, but they say that the flow of stray electrons is what causes the gfi to trip. But if you have a metal screen and leakage that will also cause the gfi to trip that is my dilemma. So if I use a fiberglass screen there will be no static buildup ? and therefore no trip, unless there is significant leakage in the mat itself that would cause the gfi to trip ???
Click to expand...

If there is leakage is is not on the ground. The tape is leaking into the soil area via the water. A gfci does not need a ground to trip it senses the amperage in and the amperage back on the hot and grounded conductor. If the tap is draing 6 amps and there is more than a 6 amp milliamp then that current which is going thru the soil will trip because it is in contact with the metal screen via the ground. If you do away with the bonding of the screen then you will potentially energize the soil and defeats the purpose of the gfci
 
That's what I was saying the whole time the static electron thing didn't make sense the metal screen is returning a path because there is a leak. I understand how a GFI works but reading the manufactures description did not make sense and I wanted validity in that fact

Thanx
 
ok so the gfi doesn't need a ground to trip I understand that its not meant to work that way. But you said if I do away with the ground bond on the screen I can potentially energize the the soil, wont the GFI sense that and trip at the 6ma ?? even though theres no ground bond to the screen.
 
FREEBALL said:
ok so the gfi doesn't need a ground to trip I understand that its not meant to work that way. But you said if I do away with the ground bond on the screen I can potentially energize the the soil, wont the GFI sense that and trip at the 6ma ?? even though theres no ground bond to the screen.
Click to expand...


If it leaks into the soil it still will return back to the panel. The current will go back thru the conductor after the leakage but it will also have the potential to hurt someone because there is potential voltage present in the soil-- not current which is what the gfi sense but voltage. Touch the soil and touch a ground then there will be some current going thru you back to the panel- it is more than 6 ma the gfci will trip.

Think ofit this way. You have the tape in the ground- strip it and pigtail a conductor to it and have it stick out of the soil. Will the gfci trip- NO.. There is voltage potential there but no current until you touch the wire and a grounded area. Now some current will go thru and th gfci will trip. If you took that pigtail and stuck it in the soil it is the same. Depending on the moisture level you may be able to get hit anywhere in that box thru the soil if you touch a ground-- even the earth
 
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