Break out the tile

[eds]

This is a basic overview of a service call I am working on and would like to know if I have overlooked anything. Floor warming mat rated at 360 watts at 120v should have a resistance reading between 31 and 35 has a GFI built into the t-stat. Matt was installed four years ago, shortly after move in day it started tripping GFI on the stat, checked it only with digital meter and found nothing that stood out. Company called the manuf found out that the changed t-stat brand been having trouble with the GFI tripping out so we installed new. We had same problem with new stat so we called tech support again and tried there next suggestion use the stat to control a contactor and feed floor mat with GFI breaker, this seemed to solve the problem last winter. This winter turn the stat on and there is a instant trip of the breaker. I went today and did these test: Turned breaker on with stat off, breaker held engage stat breaker tripped. Checked resistance of matt it read 33. Checked for continuity on branch circuit and floor matt leads everything okay. Bypassed the GFI and took amp readings Hot side 3.4 neutral 3.3, place clamp around both and read zero, check hot read 3.3 and neutral reads 3.4. I did use a megger before taking the amp readings and recorded the following at a 1000v on the branch circuit H/N, H/G, N/G all read greater than 2.2 g ohms ( I believe this is acceptable) on the floor heat cable H/G or N/G read 0 and on the meter it shows only 33 volts in the bottom right hand window (fluke 1587) this leads me to believe there is a nick in the cable. I know this is a long post but I don't want to overlook anything before tile comes out and I don't meg that often and want to be sure of my readings

Thanks

 

[electricalperson]

if you read 33 volts on the megger while its on the 1000v scale there is a short circuit i would take the tile out and repair it

 

[Fulthrotl]

on the floor heat cable H/G or N/G read 0 and on the meter it shows only 33 volts in the bottom right hand window (fluke 1587) this leads me to believe there is a nick in the cable. I know this is a long post but I don't want to overlook anything before tile comes out and I don't meg that often and want to be sure of my readings
Thanks

if you are testing on the 1000vdc scale on the fluke, check the fluke
with nothing under test, and you should show something like 1011
or 1015 volts.....

if the mat shows only 33 volts of that being maintained under load,
measuring from the leads to the braided ground covering, and the meter is
not showing something above 20 megohms, you have a dead mat.

just for grins.... set your fluke to the working voltage, and see what
your voltage from the leads to the ground is, and your megohms...
i'm suspecting that mat is dead either way....

when i do mats, i megger at the working voltage, instead of the max.
that'll tell me all i need to know, and i don't need to know if mats like
1kv or not

it shouldn't make any difference, but i learned most of what i know
about meggers in the capacitor industry, so i tend to be cautious.
20 kv mylar and foil capacitors can be cranky things, and it's no fun
finding a hole in the dielectric that i helped to be there.....

randy

 

[eds]

The floor mat company advised checking a 1000v. I did not check to the foil I checked Hot to green.

 

[cadpoint]

Can you just roll out the Mat and test it before you install it ?

 

[eds]

matt has been installed for 4 years this has been a intermittent problem

 

[Fulthrotl]

The floor mat company advised checking a 1000v. I did not check to the foil I checked Hot to green.

got it... different company.... mine had black, white, and a braided
ground encircling both.... no green wire, just braid like a coax shield.

and if *they* said you can do it, there ya are.... shoulda figured you'd
ask before zorching.... duh.

this is a dumb question, but is there any chance the cable is damaged in
the wall? any work been done there? (it'd suck to tear up the floor, and
then find out it was a drywall screw... :-( any chance someone has put
in a towel bar or ring after you?

when i do these, i put a 4s deep with a 1" mud ring set to be flush with
the finish tile, and take a piece of 1/2" ent down to a notch in the plate
that is flush with the floor and sticks out a half inch. it's nonmetallic, and
that works for me....

randy

 

[quogueelectric]

Former employee sent me to a house to try to fix this stuff and it was set with an alarm for install in case someone broke the wire an alarm would sound. Sure enough the plumber cuting the toilet hole in the tile and setting the flange cut the wire and tripped the alarm. Now what who was the idiot who ran the wires where the waste line was running????

 

[eds]

I have a deep sq with 1/2 ring for drywall and (2) 1/2 emt to floor line one for cable one for stat. The one question I do have is it possible to have a amp reading of 3.4 (H) and 3.3 (N) and have the meggar read as a bad cable and is that amp differance enough to trip a GFI breaker

 

[growler]

I have a deep sq with 1/2 ring for drywall and (2) 1/2 emt to floor line one for cable one for stat. The one question I do have is it possible to have a amp reading of 3.4 (H) and 3.3 (N) and have the meggar read as a bad cable and is that amp differance enough to trip a GFI breaker

Before breaking the tile out I would check out the leads comming up through that 1/2 emt. Make sure that the original installer put a connector on the floor end of the emt and didn't skin it out during install.

You may just have a bad heating mat from the factory and they will never tell you if that's the problem. I had some bad tank heaters at one time and every one of that batch would short out when they started to get warm. They would test good when cold but after warming they would test bad even with a meter.

If there is a nick in the cable it probably only shorts when there is enough moisture in the floor tiles so it works at times ( when dry).

 

[Fulthrotl]

I have a deep sq with 1/2 ring for drywall and (2) 1/2 emt to floor line one for cable one for stat. The one question I do have is it possible to have a amp reading of 3.4 (H) and 3.3 (N) and have the meggar read as a bad cable and is that amp differance enough to trip a GFI breaker

there's a rollover point on a digital meter, and a tenth of an amp could just
mean that you're right near that point, and it's toggling from one to the
other. it's not a definitive test... assuming you are using a clamp on....

if you are using an electronics grade meter that goes to milliamps, like
a fluke 87, and you are running the current thru the meter, and getting a
tenth of an amp differential, then yes, that is certainly enough to trip a gfci..
most of them trip at 5-7 milliamps leakage, and you've got 100 milliamps leakage....

bummer..... are you aware that the fein tool is wonderful for repairing tile?:grin::grin:

randy

 

[steved]

When we've got a problem in the heat mat itself, and we've determined that it's not in the thermostat or the wiring connected to the heat mat, we let the tile guys fix it. I don't know how they do it, but they can locate the fault fairly precisely and only have to bust out one or two tiles to repair it. They have a battery-powered gadget called a Crybaby that is hooked up to the heat mat wires while they work. It sounds an alarm if the mat is damaged.

 

[alfiesauce]

When we've got a problem in the heat mat itself, and we've determined that it's not in the thermostat or the wiring connected to the heat mat, we let the tile guys fix it. I don't know how they do it, but they can locate the fault fairly precisely and only have to bust out one or two tiles to repair it. They have a battery-powered gadget called a Crybaby that is hooked up to the heat mat wires while they work. It sounds an alarm if the mat is damaged.

All the crybaby's are is an ohm meter with a speaker connected to it.

Warm Tile easy heat makes a repair kit -
http://www.ezfloorheat.com/items/other-products-/cable-repair-kit/cable-repair-kit-dftrk-detail.htm
Looks like an overly expensive set of stuff you could supply yourself for a whole lot cheaper. Not sure how you go about finding the fault without ripping up the floor in the first place though