# ditra heat questions



## mike gunderson (May 23, 2010)

Hello out there. I just did my megger test on a roll of ditra heat. I ran a 1000 volts through the wire and I got a reading of 300 megohms on my digital megger. For most wires this would be an excellent reading I'm told. Schluter wants a reading of at least a thousand megohms. All of the other ohm test have been good. I've got calls in to my local rep and he is getting back to me sometime. He wants to make sure my megger is compatible with their wire I guess. 
A question i have is, does anyone hook up their power to the wire before tiling to see if it warms up? Is this acceptable, I forgot to ask the rep. if it's bad the gfi in the thermostat would trip maybe. I've done many jobs with wire heat and never have tested it this way. All the other companies just require the ohmmeter test.
Thanks, Mike


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## LI-Remodeler (Feb 3, 2015)

Mike,

I've installed Ditra heat in a few bathroom renovations. I always followed the directions when testing word for word. I never energized the wire prior to installation. 

Ensure your leads are securely fastened prior to testing. 

I always dread the test fearing results are not within the required ranges. 

Hopefully the rep will get you through this, but think of the good news. You're smart by doing the testing. I'm sure there are plenty of installations out there that were not tested


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## GettingBy (Aug 19, 2010)

mike gunderson said:


> 300 megohms on my digital megger. For most wires this would be an excellent reading I'm told. Schluter wants a reading of at least a thousand megohms.
> 
> does anyone hook up their power to the wire before tiling to see if it warms up?


So it fails by a wide margin 
or your megger is bad. 
Maybe somebody makes a precision 1 gigaohm resistor to test this, or you could get some kid to solder 100 ea., 10 megohm low precision resistors in series. Try Hosfelt.com or Digi-key. Each resistor can probably stand 500v. Use whatever is cheaper: 1/4 w, 1/8 w, 1/2 w.




I'd do this instead of checking continuity because it gives you more information. . .but. . . 
the heater will heat more slowly embedded in material and level out at a lower temperature, so maybe the rapid rise you'd see with an uninstalled heater is harmful, like powering a water heater element without it being in water.

The maker will tell you recommended practices but maybe you should also ask for any and all prohibited practices.


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## mike gunderson (May 23, 2010)

I contacted Schluter and the state rep. By what it was reading he thought it was a pin hole in the outer insulation. They worry that the cement based mortar would somehow get inside and start corroding the braided copper ground. I mentioned that I have a copper pipe in my basement slab that has been there for 55 years showing no corrosion. The homeowner, who is an electrician, wants me to tile away voiding the warranty. I am a little leery but may do it. I always wonder what these warranties cover anyhow. A new spool of wire or complete tear out and redo. I will find out tomorrow.
mike


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## LI-Remodeler (Feb 3, 2015)

I'm surprised the rep didn't recommend replacement.


I don't think I would go ahead with the install even if my customer was OK with it. 

It's just too much of a gamble (I can have new cables in a day.

It's not the warranty I would be looking to keep intact, it's not having to eat any work if the cables fail and you knew better.


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## GettingBy (Aug 19, 2010)

mike gunderson said:


> he thought it was a pin hole in the outer insulation.


I thought it was way more likely to be your Megger. 
Maybe the Schluter's quality control is not as good as I thought.


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## GettingBy (Aug 19, 2010)

LI-Remodeler said:


> I always dread the test fearing results are not within the required ranges.
> 
> I'm sure there are plenty of installations out there that were not tested


Maybe then the maker doesn't need good quality control. 
"We told the installer to check insulation resistance and it's not our fault if he didn't."

I assume the dread mostly comes from difficulty and lost time in returning the bad strips?


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## GettingBy (Aug 19, 2010)

Shoveling snow in the fresh air has cleared my mind. :laughing: Or not. 

You can measure 300 megohms with a 9v battery and almost any DVM; quick, easy and safe. 
Troubleshooting a corroded connection on the control board for my furnace taught me this method.

Put the meter on a low voltage DC scale in series with the battery in series with the insulation under test.

For a 10 megohm input resistance meter (look up the specs for your meter) you will read 9v x ~10/300 = ~0.3vdc.

This assumes that the insul resistance does not change with 1000v vs 9v and a quick Web search seems to confirm this idea. . .but. . .it depends on what accuracy you need to know the insul resistance. This method is quick and dirty.
If it doesn't pass this test the material under test is bad. If it does pass the material may still be bad.

There is an exact answer formula for the general case of other DC voltages and other meters.


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## Tinstaafl (Jan 6, 2008)

GettingBy said:


> This assumes that the insul resistance does not change with 1000v vs 9v and a quick Web search seems to confirm this idea. . .


Keep searching. Your insulation could fail at 100V, and once current flow is established, it can continue at well below 100V. 

If your method was valid, there would be no need for meggers.


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## GettingBy (Aug 19, 2010)

Tinstaafl said:


> Keep searching. Your insulation could fail at 100V, and once current flow is established, it can continue at well below 100V.
> 
> If your method was valid, there would be no need for meggers.


Your posts are sometimes useful to me because they cause me to rethink my reasoning and assumptions. *Sometimes.*

The Megger test is not designed to be destructive, and if the insul does break down the Megger goes into current limit. The max current with my method is 9 uA and the meter input resistance supplies the current limit.

If I ever get off my butt I will be using this to test the Romex chunks in the basement, just for laughs.

My test may give false positives; that is, it may say the insul is good when it's not. 
It does not give false negatives. If the insul fails my test then the insul is certainly bad.

Meggers are necessary for several reasons. One is that insul may act differently after one minute at high voltage. Conventional resistance measurements are not looking for this effect and there is no need.


*You* should keep searching, but on a different subject! :whistling
If you really want to get upset, look at how many medical tests give false positives and false negatives. 
And the stakes are much higher than for not installing a good floor heater due to a false negative or installing a bad floor heater due to a false positive.


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## GO Remodeling (Apr 5, 2005)

testing a wire without thinset around it voids the warranty on some heat systems. Better check your directions.

Only came across a meeger test on one system I've used. And I've probably used at least 7 different kinds.


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## mike gunderson (May 23, 2010)

I started tiling yesterday. i talked to the rep again in the morning. he repeated what he said about the pin hole on the sheathing. I said i thought it would be probably a 95 % chance nothing would come of it. He said more like 99% that it would be fine. By the way i was informed if you buy schluter products online it voids the warranty.


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## LI-Remodeler (Feb 3, 2015)

mike gunderson said:


> By the way i was informed if you buy schluter products online it voids the warranty.


warranties are worth little to begin with. What are you doing to do rip out the entire floor of a 35k bathroom to reinstall the manufactures defective wire? 

nothing like trying to reduce your warranty liabilities to below worthless. 

Doesn't State laws trump manufactures rules on their warranties?


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## Xtrememtnbiker (Jun 9, 2013)

Schluter has a fantastic warranty. It's very much worth following their instructions. They will pay total cost including demo, materials, and re install, of their product failed. But you must do the things they tell you to for it to be valid. Like log the megger results 3 specific times on Ditra heat for example.


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## GettingBy (Aug 19, 2010)

With pinhole leaks I'd be worried about energizing the entire (wet) floor.


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## GO Remodeling (Apr 5, 2005)

I've had a pinhole leak in a factory connection. Burned out about two months after the install. (BTW,the floor doesn't get energized.) The bad part will look like a cigarette burn on the wire.

There usually is a waiting period before you turn the heated floor system on to allow for the thinset to dry properly. Every thinset company seems to have their own guess as to when you are able to fire the system up.


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## tjbnwi (Feb 24, 2009)

I take a photo of the final megger test, red and black wire. Send the photos to the owner for their file.

Tom


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## LI-Remodeler (Feb 3, 2015)

tjbnwi said:


> I take a photo of the final megger test, red and black wire. Send the photos to the owner for their file.
> 
> Tom



Tom that's a great idea. 

I document everything with my camera but never the results of testing instruments. I just have customers sign off on the results. I'll now take pictures of moisture meter readings as well when installing flooring.


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## tjbnwi (Feb 24, 2009)

LI-Remodeler said:


> Tom that's a great idea.
> 
> I document everything with my camera but never the results of testing instruments. I just have customers sign off on the results. I'll now take pictures of moisture meter readings as well when installing flooring.


I do that also.

Tom


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## GettingBy (Aug 19, 2010)

Re: photos, I found a loose outlet at the local eatery. 
Probably it was just the screws worked loose from people plugging in their chargers but the manager took a photo of it because he said the maintenance people complain about not enough info when they get the call.


I guess the countermove for photo evidence is for crooks is to photoshop the photo.


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