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Author Topic: Test for working tank heaters?  (Read 758 times)

WolfgangStiller

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Test for working tank heaters?
« on: January 27, 2018, 01:29:01 PM »
I have a new (just got it) 2018 Winnebago Minnie Drop 1780 with dealer installed tank heaters. The tanks are exposed on the bottom of the trailer. It was 20 deg F this morning and I turned on each tank heater and after 30 minutes of waiting I noticed absolutely no warmth on the heating pads.  Could they still be working with no detectable warmth? 
2018 Winnebago Minnie Drop 1780

lynnmor

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Re: Test for working tank heaters?
« Reply #1 on: January 27, 2018, 02:00:54 PM »
Are the heaters 12 volt, 120 volt or combination?  If you have a watt meter or amp meter, you could test for the current draw.  If it is within spec, the heater is working.  Whether it is sufficient to do the job remains to be seen.

Gary RV_Wizard

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Re: Test for working tank heaters?
« Reply #2 on: January 27, 2018, 02:09:01 PM »
For future reference, you should turn on the tank heaters before it gets below freezing. Once the tanks ice up, it's too late to protect your plumbing. Water begins expanding at about 39 degrees and by the time it turn to ice at 32 it has expanded 9%. If its gonna break something, it is at that point.  Further, the heaters probably aren't enough to defrost an already frozen tank, at least not in any useful timeframe.

That said, it seems as though you should have been able to feel some slight warmth, but as already stated, the heater isn't real hot and maybe 20 degrees just overwhelmed it.  Checking the change in current (amps) after switching it on is the best & easiest test.
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WolfgangStiller

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Re: Test for working tank heaters?
« Reply #3 on: January 27, 2018, 02:13:45 PM »
Are the heaters 12 volt, 120 volt or combination?  If you have a watt meter or amp meter, you could test for the current draw.  If it is within spec, the heater is working.  Whether it is sufficient to do the job remains to be seen.

They are 12 volt.  I tried a check of amperage (right at the switches) and saw only  2 ma (it should be 6 to 8 amps for each tank) but it's possible the temp had climbed to the point where the thermostat decided no heat was needed. I will try that again tomorrow.
2018 Winnebago Minnie Drop 1780

WolfgangStiller

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Re: Test for working tank heaters?
« Reply #4 on: January 27, 2018, 02:15:33 PM »
For future reference, you should turn on the tank heaters before it gets below freezing. Once the tanks ice up, it's too late to protect your plumbing. Water begins expanding at about 39 degrees and by the time it turn to ice at 32 it has expanded 9%. If its gonna break something, it is at that point.  Further, the heaters probably aren't enough to defrost an already frozen tank, at least not in any useful timeframe.

That said, it seems as though you should have been able to feel some slight warmth, but as already stated, the heater isn't real hot and maybe 20 degrees just overwhelmed it.  Checking the change in current (amps) after switching it on is the best & easiest test.

That's exactly why I am running a test. Currently the trailer is winterized so each tank just has a small amount of antifreeze. 
2018 Winnebago Minnie Drop 1780

WolfgangStiller

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Re: Test for working tank heaters?
« Reply #5 on: January 28, 2018, 08:05:14 AM »
I ran the test on all three tank heaters after a cold night and saw only about 8ma of current so I think I am going to have the dealer recheck the heaters. The wiring seems fine as best as I can determine but the heaters don't seem to be kicking on after the low temps.  I think typically they should turn on below 40 or 44 F.
2018 Winnebago Minnie Drop 1780

ALLOY

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Re: Test for working tank heaters?
« Reply #6 on: January 28, 2018, 10:42:47 AM »
They are 12 volt.  I tried a check of amperage (right at the switches) and saw only  2 ma (it should be 6 to 8 amps for each tank) but it's possible the temp had climbed to the point where the thermostat decided no heat was needed. I will try that again tomorrow.

Two 2 tanks heater will draw a 200Ah battery bank down (with no shore power)  to **12.1 volts (50% capacity) in 7 hours.   

 **12.1 volts (50% capacity) is a number that is considered to be a good balance between the capacity and longevity.  Other factors that affect longevity are charge voltage(s) and percentage (SOC) of charge achieved.
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WolfgangStiller

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Re: Test for working tank heaters?
« Reply #7 on: January 28, 2018, 07:46:27 PM »
Two 2 tanks heater will draw a 200Ah battery bank down (with no shore power)  to **12.1 volts (50% capacity) in 7 hours.   

 **12.1 volts (50% capacity) is a number that is considered to be a good balance between the capacity and longevity.  Other factors that affect longevity are charge voltage(s) and percentage (SOC) of charge achieved.

Thanks for the heads-up. I am in good in regards to the heaters draining the batteries. I would typically be running one tank heater for each of my tanks so I have three heaters not two  but  I have two batteries (purchased with exactly this problem in mind) and have done the math with the power consumption plus I have a generator I can pull in as well.  It's actually tricky to calculate because the heaters can cycle on an off (via the thermostat) but when they are on they draw 7 amps each. This is the worst case but that's what I based my assumptions on.
« Last Edit: January 28, 2018, 07:49:51 PM by WolfgangStiller »
2018 Winnebago Minnie Drop 1780

grashley

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Re: Test for working tank heaters?
« Reply #8 on: January 28, 2018, 08:06:20 PM »
What happens if you make sure the batteries are fully charged, shore power off, cold night.  Measure voltage at the batteries.  Turn on the heaters and leave them on overnight.  In the morning, turn heaters off and measure voltage at the batteries.

If the two voltages are nearly identical, the heaters pulled very little power from them.  If the voltage dropped by 0.5V or more, then there was a significant draw by the heaters.  It will not tell you how big a draw, just that the batteries were drawn down some, likely by the heaters.
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WolfgangStiller

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Re: Test for working tank heaters?
« Reply #9 on: January 29, 2018, 02:31:43 PM »
I just came up with another way to test out the heaters. I am going to put in two gallons of antifreeze  into the freshwater tank for the first test. I will leave the heater turned on overnight (with temps in the 20s expected).  The specs say the heater will turn on once the temp drops below 45 F at which point it will keep heating until 67 F.   In the morning, I am going to drain the tank and measure the temperature of the antifreeze. It should be over 45 degrees.  (I am afraid to do this with water in case the heater is not working).
« Last Edit: January 29, 2018, 02:33:14 PM by WolfgangStiller »
2018 Winnebago Minnie Drop 1780

grashley

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Re: Test for working tank heaters?
« Reply #10 on: January 29, 2018, 07:38:44 PM »
Water is much easier.  If it will not drain, the heaters did not work!   ;D
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ALLOY

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Re: Test for working tank heaters?
« Reply #11 on: January 29, 2018, 08:58:20 PM »
Are you using a clamp on amp meter that reads "DC" amperage?
 

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WolfgangStiller

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Re: Test for working tank heaters?
« Reply #12 on: January 30, 2018, 01:57:14 PM »
Water is much easier.  If it will not drain, the heaters did not work!   ;D

Sure...and MUCH more expensive if it freezes solid.  :)
2018 Winnebago Minnie Drop 1780

WolfgangStiller

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Re: Test for working tank heaters?
« Reply #13 on: January 30, 2018, 01:59:31 PM »
Are you using a clamp on amp meter that reads "DC" amperage?

I connected my meter directly in circuit.   I did borrow my neighbors clamp on meter for one test but most were direct.  Now that I tried his clamp on, I want one too. Much quicker to use.
2018 Winnebago Minnie Drop 1780

WolfgangStiller

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Re: Test for working tank heaters?
« Reply #14 on: February 01, 2018, 08:19:54 PM »
I ran a test on the fresh water tank and the temps were too cold. The dealer found the heater was defective and replaced it (on their dime of course). Now I am repeating the tests and will test all three tanks.
2018 Winnebago Minnie Drop 1780

kdbgoat

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Re: Test for working tank heaters?
« Reply #15 on: February 02, 2018, 05:50:45 AM »
Glad you hopefully got it working. It sounds as if you are pleased with how the dealer handled your situation. If so, please add a topic in the reviews section with the problem and the dealer"s name and location. It's nice to hear when a dealer does right. We mostly only hear when a dealer is considered sub par.
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WolfgangStiller

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Re: Test for working tank heaters?
« Reply #16 on: February 02, 2018, 04:41:19 PM »
I am generally quite pleased with how responsive the dealer is. The first repair visit resulted in one of the the three heaters being replaced. But after a test last night the antifreeze was 28 degrees F (not what I want).  So back for another try. This time it was a wiring issue (reportedly the heaters were wired to the slide circuit).  I will test again tonight.  They offered to do the testing but that would have required them keeping it until Monday and I had other work I wanted to do.
2018 Winnebago Minnie Drop 1780

WolfgangStiller

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Re: Test for working tank heaters?
« Reply #17 on: February 15, 2018, 08:51:49 PM »
I thought I'd post my results in case anyone else needs this information. I have ThermaHeat tank heaters. (Reportedly the same heaters are marketed under some other names as well).  They are rated to draw 4.8 amps and my tests show they draw within .15 amps of that value.  It turns out that assuming the thermostat has activated the heater (in otherwards it's cold enough to turn the heater on) you *can* feel some warmth by placing your hand on the heater (it's not dramatic but definitely noticeable). The other test is to run the heater with antifreeze and measure the temperature. It should be between 45 and 67 degrees F when it's cold out. You should also see a current draw of around 4.8 amps when the heater is running.

What happened in my case is that there was a wiring error and secondly my dealer had a bad batch of heaters. The thermostats were defective in this batch. They replaced all three tank heaters and they still didn't work. They ultimately had to get a new batch of heaters.  It took four visits to finally get things right.  I did get a free wash of the trailer for my trouble.
« Last Edit: February 16, 2018, 07:12:29 AM by WolfgangStiller »
2018 Winnebago Minnie Drop 1780

 

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