How to tell if tank heat pads work ?

[Suite Sweets]

Other than waiting for freezing weather, and learning they don't work, how to tell ? There is one switch for all 3 of them, so I'd want to learn they each work. I think measuring current draw would only tell that at least one of them works ?

[wingnut60]

Are they automatically on when switched? Or are they temp controlled also?

[Suite Sweets]

Wingnut, somehow I thought it might be you that responded first. Thank you.
No temperature control with the switch. Switch is only on or off (not marked, but I assume the usual manner - push in at the top for on, in on the bottom for off.
I don't know if there are thermostats in line, down by the tanks, or not. The switch is in the main control cabinet, in the living quarters.

[OCB]

On my 2016 MS, I was told at the factory there a thermostat (most likely a Button Thermostat) that closes contracts about 40 degrees and opens at about 50 degrees. Thermostat location I do not Know but the power source is from the 12 volt source. Also the heater will not burn the tanks and valves even if the tank or valve is drained.

Clay

[Suite Sweets]

OCB - thanks for that input, especially the last sentence. After purchase, when we got it home 2 days later, I found the heat pad switch 'ON'. Could have been on 9 months (time the RV had been sitting unused) or could have been on the 2 days since purchase. I hope someone else chimes in with more info. So far, I've found DRV to be responsive, but I'm afraid as the answers get more complex, I'll have difficulty finding someone who knows the answer AND will answer the phone.

[MTK46]

Only way I knew ours was working is all three were on (different switches for each one). They killed my batteries after three days of not plugged in. ;)

[pterrydactyl]

If thermostat on heater pads then it would only matter if temp caused the pads to come on. If you winterized then little or nothing to freeze. If you use battery cut switch it wouldn’t matter even if pads main switch was on. No battery power to heat them.

Is there 1 set of 12 volt wires or 3 positive 12 volt wires behind the switch?

[dmorse68]

Can you reach them in the basement? If so, is warmth emmited from them detectable?

[Suite Sweets]

dmorse: I can reach the fresh water, but not the other two. Good thought.

pterrydactyl At the back of the switch, there are three wires to one terminal, and 1 wire to the other terminal. I think you're headed in the right direction, but I don't know where I'm going. But your question tells me - you can tell me how to get there.
Checking the owner's manual, it appears that the water tanks use heat pads drawing 4.8 amps and 65 watts or drawing 5.8 amps, drawing 78 watts, and the elbow would use 1.7 amps and draw 23 watts. If I turn on the switch, and have 4 pads (figuring 2 for the fresh water) drawing 5 amps each (rough average of the two) - plus the elbow, what should a volt meter applied to the battery indicate. Or, worded differently, if only one or two of the had pads work, I'd expect to see different readings than if all four work. Will a reading tell us how many are working ? As all can tell, I know enough to get in trouble.

[pterrydactyl]

The problem is those built in thermostats that turn on a ~40F. The circuit needs to be on and if it’s not cold enough to turn it on measurements won’t help.
I’m suspecting that the singe wire behind the switch is the main 12 volt from the battery. When you turn on the switch current flows thru 3 wire to the 4 pads. As you said 2 pads on fresh water tank and thus 1 each to grey and black. Right?
So how can you determine if the circuit is active? Hmmm. A feedback wire downstream from the thermostat would send power to a LED light by the switch. Runnng those wires would be a PITA. A button thermistor applied to the surface or between the pad and tank would give a constant reading of the temp. If the temp reading was higher than ambient temp then the pads would be heating only while in the narrow temp rang tho’. But how to run the wire without a lot of work or having to remove the underbelly covering.
I need to think on this some more. Any thoughts so far?

[porthole]

I asked the service center today why they use tank pads rated for 40 gallon tanks on tanks that are 50, 75 & 100 gallon sizes

[Suite Sweets]

Porthole - I'll be interested if they respond, and for sure, what they have to say.

pterrydactyl - Ever since you responded, I've been working on trying to come up with a solution. Here's what I think will work, but check me on this - you know a lot more about electricity than do I.
When temperature is below 40 degrees
Remove the switch and cut each of the 3 wires
Put a multi-meter in line between each of the wires
Turn on the switch and read the amperage.
Multiply by 12 (voltage of the battery) gives watts
Compare watts drawn with specification cited earlier, which I got from the owner's manual of the heating pad.
-OR-
Cut the single line, wire the multi-meter in between each of the leads.
Turn on the switch and read the amperage
Multiply by 12 for watts
Compare with total wattage of 3 pads and the 23 watt elbow. I'm thinking that DRV might have drawn 23 watts off of one wire for the elbow heater, but they probably would not draw off of one wire for 2 heating pads. I conclude that because if they would do that, then there wouldn't be 3 wires coming from the switch - there would be two.
What say anybody ?

[pterrydactyl]

Cut the tire? Can they be pulled off the switches terminals on back. Or pull the wires gently to see if they a connected somehow further down?

Watt meter inline? Something like this:

RGBZONE 130 Amps Power Analyzer, High Precision RC with Digital LCD Screen for RC, Battery, Solar, Wind Power https://www.amazon.com/dp/B01LAUKXOQ/ref=cm_sw_r_cp_api_i_v7upCbVCMWKTH

This is getting to be a good mental challenge.

[Suite Sweets]

Of course, pull the wires from the back of the switch. I hope that would have come to me before I actually cut them. I'd watched a Utube video and in that, the speaker cut the wires (different task) - monkey see, monkey do. I won't buy the power analyzer. I think that's for constant monitoring. I want to see that they're working, and then forget about them (this a new to us DRV). I'll check it out in the next week, and report.
pterrydactyl, thanks for helping in the solution.

[porthole]

Use an clamp on ammeter. Don’t cut anything.

http://www.youtube.com/watch?v=z-KfZvbjyBY

[porthole]

Porthole - I'll be interested if they respond, and for sure, what they have to say.



You know that deer in the headlight look ?

[pterrydactyl]

Here is Ultra heats answer to how to check the heater pads.

https://www.ultraheat.com/faq

[Suite Sweets]

yes, i'd read that early on. Their advise is conditioned on 'you must have direct access to the heat panel'. I don't.
I'm liking my solution (or porthole's even better if I had one of those clamp on meters) better if it will work.

[Suite Sweets]

Porthole - those clamp on meters are for 120 volt, the heat pads in my DRV are 12 volt. The multi-meter I have, I think, will not read amps. I've got an email in to a friend (with a link to the multi-meter I have) asking if I'm right - that it won't read amps. I 'worked' on the problem this morning, with no success in learning anything.

[Traveling Home]

For a DC clamp-on meter, google those words. You can get a cheap one for $20-30.

[porthole]

I use this. Mine is a bit older and lower range, but it will read up to 400 amps DC.


https://www.amazon.com/Sperry-Instruments-DSA540A-Function-Snap-Around/dp/B00279P6C4?th=1&psc=1


Another meter i use is this one.
This is typical of a meter that the leads are put in line of the circuit to read current draw.

But many meters like this are limited to 10 amps or less

https://www.amazon.ca/Ancor-Marine-Grade-15-Function-Products/dp/B018RR9O8G

[porthole]

On a standard multi meter you switch one of the leads to the current side.
In this picture the leads are set to read voltage.

If you move the red lead to the far left port marked ‘A’ you can read the current draw.

Also keep in mind - although the clamp on meter is easier to use, the positive and negative wires need to be separated when clamping around the wire.

Look before you buy. If you are going to purchase new, may as well get one that can read AC and DC amps.

[porthole]

Couldn’t load the picture in the last post.