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Old 10-20-2019, 12:45 PM   #1
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Noisy wiring

I have a 2001 Newmar Mountainaire DP. I am presently connected to a 50-amp shorepower and am running in pass through mode on my Xantrex pure sine wave inverter. The bus has bad RF (radio frequency interference) in the AM band. It's consistent across the band and pre-dates the inverter. The hum overcomes the dash radio completely and is persistent in a plugged-in table radio as well. On the table radio I was able to catch the Seahawks game at 710 and often can get 1000. But it's raining today and all I get is buzz.

I changed out and verified ground on the dash radio antenna. I ran a ground from the chassis to a water standpipe. I've turned on and off everything I can find including refer and hot water tank, one at a time. I've plugged in the tabletop radio to all the outlets. Although I get some variance to the RF by outlet, the overall problem is clearly none of the above.

I have a tone generator and tracer. I used the tracer to find the strongest point of RF. The general area is the shore power bay, just ahead of the left rear wheel. Both of the converters buzz, but the huge noise is coming from the two items in the left of the picture. The business end of the large cylinder (solenoid?) above the transfer delay relay is noisiest, with the 2/0-gauge terminal posts the loudest. I can hear them without using the probe.

The question is what is that solenoid-looking thing, is this sort of noise normal for it, and if not, what do I do to correct or suppress it?

The other question is what sort of noise level is normal for the converters?

Thanks
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Old 10-20-2019, 01:18 PM   #2
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That is the isolation solenoid. Isolates the battery banks when no charging and combines them when there is. The BIRD controller has the logic for it.

It may be noisy because it uses 12 volts to engage but the BIRD drops the voltage down lower as a holding voltage.

As a test, you could slip the wire off the relay connector to disable the solenoid.

That disables bi-directional charging. On shore power, your chassis battery will not be maintained. A trickle charger will fix that. Problem is while traveling, the engine charging system will not charge your house battery bank.
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Old 10-20-2019, 02:16 PM   #3
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Noisy wiring

A corroded or dirty electrical connection can also cause this kind of RF interference, especially on the ground side of the circuit. One at a time I would remove, clean and reconnect each of the wire connections in this bay.
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Old 10-20-2019, 07:17 PM   #4
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I agree with twinboat but I call the relay a different name - the "big boy" relay does "isolate" the house and chassis banks. You can measure the voltage (to ground) of each big lug - both of which are either the house or chassis bank (if the relay is not active).
I call the relay the "combiner" relay. The BIRD controls the relay and is looking for 13.3+V on the "coach" terminal. If it sees that voltage it will apply 12V on the "relay" terminal to fire the combiner relay and then drop the V to 3.4V to hold the combiner relay active. This "combines" both banks and charges both banks via the charger (Inverter/charger on mine).
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Old 10-20-2019, 07:46 PM   #5
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Thanks for the tips so far. Disconnecting the wire between the BIRD and the isolation relay did not reduce the noise. I've been chasing chassis grounds since I got this rig, and I've been replacing 2/0 cables and ends in the battery bay. I have one more known 2/0 terminal that needs attention. I'll start checking the far side connections next.
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Old 10-20-2019, 07:53 PM   #6
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Are you using any USB power adapters, the kind that plug into the cigarette lighter? Those are notorious for generating lower frequency broadband RF noise.

The only way a plain old relay or solenoid should generate RF noise is if it's arcing inside. You might get better test results by holding the tabletop radio cord near those components. If that radio has an internal antenna it's probably a ferrite core rod and those can have directional properties. That means you can pivot the radio in a circle and "null out" the noise. That usually lets you figure out the noise source by moving the radio around and seeing where the nulls cross each other.

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Old 10-20-2019, 08:39 PM   #7
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Noisy wiring

Quote:
Originally Posted by RKins View Post
..........I call the relay a different name - the "big boy" relay does "isolate" the house and chassis banks.

I call the relay the "combiner" relay. The BIRD controls the relay and is looking for 13.3+V on the "coach" terminal. This "combines" both banks and charges both banks via the charger (Inverter/charger on mine).
" Big Boy " is a brand name, like Sheetrock is gypsum wallboard.

B.I.R.D. = Bi-directional Isolation Relay with Delay.

Call it what ever you want but that's what it is.
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Old 10-20-2019, 08:51 PM   #8
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Your radio issue is the first I have read in a few years lurking here . Disconnect the coil see if it goes away. It would still be hard to believe the DC coil hum at coil reach into radio frequency but crazy don't surprise me anymore. The other poster may be right that is arcing cuasing the issue and radio noise. To troubleshoot You could put a jumper cable across the battery lugs of coil that would bypass\eliminate any arcing going on inside it.
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Old 10-21-2019, 06:26 AM   #9
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Quote:
Originally Posted by 153stars View Post
Your radio issue is the first I have read in a few years lurking here . Disconnect the coil see if it goes away. It would still be hard to believe the DC coil hum at coil reach into radio frequency but crazy don't surprise me anymore. The other poster may be right that is arcing causing the issue and radio noise. To troubleshoot You could put a jumper cable across the battery lugs of coil that would bypass\eliminate any arcing going on inside it.
Wouldn't that cause a short circuit, fire, smoke and hopefully a blown fuse?

Jumping the contactor section might make sense but I'd never do that. Too dangerous if you slip up or are a beginner. I'd disconnect it first and see what happens.

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Old 10-21-2019, 07:41 AM   #10
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Why don't you just put a noise filter on the radio's power cable?
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Old 10-21-2019, 07:52 AM   #11
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Wouldn't that cause a short circuit, fire, smoke and hopefully a blown fuse?

Jumping the contactor section might make sense but I'd never do that. Too dangerous if you slip up or are a beginner. I'd disconnect it first and see what happens.

Ray
Actually, I've read many posts here over the years, where a jumper is used on these solenoids to bypass the battery switch to troubleshoot to see if the battery switch is OK or not. If the jumper does in fact solve the problem you can leave it that way temporarily until you can buy and install a new solenoid. I've read many other reasons while trouble shooting various things applying a jumper here is used.

I've never had the need to do this myself, and I'm not sure what 2 lugs you actually attach the jumper to. But like I said I've read many people do this all the time for testing and trouble shooting multiple issues.

Maybe someone can post a picture of how and where you actually run this jumper so he can test these solenoids.
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Old 10-21-2019, 08:21 AM   #12
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I was talking about making the positive battery connection already being made by the solinoid. Voltage will take path of least resistance , now any arcing inside should stop. The magnetic portion still going see what happens with radio.You can try a a car set of jumper cables only need one, for a few minutes or even move both cables to same lug or bolt them together with nut and bolt.Or buy a short cable same gauge to bolt down between two lugs.
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Old 10-21-2019, 08:38 AM   #13
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I went back expanded your pic they must of used black cables for positive that may be you confusion . Maybe someone replaced cables and only had black those are huge.
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Old 10-21-2019, 05:41 PM   #14
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Quote:
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Why don't you just put a noise filter on the radio's power cable?
Radios normally have sufficient power line filtering built in. Most likely the noise is either radiating directly to the antenna of propagating along the RV's wiring.

Noise filters on the source could help, but only if the noise is leaving the source via the power lines.

Yes, I've dealt with RF noise problems for many decades as part of jobs and hobbies.

Ray
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