Noisy Isolation Transformer on 2004 Hunter 36

dlochner · Nov 14, 2023

There should only be one transformer.

It should be located near the shore power inlet, it will be a fairly large box, find the shore power inlet and follow the wire, it won't be far.

Transformers often hum, it is a 60 cycle hum because that's the cycle of US AC power. Newer transformers are available, search for an isolation transformer, they are both heavy and expensive.

Ralph Johnstone · Nov 14, 2023

Just a shot in the dark but IF you ever do find it, maybe unscrew and lift it up and slip a soft rubber pad under it as a vibration isolator. Make sure the pad is silicone or something fire resistant.

No promises. No guarantees. No returns. Just like most companies.

Johann · Nov 15, 2023

If you’re looking to replace, the Victron isolation transformers are relatively lightweight and very quiet. We installed the 2kW version about six months ago and haven’t noticed any hum. I can hear the fan if it’s at higher power and I open the compartment it’s in.

Isolation Transformers - Victron Energy

Isolation transformers are essential in professional ship installations and prevent electrolytic corrosion. Ensure a safe electrical system.

www.victronenergy.com

dlochner · Nov 15, 2023

Try opening the AC panel and trace back to the plug. What you are getting is a resonant sound, it may not be coming directly from the transformer, rather it is causing something else to vibrate. Sort of like the body of stringed instrument, you don't hear the string itself, you hear the sound resonating from the body of the instrument.

AndyL · Nov 15, 2023

We have the same model and year and our isolation transformer is in the port locker on the swim platform. You have to put your head down into the locker to see it. It does hum.

George Braun · Nov 15, 2023

on our 2008 H36 the isolation xfrmr (we have 2 because of aircon on separate 30A circuit) are mounted portside inside and above the stern locker. From the outside, on the inside of the vertical surface of the stern above the locker. Pretty much inaccessible.

AndyL · Nov 16, 2023

Access looks very tricky and I'm not sure whether you're better off on the hard or in the water. I found it by laying across the swim platform and leaning down into the port locker - something I would not like to do on the hard in case I rolled off! On the other hand you may be able to get at it from a different angle on the hard. If you're in the water now, I'd suggest you try and see how it works.

George Braun · Nov 16, 2023

Kupe said:
Thanks George! Heading up to the boat tomorrow and will try to look there. Our 2004 H36 also has two 30amp Shore Power inputs with the Air Conditioning on Line 2. Does that mean we necessarily have two Isolation Transformers? From the location you describe, it doesn't sound safe or practicable to access unless on the hard.

Cheers!

From recent past experience, there is a bunch of stuff that Hunter installed into these boats before they joined the deck to the hull, making access at a minimum difficult if not impossible. The holding tank is another one. I went through the same thoughts as you, laying across the stern while on the hard isn't fun, but in my case it was better than cutting open the aft cabin. For the isolation xfrmr, i might suggest cutting open the aft end of the cockpit locker. Hidden out of sight, and would be simple to put right afterwards.

artboas · Nov 17, 2023

Kupe said:
Hey gang-

This summer we purchased our new-to-us 2004 Hunter 36. Love it! Unfortunately we have recently become aware of a loud electrical humming in the aft cabin. Until this month we have always had fans and/or air conditioning running, so this noise went unnoticed. So I did some searching here in the forum and turned up this excellent discussion (now closed) from 2004. A number of Hunters were experiencing this at the time, including the H36. The sound apparently eminates from one (or more?) Isolation Transformers. The only way to silence it is to turn off shore power altogether which I did last night in order to get some sleep.

A couple questions if I may.

1) Where is this sucker located? I've opened every panel and cubby I could think of and can't find it. It is loudest in the rear outboard corner of the aft cabin (starboard side on the 36).

2) Can replacements be found? I searched the parts store here at Sailboatowners.com and don't see it. I ask cautiously since posters in that older thread indicated new boats were delivered with this problem and replacement transformers didn't always fix the problem.

3) Assuming replacements are not available, has anyone found a solution?

Thanks gang- the expertise here in the group is amazing!

Cheers!

On my 49 I have the massive 12kw Charles transformer
I use this for a number of things …
CAUTION!!
Unless you are competent with AC wiring, know how all aspects of what transformers do, and so forth….
Don’t do what I’ve done.
My 49 runs from 50 Amp “220” dock power.
Now, “220” isn’t necessarily 220z
Depending on how the shore service is wired (Delta vs Star), you could have 208v at your shore power.
Which means that each leg is (optimistically) 104vac
Now, I’m taking about a 220v boat. The smaller boats are wired 120, and only use the transformer for isolation.
I’ll discuss both.
If your boat is 220, you’ll sometimes find yourself in a marina that only has 30A 120 outlets.
You can get a “smart Y” from Marinco, Hubble, etc, which converts 2 30A outlets into one 50A 220v

I cannot emphasize this enough…. Be very careful.
Firstly, the 2 30A outlet Hot connections must be out of phase with each other for this to work. If you take a dvm, connect the leads across the hot connections of each outlet, you need to read approx 200vac.
If they are on the same phase, you’ll read only a few <10 volts.
Option 2.
Unplug boat.

look at the wiring diagram for the transformer.
In most transformers. You can move one of the primary windings to a different terminal of the transformer, making it a “step up” transformer.
In this case. You will have 120vac in, and 220 vac out, just by moving 1 wire.
You will need to fabricate, or purchase) an adapter cord 50A Female to 30A 120m

You will only have 1/2 current, which is good enough for charger, HW heater, and 1 airco & your tv.
HUGE CAUTION!!!!

Put a sign on your panel down below, stating “caution 120 volts”

if you plug your boat into 220 without changing the tap back, there will be major damage

You can also do voltage boost, 208 -220, but this is a little complicated. PM me in this

good luck !!

JamesG161 · Nov 17, 2023

artboas said:
I cannot emphasize this enough…. Be very careful.

This is what is recommended now.

I am not sure about the Hummmm will improve. The noise may be caused by nearby by boats with a 50Hz wiring

The shore power connection may be at fault.

Jim...

PS: Prevents Grounding Wire [Green] feed back from other Boats on same Shore Power line.

George Braun · Nov 17, 2023

JamesG161 said:
This is what is recommended now.

View attachment 221456

I am not sure about the Hummmm will improve. The noise may be caused by nearby by boats with a 50Hz wiring

The shore power connection may be at fault.

Jim...

PS: Prevents Grounding Wire [Green] feed back from other Boats on same Shore Power line.

Kupe - If you end up having replace one or both of your Xfrmr's , on a Hunter 36 in US waters, no need for anything but the smallest of these.

artboas · Nov 28, 2023

Kupe said:
Thanks George and all!

Alas, I've learned the Charles Marine Isoguard Transformers were discontinued in 2016. Thanks George for the recommendation on the ProSafe units and [EDIT] to Johann for the Victron units. Also found out the IsoGuards weigh 76 pounds each, which certainly speaks to the accessibility issue. I located the owners manual here online. I found the Transformers as others said inside the port swim platform locker (photo attached). Yep- zoom in to see how Hunter disregarded the labeled vertical mounting.

The Isoguards connect via twist-on Cord Grip Connectors-- not sure if they are proprietary or not if hoping for a plug-and-play swap with the Prosafes?

BUT....I think I've discovered a livable workaround for now. As it turns out, my Line 2 Transformer is the louder of the two (though both do hum). But the good news is that I only need to power Line 2 if I'm running Air Conditioning or Heat. And if I'm running that, then of course I don't hear the hum. So when not running those, I turn off the Line 2 shore power breaker in the port locker. I can live with the relatively quieter hum from the Line 1 Transformer.

There are always punch lists and to-do lists, and this remains on mine. But I think I can award it a lower priority for now at least. Besides, my wife says to get working on the shower sump! I'll post details when able. Thanks gang this forum has been a god-send!

For the shower sump, use the Whale IC system. It is by far the best solution. Install it, and you’ll never have any service issues again

MFD · Dec 16, 2023

Kupe said:
Alas, I've learned the Charles Marine Isoguard Transformers were discontinued in 2016. Thanks George for the recommendation on the ProSafe units and [EDIT] to Johann for the Victron units. Also found out the IsoGuards weigh 76 pounds each, which certainly speaks to the accessibility issue. I located the owners manual here online. I found the Transformers as others said inside the port swim platform locker (photo attached). Yep- zoom in to see how Hunter disregarded the labeled vertical mounting.

For the older Charles Marine units - to the best of my knowledge you can still pick up an identical factory-new replacement unit off e-bay since the original factory stock was sold off to a 3rd party when they discontinued it. If it was up to me, and I had time - I would go with something new/victron with fancy features. Sometimes however, just 'bolts right back in place like the old one' makes boat projects go a lot faster

Noisy Isolation Transformer on 2004 Hunter 36

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