MS400 low dock voltage (~100Volts +/-) solution

[garmstro55]

Thanks to Red Pearl (https://sway.office.com/F0aSm8VOnaj0iz58?ref=Link) I identified and solved my problem with low supply voltage at my home marina.

With my new (to me) MS400 I was seeing only about 100 volts on the panel meter when on shore power and almost 120 volts when running the generator. This made me go hmmm, but I had no idea what was going on.

According to the detailed report on the Red Pearl site, it has to do with the way the marina is wired, coupled with the 50 amp 240 volt boat power inlet design of the Mainships.

This concerned me as some equipment and appliances don't like low voltage supply. I encourage anyone with a MS who has this issue to carefully read the explanation and solution posted by Red Pearl.

In a nutshell as I understand it, my marina is wired with 208 split phase service at the pedestals. This isn't a problem for the 30 amp, 120 boats as you can get 120 from this design. BUT, the MS is getting only 208 and it is fed to the isolation transformer, where it gets cut it in half. I was seeing something like 101 or 102 volts. Not good.

As it turns out, the Charles isolation transformer has a "boost" feature that will give you 120 volts or so with the 208 V coming in. You just need to add a couple of switches as explained in the writeup.

I just had my electrician finish the job last week and yippee, I am now getting close to 120 to my panel with the transformer in boost mode.

I added a label to the panel to remind me to switch to "un-boosted" when traveling to other marinas until I find out what voltage the transient marina is providing.

The transformer is behind the panel in the back of the guest stateroom closet. Here's a shot of the transformer and also the switch installation.

I am surprised I have not seen anyone on this forum complain of this problem before. I think my stove, oven and summer kitchen grill will now work better and the fridge and AC might last longer now that they are getting the correct voltage.

One more thing to mention, I had Blue Sea add the led's and labels, but they don't actually work because of the way it must be wired. I have to add my own labels to keep it straight.

 

[jefndeb]

Great Info, where can I find more tech data on this isolation Transformer?

 

[garmstro55]

Great Info, where can I find more tech data on this isolation Transformer?

Did the link to Red Pearl work? That's where I got my info? Do you have the low voltage at your home dock?

 

[jefndeb]

I have heard the hum noise from behind that guest closet and saw the placard indicating it's location but never really digested what it's for....now, thanks to your post I am getting an understanding....I will take a closer look at his web site...

 

[tiltrider1]

This issue has been discussed on the forum many times. Many marina’s use a Y transformer. On a Y transformer each leg is 120 volts but they are not completely out of phase with each other. When you grab two legs to make 220 you only get 208.

 

[Capt Mike]

Gary - Where did you buy the Blue Sea Systems switch?

 

[garmstro55]

Gary - Where did you buy the Blue Sea Systems switch?

Blue Sea sells through distributors but has a "build a panel" type of application on their site. I stumbled through that process for the design and then ended up ordering through Peter Kennedy of PKYS in Annapolis. Apparently Peter is a marine electronics guru and was extremely patient with my dumb questions.

My order number was QB-44895 so if you contact Peter he can probably just duplicate it. pkys@pkys.com. If you need more detail let me know.

Not cheap, $324.00 but less expensive than replacing the AC, fridge, controllers, etc. on the boat.

Do you have the low voltage problem at your marina?

 

[Capt Mike]

Gary - thanks for the information. Shore power voltage at my marina is 103 to 105v. I also read the Red Pearl site information on using the boost taps in the transformer and I have been planning to do this upgrade.

 

[jefndeb]

Since there are already Breakers installed for shore power, can this not be used instead of another in-line $300 Blue Sea Breaker to switch the Xfmr feed?

https://www.amazon.com/gp/product/B07N11925K/ref=ox_sc_act_title_2?smid=A1PT2K18XDMFJ8&psc=1

 

[twistedtree]

It's common, though not universal, for transformers to have multiple taps for this purpose. How it works will depend on the exact transformer that you have, so you will need to determine make and model, then go find the wiring diagrams. Or you might get lucky because many show the taps and wiring right on the transformer placard.


If this is inspiring you to add a transformer, just beware that Charles dropped out of the business a few years ago. You might still find stock here and there. However Hubbell/Acme sell a line of proper marine isolation transformers with all the requisite taps. This is what I'm using on our current build. "Marine" isolation transformers are indeed different with separate, isolated grounds for the shore and ship sides. It's not just shiny metal and a big markup. So don't be tempted by a non-marine transformer.

 

[garmstro55]

Since there are already Breakers installed for shore power, can this not be used instead of another in-line $300 Blue Sea Breaker to switch the Xfmr feed?

https://www.amazon.com/gp/product/B07N11925K/ref=ox_sc_act_title_2?smid=A1PT2K18XDMFJ8&psc=1

Jeff, I am not qualified to answer your question, but I can offer some additional information.

My electrician wanted to use these two items:
https://www.amazon.com/AC-Rotary-Sw...x=blue+seas+9019,aps,343&sr=8-2&tag=coa_us-20 ($279) AND this panel https://www.amazon.com/Blue-Sea-Sys...s=120/240V+AC+Main+7372&qid=1586460202&sr=8-1 ($250) for a total of over $500. I insisted instead that he use what the owner of the other Mainship used because I was confident it would work.

The Blue Sea switch in the link above looks the same as the one you found, but there must be significant differences given the price delta.

 

[PaulB.]

I had the Blue Seas switch unit installed as well after a summer of my air conditioning stopping at 208 volt docks. A good 208 volts would run the cooling pump but sub 208 would not. My air conditioners are rated for 208 to 215 volts so the issue was confined to the AC cooling pump. I didn't worry about low voltage to the stove or BBQ. Toaster de-hydrates rather than toast. I run the fridge off the 12volt DC all the time to avoid the risk of low AC voltage coming in from the Charles isolation transformer being transformed by the fridge into low DC voltage. We did the whole loop last year without needing to use the switch. No sub 208 volts when we needed AC. So;
1) Don't rush to install the switch if you are good at your home base and are prepared to rough it for occasional need.
2) I keep a big orange hose tie wrap marked " DANGER BOOST" at the switch which I move to the pedestal plug in end of the shore power cord when in boost mode to protect me from accidentally leaving the switch in boost mode and plugging in to a 220/230 volt pedestal. Concerned the 232+ could cause problems.
3) An AC cooling pump that can work with 208 volts might be another option and would be able to be handy man installed. The rewiring of the isolation transformer is beyond ...

 

[Pmcsurf1]

We just had this same problem. We have a 2004 ms400. I wouldn't call the marina our main port but we were staying there for over 1 month for repairs and some family stuff. We've left that marina and now we're cruising and staying on the hook mostly. In the last 2 weeks we've stayed at 3 marinas as transients. All three had proper voltage. I'm just gland my transformer isn't bad like my AYBC electrician said. I paid him $200 for bad info.