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Old 24-03-2011, 01:53   #1
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Marine Air a/c Conversion

Hi,

I have recently completed the conversion of my boat from 110VAC 60hz to 240 VAC 50 hz. I have the three Marine Air "Cabin Mate" (VCP12k and 2 x VCP7k) a/c units disconnected.

Is it possible to convert these 110VAC 60hz units to accept 240 VAC 50 hz by simply switching out the compressors for suitably rated ones or is it more complicated than that?

Thanks

Bob
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Old 24-03-2011, 06:26   #2
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Re: marine air a/c conversion question

compressors might be the easy part if you can match the capacity.
all centrifugal devices may be the bigger issue as the speed of a 50 cycle motor will be slower so less water and air flow. then you have the control system. check and see if the same system is available in 240/50 and compare part numbers to get a better feel for whats what but I suspect you have an expensive experiment if you try to convert.

some equipment is rated 50/60 cycle with somewhat reduced capacity at 50 cycle. are your systems rated by any chance 50/60? if so transformer may be your best bet.

good luck and if you do modify would like to hear the results
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Old 24-03-2011, 07:33   #3
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Re: marine air a/c conversion question

Water pumps, fans and compressors. Check the ratings. What size of boat and how much money? Short of replacing all three A/C units, (ideal), and trading them to someone going the other way. Is this going to be temperary or permanent? Some units may be able to be rewired to accept the other voltage. Some motors can work off of both frequencies. You would have to check each motor, (it should be stamped on the side somewhere). Best consult with a professional, this could easily exceed the range of a do it yourself project.
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Old 24-03-2011, 08:03   #4
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Re: marine air a/c conversion question

According to the literature they can be connected to both 115VAC and 230VAC. The only problem may be the water pump. Either way, expect a overall BTU reduction on 50hz power, as everything will be spinning more slowly.

http://www.dometic.com/FileOrganizer...-Operation.pdf

see page 11 by adobe, 13 by index.
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Old 24-03-2011, 17:18   #5
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Re: marine air a/c conversion question

thanks for the responses.

sailmonkey: i had previously looked at those wiring diagrams but had thought they meant you could have either 110/60 OR 240/50 (i.e. not 110/60 AND 240/50). certainly they're sold in the u.s. as 110/60 and in the uk as 240/50 but they may be listed like that simply because of the target markets.

i think it may be time for an email to dometic!!
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Old 25-03-2011, 17:10   #6
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Re: marine air a/c conversion question

From the horses mouth (or at least Dometic Ltd):

"The circuit boards are dual voltage 115/230v

However, compressor, fan, reversing valve solenoid & sea water pump will be either 110v or 230v. Changing a compressor is about 4-5 hours labour per compressor + parts, it would be a lot cheaper to buy a transformer to convert 230 v down to 115v for each device. If you would prefer to not use Transformers, we could quote you for new units"


I have gone back to them to ask if there is an issue with the transformers inasmuch as the frequency will be 50hz and not 60hz
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Old 26-03-2011, 01:50   #7
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Re: marine air a/c conversion question

Quote:
Originally Posted by bobsadler View Post
From the horses mouth (or at least Dometic Ltd):

"The circuit boards are dual voltage 115/230v

However, compressor, fan, reversing valve solenoid & sea water pump will be either 110v or 230v. Changing a compressor is about 4-5 hours labour per compressor + parts, it would be a lot cheaper to buy a transformer to convert 230 v down to 115v for each device. If you would prefer to not use Transformers, we could quote you for new units"


I have gone back to them to ask if there is an issue with the transformers inasmuch as the frequency will be 50hz and not 60hz
4-5 hours labour including long tea breaks
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Old 26-03-2011, 15:49   #8
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Re: marine air a/c conversion question

Actually no tea brakes. Working in the marine AC and refrig buisness for the past 5 years, that is about what it takes for a compressor replacement. By the time you remove from boats locker, recover refrigerant, remove compressor wiring, cut tubing for old compressor, remove fasteners, install new compressor, fit new tubing, silver solder, leak test, vac pump, recharge, and run. Then reinstall in the locker reconnect ductwork, water, wiring, etc. Get the picture-easily 3-5 hours. It is more cost effective to fit a small transformer, or replace as they commented on. Just some first hand experence-
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Old 26-03-2011, 15:58   #9
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Re: marine air a/c conversion question

Quote:
Originally Posted by bobsadler View Post
From the horses mouth (or at least Dometic Ltd):

"The circuit boards are dual voltage 115/230v

However, compressor, fan, reversing valve solenoid & sea water pump will be either 110v or 230v. Changing a compressor is about 4-5 hours labour per compressor + parts, it would be a lot cheaper to buy a transformer to convert 230 v down to 115v for each device. If you would prefer to not use Transformers, we could quote you for new units"


I have gone back to them to ask if there is an issue with the transformers inasmuch as the frequency will be 50hz and not 60hz
I have had the same question for my installation too, but have only done a little research on the subject as I am still a few years away from needing to answer that question!

What I had seen is Dometic has bought out several marine air manufactures; it was only on the 'Cruisair' brand-labeled product that I did see the compressor rated to handle both 60 and 50 Hz frequencies. The units I have are, I believe, the same as yours, and the compressors on those units didn't show the motors (compressors and fan-blowers) were rated to run on 50 cycles.

I too will be going with perhaps a Charles Muilti-Tap 230-to-120 step-down transformer, but I believe my AC compressors 'could' possibly overheat running at the slower turning 50 Hz power. I am not too worried about the blower as I am sure it can handle just running slower on 50hz, and as far as the raw water pump goes, I can cheaply switch it (one runs all A/C units) to a 50Hz pump, if indeed that is an issue for the Marche AC pumps. Reversing relays and solenoids (just electromagnets) shouldn't have an issue running 50/60Hz since these are just on/off as energized or not, and not a freq regulated switch).

An interesting side note is that I found some information about the possibility that a light weight marine freq / voltage transformer units using 'switched' technologies may come on the market (literally working like the 'new' technology multi-mode combi inverter/chargers that do not use a toroidal-type --heavy-- chargers, except in reverse, converting AC to DC, and then converting DC to AC at the correct volts/freq). This was briefly mentioned at one time or another on both the MasterVolt and Victron websites, but I have not seen any outcome since, and since then (2006), I have no longer have seen any mentioning of the possibility of such a product.

This would beat having to use a very heavy Charles 7KVW step-down transformer, that only does only the voltage and not the freq. I have also noticed some new electric gensets running high freq inverters (360 Hz to 60 Hz for variable speed engines that are on-demand and don't need to run full-fixed RPMs just to get the correct cycles-per-minute), as this is too simply a lightweight high speed switched technology, handling up-to 5KVW, as an AC-DC-AC inverter/converters (voltage and freq).

(Baldor makes one but I am not sure it's rated to run the whole boat --KV-wise! I have one of these on my dive compressor --for filling dive tanks-- which allows my smallest 4.2KW genset --plus the MasterVolt inverter with genset support function-- to 'soft' start the compressor motor, by running the 110V/60hz genset/inverter output into the 230V 3 phase 50hz compressor motor, using the Baldor freq drive.)

The less economical (costs and efficiency-wise) way would be to simply have a 230V/50 electric motor geared to spin a 120V/60 generator at 3600 RPMs or 1800 RPMs (four field system)... Otherwise we will just have to wait for the for what we really need to show up on the market (finally )...
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Old 26-03-2011, 16:21   #10
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Re: marine air a/c conversion question

I would be looking at transformers and VFD that way you can still have 60hz, if you get the right set up, you can use any volts and any hz, some will even take dc in.
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Old 26-03-2011, 18:59   #11
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Re: marine air a/c conversion question

if dometic come back and say there's no problem with running at 50hz then i think the simplest solution on my boat is to isolate the a/c units from the genset supply and have them supplied via shore power only.

my isolation transformers function equally as step-up/step-down tx depending on the tapping line up.

from a practical point of view i suspect i'm very unlikely to run the a/c unless docked.
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Old 27-03-2011, 00:39   #12
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Re: marine air a/c conversion question

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Originally Posted by bobsadler View Post
if dometic come back and say there's no problem with running at 50hz then i think the simplest solution on my boat is to isolate the a/c units from the genset supply and have them supplied via shore power only.

my isolation transformers function equally as step-up/step-down tx depending on the tapping line up.

from a practical point of view i suspect i'm very unlikely to run the a/c unless docked.
I was looking at your diagram --I guess this is a new build-- and if there were one less A/C unit, the system could have been simplified and the costs lowered significantly going with a single 50 amp shore power connection and one 7KVW isolator. (That's a 250/50 3-wire running two 125V legs, or going with a 4-wire 250/50 shore cable since those cables are --for whatever reason?-- 1/2 the price of the 3-wire 250/50 cables...)

But doing the red-X would keep you from being able to run the A/C off the genset, which you will more than likely want to do (running the A/C off of the genset 'is' something you will want to do), if you get to keep the 120VAC compressors. If you can't, then you should go with the Cruisair scroll compressors that 'can' run (rated for) 50/60 Hz 120VAC. (This is if the 'other' Dometic A/C can't or are not rated for 50/60 Hz.) Also, there's no need to isolate all the other circuits from being able to run off of the 50 Hz, as just about everything else listed on the diagram will easily run off of 50Hz shore power, except possibly the ice-maker.

Also, if this is a new build or a refit, you may want to look into getting either the MasterVolt or Victron inverter/charger instead, as this unit will greatly simplify the wiring, and give you the added benefit of having the inverter assist to help the generator starting heavy loads. Note, do not get caught up in marketing hype, as these two units are the 'only' ones on the market that have the capacity to blend inverter output with generator output; all the other brands hype 'power share' which just limits the charger output to not overload the AC input, when running 'other' heavy loads. The Victron and MasterVolt units have that too, but it is the 'assist' function that is the real benefit.

With the MV or Victron units your diagram would eliminate the Water Heater S2 switch (to prevent the resistive load of the heating element from hitting the inverter --this type of load looks like a dead-short to your batteries and is something you'd rather not want to run off the inverter)... And you could run the boat on a smaller genset too...

Anyway, with the genset isolation switch (selector for shore or gen power) there's no need to do the 'red-x' in the diagram, and certainly doing so will prevent the genset from running the A/C units while the boat's is off the grid. And there's no reason to eliminated a water heater, microwave, TVs, etc from the 50Hz power, as all of these devices/appliances can work perfectly fine on 230/50Hz step-down on your multi-tap isolator at 120V/50Hz, while shored to 'foreign' power sources.

And also checkout the MasterVolt or Victron inverter/chargers vs. the Xantrex (Trace and Heart) and Outback brands... The MV and Victron have a major advantage over these other brands that isn't obvious that seems to be overlooked by a majority of the builders, simply do to a lack of knowledge on the current state of the inverter market.

-Rob.
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Old 27-03-2011, 01:04   #13
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Re: marine air a/c conversion question

rob - not a new build. she' about 7 years old. purchased in the u.s. but now in europe and eventually australasia via asia.

i've already had the conversion to 240VAC/50hz done.

the boat is going to spend pretty much the rest of her life in areas with that power supply so i decided to go ahead and switch over. the genset has been re-configured for 240VAC/50hz

i figured the costs of tv and microwaves these days is so modest that changing them out wasn't a big deal (and the tv uses a different system: ntsc vs pal). the ice-maker has problems anyway so is going to removed and a room temp "wine locker" put in its space (non-americans tend to use far less ice than americans and there is a freezer).

the a/c was the big issue.

if it will run on 50hz that's fine because as you can see from the wiring diagram that AC system can be isolated and we'll just step down the 240VAC via the isol tx. if it won't run on 50hz then in the non-110VAC/60hz world it was never going to work without some sort of frequency converter and most of the ones i looked at cost a fortune and were way too big for a 42ft sailboat.
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Old 27-03-2011, 02:03   #14
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Re: marine air a/c conversion question

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rob - not a new build. she' about 7 years old. purchased in the u.s. but now in europe and eventually australasia via asia.

i've already had the conversion to 240VAC/50hz done.

the boat is going to spend pretty much the rest of her life in areas with that power supply so i decided to go ahead and switch over. the genset has been re-configured for 240VAC/50hz

i figured the costs of tv and microwaves these days is so modest that changing them out wasn't a big deal (and the tv uses a different system: ntsc vs pal). the ice-maker has problems anyway so is going to removed and a room temp "wine locker" put in its space (non-americans tend to use far less ice than americans and there is a freezer).

the a/c was the big issue.

if it will run on 50hz that's fine because as you can see from the wiring diagram that AC system can be isolated and we'll just step down the 240VAC via the isol tx. if it won't run on 50hz then in the non-110VAC/60hz world it was never going to work without some sort of frequency converter and most of the ones i looked at cost a fortune and were way too big for a 42ft sailboat.
Awe yes, now I see said the blind man! Looked at your original post and now I understand. I had seen your profile location listed as Shenzhen, China and thought your were in China getting a new build. After all, I am not use to seeing older boats with wiring diagrams ...

(I have now gone to your boat's website --nice boat with nicely done systems--, and have even a 'better' understanding...)

Anywho, taking about ice-makers, I have a friend who spent $1200 USD on a 'marine' ice maker, while I went on Ebay and spent $33 for an ice-maker kit for a house frig and installed it in my existing freezer. Both make tons of ice, because, if you're an American, everyone expects you to have ice on-board! Go figure!

It sounds like your best bet is then to switch the A/C units to 230V/50Hz European models. You might want to explore either the new Vetus or Eberspacher units? Unless a drop-in replacement makes more sense, the Climatic units were once a good choice, but I believe these are now owned all under the Dometic name.

BTW, did the conversion on the genset simply slow the generator to 3000/1500 RPMs, and that's why you've listed it as 240V/50 instead of 230V/50? I guess this isn't a big deal as most State-side power runs between 110VAC and 120VAC (and 220VAC to 240VAC)...

As far as the cost and size of freq converters, you're correct, these are for mega yachts; however, the technology is there (I guess just not the market) to build lightweight 'switched' freq transformers. I was hopeful that either MV or Victron would deliver theirs to the market place soon. (Or at least just before I get to sail from the US to Europe!)

-Rob.
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Old 27-03-2011, 02:46   #15
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Re: marine air a/c conversion question

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Actually no tea brakes. Working in the marine AC and refrig buisness for the past 5 years, that is about what it takes for a compressor replacement. By the time you remove from boats locker, recover refrigerant, remove compressor wiring, cut tubing for old compressor, remove fasteners, install new compressor, fit new tubing, silver solder, leak test, vac pump, recharge, and run. Then reinstall in the locker reconnect ductwork, water, wiring, etc. Get the picture-easily 3-5 hours. It is more cost effective to fit a small transformer, or replace as they commented on. Just some first hand experence-
Yeah i get the picture after 39 years in marine refrigeration you are new at this with only 5 years and work slow
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