Where to put the refrigerator compressor? & Battery Float Discussion

[Dancrosswis]

Hi All,

Where is your refrigerator compressor/condenser?  Any pros or cons to its location?

The frig on Ennui Went hasn't worked since our purchase three summers ago.  We've always been icebox sailors, but the budget allows for an upgrade this year, and the fridge is it.

My original compressor was in the aft lazarette.  The lines to the icebox are roughly 15 feet, which is longer than I'm finding in stock evaporators.  Before I pay more bucks for line extensions, I'd thought I'd canvas the tribe.

Thanks for your input.

Dan

[Stu Jackson]

On a Catalina 34, there are only a few places to put one.  The aft lazarette works because it removes any noise, except some folks who use the aft cabin complain about the noise when sleeping.  My read is that they'd have to be really seriously sensitive.    The large air volume back there usually means adequate cooling for the condenser fan.

Next is under the forward seat in the saloon.  Most have had to add a ventilation grille to assure air movement over the condenser coil.  In some cases a fan assist was required.

I've heard of one under the galley sink, although I don't see enough room for one there.

Another place is just forward of the starboard water tank, way outboard.  Measure carefully, because the hull curve may preclude it.

Finally, I read of one in the nav station hanging locker, tricky to get the refrigerant lines across the boat.

I suppose you could also consider under the smaller opening in the aft cabin, haven't heard of anyone who did that, but it could work.

I understand the issue of the tube length for the lazarette location, but you may make it if you place the evaporator on the aft side of the box, where mine is.  Again, measure carefully before you commit.

In all cases, make darned sure the wire size you use is more than adequate for the length.  99% of all fridge problems are electrical.  I've doubled up my existing wiring, and after I finally replaced my old electronic module last year (search on rParts), my 30 year old unit remains perfectly functional.


Dan, please add your boat info to your signature, it helps us to help you if we know what boat you have, i.e., Mark I or II, engine type when you ask those kind of questions, etc.  Thanks.

[Sundance]

Search for "Refrigeration Replacement on 1989"

This:  http://c34.org/bbs/index.php/topic,9002.msg65169.html#msg65169  [Stu]

I don't know what year your boat is, but I did this project last year and shared my experience.  You should be fine with the standard 15', but as I detailed and heard from others, the length is closer to 14'4".  Second year with my new fridge and wish I had replaced the old one 10 years ago.  What a difference.

[Steve W10]

Hey Dan,

This thread may have a bit of info for you too....
http://c34.org/bbs/index.php/topic,7711.0.html

I guess my Nova Kool is about 7 years old now, still working great even with the dreaded 17' pipes. :)

[Dancrosswis]

Thanks all.  This helps.  A good reminder I took from the threads is:  call 'em.  I've fallen too deep into the click and buy habit.

I'm considering two options and am interested in feedback:

• Mobiltronic/Dometic/Waeco MPS-150.  This unit inputs AC and DC.  If AC is present, it supplies the power to the compressor.  If not, it supplies via DC.  It appears to be a cheaper option than getting the Danfoss AC/DC controller.  My thought is the house bank will benefit from fewer amps flowing through when AC is present.
• Isotherm Smart Energy Control.  This unit attaches to the Danfoss controller and purports to save energy by modifying compressor speed and cooling temperature to cool quicker and deeper when extra current is available.  I think this may help during our summer cruise when we're at dock every 3-5 days and want a quick cool down.

Ennui Went's home port is in cool Menominee, MI (UP above WI).  When not cruising, our dock/anchor ratio is about 70/30.  We take a 5-6 week cruise to the North Channel each summer.  During that cruise the dock/anchor ratio flips to about 35/65.

Thanks,
Dan Cross
Ennui Went
1986 C34 #159

[Jon W]

Mine is located just forward of the starboard water tank under the salon seat. There is a vent grate with a fan behind it to draw cooling air. You can't see it unless you look under the table.

Pro's are easy to get to for service and has short runs to fridge. By not being in the aft lazarette, I had ample room to upgrade the propane locker and increase capacity.

Negative is it takes away some storage space, but to use that storage space is not very convenient in my opinion. The compressor and fan can barely be heard so don't think it is an issue.

[Noah]

Jeff- I re-read your old link/post on your compressor install and was surprised you hit a road block removing the aft water tank, saying "the boat was built around it." I have removed mine twice and it is a fairly easy job. Take another look. Drain water, remove the bulkheads, disconnect/move morse cables out of the way, disconnect two hoses, lift up and out.

[patrice]

Hi,
My compressor is located under the stove.  By previous PO.
Might not be ideal, but works.
Pretty close to box.  No venting issue.  I made a small panel to cover the area with vent slot.
It is not close to the berts, so it does not disturb at night.

[Dancrosswis]

Thanks to all for the replies.

Here's what I'm going with:
Vitrifrigo cooling unit, with 3 meter line set extension (should give me total line set length of about 15'8")
Istotherm Smart Energy Control.  To try to increase efficiency.
Waeco/Dometic/Mobitronic MPS-35.  To allow operation from AC when available.

As I begin the install, I still have a couple of questions, which make take the installation itself to answer:

First, will the Smart Energy Control work with the MPS-35?  The MPS-35 outputs 24v to the compressor when it's running on AC, 12v when it's passing through the battery voltage.  The Smart Energy Control will run on either 12v or 24v.  What I don't know is whether the Control can automatically handle the switching between 12v and 24v.  I've communicated with Indel Webasto.  They just don't know.  BTW, they (Dave Lerbs@iwmarine.com) responded quickly.  A good shout out to them.

Second, should the MPS-35 be mounted closer to the battery bank or to the compressor?  It will be more convenient to locate it closer to the battery.  I'll then only have a single set of DC lines running back to the compressor.  If I locate the MPS-35 at the compressor, then I need both AC and DC making the long run to the aft lazarette.  My only concern (based upon my lack of knowledge, not a known problem) is:  does the fact that the MPS-35 output switches from 12v to 24 create any fusing/wiring issues?  I plan to run oversize (based upon 12v) DC wires to the MPS-35 and from the MPS-35 to the compressor.  The circuit will be fused at 15 amps (as recommended for the compressor) at the distribution panel.  Will this be okay for MPS output wire when it's sending 24v?

Any suggestions will be appreciated.  I'll report on the installation when its completed.

Dan Cross
Ennui Went
1986 #159

[Noah]

What is Vitrifrigo cooling unit? Can you provide link and or pics, please? And why do you need the A/C-D/C converter box? Why not just run the compressor on DC when plugged into dock with your battery charger on "like normal."?

[Dancrosswis]

Hi Noah,

Vitrifrigo is the brand of ice box conversion kit I bought.  The "cooling unit" is the compressor/condenser/control box component of the kit.  Photo below.  Sorry if my post was a bit cryptic.

I don't need the MPS-35.  I'm adding it assuming (here I go getting dangerous again) that it's better for my batteries not to be running amps through them to fuel the refrigeration, if shore power is available.  It's essentially the same as putting the Danfoss AC/DC controller on the compressor, but cheaper, and the Isotherm Smart Energy Control doesn't fit the AC/DC controller.

Thanks for your reply.  Hope the foregoing makes some sense.

Dan

[Dancrosswis]

Oops.  The photo I posted with my last message has the AC/DC controller installed.  Mine won't.

Dan

[Noah]

Not an engineer, but I believe if you have a properly sized smart charger, with battery sense, running your reefer on 12v while plugged into shore power, should have no negative impact on your battery life.

[J_Sail]

Noah is correct, there is no need for an separate AC power module for your 12v fridge. That device is for owners of portable 12v fridges who want to also plug them in at home. There is no benefit on a boat with a shore-power battery charger.

When your battery charger is on, the power to run your fridge is coming from the charger, not your batteries. (Similarly when the engine is running it comes from your alternator.) That's because the charger or alternator puts out a voltage higher than the battery voltage (in order to charge it), thus the fridge simply slightly reduces the max rate of charge. It does not drain or in any other way, tax your batteries.  Also, you would need complicated wiring to accommodate it.

The IsoTherm, on the other hand, is a clever device that temporarily lowers the temperature setting of the fridge when energy is "free" from either the shore-power/charger or the engine running. It does so by detecting the higher 12v system voltage present under those circumstances (i.e. >~13v) and substituting its own thermostat. The idea is that chilling the fridge extra cold during those times, will cause it to cycle on less later, when you are on battery. If you are a cruiser whose use of engine or shore power fits the pattern it could be useful. If you have solar or wind power, though, it may be fooled into doing its extra-cool when you would rather have the solar charging your batteries. 

Jeremy

[Dancrosswis]

Thanks gentlemen.  I suspect I'll return the MPS-35 and put the savings back into the boat projects budget.

Regards,

Dan
Ennui Went
1986 C34 #159