Recycling ballast water with AC sea water pump.

[dxg4848]

I think I am going to give up that ballast tank cooling idea. Too many unknowns. You guys brought up many valid points. A week ago I was convinced that it would work, but you steered me away from making mistake. I just need to regroup and rethink that whole water cooling circuit. Probably go back to normal setup with through hull intake/discharge, and leave ballast water alone Thank you all again for your input and steering me in the right direction!

[Jimmyt]

Just to be clear, if I knew that it was a sure failure, I would tell you. I just got my M a few months ago and haven't drilled through the hull yet to know how thick it is. The hull thickness info I can find is not consistent. I am a Mechanical Engineer, and I do HVAC design - buildings, not boats. I'm not exactly sure of the available bottom area for transfer. In summary, I don't think you'll be happy with it, but I can't positively say it won't work - because I have insufficient information.

I don't want to see you trash your new unit due to high condenser temps, or drill a bunch of holes in your ballast tank that you have to patch.

If you want to test the idea with a temporary hookup, there is no risk. Make sure you have condenser water flow, and monitor your tank temp. The unit info should give you a range of water temps that it was designed for. Typical range for the equipment I work with is 75 - 85 deg f water inlet temp, but some of the special purpose equipment will cool with over 120 deg entering water. Don't run it too long before you check the temp and check it every half hour. You may see 5-10 deg per hour rise, so it shouldn't be a catastrophic event that you can't see coming. Just shut it off if it exceeds the manufacturers recommended temp, and figure out a new place to get water.

The rest of the install should be the same, so you only have the water connections at risk.

Good luck with it.

[Stevenhigbee]

A through-hull will be more efficient. MUCH more efficient. That's a hands-down no-brainer. The only reason I can think of to even consider it, would be to have water-cooled heat exchange while beached. That MIGHT be more efficient than air-heat exchange. But with that many BTU's, I wouldn't count on it.

[Jimmyt]

Agree that the thru hull is better - not sure it will even work otherwise.

Beached operation with that much capacity won't work. A good portion of the ballast tank will be exposed to air - which won't work as good as water (or likely be as cool). Fiberglass to air won't be as good as an aluminum or copper fin with forced air either. The part that is exposed to the sand might be better than hull-to-air; particularly if the sand is wet, but I'd still bet that this is not going to work for any significant length of time.

His primary goal seemed to be avoiding a thru hull. Thus the reason for trying to evaluate the possibility. You are absolutely correct, though. The thru-hull is the more efficient way to go - and likely the only workable solution.

If he intends to beach overnight, air-cooled would be his best solution. That thru-hull won't do him much good when it's crammed full of sand...

[dxg4848]

I gave up on the idea of using water ballast tank. Will do it normal way via through hulls

Another problem I might be running into is condensation drain. Ideally it would be nice to plumb it to sink drain. Sink/cockpit drain through hull is just above the water line. I was going to mount AC unit near the ballast vent plug, on flat area of the tank under the v-berth on starboard side.

Because of 100' of chain in bow chain locker water ballast level is about an inch above the vent plug (inside the holding cap). I am not sure if I be able to raise AC unit high enough for condensation tray to be above the water level and still fit it under the v-berth. I will have to measure everything when I get the unit.

[Russ]

Some links

http://www.macgregorsailors.com/forum/v ... id#p300643

http://www.macgregorsailors.com/modt/in ... ?view=1940

[dxg4848]

Some links

http://www.macgregorsailors.com/forum/v ... id#p300643

http://www.macgregorsailors.com/modt/in ... ?view=1940

Yes, I saw it. This is exactly what I have in mind. You can see in this picture (from wbpenney's excellent blog post) that condensation tray is slightly below the vent plug level. It is about level or slightly above normal water ballast level. So sink drain should work. In my case because of extra weight in bow chain locker water ballast level is about an inch above the vent plug, and the AC unit may not fit under the v-berth.



On the other hand I am planning on adding Minn Kota 24 VDC 80 lbs thrust trolling motor. Trolling motor on kicker bracket plus two new group 31 batteries under aft dinette seat will add some weight to the aft. But AC unit will add some weight to the bow... So I just have to wait until I have everything in place to see if I can fit AC unit under the v-berth.

[Jimmyt]

If you can't work your way around it, you can always use a small basin and pump/float switch to pump the condensate out.

[dxg4848]

If you can't work your way around it, you can always use a small basin and pump/float switch to pump the condensate out.

I was thinking about it. But then I would probably need a dedicated through hull for this pump. If I pressurize sink drain line then water might come out from the sink. If I can't raise AC unit high enough, then I will have to figure something else out.

[grady]

If you can't work your way around it, you can always use a small basin and pump/float switch to pump the condensate out.

I was thinking about it. But then I would probably need a dedicated through hull for this pump. If I pressurize sink drain line then water might come out from the sink. If I can't raise AC unit high enough, then I will have to figure something else out.

Any heavy items should be mounted as low as possible. If you mount them below the CG it will improve your stability, If it is mounted above the CG it will degrade it.

[dxg4848]

I started this thread a while ago and now posting my AC install. I did it the right way with through hull intake and discharge. I installed 12K BTU Webasto. Plenty of heat and cool even at low fan speed. I tested heating in 46 degree weather and cooling in 90+ and both worked great!



AC, control box, and condensate removal kit installed under V-berth.

[dxg4848]

Supply and return grills. I removed flotation foam from overhead compartment, sealed it completely, and insulated entire compartment with 0.5" foam insulation and sticky foil. There is no condensate buildup anywhere. Black supply box next to TV is also insulated from inside. I am getting all air flow I need at low fan speed.

[Jimmyt]

Beautiful job! Well done.