Kind of a weird question on a/c for boat

[Bob Sander]

bayliner ciera 2755

I have to put (shore) a/c on my boat. I don't need the a/c while running.... just while parked at the dock. We use the boat not just for day trips on the water but for extra sleeping quarters at the cottage for the extended family, but it's hot in there during the height of Summer.

I thought just a 120 volt portable a/c mounted outside on the upper deck under one of the seats and ducting it into the cabin area. They're pretty cheap and quite adaptable. Of course it would require some exhaust ducting too and a thermostat control mounted inside, but my main concern is... how many btu. My shore power is only 15 amps and I have to run the fridge as well as the battery charger and some lights, so there is not a lot to work with.

Do you think a 5000 or 6000 btu machine do the trick? 6000btu is about 7 amps and that's probably about the highest I can go.

 

[KD4UPL]

What size wire and how long a run to your dock? You may not even be able to pull 15 amps with acceptable voltage drop.
Do you have or need an inverter? A Magnum hybrid inverter can use battery power to support the AC and ref. when they cycle on and then recharge when they cycle off.

 

[Scott Danforth]

are you talking a portable room air conditioner that gets set in the room and the condensate and hot air get routed outside?

are you talking a window unit where you need to duct incoming and outgoing air along with condensate?

or are you talking a portable hatch mounted unit where you just plug it in, and toss the condensate hose over the side. then remove it when not needed

like this one http://www.norrislakenews.com/Store...Thru-Hatch-Portable-Air-Conditioner/15970056/

or this one http://myboatsgear.com/2017/01/09/carry-7000-portable-air-conditioner/

 

[Bob Sander]

What size wire and how long a run to your dock? You may not even be able to pull 15 amps with acceptable voltage drop.
Do you have or need an inverter? A Magnum hybrid inverter can use battery power to support the AC and ref. when they cycle on and then recharge when they cycle off.

It's not too far. The dock is maybe 60 yards from the cottage. We already have 240volts @ 20 amps at the dock to run the cottage water supply pump and other accessories (we pull our water for the cottage from the river). Not a lot of voltage drop. Up until now I have just biggy-backed off of that for the boat shore power. This Summer though I plan to run a dedicated 120 line to the dock for the boat.

 

[Bob Sander]

are you talking a portable room air conditioner that gets set in the room and the condensate and hot air get routed outside?

are you talking a window unit where you need to duct incoming and outgoing air along with condensate?

or are you talking a portable hatch mounted unit where you just plug it in, and toss the condensate hose over the side. then remove it when not needed

like this one http://www.norrislakenews.com/Store...Thru-Hatch-Portable-Air-Conditioner/15970056/

or this one http://myboatsgear.com/2017/01/09/carry-7000-portable-air-conditioner/

Small portable floor model. I hate window ac's... too much noise.
Something like this, just as example:


There is enough standing room under the bench on the upper deck to get one of these portable units in. Just have to add an insulated duct take-off and a bit of pipe work to duct it down through the floor (cabin is underneath). It should be pretty quiet since the machine is on the outside of the cabin. It would be a permanent mount. No need to remove it. It will be out of the way and won't be seen.

 

[dingbat]

What is “hot”?
What temp is the lake water?

 

[Scott Danforth]

Small portable floor model. I hate window ac's... too much noise.
Something like this, just as example:
View attachment 354831

There is enough standing room under the bench on the upper deck to get one of these portable units in. Just have to add an insulated duct take-off and a bit of pipe work to duct it down through the floor (cabin is underneath). It should be pretty quiet since the machine is on the outside of the cabin. It would be a permanent mount. No need to remove it. It will be out of the way and won't be seen.

you know those need to be located down in the room you intend to cool (not outside the room) and you only vent the hot air out. additionally, the condensate needs to drain, so you would be filling your bilge with water unless you only want it to run for 20 minutes.

they also do not last long if you bounce them around. you would need to remove it every day vs bouncing around on the lake with them

Im on the second one. we use it for camping in the tent in Florida. when the first failed, I tore it apart to understand what failed.

 

[Bob Sander]

What is “hot”?
What temp is the lake water?

It's not the water temp. This is Canada.... our water never gets that warm. It's the air temp and having the cabin closed up at night while sleeping. In the height of Summer we can go into the 90's.... hot enough to make things uncomfortable for sleeping.

 

[Bob Sander]

you know those need to be located down in the room you intend to cool (not outside the room) and you only vent the hot air out. additionally, the condensate needs to drain, so you would be filling your bilge with water unless you only want it to run for 20 minutes.

they also do not last long if you bounce them around. you would need to remove it every day vs bouncing around on the lake with them

Im on the second one. we use it for camping in the tent in Florida. when the first failed, I tore it apart to understand what failed.

Hence the reasoning behind the insulated duct take off and duct work... to redirect the output into the cabin. Not too worried about the condensation. At 5000 or 6000 btu they usually evaporate the condensation... and if there is any overflow it's just going out the scupper, not into the bilge.

Yeah.. they're not the sturdiest things in the world, but they are cheap enough so that replacement isn't the end of the world.

 

[dingbat]

It's not the water temp. This is Canada.... our water never gets that warm. It's the air temp and having the cabin closed up at night while sleeping. In the height of Summer we can go into the 90's.... hot enough to make things uncomfortable for sleeping.

Is that 90’s as in Death Valley or 90’s as in Miami?

Big difference in the amount of cooling capacity required.

Water to air heat exchanger.
Got away from refrigerated units long ago if we have an available source of water.
Cuts power consumption by roughly 50% if not more

 

[Bob Sander]

Is that 90’s as in Death Valley or 90’s as in Miami?

Big difference in the amount of cooling capacity required.

It's a relatively dry 90's... certainly not the humid 90's of Miami and alike. We're about a two hour drive North of North Dakota so a climate in that area.

Not too concerned about power consumption. It's about $0.08 to $0.10 a KWh here.

 

[Bob Sander]

Inetresting....
In my search I found EPA's rule of thumb is about 20 btu per square foot while Energy star's rule of thumb about 33btu per square foot. These I would imagine are based on 8 foot ceilings, though. So that's 250sqft and 150sqft respectively

I'm not sure which one is more accurate but either way a 5000 SHOULD work.

The Bayliner rough cabin size (27 feet - 3.5 feet for engine bay) x the beam which is 8 feet at its widest... probably averaged out more to 5 feet though. gives a square footage of 117 (6 feet at the tallest point). That's under BOTH rule of thumbs.

 

[jhande]

Speaking about the electricity...
I live in a house built in the 1800's and the electricity was updated but too many things on each circuit, anyway...

I have a 12,000 BTU A/C unit 1st floor living room.
A 12,000 BTU A/C 2nd floor bedroom.
Each unit is plugged into and outlet on a run that has many other things plugged into. Been running for 4 years and never once popped a 15A circuit breaker.
For the most part I leave them on auto mode set at 62F. When our temps (New Hampshire) get in the upper 80's to 90's F I set them to max and open the doors to cool off the rest of the house.

 

[Scott Danforth]

Hence the reasoning behind the insulated duct take off and duct work... to redirect the output into the cabin. Not too worried about the condensation. At 5000 or 6000 btu they usually evaporate the condensation... and if there is any overflow it's just going out the scupper, not into the bilge.

Yeah.. they're not the sturdiest things in the world, but they are cheap enough so that replacement isn't the end of the world.

you cant separate the unit and the thermister on the main board on these. the whole unit must sit in the room you are trying to cool.

for canada, and a boat sitting in the water, you should not need more than a fan.

here in florida, that unit will run between 10 and 20 minutes and shut off if you dont have the condensate draining. and that is on a 98 degree day, with 70% humidity (dew point at 87)

 

[Bob Sander]

you cant separate the unit and the thermister on the main board on these. the whole unit must sit in the room you are trying to cool.

Don't really need to.
Set the machine to ON and set to the lowest temp and leave it that way. Most of them have non destructive memory now, so they remember the settings even when the power goes out. That being the case, use any external wall thermostat and relay to turn on/off the outlet it plugs into.

 

[Texasmark]

bayliner ciera 2755

I have to put (shore) a/c on my boat. I don't need the a/c while running.... just while parked at the dock. We use the boat not just for day trips on the water but for extra sleeping quarters at the cottage for the extended family, but it's hot in there during the height of Summer.

I thought just a 120 volt portable a/c mounted outside on the upper deck under one of the seats and ducting it into the cabin area. They're pretty cheap and quite adaptable. Of course it would require some exhaust ducting too and a thermostat control mounted inside, but my main concern is... how many btu. My shore power is only 15 amps and I have to run the fridge as well as the battery charger and some lights, so there is not a lot to work with.

Do you think a 5000 or 6000 btu machine do the trick? 6000btu is about 7 amps and that's probably about the highest I can go.

A 5-6k BTU AC is for an insulated bedroom in your house. For a cooling device to work it has to eliminate more BTUs from the area than are input...from weather, occupants, and heat sources.

 

[Bob Sander]

A 5-6k BTU AC is for an insulated bedroom in your house. For a cooling device to work it has to eliminate more BTUs from the area than are input...from weather, occupants, and heat sources.

Understood.
It'll most likely be marginal, but it won't be a hotbox. Just has to be cool enough so people can get a good sleep.

 

[H20Rat]

How often do you need to use it? other option is one of those coolers-filled-with-ice temporary AC's. They are surprisingly effective, and if you only use it to provide a little cool air before bed, it should work well. Your nighttime temps are very likely below 70F even in July/August.

 

[Bob Sander]

How often do you need to use it? other option is one of those coolers-filled-with-ice temporary AC's. They are surprisingly effective, and if you only use it to provide a little cool air before bed, it should work well. Your nighttime temps are very likely below 70F even in July/August.

We have 2 to 3 weeks in July where it's hot enough so that you can't even sleep with windows open. You NEED a/c. Other than that, it's just like a car which has been closed up all week under the hot sun. Friday when you come... you need the a/c to cool it down. Of course these weather patterns seem to be changing too and our Summers seem to be getting hotter with each passing year... so there is that to figure in as well.

Ice is nice, but this is somewhat isolated cottage by a river. The nearest convenience store is a 40 minute drive which means I would have to make my own coolers of ice... then I would have to haul it all down to the dock. Easier just to flip a thermostat switch.

 

[dingbat]

Ice is nice, but this is somewhat isolated cottage by a river. The nearest convenience store is a 40 minute drive which means I would have to make my own coolers of ice... then I would have to haul it all down to the dock. Easier just to flip a thermostat switch.

No ice required...... simply use lake water. Use 4" PVC duct to route