420DB – Bridge A/C and Heat Installation

[Turtlesboat]

doesn't sea ray bump up the gen to a 15KW unit when they put in a Bridge AC?

 

[Alex F]

They do to 11.5KW, mine is 9KW. I see no concerns for my genset by adding a single unit to the bridge. I never run all systems at the same time and have no intention running all 4 A/C units at the same time.

 

[fc3]

Let's say that the boat currently has about 3 tons for the cabin. You can remove the existing units and replace the integrated ones with evaporator units. Put a three ton evaporator on the bridge and connect all the air handlers to a 5 or 6 ton remote compressor. The compressor will use 20-23 amps, about half of the genset's output. So starting probably will be ok. Total draw with the air handlers is about 30 amps leaving 2kw headroom. Marginal, but possible. Then mod the gen to output 230 VAC. it's usually pretty easily done by changing a few jumpers. Finally, upgrade the boat to 50 amp shore power service.

I did the homework regarding air conditioning my cockpit, but the gen is too marginal on capacity. Decided its just easier to find a nice Regal 4460 with IPS that already has a hardtop and air conditioning in the cockpit. Air conditioning a soft top is possible, but doing it right really needs a generator upgrade to make it workable.

 

[Alex F]

Let's say that the boat currently has about 3 tons for the cabin. You can remove the existing units and replace the integrated ones with evaporator units. Put a three ton evaporator on the bridge and connect all the air handlers to a 5 or 6 ton remote compressor. The compressor will use 20-23 amps, about half of the genset's output. So starting probably will be ok. Total draw with the air handlers is about 30 amps leaving 2kw headroom. Marginal, but possible. Then mod the gen to output 230 VAC. it's usually pretty easily done by changing a few jumpers. Finally, upgrade the boat to 50 amp shore power service....

I'm not sure I'm following you, Frank. My boat's Shore Power, Dual 30 Amp/120V/60 Cycle. That's 60AMPs total between two lines.

 

[Greg]

I'm not sure I'm following you, Frank. My boat's Shore Power, Dual 30 Amp/120V/60 Cycle. That's 60AMPs total between two lines.

Alex,

It is 60 Amps of 120V. So it is more current, but not more power.

Using Ohms law: P=IV

120V x 60A = 7200W

now if you went to a 50A/240V shore power cable

240V x 50A = 12,000W

 

[cod]

Alex,
Doesn't your boat model have the option of bridge air condition and if so, is the generator the samer size as yours?

I just want you to think of something else in regards to the bridge a/c. which is just as important as the size of the unit IMO and experience. Probably the most important thing for me are the locations of the a/c outlets. I have 4 adjustable circle style outlets(similiar to a car) along with 2 larger rectangular registers. 2 of the helm outlets blow at the captain(me), the other 2 blow at the passenger seat and the larger rectangular outlets blow at the seating area in front of the helm. Bottom line is everyone is feeling the cool air blowing at them and you always here "that feels so good". I also typically keep the canvas open at the same time. I rarely have a completely enclosed environment. On long cruises I may shut the canvas and hatch to the stairs but not very often. My point is just having the cool air blow on you gives you the relief your looking for regarless of the temperature of the surrounding environment.


Just for reference, my unit is 24,000 BTU's and my bridge measures approx. 17' long x 9'-3" wide x 6'-7" high. If I create a closed environment (which I do less than 5% of the time), it will get nice and cold......


Hope this is helpful to you.......

 

[Alex F]

Alex,

It is 60 Amps of 120V. So it is more current, but not more power.

Using Ohms law: P=IV

120V x 60A = 7200W

now if you went to a 50A/240V shore power cable

240V x 50A = 12,000W

Greg,

No question that 240V gives a lot more advantages and the "power users" need less AMPs. But, I don't want to have this project turn into one of this house projects...."Honey, let's change the sink in the bathroom......well, if we're changing the sink we need a new vanity. Oh, now that we're making the mess, let's change the tiles and repaint the whole room...."

Granted that I have too keep my eyes open and look "outside the box", but I want to keep my focus on a primary target with minimal overhead. I'm not going to upgrade my genset and I'm not going to re-engineer my power from 110vac to 220vac.

Using Ohms law: P=IV

120V x 60A = 7200W

This also reminds me that my 9000W genny has 1800W reserved capacity. So, I don't understand why the size of my genny is a concern? If I overload the system (for whatever reason) the breakers will pop at the panel and/or generator. So, I see no harm as the system is designed with good protection in mind.

 

[Alex F]

Alex,
Doesn't your boat model have the option of bridge air condition and if so, is the generator the samer size as yours?

I just want you to think of something else in regards to the bridge a/c. which is just as important as the size of the unit IMO and experience. Probably the most important thing for me are the locations of the a/c outlets. I have 4 adjustable circle style outlets(similiar to a car) along with 2 larger rectangular registers. 2 of the helm outlets blow at the captain(me), the other 2 blow at the passenger seat and the larger rectangular outlets blow at the seating area in front of the helm. Bottom line is everyone is feeling the cool air blowing at them and you always here "that feels so good". I also typically keep the canvas open at the same time. I rarely have a completely enclosed environment. On long cruises I may shut the canvas and hatch to the stairs but not very often. My point is just having the cool air blow on you gives you the relief your looking for regarless of the temperature of the surrounding environment.


Just for reference, my unit is 24,000 BTU's and my bridge measures approx. 17' long x 9'-3" wide x 6'-7" high. If I create a closed environment (which I do less than 5% of the time), it will get nice and cold......


Hope this is helpful to you.......

Steve,

Sea Ray states that they upgrade 9KW genny to 11.5KW unit when adding bridge A/C. But, let's be real, this only takes place when a boat is ordered new and the owner goes for both options. I can't even imagine for anyone with standard 9KW genny replace it with 11.5KW. This would make $8K project in to $50K. So, I'm not even considering any changes for the genny side of the house. As I mentioned in earlier post, I see no way of damaging the genny by overloading it as the main breakers would start tripping before genny starts to cough and sneeze.

Your point on cold air circulation is on the same page with my theory. I don't plan on running with bridge A/C 24/7, so I'll be opening my side panels at times as well (not when the genny is running, though). You're right, choosing the vents position is something I'm thinking about all the time. I have some basic ideas, but I was going to post this as part of my "installation phase" questions when I'm all set and done choosing the right unit for the job. How many is too much or the more the better?

Here's where I see people install the primary vent, so I'm planning to install mine the same way and add few round vents:




My biggest question right now is which unit to buy considering that I'd need to have it 120v and within 13-15amp. As I mentioned earlier, I was debating between regular 18K vs 16K Turbo, but seeing that Ocean Breeze offers units like 20K and 22K at similar power consumption makes me think that 22K OB unit could be the best solution.

 

[Greg]

I agree. I think the easiest thing would be to upsize your current pump (so you can utilize the existing intake & strainer), then go with one of the self contained units (so you don't have to deal with a split system). I guess you will still need to poke a hole for the oulet? or do you have a common drain or some other way to get rid of the water?

Of course I didn't do any of the calculations of how the pressure head from the bridge air will affect flow to that unit, since the pump is also feeding the units downstairs.

I think you could easily manage the power load manually, and if you really wanted to get fancy you could put a relay or contactor to de-energize one of the downstairs units when the bridge air is on. But you are correct, the breakers should keep you from blowing things up. I would double check that though.

I also liked Steve's comments about vent placement. I also have two small vents that blow on me, But there is a big rectangular vent that blows on the seat next to me. Anyone that sits there freezes. So I have to put towels or a PFD over it to redirect the flow. I think I want to tap into that big duct and put a vent facing the forward seating area. So think carefully about vent placement.

You may also want to keep a few small fans up there just to keep the air moving.

Of course, you have all winter, so swapping the genny and re-wiring the boat for 240 might be a fun project.


edit - I was typing this at the same time. I see you are already thinking of the vent position.

 

[Alex F]

Greg,

Based on this and considering other things we discussed, do you see any reason why not go with 22,000 BTU from Ocean Breeze (all are 120v units)?

Some numbers from the specs:

16K Turbo (Dometic):
Full load Cool = 10.40amp
Full Load Heat = 13.60amp

18K (Dometic):
Full load Cool = 11.1amp
Full Load Heat = 15.1amp

20K (Ocean Breeze):
Full Load = 13.9amp

22K (Ocean Breeze):
Full Load = 14.5amp

.....Of course I didn't do any of the calculations of how the pressure head from the bridge air will affect flow to that unit, since the pump is also feeding the units downstairs....

Good point, but I'm under the impression that if SR uses 1500 pump, then it should be fine. BTW, I don't plan on using all 3 unit at once. But, considering worst case scenario and let's say I manage the power and run all 3, in the event of low water pressure the unit that suffers the most should throw an error code (something about low pressure) and shutdown. This is similar as having clogged seastrainer when only one or two units running. In any event I will test all the systems to learn my limitation. Also, if the 1500GPH pump is in question, I should be able to get the next size over.

 

[mistercomputerman]

What happens when the breaker DOESN'T trip.

 

[Greg]

What happens when the breaker DOESN'T trip.

Then he gets to upgrade the generator.


But circuit breakers are very reliable, when they start to go they typically trip at a lower threshold than rated.

Alex,

Just note that the pump will be pumping water through all of the A/C units whether they are on or not. So the flow should be considered. Once you get it all hooked up though it should be easy to measure the flow with a stopwatch and a bucket.

I see no reason to not go with the bigger unit, provided you find out that they are a reputable company with a quality product. If that all checks out I think you would be better off with the bigger one.

 

[Alex F]

Rick,
There's more than one breaker in line of defence for genset. So, it's not like I have dependancy on only one small breaker controlling the health of my generator.

Thanks Greg,
I totally agree with you. In regards to the pump, I guess I'll call the vendor and make sure that 1500 model is the right unit for the job.

 

[mistercomputerman]

What's a 420DB worth that has burned to the waterline?

 

[quality time]

I'm surprised they are only using a 1500 GPH pump for three units. My in laws Ocean runs a 4200 GPH pump for four units (3 + bridge).

 

[douglee25]

Charts show you need about 200-250 gph water flow per ton (1 ton=12,000 BTU's) of air conditioning.

Doug

 

[Turtlesboat]

I don't see how the same pump is going to work for waterline units and a bridge unit off the same feed. The water is going to take the path of least resistance and go through the lower units before the upper, unless it just hits the units flow through capacity and forces it up to the upper unit.

I've never tripped a breaker on the gen so I don't know what's involved, but don't things shut down? Don't you have to shut all of the breakers off, climb into the ER to flip the main breaker, go back to the panel and kick those back on? You know if it's going to trip, it's going to trip in 8' seas in the middle of nowhere.

 

[jg300da]

Charts show you need about 200-250 gph water flow per ton (1 ton=12,000 BTU's) of air conditioning.

Doug

Correct, 3GPM per Ton is the benchmark.

 

[Alex F]

Charts show you need about 200-250 gph water flow per ton (1 ton=12,000 BTU's) of air conditioning.

Doug

Is my math correct here:

I have 2x16,000btu units and I'm looking to add 22,000btu unit = 54,000btu total

54,000 / 12,000 = 4.5tons

4.5tons x 250gph = 1,125gph.

Considering the 1500gph pump SR installs, it'll have 375gph reserved capacity. I'd say it's pretty good, especially since they use 18,000btu units instead of 22,000 I'm thinking on installing.

Correct, 3GPM per Ton is the benchmark.

I guess, I'll need about 13.5GPM pump.

I don't see how the same pump is going to work for waterline units and a bridge unit off the same feed. The water is going to take the path of least resistance and go through the lower units before the upper, unless it just hits the units flow through capacity and forces it up to the upper unit...

Are you saying the SR don't know what they're doing?

.......I've never tripped a breaker on the gen so I don't know what's involved, but don't things shut down? Don't you have to shut all of the breakers off, climb into the ER to flip the main breaker, go back to the panel and kick those back on? You know if it's going to trip, it's going to trip in 8' seas in the middle of nowhere.

The first breaker to trip is the main breaker on the line that was overloaded. My boat has 2 x 30amp lines. I've had it happened on couple of occasions, thanks to the electrical tea cattle, the stove, HWH, FWD A/C and hair dryer all on the same line. That's what my girls were going through as a learning experience. Now they're aware of power management. Anyway, as you can imagine, as soon as the line that's overloaded goes "kaput", genset has nothing to worry about, b/c it actually just gained 30amp extra "breathing room" until that line is back ON.

 

[douglee25]

Your math is correct but I think you may need a separate pump regardless due to the difference in elevation.

If all 3 units were on the same level, things would probably be fine. Call SeaRay and verify that they used an additional pump for the bridge. I'm betting they did.

Doug

Edit - Remember for the bridge case, it's not just flow you're concerned with, it's also a pump that is able to pump the additional head needed. The stock pump I'm betting is limited to the 8'-10' head range.