420DB – Bridge A/C and Heat Installation

[Greg]

I believe he already checked, and SeaRay does use a single, albeit larger pump.

I too would be a little concerned with the difference in elevation, but perhaps a flow restrictor on the the line that feeds the lower units would be an easier way to go.

If it were me I would plumb it all up with the bigger pump and measure the flow from each unit. You can always add a restrictor afterwards if you really need to.

 

[douglee25]

I missed that point that SeaRay uses one pump.

Go find the pump part number currently in your boat and verify what kind of head it can support.

If it doesn't support your bridge elevation, I guess you'll need another pump.

Doug

 

[Alex F]

This from earlier posts:
I just got an official confirmation from Sea Ray on what my original got feeling was.

"When we did the bridge ac we used a 18K and went up to a 1500GPH pump from a 1000GPH. Additionally we upped the generator size from a 9.0KW to an 11.5KW.

Regards,

Rick Bressner
Customer Service Specialist
Sea Ray & Meridian Boats
350 Sea Ray Dr.
Merritt Island, FL 32953
"

There's no doubt that I'll need to replace the pump. My only question is if the 1500GPH would be good enough if I'm doing 22K unit, instead of 18K SR uses.

The parts manual shows that I have "A/C COMP, PUMP SEAWATER 115V PMA1000 W/BASE"

 

[Alex F]

I just looked at the March pumps and looks like these are good candidates:

...I too would be a little concerned with the difference in elevation, but perhaps a flow restrictor on the the line that feeds the lower units would be an easier way to go.

If it were me I would plumb it all up with the bigger pump and measure the flow from each unit. You can always add a restrictor afterwards if you really need to.

I've never seen a restrictor, what does it do, just creates a minor blockage?

 

[fc3]

I'm not an engineer, just a humble mathematician. But I know enough of engineering that relying on the breakers is foolhardy. A sensible person engineers a system where all components are considered under best case, average case and worst case. Protection and safety are engineered intrinsically to the design of the system, not by relying on protective devices. A system that's designed to be marginal at best is bad design.

 

[jg300da]

Alex, in a real engineered water cooled A/C system the pump is sized based on total tonnage at 3gpm/ton and resistance to flow due to elevation measured in ft of head.
The pump is slightly oversized and items called circuit setters (adjustable restrictors) are installed at the units to insure proper flow to all units.
In a much more simplistic system like the ones on boats you can simply add a ball valve or globe valve to adjust the water flow and ensure all units are getting the required gpm.

 

[Greg]

I'm not an engineer, just a humble mathematician. But I know enough of engineering that relying on the breakers is foolhardy. A sensible person engineers a system where all components are considered under best case, average case and worst case. Protection and safety are engineered intrinsically to the design of the system, not by relying on protective devices. A system that's designed to be marginal at best is bad design.

OK. I think Alex understands that the best design would be to change out the genny for a bigger unit. Sometimes the best designs are not practical and compromises need to be made.

In this case, he is not relying on the breakers as part of the design. He is relying on his own good sense and knowledge not to overload the generator.

The breakers are there merely as a safety.

If you plug an electric heater into every outlet in your house will it trip a breaker? Does that make it a bad design? You have to use common sense sometimes.

 

[mistercomputerman]

So, when the next owner catches the boat on fire, is Alex liable for the damages and or loss of life because the new guy didn't know how not to overload the system?

 

[Alex F]

Alex, in a real engineered water cooled A/C system the pump is sized based on total tonnage at 3gpm/ton and resistance to flow due to elevation measured in ft of head.
The pump is slightly oversized and items called circuit setters (adjustable restrictors) are installed at the units to insure proper flow to all units.
In a much more simplistic system like the ones on boats you can simply add a ball valve or globe valve to adjust the water flow and ensure all units are getting the required gpm.

That's great, thanks for the explanation. It sounds like when all is set and done and if for some reason things are not working desired I have some additional options for improvement.

I'm not an engineer, just a humble mathematician. But I know enough of engineering that relying on the breakers is foolhardy. A sensible person engineers a system where all components are considered under best case, average case and worst case. Protection and safety are engineered intrinsically to the design of the system, not by relying on protective devices. A system that's designed to be marginal at best is bad design.

So, when the next owner catches the boat on fire, is Alex liable for the damages and or loss of life because the new guy didn't know how not to overload the system?

You guys blowing it way out of proportion. :smt101 Is this a 'secret club' thing?

Why would you think I'm relying on breakers and why should my boat catch a fire? Oh wait.......it's probably b/c I'm installing bridge A/C..........Oh FUG.

I've said it earlier, but I'll say it again. Ever since I got my 320DA (in 2007) I've been dealing with MANUAL power management simply b/c the boat's electrical system was not designed to handle basic day to day usage. The engineers must have thought that if you own mid 30s footer you're eating out and don't use the stove and don't use anything other than a crappy coffee maker they supply. My 420 is not a lot different. So, forget the bridge A/C. Whether it's installed or not, I'm manually managing my load every day. So, if my boat catches fire where do I go????

I honestly would be very surprised if your boats are much different and I don't think I'd buy a story that you've never tripped a breaker on your boats.

OK. I think Alex understands that the best design would be to change out the genny for a bigger unit. Sometimes the best designs are not practical and compromises need to be made.

In this case, he is not relying on the breakers as part of the design. He is relying on his own good sense and knowledge not to overload the generator.

The breakers are there merely as a safety.

If you plug an electric heater into every outlet in your house will it trip a breaker? Does that make it a bad design? You have to use common sense sometimes.

Thanks Greg, it sounds like Frank and Rick are living in a perfect world, while you and I are shlepping our a$$es in the practical world.

 

[douglee25]

Regardless of what boat we're talking about here, every person could potentially overload their genset regardless of what capacity they have. If you have a 9, 11, 15 kW generator and you have all the AC units running, your daughter is blow drying her hair, your wife is running the coffee pot, the microwave, and using the hot water, your son is flushing the toilet, and your guest is taking a shower - you still have the potential to overload the generator, correct? Again, how is that different that what Alex is attempting to do? As long as you're under 9kW in his case, he's in the clear.

If SeaRay upgrades the genset size to 11kW, all this does is give additional capacity for residual loading ie the hair dryer, the coffee pot, etc. It has nothing to do with the AC(s) running. Now if the generator was overloaded, the breaker trips on the generator, not the panel breakers for an individual circuit. The individual circuit or wiring is not being overload, it's the generator's capacity that is overloaded.

Like Alex mentioned, he already load balances with a 9kW, so he's cognizant of what's running and what's not. He could already overload the generator if he wanted to right now. By adding an additional load - the new AC unit - it's just another item to add to the mix and be aware of. It's doesn't create a fire hazard or a liability. Again, it's no different than today for him or anyone else who's reading this thread and has a genset. So instead of running the two units he has now, he runs the bridge unit and one unit below. When the night drags on and people move down below, he shuts off the bridge and turns on the other lower unit. I'm not seeing the risk here.

Doug

 

[carterchapman]

Is this a 'secret club' thing?

Yep.

 

[Alex F]

Regardless of what boat we're talking about here, every person could potentially overload their genset regardless of what capacity they have. If you have a 9, 11, 15 kW generator and you have all the AC units running, your daughter is blow drying her hair, your wife is running the coffee pot, the microwave, and using the hot water, your son is flushing the toilet, and your guest is taking a shower - you still have the potential to overload the generator, correct? Again, how is that different that what Alex is attempting to do? As long as you're under 9kW in his case, he's in the clear.

If SeaRay upgrades the genset size to 11kW, all this does is give additional capacity for residual loading ie the hair dryer, the coffee pot, etc. It has nothing to do with the AC(s) running. Now if the generator was overloaded, the breaker trips on the generator, not the panel breakers for an individual circuit. The individual circuit or wiring is not being overload, it's the generator's capacity that is overloaded.

Like Alex mentioned, he already load balances with a 9kW, so he's cognizant of what's running and what's not. He could already overload the generator if he wanted to right now. By adding an additional load - the new AC unit - it's just another item to add to the mix and be aware of. It's doesn't create a fire hazard or a liability. Again, it's no different than today for him or anyone else who's reading this thread and has a genset. So instead of running the two units he has now, he runs the bridge unit and one unit below. When the night drags on and people move down below, he shuts off the bridge and turns on the other lower unit. I'm not seeing the risk here.

Doug

You're very much correct, Doug.

I've never asked that question, but it's very possible that yachts with 240VAC electrical systems might be able to carry all the load from ALL of the equipment on board, but boats with 120VAC not a chance. It's like the first grounding, it's not if, it's when.

My 420 came with 2 HWHs, the 2nd one was installed later on, obviously. Guess what? It was overloading the #2 line and the main breaker would trip if both HWHs were on and FWD A/C would kick in. So, captain's manual power management is the key here. In any event, I'm in this boat for 2nd year and despite undersized electrical system I'm VERY happy with the boat and as most of you know, we use it a LOT. My original HWH went bad and is our of the boat, so by adding bridge A/C I'm not introducing anything "new" to the boat. It'll be a sort of a replacement of a "power user".

Originally Posted by Alex F


Is this a 'secret club' thing?

Yep.

Of course, it wasn't hard to figure that out. I can only imagine the discussion goes on there about this thread.....LOL

 

[Havana Shamrock]

I'm not an engineer, just a humble mathematician. But I know enough of engineering that relying on the breakers is foolhardy. A sensible person engineers a system where all components are considered under best case, average case and worst case. Protection and safety are engineered intrinsically to the design of the system, not by relying on protective devices. A system that's designed to be marginal at best is bad design.

My buddys 320 has a 5kw kohler he cant run all systems at once, a marine mechanic at work did research and gave him a larger breaker and told him he now,has a 7 kw genset. If this where true then all gensets are created equal, just install a larger breaker(failsafe) ? I think its a foolish move you cannot increase your gen output by increasing its safety.

 

[mistercomputerman]

It's one thing if a manufacturer with really deep pockets designs an AC system that they stand behind. It's a whole 'nuther thing for a computer guy to go designing an add-on cool mod to his AC system.

You do what you want. Make sure our insurance is paid up.

 

[alnav]

FWIW, my 40MY has a a 16,000BTU Bridge/Cockpit AC and a 9KW generator; never had any power management problems. The AC works reasonably well in a space I imagine is larger than the 420DB although it does have a hardtop and glass windshield. She does have 240V/50A power which is suppose is the major difference.

 

[Morgan Jane]

Alex, not trying to discourage what you are doing in any way. Taking on a project like this can be quite rewarding. However, I would not use the logic that if Sea Ray did it, then it must be the way to do it. When you are talking about hulls, and drive trains, maybe so, its what they do. They are very good at the big stuff. And I am a tried and true Sea Ray believer and the only boat I will ever own is a Sea Ray no doubt. But when it comes to things like the AC system, my opinion is that Sea Ray does not think everything thouroughly thru and/or spend much time on it. I am ok with that, I want the boats to be affordable for us. I did a serious rework of the entire AC system on my boat and the biggest thing that I discovered is that what makes the AC system really work is the details. Such as, proper balancing of water flow, nice clean runs or ducting, minimize the small outlets and maximize the big outlets. My boat came with a 24K BTU Cockpit unit, a 12K Salon unit, a 7K Fwd Stateroom unit, and a 7K guest room unit. Along with 2-1000 gpm water pumps. I Actually got rid of the 7K guest room unit, tee the duct work for the Salon unit so that it also feeds the salon and the guest room with air. I have one 1000 gpm pump feeding the 12K unit and the remaining 7K unit. The other 1000 gpm pump feeds the Cockpit unit. What I found that from the factory, the three smaller units were feeding from one 1000 gpm pump. However, the majority of the water was going thru the 12K unit and the guest 7K unit. Very little was making its way to the FWD 7K unit. By elimiating the rear unit, the system works better over all because more water is flowing thru the 12K unit and the remaining 7K unit. There rear unit was covering such a small volume of area anyway that the unit was short cycling. The air was either freezing cold or starting to get hot between cycles. Something to think about. I also think you will need a seperate pump to get the right amount of water to the bridge.

If I was doing your project, I would go with a split system with the condenser unit somewhere below the cockpit floor and have 2 evaporator units on the bridge and even then I would install a seperate pump and scupper feeding this new unit even though the water cooled part isn't up on the bridge. Even then even if you go with a 32,000 BTU unit, it really won't lower the air temperature as much as you think but as long as there is cold air blowing on the occupants it will make a huge difference. I know its hard to believe, but the greenhouse effect is unbelievable. If I turn my cockpit AC system off on a 90 degree day, it gets hot in there within 3 minutes, and I have a complete fiberglass top and tinted hardglass all the way around.

 

[Alex F]

It's one thing if a manufacturer with really deep pockets designs an AC system that they stand behind. It's a whole 'nuther thing for a computer guy to go designing an add-on cool mod to his AC system.

You do what you want. Make sure our insurance is paid up.

Rick,

I appreciate the concern and point regarding the insurance. But, if you'd seen all the work I've done in my house your comments would be VERY different. Talking about fire hazard, just one of the highlights I've built Finish Sauna I've always dreamed of. All components were custom ordered (not a pre-build kit) and imported from the top brand in Finland. I've done all the installation myself, which included any type of work like building walls, insulation, all electrical work running 60amp line for over 100' of distance, plumbing....yadda, yadda, yadda...all work was approved and passed the inspection.

I'm not a wingtard, my cool mods are different and are done differently.

My buddys 320 has a 5kw kohler he cant run all systems at once, a marine mechanic at work did research and gave him a larger breaker and told him he now,has a 7 kw genset. If this where true then all gensets are created equal, just install a larger breaker(failsafe) ? I think its a foolish move you cannot increase your gen output by increasing its safety.

Thanks Joe, I think you just fixed my biggest problem. All I have to do is to replace my 2x30amp breakers to 2x50amp and my wife can plug in 10 hair dryers and I can have my bridge A/C, even 32K one. :grin:....Just kidding. That some "very knowledgeable" mechanic you got there.

 

[Alex F]

Alex, not trying to discourage what you are doing in any way. Taking on a project like this can be quite rewarding. However, I would not use the logic that if Sea Ray did it, then it must be the way to do it. When you are talking about hulls, and drive trains, maybe so, its what they do. They are very good at the big stuff. And I am a tried and true Sea Ray believer and the only boat I will ever own is a Sea Ray no doubt. But when it comes to things like the AC system, my opinion is that Sea Ray does not think everything thouroughly thru and/or spend much time on it. I am ok with that, I want the boats to be affordable for us. I did a serious rework of the entire AC system on my boat and the biggest thing that I discovered is that what makes the AC system really work is the details. Such as, proper balancing of water flow, nice clean runs or ducting, minimize the small outlets and maximize the big outlets. My boat came with a 24K BTU Cockpit unit, a 12K Salon unit, a 7K Fwd Stateroom unit, and a 7K guest room unit. Along with 2-1000 gpm water pumps. I Actually got rid of the 7K guest room unit, tee the duct work for the Salon unit so that it also feeds the salon and the guest room with air. I have one 1000 gpm pump feeding the 12K unit and the remaining 7K unit. The other 1000 gpm pump feeds the Cockpit unit. What I found that from the factory, the three smaller units were feeding from one 1000 gpm pump. However, the majority of the water was going thru the 12K unit and the guest 7K unit. Very little was making its way to the FWD 7K unit. By elimiating the rear unit, the system works better over all because more water is flowing thru the 12K unit and the remaining 7K unit. There rear unit was covering such a small volume of area anyway that the unit was short cycling. The air was either freezing cold or starting to get hot between cycles. Something to think about. I also think you will need a seperate pump to get the right amount of water to the bridge.

If I was doing your project, I would go with a split system with the condenser unit somewhere below the cockpit floor and have 2 evaporator units on the bridge and even then I would install a seperate pump and scupper feeding this new unit even though the water cooled part isn't up on the bridge. Even then even if you go with a 32,000 BTU unit, it really won't lower the air temperature as much as you think but as long as there is cold air blowing on the occupants it will make a huge difference. I know its hard to believe, but the greenhouse effect is unbelievable. If I turn my cockpit AC system off on a 90 degree day, it gets hot in there within 3 minutes, and I have a complete fiberglass top and tinted hardglass all the way around.

I appreciate your suggestions. I remember your thread on how you redesigned your boat's cooling and heating system, you did a great job. I totally agree that despite the fact that Sea Ray designs great boats they're not perfect. However, I'm looking at their approach as basic guidance. The most importantly I want to keep my projects simple with minimum overhead and minimize any kind of extra work. I'm not looking to make a meat locker out of my bridge and I think that my expectation are properly set. I like the fact that there's an option to use existing system components and instead of drilling extra holes under the water line I can simply upgrade the pump and have 3-way splitter. I've seen this done on my friend's boats and it seams to work well. I currently prefer going with the self-contained unit, which makes the installation much simpler in all respect. Granted it's not going to perform as a split system with 2 evaporators, but if I end up going with 22,000BTU unit from Ocean Breeze I think it'll be a very good alternative.

I guess the big point in my overall plan is that I'm not expecting my bridge to stay at 72* on 95*+ day.

Keep the comments coming, they're a great value.

 

[kaz911]

I would suggest to add a good quality Inverter/Power manager that can supplement the Genset. Some of the good marine inverters - you can "plug in" the genset and shore power - and the Inverter will then manage the power sources for you. And if power draw is higher than genset can supply - the inverter will kick in - and add the "missing" power via the batteries. Look at Victron Multiplus or Quattro - or similar products from Mastervolt or Xantrex.

 

[Alex F]

I don't understand at what condition would my genset be at risk of being overloaded if at the max capacity my electrical system can only handle 7200W and the genset is 9000W. Anytime I operate anything I'm very much aware what goes on and I keep an eye on the gauges. I'd say that on AVG my genny is under 30%-50% of the load by looking at the AMP gauges. I can see only one circumstance is when both main breakers on the main panel fail to trip and the main breaker on the generator fails to trip. That means that 3 levels of protection have to fail for the overload to occur, that of course is in case if I fail to manage the load in the first place. That's is way extreme scenario, which I've never heard happening. So, if you're suggesting to have inverter to be there just in case that extreme scenario takes place, I think it's big time overkill and this unit will be just sitting and collecting dust all the time.