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Airconditioned engine rooms

Discussion in 'General Sportfish Discussion' started by Hattsoff, Aug 4, 2010.

  1. Hattsoff

    Hattsoff New Member

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    I've come across a few battlewagons in the 60-80 ft range advertised with A/C in the engine room. What is the biggest reason for this? My first thought is it obviously makes it more comfortable to do maintenance in the engine room on a hot day. Is this the only reason?

    Do some like to use the A/C in the engine room after a run to cool the engines off quicker and help keep the heat load from coming into the salon?

    How about running the A/C while the engines are running and the boat is in use to keep engine room temps lower? (somehow I don't see that making much difference especially if you have a system like delta T or the like moving a fair amount of air through there)

    Perhaps keep it on to keep the engines more dry (less humid) when the boat is sitting inactive?

    Or is it a combo of all the above. I'm just asking out of curiosity as this is interesting to me.
  2. AMG

    AMG YF Moderator

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    I think it is mainly to make it better for maintenance work, especially after a run when the engines are heating up the room. Normally you just have fans for this, but in the past you had portholes that could be opened for ventilation.

    Many boats are also operated in very hot areas, so having AC in the ER must be nice...
  3. Bill106

    Bill106 Senior Member

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    Adding a reverse cycle AC unit in the engine room actually has several benefits. In hot climes it makes things way more comfortable when you are doing maintenance and service. It also helps keep the humidity down which slows the inevitale corrosion you will get no matter how well you maintain things. Having a cool, comfortable place to work in also keeps captains and mates in there more easily so they can "take care of business" and keep the kitties purring. It takes a lot of BTU's to cool down the huge chunks of iron after a hard days run, so they aren't really that effective unless you already have a good ventilation system.

    In cold climates, they also can be used in heat mode, which aside from making it a comfortable place to work, keeps the blocks warm enough that you don't have to use those power gobbling block heaters (unless your compression is way down :rolleyes:

    About the only thing they aren't good for is cooling the engine room while running. With the big engines nowadays, the engines inhale the volume of air in the engine room several times a minute.
  4. Marmot

    Marmot Senior Member

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    You might find it interesting to run the numbers on that theory. ;)
  5. Jorge Lang

    Jorge Lang Senior Member

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    From experience, entering an air-conditioned engine room in South Florida feels like luxury. More so during the summer months between March and October. My worse experience was entering an engine room in Dubai. The estimated temperature in there was 145 and that is without the engines being run. It is not easy to sit in a meeting afterwards when you are dripping as if you came out of a swimming pool. Fortunately, the folks there understand to the point that you have three cups of water and ice cream waiting for you to cool off.
  6. Bill106

    Bill106 Senior Member

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    I did, which is why we haven't hooked up the block heaters on the last several engine packages. Take for example the CAt C-32 which comes with two 120VAC/1500 watt block heaters, one per side. multiply that times two for the pair of engines and all the block heaters combined can draw 50A at 120V.

    Granted, once the blocks are heated up, the draw will decline, and you could wire only one per engine, but compared to the draw of a 16,000 BTU AC unit at 6A/240V (or 12A/120V), the AC unit is still far less draw. I maybe should have been more specific on engines/block heaters. I guess smaller engines, or single installations would make the comparison much closer, sorry!
  7. Marmot

    Marmot Senior Member

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    No, you didn't. You compared the wattage of the different units.

    Until you calculate the watts required to maintain the engine block at a given temperature for a given time compared to the watts required to heat the air in the engine room plus the hull plus the conduction and radiation to the outside world plus the engine block and all the other machinery, diving gear, oil cans, tools, coolant jugs, coke bottles, etc, etc, etc, in the engine room to the same temperature for the same time, you haven't run the numbers.

    And that is assuming the engine and all the junk started out hot. If you have to heat a cold engine block by warming the air around it first then you will be even further in the hole.

    But you are correct, you don't have to use those power hog block heaters, you just have to wait a lot longer and pay more to get the engines to the same temperature and pay a lot more to keep them there. ;)
  8. CaptPKilbride

    CaptPKilbride Senior Member

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    Not to mention ....
    The block heaters heat the block directly by heating the coolant circuit. The blocks on the boat I run now are at 110F when the thermostats shut the heaters off. The result is an easy starting engine, with immediately warm and viscous fluids in the block.
    I highly doubt any reverse cycle air system could do the same thing. Especially when the water temps start getting colder, the reverse cycle compressors will have to work longer and longer to deliver any heat output.

    With that said, an air conditioned engine room is a nice luxury. Just remember to turn off the block heaters when you want to cool down the space.
  9. jhall767

    jhall767 Senior Member

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    I agree. My block heaters will get the engines to about 30 degrees above the engine room temp on a cold day. Given time the engine room temp slowly rises also but will lag behind the block temps. Heater thermostats are set at around 100F. I can't see how you could get the blocks even close to that by heating the engine room. I have 120V 1000W heaters in each block. I can switch them between series and parallel. In parallel they each draw the 1000W. In series they draw around 300W total. Just enough to keep the engines a little warmer than the engine room and thus no condensation.
  10. Hattsoff

    Hattsoff New Member

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    Thanks everyone. All good replies and interesting to read them.
  11. Berean

    Berean Senior Member

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    About those block heaters...
    Do you guys leave them on all the time or just prior to anticipated start up?

    If the later, how long before start up?

    Thanks
  12. K1W1

    K1W1 Senior Member

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    Hi,

    I leave them on on the 3516's,C 18'S and C 9 I have 24/7.

    One Genset will be running so it's heater will be off and the other Gensets are in auto and the Mains are ready to go.

    They can be started without heating but it produces less smoke and they are up to operating temp a lot quicker if they are nearly there at the get go.
  13. Berean

    Berean Senior Member

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    Got it. Thanks
  14. wdrzal

    wdrzal Senior Member

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    A engine room is like a commercial kitchen, you best bet is for them to be well ventilted, not Air conditioned. But if you want to AC a engine room you can start buy adding your total fuel burn from your engines and gensets. Each gallon of #2 fuel oil is ~144,000 btu's/gallon. How many gallons per hour do you burn??? you can subtract the C.O.P. of the interstage heat exchangers dumping heat over board..... Don't forget to add all the other electrical equiptment @ 3.412 BTu's for every watt they consume.That includes pumps/ lights/ hydraulics ,battery chargers and every thing else electric.plus 4oo BTUs for your self if you hang out in the engine room.Plus the general heat gain of the hull.
    There can be some safety issues with recirculating air in a engine room.

    If you do the math it's not economical.

    But a system can be designed that uses 100% outside air,none is recirculated. We do this in nuclear medicine sweats that require 100% Outside air. That means if it's 100f outside ambiant air, it is cooled to 68f in one pass over a evaporator and discharged outside.(or in a yachts case out through the interstage heat exchanger). Most Ac units are designed to cool 20 degrees F per pass over the evap.

    (Normal AC units are not designed to do this) This takes a lot of cooling capacity,not to mention the inverse heating the rooms to 68f when its 0F outside.

    I compared the two because they should both have at least 6 to 8 air changes per hour.I'm not sure of how many air changes a hour a yacht engine room requires ,but I'm sure someone here can chime in on that spec.
  15. Capt J

    Capt J Senior Member

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    I have only worked on 1 yacht that had air conditioning in the engine room. It made life VERY nice in South Florida in the summer time to work on the boat. A/C is a waste of time to try to cool the engine room while the engines are running. It does help cool the engine room off once you get to the dock, and need to work in there after a day running. It may help keep the engine room warmer in the winter time in Moderate climates, but block heaters are probably more effective and the warm engine blocks tend to warm up the engine room a little bit.
  16. Bill106

    Bill106 Senior Member

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    Capt J, you've just got to find better rides! :D
    I thought engine room AC/heat was pretty much standard equipment especially for boats destined to live in south Florida, even as small as 40'ish expresses. If for no other reason, having a climate controlled ER encourages captains to spend more time in there on maintanance and general upkeep, on 95+ days with no air movement makes it a sweatshop no one wants to spend time in.
  17. Marmot

    Marmot Senior Member

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    Before you do the math or tell other people how to figure it out, learn what "heat balance" means.