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Old 12-08-2015, 01:45 AM   #21
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Intake (shown here) and exhaust vent (on the opposite side) of the engine compartment are of the same size. Note the intake grill at the lower aft end of the pilothouse in this photo:

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Old 12-08-2015, 06:29 AM   #22
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"I assumed it was an exhaust blower, but I suppose it is at least possible it is an intake blower."

On our sized boats exhaust is most common.

The reason is most ER are not well sealed from the living spaces and most folks do not want the ER stink/noise of hot engine(s) pushed into the cabins.

The engine intake system hopefully is designed to feed air at max throttle , since many cruise well below that a tiny DC fan is meaningless.

Use it to lower ER temps after shutdown if desired.
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Old 12-08-2015, 08:13 AM   #23
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Is it an intake or exhaust blower?
I tested it this morning, and much to my surprise, it was an intake blower. But, after reading the posts from this thread, I can understand the reasoning for installing an intake blower rather than an exhaust blower. And, I would guess that even with an intake blower, it could still be used to cool off the engine room at the end of a day's run, since there are air vents built into the hull for engine room ventilation.
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Old 12-08-2015, 09:11 AM   #24
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My sporty has eight 10 inch fans, 4 intake and 4 exhaust with an adjustable temp switch. Basically they just move a lot of air thru the engine area. 10,000 lbs of 180 degree iron is a pretty good load for the aircon system to handle. The fans help with that. They dont usually come on while underway, so I assume the engines are moving enough air on there own.
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Old 12-08-2015, 09:28 AM   #25
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In FL exhaust blowers help cool the ER after a run. In my boat it helped the cabin AC a little. I wished there was room for a large exhaust fan.


Air will flow in through turned off exhaust fans if the ER becomes lower pressure than outside.


Big diesels running at high power levels consume a large amount of air.
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Old 12-08-2015, 10:34 AM   #26
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"Big diesels running at high power levels consume a large amount of air."

However the fuel to generate the the amount of DC (10A?) will probably slow the engine down more than the high altitude a 10A fan might produce.
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Old 12-08-2015, 10:37 AM   #27
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I tested it this morning, and much to my surprise, it was an intake blower. But, after reading the posts from this thread, I can understand the reasoning for installing an intake blower rather than an exhaust blower. And, I would guess that even with an intake blower, it could still be used to cool off the engine room at the end of a day's run, since there are air vents built into the hull for engine room ventilation.
Or it's just going to push hot air and fumes into the boat.
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Old 12-08-2015, 11:31 AM   #28
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I am not sure how much "altitude" increase a fan will produce but you can achieve 200 or more cf per minute with about 1 amp ac 120v .25 hp blower.
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Old 12-08-2015, 01:25 PM   #29
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"Big diesels running at high power levels consume a large amount of air."

However the fuel to generate the the amount of DC (10A?) will probably slow the engine down more than the high altitude a 10A fan might produce.

I don't think you could measure either.
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Old 12-09-2015, 07:36 AM   #30
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The other fear of an intake blower is spreading a fire from the ER to the vessel.
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Old 12-09-2015, 09:28 AM   #31
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On a dry stack vessel ER cooling can be a necessity, especially at lower latitudes. The Nordhavn line is a good example of this. Kulas, isn't your vessel dry stack too which would help explain the number of vent fans on your vessel?

Some vessels have higher temp transmissions, close to 160 F. Lots of different heat sources and subsequent needs for ER cooling especially for crew comfort when ER chores required. I've seen several high CFM systems on larger yachts so system checks and maintenance can be accommodated.

I would guess some Navy vets have seen a few large ER ventilation and cooling arrangements. Especially on nuclear subs.
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Old 12-09-2015, 09:30 AM   #32
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My Hatteras was equipped with two sets of ER exhaust blowers, AC and DC. The DC blowers are specifically ducted low and purposed to exhaust battery fumes prior to starting the engines, with instructions not to run them at cruising speed. The AC blowers are ducted high to clear heat out of the room after running, or clear the space, along with the DC blowers if the ER CO2 fire system has discharged. The generator room has its own DC exhaust for the latter purposes as it was originally designed not to have batteries in it.
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Old 12-09-2015, 10:06 AM   #33
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All blowers intake and / or exhaust should be off in the event of a fire and prior to fire suppression systems being deployed. Several auto-suppression systems allow for this in their functions, if not place remote electrical switches for blowers near manual fire suppression activation location (outside of ER).
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Old 12-10-2015, 10:34 AM   #34
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The local Power Squadron was giving my boat a safety inspection and a new person was being trained by an older person. The new person was giving me grief when she asked about the engine room blower and I told her I didn't have one.


She didn't know a diesel engine boat isn't required to have one.


I would think the best advice on when to use the blower (on a diesel powered boat with a blower) would come from the manufacturer of the boat. Of course if it's a gasoline powered boat (or genset), standard procedures would be to run the blower after fueling and before starting the engine.
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Old 12-10-2015, 11:50 AM   #35
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I also would like to add to all this, that while a gasser ER blower HAS to be marinized, ie spark free, the optional blower on a diesel boat doesn't.
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Old 12-13-2015, 01:43 PM   #36
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ER Temperature Monitoring

Quote:
Originally Posted by seattleboatguy View Post
My trawler has a blower in the engine room; something I never had on the sailboat. Both the main engines and the generator are diesel. Is the blower simply to cool off the engine room after running on a hot summer afternoon, or is there more to it than that?
I bought my 2007 trawler this summer. It has two ER exhaust blowers. I recently bought a digital indoor/outdoor thermometer. I put the outdoor sensor in the ER. I intend to monitor during in water layup to be sure the 2 small electric heaters keep the temp well above freezing in the ER. The unit I have records high and low temp over last 24 hours, so when I check boat I can make thermostat adjustments as needed. Same for cabin areas. Cost: about $25.

Next boating seasons I will monitor ER temp, and run blowers if temp gets much more than 15 degrees above ambient. Also will run for awhile after engine shutdown unless the heat needed in cabin.
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Old 12-13-2015, 02:25 PM   #37
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I recently bought a digital indoor/outdoor thermometer. I put the outdoor sensor in the ER.
I like that idea.
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Old 12-13-2015, 02:31 PM   #38
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Am I the only one here without ER fans on a diesel boat?

Mine is hull #1, so maybe they were added to later models, but all I have are directional louvered vents to promote fore-to-aft air circulation while underway. I don't currently have a thermometer in the ER, but that will change soon.

Santa will be delivering me a new 2-probe wireless thermometer for my fridges. I'll be reassigning the current single probe temp sensor to the ER for permanent duty down there.

Are there other Marshall Californian 34 LRC owners with ER fans?
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Old 12-13-2015, 02:51 PM   #39
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Next boating seasons I will monitor ER temp, and run blowers if temp gets much more than 15 degrees above ambient.
Curious as to why.
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Old 12-13-2015, 08:48 PM   #40
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There are so many considerations when it comes to ER ventilation. I've been digging into this over the past year in preparation to making some improvements to mine. In no particular order, here are some of the considerations that I have learned.

- Every engine has specs for its ambient heat rejection. That's the amount of heat that it puts into the surrounding space. It does not include the heat taken out through the cooling system - just what it dumps into the ER space.

- Every engine also has specs on it's max operating environment. Other equipment in your ER will have such specs too. Typical limits are 130F max ER temp, and/or max 30F temp rise from outside ambient to ER ambient.

- A hot ER is not only stressful on equipment, it is stressful on you if you need to get in there to do something. 120F or 130F is dangerously hot and can quickly lead to heat stroke and other nasty things.

- To take the heat out of the ER, there needs to be air movement from outside, through the ER where it picks up heat, then out again. There are formulas that you can find that will tell you how much air flow is required to remove the engine heat, and what temp rise will result.

- Your engine itself is a pretty good exhaust fan, pulling air in from the outside where it passes through the ER and picks up heat, then gets sucked out of the ER through the engine intake and out the exhaust. The engine specs will tell you how many CFM of flow this will be. Note that this is only true if the engine pulls its intake air from the ER. If it has dedicated ducting to pull air from outside then it will not air in ER venting.

- In some case, the engine air flow may be enough to keep the ER sufficiently cool. In other cases additional air flow is required.

- Air will enter and exit your ER through vents of some sort. They may be big, small, or anything in between.

- The vents may be large enough to provide sufficient cooling via convection. Or you may have (or need) mechanical air flow assistance in the form of either exhaust or intake blowers.

- If your intake vent area is too small, then a vacuum can develop in the ER. This will be exacerbated by any exhaust fans. If there is too much restriction, you won't get the needed air flow. Also, the more vacuum, the more air will be pulled from other sources like wire chases, conduits, voids behind walls, etc. Air will get drawn in from all sorts of places following the paths of least resistance.

-If your exhaust vent area is too small, then pressure can develop in the ER. This will be exacerbated by intake fans. The more pressure there is in the ER, the more air will get pushed out through all sorts of voids and passages throughout the boat. Exhaust restrictions can also severely limit the flow of exhaust air.

- Fans all have a flow rating that is normally in free air, i.e. no intake or exhaust restrictions. Flow drops quickly when there are restrictions, and fan specs usually have a chart showing this. It can have a significant impact. I encountered a 1200 CFM fan once that was exhausting through a hose to an outside grate. The restriction from the hose had reduced the actual air flow down to about 350 CFM. That fan was WAY less effective than anyone thought.

- Ideally you want very little intake or exhaust flow restriction (Delta-T shoots for 0.5" H2O), with a slight vacuum in the ER. The slight vacuum ensures that any ER and bilge smells get pulled into the ER and out the exhaust fans rather than getting pushed into the boat's living spaces.

- If you have an automatic fire suppression system in the ER, it should be wired up to shut off all fans in the event of a fire. That is to contain the fire suppressant so it can do its job, and also to cut off sources of combustion air. Fancier system even have louvers that close off vents.
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