53MY benny room heat

[MikeP]

The recent issue with my generator got me to thinking about Genny room heat.

Basically, there is no ventilation for the Gen room other than the ventilation blower that is to vent fuel vapor from the low part of the room; there is no ventilation system per se for the components.

When our NL genny's regulator malfunctioned and basically shunted the generator coils so as to present an extreme load to the engine, the generator had been running for many hours AND, for the first time ever since we have owned the boat, 3 AC systems were running the full time. So there was probably more heat in the genny room than ever before. I suspect that the genny room temp was higher than recommended.

So I'm thinking about setting up some ventilation using 120vac fans to provide a significant volume of cooling air that would switch on automatically when the generator was running. Since the inverter is also located in the Genny space, the cooler temps would probably be a good thing for it as well, even though it has never shown any sign of concern for the temps.

I realize that Hatt made no provisions for this and, when you factor in the fact that back in the day, it was fairly often viewed that with a boat like a 53, you turned on the Genny when you left the dock and it stayed on 24/7 until you returned. Obviously there weren't a lot of problems caused by this so maybe it's not even worth considering.

But if you read the guidelines for installation, the NL says temps should not exceed 104F and I'm sure that is exceeded though I never actually checked.

At the moment this is more "thinking about it" than anything else...

 

[rsmith]

As long as the generator is running their is typically enough combustion air pulled in by the engine to keep the area relatively cool. Like the ER the heat soars when the engines shut down and those big pieces of cast iron start radiating heat. I would run the blowers when the gen os off to keep the heat down. If you run the blowers as exhaust fans with the gen running you could starve it for combustion air.

 

[Pascal]

The heat is probably more of a problem for the inverter than it is for the genny. Gennies are often installed in engine rooms which Will be a lot hotter than the hatt genny room.

On the boat I run we have two NL20s in the same room as the two big 3412, I ve never brought a thermometer in but I know it s way over 104 after a run even with the massive blowers running.

That said some cooling never hurt. I woudlnt worry about starivng a generator for air as there are so many holes in those genny rooms for air to be pulled in...

 

[MikeP]

RS, I have always viewed it pretty much as you described.

Curiously, I was just now reading the original instruction manual for the boat and, for the first time, noticed this instruction on the pictorial for operating the genny:

1. Turn On Blower CAUTION operate blower at least two minutes before starting generator. [more other info follows for item 1 but nothing more about the blower]

There are 5 additional instructions but none stating to turn OFF the blower at any time.

It appears, if I interpret Hatt's instructions correctly (and maybe I don't), that they intend for the blower to be running anytime the Genny is running. I have never done that...

Further, I discovered that in the engine operating section, Hatt says to turn on the eng room blowers anytime the boat is not operating at "cruise speed." I'm assuming that cruise speed back then was at planing speed but maybe not. Never done that procedure either...

Amazing what you can find by reading instructions!

 

[AL BAUMER]

I owned a 58YF and a 58CY in the 1970's and 80's. On each of these boats, I had a 120volt squirrel cage blower mounted on the gen room ceiling, with the discharge hose run through the wall in the port engine room and ducted out the forward end of the engine vent box.

 

[MikeP]

Did you run that blower full time when the Gen was operating or only after shutdown? Seems like a good idea and one I am considering. The PO of our boat had installed 120vac engine room blowers that they turned on when the mains were shut down for the day to reduce ER temps. They pretty much ran the Gen 24/7 when they left the dock but I don't know if they operated the oem gen room blower or not. They did not install any additional blowers in the Gen area.

 

[GJH]

My 56 had a separate intake vent for the gen room as well as an exhaust blower. I wonder if this was a 1981 enhancement? It was OEM and in the drawings. With the generator off, even for days, it could get hot and humid down there. I would run both the exhaust fan and a small 120v fan as well as keep the hatch open if practical when working down there especially if it had been recently run.

 

[jim rosenthal]

On my boat, I installed a 120vac squirrel-cage blower on a timer that runs for an hour after I shut the engines down. That doesn't get rid of all the heat in there, either.

Where does fresh air get into the generator room? Is there a specific intake or does it just get in through various informal openings? Is there a place to put a large ventilation blower- I mean is there a place for it to exhaust through?

There are all kinds of these items in McMaster-Carr if you want to look at them, pages and pages of them.

 

[MikeP]

Our 1980 53MY has two oem 4" diameter "intake" vents for the Genny area, one on each side of the boat. They supply the outside air to the Gen room and the oem 32V Gen room ventilating blower. So there is probably plenty of air vent area/circulation available if the blower is running.

I ordered some window fuzz/tracks (Oh BOY!) from Sams today and, during the conversation, asked Steve if those oem blower motors were considered constant duty and he said yes. So it would seem reasonable to run it whenever the Genny is running. Those blowers definitely move a good bit of air but the vent hose is situated to pull air from the lower part of the room as opposed to the hotter area at the ceiling. But that's just a matter of shortening the hose.

 

[davidwigler]

Windsong has 32 volt blowers in the engine rooms, but none in the genny room, just the two 4" vent lines.

I have thought about running one of the vent lines directly to the genny's air intake. The 21 kilowatt Kohler is in a sound shield, so the intake air is really warm. It runs well, though.

 

[MikeP]

I apologize for asking this but are you sure there is no Gen room blower? The reason I ask is because our Genny blower is not actually located in the benny (damn auto spell check!) room. It's in the area between the Gen room and the starboard eng room.

Does your master elec panel have a Gen blower switch in the panel section that turns on the Genny? Ours is the far left of the three panels and the blower switch is on the upper left of that panel. There is (left to right) a blower switch, a generator "On" light, the spring loaded Gen preheat switch and then the Gen start/stop switch which is spring loaded to the center position - up to start, down to stop.

 

[bigbill]

my 1972 58 yf does not have a gen room blower, nor does it have any switches or breakers. it does have the two 4 inch vent hoses.

 

[davidwigler]

No problem asking me anything, Mike.

No fan switch on the genny panel, just the on-light, preheat and start switches. What is the area between your genny room and starboard ER? Mine are adjacent.

 

[MikeP]

On our 1980 53MY, there is an "area" between the outer 1/3 of the starboard engine room and the genny room where, on our boat, the starboard side Cablemaster (and the Gen blower) is located. It can't be accessed from the Gen room side - at least from within the Gen room. It can be partially accessed from the galley by removing an access panel after removing the aft dinette seat. But the main access is through a panel in the Star eng room. I'll take a couple of pics later - maybe it was set up that way at Hatt or at the dealer before delivery specifically for the cable master.

Here are some pics:

First shows the access panel; second shows the panel open with the cable master "bucket" visible; third shows a closer view of the Gen room blower. Hmmm...pics came out in strange order/configuration on post but you can figure out which is which...

 

[bobk]

While we are on blowers, I thought I'd mention my experience (1981 48MY). The squirrel cages were a plastic that was totally disintegrated by 2008. I didn't realize it until one quit and I was replacing both. Make sure they are moving air.

Bobk

 

[MikeP]

Yes, I had two disintegrated blower impellers and one seized blower motor when we bought the boat. So I bought new impellers for all of them and cleaned/lubed the motors. A few months ago I checked/re-lubed them. One thing I find interesting - one blower motor runs much cooler than the other two. They all sound as if they are running at the same RPM but two of them will hit 200F on the hottest part of the motor housing after running for an hour whereas the other one will only get to around 140F.

I realize that the external temp of a motor doesn't really tell you anything at all but one would think that three motors of the same type would run similar external temps. I've been meaning to do an amp check on them all to see if there is any difference in what they are pulling; maybe I'll use my new Fluke DMM to do that! They are individually protected by 5A breakers and none of them ever trip so if the two hotter ones are drawing more than the cool one, they are apparently not exceeding the design spec.

 

[Victor_Chat]

I have a 12v blower (attached to an converter from 32v) in our generator room. Originally, it was sucking in air, though I changed it to blow out. Figured it was safer this way. There is a power switch (setup by the PO) on the generator control panel.

 

[bobk]

Yes, I had two disintegrated blower impellers and one seized blower motor when we bought the boat. So I bought new impellers for all of them and cleaned/lubed the motors. A few months ago I checked/re-lubed them. One thing I find interesting - one blower motor runs much cooler than the other two. They all sound as if they are running at the same RPM but two of them will hit 200F on the hottest part of the motor housing after running for an hour whereas the other one will only get to around 140F.

I realize that the external temp of a motor doesn't really tell you anything at all but one would think that three motors of the same type would run similar external temps. I've been meaning to do an amp check on them all to see if there is any difference in what they are pulling; maybe I'll use my new Fluke DMM to do that! They are individually protected by 5A breakers and none of them ever trip so if the two hotter ones are drawing more than the cool one, they are apparently not exceeding the design spec.

Mike,

Many motors are designed for a 60 degree C (about 110F) temperature rise. You are probably pushing the limit with the units at 200F. Any chance there are blocked cooling passages?

Bobk

 

[MikeP]

"You are probably pushing the limit with the units at 200F. Any chance there are blocked cooling passages?"

I don't think so. They are just standard-looking blower motors with with the motors mounted externally to the airstream and no cooling passages at all. I did an amp check - each of them draw 1.7 to 1.8A on a 5 Amp breaker. I agree the two seem awfully hot, especially compared to the third one but I can't think why there would be such a difference with the same motors pulling the same amp load. To be honest, I was expecting to see the hotter motors pulling more amps but the amps/volts were almost identical on all three.

 

[bobk]

"You are probably pushing the limit with the units at 200F. Any chance there are blocked cooling passages?"

I don't think so. They are just standard-looking blower motors with with the motors mounted externally to the airstream and no cooling passages at all. I did an amp check - each of them draw 1.7 to 1.8A on a 5 Amp breaker. I agree the two seem awfully hot, especially compared to the third one but I can't think why there would be such a difference with the same motors pulling the same amp load. To be honest, I was expecting to see the hotter motors pulling more amps but the amps/volts were almost identical on all three.

Mike, I was thinking more in terms of life of the windings. The insulating varnish on the windings will be more subject to oxidative deterioration the hotter it gets. The rate of chemical reactions roughly double for every 10 degree C rise. There is not likely a fire hazard so long as no combustibles are close.

Bobk