Using a/c at cruising speeds

[Connerkip]

Are there any concerns running the generator to power the A/C's while cruising at say 15 knots. Could this be a problem with generator cooling or impellor life? Similarly could this be stressful on the A/C's at all? In my case I have a C30.

 

[stwendl]

I think there was some discussion about this before in regard to genset and ac not being able to pick up water for cooling resulting in air being ingested and thus planing speed was not recommended. Even at higher speed in non planning mode water may be starving which is the reason a scoop type pickup is used for the engine. If the ac and genset use the same pickup they may compete with the engine for cooling water.

 

[Connerkip]

Sounds like my boat having the three on separate intakes is in my favor (a/c, motor, gen) Thanks. I am hoping the factory will still chime in, but certainly welcome other responses and experience.

 

[Scuffy]

We have a R27 and have run with the AC on while cruising. It's been our experience that running faster than 14 mph or so the AC through hull pickup does not get enough water and the AC unit shuts down. The generator never showed signs of over heating in our experience because of speed. Typically we would run with the AC on at 7 or 8 mph. If your cool what's the rush.

 

[Irish Mist]

I run ours at slower speeds with no problems... I seem to remember something about the engine has a high speed pick up and the rest are not.... I'm sure if it is important you could change things easily to make this work.
Good luck

 

[Connerkip]

I don't seem to have problems with the a/c, however I lost an impeller, on my Cummins Onan 5 kW, at 85 hours then again at 120. I was wondering if speed may have something to do with it.

 

[Scuffy]

Maybe an Aqua Alarm would be a good idea on our generator raw water intake for those who use the generator while cruising along at faster than displacement speeds.

 

[Boatdreamer]

We don't have a problem running the genset at any speed because it has a scoop to help it pickup water, but with the A/C we're limited to about 10 kts. If we run faster than that it will loose it's prime. The A/C pumps aren't self priming and don't have enough power to pull water while running fast. I think Ranger Tugs started using larger A/C water pumps on the newer models but I don't see any reason to change ours out. Most of the time we run 8-9 kts so it's not a problem.

Tim and Donna
Gratitude

 

[Lehill]

On the cb31 it is not advisable to run the genset while cruising at speed. I managed to chew up an impeller on the Onan in no time at all due to lack of cooling water pickup. The thruhull on the genset is not scooped for pickup at speed.

 

[Andrew Custis]

Hello. You should be able to run your AC above those speeds. We use a high speed pickup on the AC thru hull which should help keep the pump running.

Thank you,

 

[Connerkip]

Thanks Andrew, the a/c does run fine at high speeds, however does the generator through hull also have the same high speed pick up? I ran yesterday and watched the strainer. Seemed like a lot of air was passing through the generator strainer.
The a/c thruhull is egg shaped with grating, the generator is round.

 

[Andrew Custis]

You cannot put a high speed pickup on the generator or it will force too much water to the generator at speeds. The generator should be able to operate just fine at speeds of 15 knots.

Thank you,

 

[Lehill]

While I agree with Andrew's advice on the genset raw water pickup needing to be flat and not scooped, I would be very cautious on operating at 15 knots with the generator running. I chewed up the raw water impeller on the genset at about 13 knots. The generator had around 11 hours run time on it. Previous to this event we had run the genset at slower speeds of 6 to 8 knots without problems. In the 31 the removal and installation of a new genset impeller was a 2 hour job requiring 2 people and rubber arms. My perspective is now to avoid doing anything that will cause a repeat of this event before a regularly scheduled maintenance impeller change.

 

[Boatdreamer]

Oops, I might have misspoke about the genset having a scoop. I guess if it had a scoop and the thru hull was open it could push water back into the exhaust and into the cylinder, that would be very bad. Now I'm really curious why above 10 kts the A/C shows a code of HPE after a few minutes even after the strainer was replaced with a larger one. As I said before, we run 8-9 kts most of the time anyway, but now I wonder if we have a problem that needs to be addressed.

Tim and Donna
Gratitude

 

[SGIDAVE]

On the cb31 it is not advisable to run the genset while cruising at speed. I managed to chew up an impeller on the Onan in no time at all due to lack of cooling water pickup.

I don't seem to have problems with the a/c, however I lost an impeller, on my Cummins Onan 5 kW, at 85 hours then again at 120. I was wondering if speed may have something to do with it.

Sounds like you might benefit from a "Save Your Engine Kit" from Aqualarm.

I have one on my 21EC with Yanmar 3YM engine; I like it!

They are sold in many places; including Defender.

/dave

 

[Lehill]

Agree 100 percent on the aqualarm comment for the main engine. I installed this solution on the Volvo D4 last year. Nothing like some added notification on a raw water flow problem for main engine protection. The Onan genset has a water flow sensor built in. It shuts down automatically in seconds once no flow is detected but alas this is not soon enough to avoid impeller destruction. .....Lance