March Pump Overtemp Protection

[Anonymous]

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Start of attached email. Subject: Re: March Pump Overtemp Protection

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very helpful, John, thanks – best regards

~~~ ~ (_~~ (_~ ~ ~ fair winds ~ ~ (_
Capt Bill Tice, aboard s/v CHARISMA

In a message dated 7/24/2015 7:58:53 A.M. Eastern Daylight Time,
writes:

I may be the last person to learn this, but i’ll share it anyway.

Those of us who have sea water cooled A/C and frig systems (I have both)
are very aware that the plumbing can become blocked due to silt and debris
in the waters around most marinas. Even with an external screen on the
intake and a Groco strainer upstream of the pump, stuff will get through
and eventually reduce the water flow to a level that causes the A/C or frig
to shut down. Most of the time the blockage is in the strainer basket,
and
only takes a few minutes to fix or prevent. Other times I have to flush
the hoses and condenser with fresh water.

Over the past 5 years I’ve kept Sarah in some pretty skunky waters – a year
on the Trent River in New Bern, NC and several years on the Ortega River
in
Jacksonville, FL. All the time I’ve got 2 March pumps that are heavily
used when on shore power. This summer I learned for the first time that
the pumps have an over temp switch to shut them down. I also learned that
the pumps have small tubes that divert some of the water flow to cool the
pump motor.

My learning curve on this feature began a week or so ago when my SeaFrost
SA3 compressor shut down. The strainer basket was pretty full so I cleaned
it and thought I was golden, but the frig shut down again later the
evening. I re-checked the strainer basket, which was OK, so I disconnected
the hose to the frig condenser from the pump and flushed it with fresh
water from the dock. Again the frig started up fine and ran with solid
water coming out the discharge through hull, but once again the frig
eventually shut down and had to be manually restarted via a reset switch.
I was mystified. I had solid water coming through the system and the frig
ran long enough to freeze the holding plates. It just would not cycle back
on when the temp in the box started to climb.

I figured there must be a problem in the frig unit so I called SeaFrost
for
help. Cleve said it must be a problem with the pump, although he couldn’t
explain the fact that the pump was pushing a full flow of water through the
condenser. He gave me the phone number of one of his installers in St.
Augustine, MasterCool. When I contacted the contractor and described my
problem he immediately said my problem was the over temp switch in the
pump.

Turns out there are two small SS tubes on these pumps (March LC-2CP and
LC3CP – the LC stands for Liquid Cooled) that divert part of the water flow
to cool the motor. If these tubes become partially blocked by small debris
(like silt) the pump will eventually shut down. Within a minute or so the
compressor will shut down because no water is flowing through the
condenser. The pump over temp switch resets in about 5 minutes when the
pump has cooled a bit, but the compressor must be manually reset. So that
is the reason the system appeared to restart successfully every time I
pressed the reset button on the compressor.

Anyway my frig has been running and cycling for over 24 hours. The tubes
on the pump are cleaned by removing the face plate on the pump and running
fisher line or leader through the tubes.

Regards,
John Stevenson
http://www.svsarah.com
Sarah’s Blog <http://www.sailblogs.com/member/svsarah/>

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[typhoontye]

Similar experience on my last cruise, about two weeks ago! The little handle on the basket screen assy had broken off, but I continued to use it. The little basket handle contacts the bottom of the lid on the strainer assy, holding the basket down, so without the handle, my strainer could ‘float’ upwards. During the middle of the night (of course) I noticed the AC unit cycling…not good. Got the wife up to so we could troubleshoot. No water exiting the boat, so checked to see the pump was operating. It wasn’t, but was hot as a fire cracker. The pump is pretty new, so I was upset. Took the strainer out and it was clean. Re-installed, screwed the lid on, and turned on the unit. Now it was working! I could only surmise there was a thermal switch in the pump unit itself, and when it cooled, it began to operate normally. Of course I’ve purchased a new strainer basket to prevent re-occurrence, and all has been well since.

David Tye
#189

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