March pump overheated???

[sjlammer]

I was brewing yesterday and I had been recirculating using my march 809. After I mash, I mashout by raising the HERMS temperature to 175, and continue to recirculate my mash water until it hits 175 on the outlet of my herms.

Then I stopped the pump, and switched the hose to pump into the BK. I had almost filled the BK when I noticed that the level had not been changing for some time. I touched the motor housing and it was really hot, but the motor fan was still running. At this point the pump had been running for 1.5 hours with a one minute break.

I switched to use my other pump, and I pulled the pump head off to see if I had a clog. There was nothing in the pump head. I put it all back together and turned it on and the pump worked again.

It seems like my motor overheated and shut off. I have run the pump like this before without a problem. Could 1.5 hours of continuous duty be too much? What do you guys think?

 

[Catt22]

If the fan was turning, the motor was also turning. The fan is on the same shaft as the motor armature. Sounds like the impeller was stuck or there was an obstruction somewhere. I would just flush it out really well and proceed as usual. Should you dismantle the pump head/impeller, be sure you install the thrust washer and everything else in the proper order. It's easy to lose the small thrust washer and this can cause the impeller to stick. The pump may have lost prime for one reason or another. Was the pump making any unusual noise? A rattling sound could indicate that the pump was cavitating or lost it's prime. It's normal for the motor housing to get fairly hot when running under a load, but that's nothing to be alarmed about. These pumps are designed for continuous duty, so that should not be an issue.

 

[sjlammer]

I took it apart very carefully because i did not want to disturb anything that was stuck (for trouble shooting), or loose any pieces. I did find the thrust washer, and put it back, although i think i will try to get a replacement.

The pump was making a strange noise.... none.. normally my march pump is fairly loud (compared to my Little Giant).

I am going to do a clean in place soon, so i will just run the pump for a couple hours and see what i get.

A stuck impeller seems to be the most simple answer, but i find it hard to believe when i had been recirculating for 1.5 hours, The filter bed must have set up by then. also i was very careful not to disturb the pump housing while dismantling, so i would have seen any stuck particles.

Dam march pumps... wish i had gotten two little giants.

 

[Catt22]

Yeah, I've got an LG and never had any problems with it. Many of my friends have the March units. Some have had problems and others none. I've read reports of the impeller shaft getting gummed up with wort residue and causing it to get stuck, but I would think that if it was running along fine, it would continue to do so. The sticking would likely only occur if the pump was turned off for awhile with nothing moving.

 

[rshosted]

I had a similar problem in the middle of a brew yesterday. I was using the march pump to push my sparge water up to the sparge arm. I noticed my sparge was a little cold, so I turned up the temperature of the sparge water. It got up to about 190-200 and the water would stop pumping. I took the head apart and everything looked good. I put it back together and the pump did not work. The water cooled to 185 and the pump worked again. It was pushing very strong again. As soon as I turned the water pressure back up, boom no work again.... any ideas on this?

 

[kladue]

You have enough pressure drop on the inlet side that the water is boiling inside the pump head, mount it as low as possible to help overcome this problem.

 

[bigjoe]

I've had mine do this twice. I assumed it was a "safety" feature to keep the pump from getting hot. I've worked with electric motors in the past that operated similarly.

The first time I got a little uptight but thought I'd just give it 5 minutes. I figured the reason was because I had it mounted in a toolbox for portability and I didn't notice the lid being closed. The second time the lid was open but the black motor was baking in the sun the whole time. I've gotten to the point that I don't recirc for the whole mash. I'll recirc when firing the kettle and when mashing out. I get wort just as clear as if I left it on the whole time.

 

[Catt22]

You have enough pressure drop on the inlet side that the water is boiling inside the pump head, mount it as low as possible to help overcome this problem.

+10 I've had exactly the same experience and as Kladue said, increasing the positive head on the suction side will help and the more the better. It's definitely a pump cavitation issue IMO. I can pump water up to about 200F with about 1 ft of head on the suction side pushing it up to my HLT against about 5-1/2 ft of head on the output side. What's interesting is how it won't pump at all, then suddenly the cavitation ceases as the temp drops below 200F and at that point it will pump the entire 12 gallons in only a few minutes.

 

[Lonnie Mac]

The only time I have had this problem is reaching boiling temps as well, although it is rare that I have this occur. It's because at 200+, your water is developing little micro bubbles at this temp as it is starting to boil. Of course your outlet is right at the heat source. At least in my case, I have seen these bubbles build up in the head and loose prime. A quick turn off, clear the big bubble that all these little ones turned in to, and away we go...