March pump wont pump high temperatures. above 190...

I had a 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?

Just a few notes: the pump worked very well below 185. I am using 1/2 line and was not pushing much head (5' or so). Primed the pump well with a good feed line.

I'm assuming the pump is still spinning, but not moving anything? The pump is probably cavitating at higher temperatures and trying to push steam around doesn't work well. Some times you can restrict the output flow (increasing back pressure) and reduce the cavitation. The other alternative is to mount the pump lower to increase the input pressure.

You have to limit the flow rate as david mentioned. I can pump up to 210F with a restricted output. Once you hit boiling, you have to kill the flame to be able to pump because boil bubbles will start collecting in your siphon tube and you will lose prime in the pump.

Essentially what is happening is you're creating a slight vacuum on the pump input line and liquid boils at a cooler temp under vacuum.

How do people recirculate during the last 15 minutes of a boil then to clean a CFC? I thought this was common practice and one advantage I am really looking forward to when incorporating my 809.

The pump is cavitating at the higher temperatures. Increasing the positive head on the suction side of the pump (ie mounting the pump lower) will help to mitigate the problem, but I don't think restricting the output flow would be a good idea at all. I've found that it's best that all hoses and fittings have a minimum ID of 1/2" (equal to or greater than the pump inlet ID). Check the inside diameter of all fittings on the suction side. I would bet that some have less than a full 1/2" clear opening. A fitting for a 1/2" hose will typically use a barb with an inside diameter of only about 3/8" and sometimes less than that. Those can be a major bottle neck and on the suction side it's critical to minimize restrictions of any kind for maximum performance.

Catt22 said:

The pump is cavitating at the higher temperatures. Increasing the positive head on the suction side of the pump (ie mounting the pump lower) will help to mitigate the problem, but I don't think restricting the output flow would be a good idea at all. I've found that it's best that all hoses and fittings have a minimum ID of 1/2" (equal to or greater than the pump inlet ID). Check the inside diameter of all fittings on the suction side. I would bet that some have less than a full 1/2" clear opening. A fitting for a 1/2" hose will typically use a barb with an inside diameter of only about 3/8" and sometimes less than that. Those can be a major bottle neck and on the suction side it's critical to minimize restrictions of any kind for maximum performance.

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+1 Def try reducing any restriction on the inlet before reducing output. Even tight bends can cause cavitation.

IrregularPulse said:

How do people recirculate during the last 15 minutes of a boil then to clean a CFC? I thought this was common practice and one advantage I am really looking forward to when incorporating my 809.

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You can't pump boiling wort due to the cavitation problem You can, however, pump wort that is slightly below boiling temperature. How much below depends on the head pressure on the suction side of the pump. Typically, when circulating in a loop through a CFC and back to the kettle, the kettle will be full which provides maximum positive head on the suction side while doing the circulation thing. This is a little different than say pumping hot water from a kettle to an elevated HLT as the head on the suction side will drop as the water level in the kettle falls. We're talking about a very small pressure change, but when it's borderline to begin with, it makes a noticeable difference as it will often be a go/no go situation. The second thing is that when circulating through a CFC like that, you are mostly just pumping horizontally and not up to an elevated kettle, so there is little head on the output side working against the pump. I can easily pump through the CFC and back to the kettle very shortly after shutting down the burner.

IrregularPulse said:

How do people recirculate during the last 15 minutes of a boil then to clean a CFC? I thought this was common practice and one advantage I am really looking forward to when incorporating my 809.

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I just run it really slow through the CFC and back into the kettle, nothing like boiling wort to sanitize things But I usually just do the last 5 or so of the boil.

I gotta be honest, I would not buy another march pump. They are too tempermental. I'm really interested in changing pumps.

rshosted said:

I gotta be honest, I would not buy another march pump. They are too tempermental. I'm really interested in changing pumps.

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IMO, you could get the March pump to operate just fine if you use short, large diameter hoses on the suction side to minimize the restrictions. That and a bleeder valve I am sure would solve the problems. IOW, I don't think the pump itself is at fault. I use thick walled 5/8" ID hose throughout my system and have no problems at all with the pump. The 5/8" ID allows you to use barbed fittings that have an ID of 1/2", so nothing is less than that anywhere. I really think this is the key. The thick walled tubing resists kinking when used to pump very hot liquids. Often I see people using 1/2" ID tubing without giving any thought to the ID of the connection fittings and that can sometimes cause problems.

rshosted said:

I gotta be honest, I would not buy another march pump. They are too tempermental. I'm really interested in changing pumps.

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I'm with you 100%. The problem is you won't find anything that will perform any better than the March pump at anything less than double the price and then even that is a gamble.

On my last system, I just hung the pump right off the vessel valve QD and that elminated most all of my problems by elminating the supply hose completely.

Although I do have occasional issues with the March pump I have no problem pumping boiling wort through the plate chiller for the last few minutes of the boil. I am using 3/4 OD x 1/2 ID silicone tubing with Colder Poly QD's.

I've had much better pumping since I took off the euro style hose clamps and replaced them with cable ties. I think I was leaking some air inline with the hose clamps.

Derrin said:

On my last system, I just hung the pump right off the vessel valve QD and that elminated most all of my problems by elminating the supply hose completely.

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What kind of QD are you using? Did you need to do anything to support the weight of the pump or was it all just hanging of the QD? I am planning on adding a pump to my system shortly but have no intention permanently mounting it to a frame so this idea appeals to me.

I don't plan to retool my whole brewery to different tubing and connectors just to facilitate a pump that has been sporadic at best. And really I have very short r s, thick wall 1/2 tubing. If anything changes it will be the pump. I just want to make sure I'm verbal about the peformance so others can consider thier own purhases. When. Bought no one spoke of problems with the pump and I had high expecations.

I think the steam arguement is interesting and I hadn't considered that. Although I wouldn't think that should happen as low as 190. But I will have to watch mre closely now.

But I don't think I can communicate the frustration I had when halfway though a sparge whnthe pump stoopped working. Also I did havethe out side metered down to a slow trickle speed to accomidate a good sparge.

Catt22 said:

IMO, you could get the March pump to operate just fine if you use short, large diameter hoses on the suction side to minimize the restrictions. That and a bleeder valve I am sure would solve the problems. IOW, I don't think the pump itself is at fault. I use thick walled 5/8" ID hose throughout my system and have no problems at all with the pump. The 5/8" ID allows you to use barbed fittings that have an ID of 1/2", so nothing is less than that anywhere. I really think this is the key. The thick walled tubing resists kinking when used to pump very hot liquids. Often I see people using 1/2" ID tubing without giving any thought to the ID of the connection fittings and that can sometimes cause problems.

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I share CAT's observation(s). I had a similar issue with my Little Giant 3-MD-HC using thin-walled 4ft 1/2" ID hoses. I moved to thick-walled 4ft 3/4" ID hoses which affix properly to 1/2 ID hose barbs.

rshosted said:

I don't plan to retool my whole brewery to different tubing and connectors just to facilitate a pump that has been sporadic at best. And really I have very short r s, thick wall 1/2 tubing. If anything changes it will be the pump. I just want to make sure I'm verbal about the peformance so others can consider thier own purhases. When. Bought no one spoke of problems with the pump and I had high expecations.

I think the steam arguement is interesting and I hadn't considered that. Although I wouldn't think that should happen as low as 190. But I will have to watch mre closely now.

But I don't think I can communicate the frustration I had when halfway though a sparge whnthe pump stoopped working. Also I did havethe out side metered down to a slow trickle speed to accomidate a good sparge.

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I sort of expected that kind of a response. Odds are you will continue to have problems no matter what pump you use. The cavitation problem won't go away with a change of pumps and a more powerful pump will only make the problem worse. Yes, the vapor bubbles can form with temperatures as low as 190F and possibly lower than that if the pressure reduction is great enough. The inside diameter of the connectors on your 1/2" tubing is probably only about 3/8" which is about a 44% reduction in the cross sectional area. That's a relatively large decrease. There are an awful lot of home brewers using the same common March 809 pumps without issues. IOW, it ain't a problem with the pump, so your warning to others may be unwarranted. You could very easily and cheaply test out what I'm trying to tell you. You need only change out one hose for a larger one on the suction side of the pump. Make sure that all fittings and connections have a minimum of 1/2" inside diameter clear opening on the suction side, including any pickup tubes etc. The output side is not as critical as the suction side, so you could keep those as they are. It would not cost much to give it a try and might save you from having to purchase another pump. OTOH, if you are dead set on blaming the pump, then go ahead and buy a different one, but promise to report back with the ongoing problem after you do so.

Oh yeah, I wanted to again suggest using a bleeder valve on the ouput side of the pump and ahead of the flow control valve. This makes priming the pump much easier and it's also a handy place to grab a sample when pumping wort. Sometimes these pumps can get sort of half primed when a minor amount of air gets trapped in the pump volute. When that happens, they will still pump some, but way below their capacity and sometimes with not enough force to clear out any vapor bubbles. The bleeder valve takes care of that and you can visually see when you have the pump fully primed as the flow from the valve will be quite forceful. Not everyone uses a bleeder valve, so it is certainly optional, but I would not use a pump without one. It makes priming the pump just too easy.

Well apparently the pump does have limitations, next brew day I'll have to see if I can hook my 1/2 silicone without the smaller hose barbs to see if that helps. Although, it seems I have read a few people talking about better luck with different pumps.

I do appreciate the suggestions on getting the march to work though, and plan to try them.

And for the record the pump was primed very well.

Cuzco_Brew said:

What kind of QD are you using? Did you need to do anything to support the weight of the pump or was it all just hanging of the QD? I am planning on adding a pump to my system shortly but have no intention permanently mounting it to a frame so this idea appeals to me.

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Initially I was using brass garden QD's but they tend to leak a little which is just enough to allow a slight air-bleed into the pump and cause cavitation. I switched to tri clover fittings and never had a problem again. When I first did it, I used a piece of wire looped around the pump and then hooked over the edge of the kettle. Then I lost the wire, tried it without and never had a problem with the welded fitting supporting the weight of the pump.

FWIW, having the pump motor below the impeller housing and having the motor shaft vertical like I did is NOT recommended by March. I just figured for the relatively short periods it would be running at a time it would be OK.