March pump pressure when fly sparging

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Bizoune

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I seem to have a bit of a March pump issue that's getting annoying. Maybe somebody has a solution.

When comes time to fly sparge, I'm pumping my 175F water from my HLT to my MT and then letting to wort trickle down via gravity to my BK. I can regulate flow easily during the first 15 minutes so that my input (water going on my grain bed) equals my output (wort coming out of my MT). Ball valve on the output of my HLT is always wide open and I'm regulating flow from the pump head. After a while though the water pressure from the HLT to the MT seems to drop and my sparge water slows down to a trickle, so if I'm not watching the MT properly I risk the chance of drying up the grain bed. To get the flow back up, I then have to bring my hose down to the same level as my pump head, prime it then bring it back up to my MT and continue with sparging. Usually, I have to do this twice during a 50 minute sparge, mostly during the first 20-30 minutes.

My system is a 2 tier: BK and HLT on one level; MT on the other, higher up. I'm under the impression that it's a fluid dynamic issue related to temperature and probably height.

Any ideas on how to solve this? On the shot you can see the output coming out of the pump going up to my MLT then MLT draining to BK.

DSC_5241.jpg
 
If thats how you typicaly have your setup going during brewing the first thing i would do is shorten the inlet hose up as much as possible. I'm assuming you have the pump mounted in the box and thats the inlet we can see just poking out tot he right and theres what looks like a coil of hose there....cut it and make it as short as possible. Next thing would be to get rid of the 90* fitting on the inlet of the pump and just let the hose go straight in. Then i would also drill your impeller with a 17/64" drill bit to open it up a bit just so the impellers is happier during operation. If all that doesnt fix it then send me the pump and i will test it under boiling conditions here to make sure the impeller magnets are up to the task. :)
 
Oh and i'm assuming that you have the 809-HS model pump that turns at 3450rpm...if you have the standard 809 that runs at 1750 then the issue is you have is the MLT is too high and the pump is working against to tall a head height. You would be probably getting a trickle at that height out of the line and if the pump sucks any air into the lines and starts to cavitate then you would loose flow....and by you lowering the line to get it to prime again all you are doing is helping the pump move the air out of the line to get going again.....does that make sense?? i think i had too much pepsi this morning and am typing in circles! :D

-Walter
 
WalterAtMarchPump said:
Next thing would be to get rid of the 90* fitting on the inlet of the pump and just let the hose go straight in.

Why get rid of the 90* at the inlet? I have a 90* on mine and no problems.
 
The water level in the HLT will be dropping as you pump it out. This will result in a gradual decrease on the suction head and in turn, the pump output. IOW, you will not have a steady flow rate even though you are pumping the water. It's also difficult to adjust a ball valve with much precision and you have two of them to deal with simultaneously (one at the pump and one at the drain port on the MT). That's why I no longer use ball valves at those two points.

I have a somewhat similar system, but I have the HLT elevated and the MT on the burner where you have your HLT. I gravity feed the electrically heated sparge water and pump from the MT to the BK while sparging. There is still the problem of a gradually decreasing flow rate from the elevated HLT, but it's easy to tweak the flow rate with precision the way I have it set up.

The reason I prefer the MT at ground level is that it requires the most attention. I like to be able to easily view the mash and having it low makes stirring much easier. The HLT is just a water tank and really needs no attention once filled and heated. I fill it directly from a hose, so no lifting or pumping is required. I pump from the MT to the BK, so both kettles can be at the same level.

FWIW, IMO regarding the hoses, I've found that it's best to use large inside diameter hoses and keep them as short as conveniently possible for optimum performance.
 
Why get rid of the 90* at the inlet? I have a 90* on mine and no problems.

If theres no problems then no need to worry about it....i was just trying to get as many possibilities out of the way for him to get it working right.
When you have a 90* on the inlet, its one more turn (ie: restriction) that the water needs to make before getting to the pump....it slows the velocity down and with every restriction you have it starts to starve the pump... With the inline pumps if you look at the pump head you will see it allready makes a 90* turn just to get into the pump....so with an elbow the liquid now makes two 90*'s before getting pumped.... :)

-Walter
 
Oh and i'm assuming that you have the 809-HS model pump that turns at 3450rpm...if you have the standard 809 that runs at 1750 then the issue is you have is the MLT is too high and the pump is working against to tall a head height. You would be probably getting a trickle at that height out of the line and if the pump sucks any air into the lines and starts to cavitate then you would loose flow....and by you lowering the line to get it to prime again all you are doing is helping the pump move the air out of the line to get going again.....does that make sense?? i think i had too much pepsi this morning and am typing in circles! :D

-Walter

Yep it's the 809HS. How can it suck in air if all my connections are tight? Air pockets stuck in the 175F water? Unlikely no?
 
The water level in the HLT will be dropping as you pump it out. This will result in a gradual decrease on the suction head and in turn, the pump output. IOW, you will not have a steady flow rate even though you are pumping the water. It's also difficult to adjust a ball valve with much precision and you have two of them to deal with simultaneously (one at the pump and one at the drain port on the MT). That's why I no longer use ball valves at those two points.

I have a somewhat similar system, but I have the HLT elevated and the MT on the burner where you have your HLT. I gravity feed the electrically heated sparge water and pump from the MT to the BK while sparging. There is still the problem of a gradually decreasing flow rate from the elevated HLT, but it's easy to tweak the flow rate with precision the way I have it set up.

The reason I prefer the MT at ground level is that it requires the most attention. I like to be able to easily view the mash and having it low makes stirring much easier. The HLT is just a water tank and really needs no attention once filled and heated. I fill it directly from a hose, so no lifting or pumping is required. I pump from the MT to the BK, so both kettles can be at the same level.

FWIW, IMO regarding the hoses, I've found that it's best to use large inside diameter hoses and keep them as short as conveniently possible for optimum performance.

That's great info Cat. Regarding my HLT on top, won't I be breaking siphon if I'm sparging really slowly? With my pump, I can get every single drop of water. I'm assuming that once I get the water below my ball valve, even though I have a pickup tube that goes to the bottom, I'll be leaving a lot of water behind.
In either case, I'll probably change my setup this weekend. HLT on top, BK and MLT side by each lower down. Then see how things work out.
 
Is drilling the impeller a standard modification?

Drilling the impeller is not something we do here at the factory only due to the fact we don't know where these units will be used. 99% of the applications for these little pumps are for the solar industry or residential hot water systems. And they never have any problems with the impellers sticking due to the liquid being water most times. The issues with beer brewers is that there are sugars in the liquid and they can crystallize between the shaft and the impeller and bind the impeller from working properly. By drilling out the ID if the impeller it opens it up a few thousands more and lets more fluid turn over to keep the sugars from crystallizing.

-Walter
 
Yep it's the 809HS. How can it suck in air if all my connections are tight? Air pockets stuck in the 175F water? Unlikely no?

There are many variables when it comes to pumping..we have seen some strange things happen over the years with plumbing....you may have tight connections but can still suck air through a pinhole thats not been covered by threads or teflon tape if used....you could have an air bubble trapped at the highest point in the extra hose you have sitting there and not know about it cause the liquid is flowing slow enough at first that it may be creeping along the line and eventually get sucked into the pump head. You could be sucking in air through your main supply tank if there happens to be a vortex swirling around inside....
The more things that yo ucan eliminate as far as potential problems for the pump go the easier it will be to keep it happily pumping along :)

-Walter
 
That's great info Cat. Regarding my HLT on top, won't I be breaking siphon if I'm sparging really slowly? With my pump, I can get every single drop of water. I'm assuming that once I get the water below my ball valve, even though I have a pickup tube that goes to the bottom, I'll be leaving a lot of water behind.
In either case, I'll probably change my setup this weekend. HLT on top, BK and MLT side by each lower down. Then see how things work out.

There is no siphon if you have a drain port on your HLT. It's just straight gravity flow. The sparge rate will not matter. I sparge at a trickle of about a quart/min, but I just kinda eyeball it and keep it very slow.

Regarding getting every drop of water with the pump. What does it matter? It's only water, not wort. I always heat a lot more water than I will need for the sparge. I use the excess for clean up at the end, but there usually is not much surplus when doing 12 gal batches. I use an Igloo 50qt Marine Ice Cube cooler for my HLT. I heat the sparge water with a bucket heater operated with a timer. I can alternately heat the water with propane and pump it into the HLT, but I only do that when I go mobile a couple of times a year. You can also tilt the HLT to get the last water out if absolutely necessary.
 

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