Keg King MKII Pump - Low Flow Rate

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SmithyA

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I run a single tier fully electric 3V HERMS system with two Keg King MKII pumps to recirculate the HLT water and the wort through a 1/2" stainless steel coil mounted in the HLT.

One thing I've noticed is the significant delay between the HLT temp and MT temp on my PIDs when I'm ramping up temps. I've conducted a lot of research and have insulated my kettles, increased the size of my coil (now 15m), bought Auber PIDs and temp probes (in case of inaccuracy/delay etc) and have identified a possible issue as the flow rate of the pumps.

The pumps specifications state they're capable of 19L/min however when I stuck a 5L jug in the mash tun when it was circulating I timed how long it took to fill it to 5L at 1 minute 13 seconds.

What could be contributing to the decline in flow rate? I recently read an article where it was claimed camlocks have better flow rate over the quick disconnects I have installed, however that's some expense simply for a test, unless anyone can confirm the improvement? Could the system have issues with not being fully primed? I wait until fluid flows out of the output hose and then connect it before turning the pump on. No air bubbles come out.

I tested the pump directly into the 5L jug (remove distance and priming variables) and it filled to 5L in 27 seconds. While that's a huge improvement, it's still nearly half the performance these pumps claim.

Any thoughts or experiences with this?

Cheers,
Adrian
 
Those flow rates are at the pump head with no head. The length of hose/pipe and number of connections will affect the flow rate
 
Ok so that's out of my control. Is there any appreciable difference with camlocks over quick disconnects for flow rate?
 
Internal diameter of your piping and any connections will effect flow rate. Every time there's a step down in diameter (a fitting, different sized hose etc), there'll be a decrease in flow rate.

Some scientific type may shoot me down, but this is what I have observed in my system using that same pump. My 1/2" ID hoses flow a fair bit faster than my 3/8" ID wort chiller.
 
Yeah I'd say that makes sense. I run 1/2" on everything but I recently read a thread on HBT and there was a youtube video showing that camlocks have a bigger ID than quick disconnects. I wonder if it would be worth the expense and hassle to change over. I find the QDs a bit hit and miss with leaking so it might be an upgrade worth considering anyway.
 
The guys above are correct, and slow recirc will show significant mash bed lag. However your mash bed temp isn't the important one. The temp at the exit of your hx is what you need to control. Having said that a centre flow march 815 would probably show marked improvement.
 
I did a post on here a while back about how centrifugal pumps work but the crux of it is that the figures are conditional. Max pressure is when there's no flow, max flow is when there's no pressure.
The main restriction to your flow will be the length of your coil. By increasing the length you've increased the losses due to pipe friction. The main losses in a system will be:
- Pipe friction
- Bends
- Components with reductions in diameter (fittings, meters etc)
For a small system like these the fittings aren't much to worry about. 15m of 1/2" pipe on the other hand is. Unfortunately by reducing the flow rate you've inadvertently affected the overall performance of the system depending on how much heating power you've got. Considering you're saying that the MT is lagging the HLT, heating's not the issue. Flow rate is.
You either need to upgrade the pump or reduce the length of your coil.
Ed: and yes the quick disconnects have more restriction than camlocks. What's the size of your vessels?
 
57L x 3. My guess is there'd be negligible improvement using camlocks if the pump is under powered for the application?
 
TheWiggman said:
I did a post on here a while back about how centrifugal pumps work but the crux of it is that the figures are conditional. Max pressure is when there's no flow, max flow is when there's no pressure.
The main restriction to your flow will be the length of your coil. By increasing the length you've increased the losses due to pipe friction. The main losses in a system will be:
- Pipe friction
- Bends
- Components with reductions in diameter (fittings, meters etc)
For a small system like these the fittings aren't much to worry about. 15m of 1/2" pipe on the other hand is. Unfortunately by reducing the flow rate you've inadvertently affected the overall performance of the system depending on how much heating power you've got. Considering you're saying that the MT is lagging the HLT, heating's not the issue. Flow rate is.
You either need to upgrade the pump or reduce the length of your coil.
Ed: and yes the quick disconnects have more restriction than camlocks. What's the size of your vessels?
spot on, I was thinking of flow rate and piping size fro my next system upgrade, I'm running 1/2 but want to go larger on the next build
 
Where would I source a high LPM pump such as the March 815 suggested? Google and eBay searches seem to be a little hit and miss between off the charts expensive to "I think my money would end up in Nigeria" deals
 
try looking up chugger for comparable pumps.. I would have said Ring Full Pint but dont know the Chugger status...

check forum sponsors mate
 
I believe that pump is rated to 12 l/m at 1.5 Bar head.

Running the numbers on this: 12 l/m through a 1/2" tube (assuming 1.6mm wall thickness) is a flow velocity of 2.8 m/s, towards the upper end of the recommended range, meaning a high pressure drop: for 15m of tube this comes out to about 2.5 Bar, above the rated pressure of the pump.

First thing to do is to get the flow velocity down: one way of doing this is by splitting the tube and connecting it in parallel, resulting in a flow velocity at 12 l/min of about 1.4 m/s in each side, a much happier number.

If you try to just uprate the pump you'll need a minimum hydraulic power of 50 watts, at typical efficiency of ~60% for a small centrifugal pump that's a shaft power of around 80 watts, at typical single phase motor efficiency of around 70% that's an electrical power of >110 watts.
 
Lyrebird_Cycles said:
I believe that pump is rated to 12 l/m at 1.5 Bar head.

Running the numbers on this: 12 l/m through a 1/2" tube (assuming 1.6mm wall thickness) is a flow velocity of 2.8 m/s, towards the upper end of the recommended range, meaning a high pressure drop: for 15m of tube this comes out to about 2.5 Bar, above the rated pressure of the pump.

First thing to do is to get the flow velocity down: one way of doing this is by splitting the tube and connecting it in parallel, resulting in a flow velocity at 12 l/min of about 1.4 m/s in each side, a much happier number.

If you try to just uprate the pump you'll need a minimum hydraulic power of 50 watts, at typical efficiency of ~60% for a small centrifugal pump that's a shaft power of around 80 watts, at typical single phase motor efficiency of around 70% that's an electrical power of >110 watts.
Haven't done pressure and flow for like 20 odd years but 1m of head = 10kpa of pressure, 1.5 bar would be 15m of head. I may be confused as to which pump your referring.
 
Also remember restricting the flow at the inlet is way worse than at the outlet. Also these kk pumps clog fairly easy I don't know you cleaning regime but if you haven't yet pull the head off and give it a clean.
 
I've entered a new low and am going to quote a quote -

The little green pumps are centrifugal pumps which means they have an impeller that spins to apply pressure to move the water. Picture this -
  • You have a hose that goes vertically. The pump will push water up the hose until it reaches it's max operating pressure at the discharge of the pump. The height of this column of water is referred to as maximum head / pressure (pressure = density x height x accel. due to gravity. Or simply, 10m = 100 kPa). For these pumps, max head = 2.4m* or 24 kPa. Hence the water will be pumped up to a height of 2.4m REGARDLESS of the diameter.
  • Imagine you trim the pipe off at 2.39m. A tiny, little bit of water will trickle out. Your pump is now pumping. Pressure will be 23.9 kPa at the pump discharge.
  • If you continue to trim the pipe off lower and lower, more flow will come out because there is less water in the pipe vertically applying pressure at the pump.
  • Continue this until the pipe is gone and the pump is spitting out water. This is the max flow it is able to achieve, at essentially zero pressure.
16/19 l/min refers to 50 Hz and 60 Hz power sources respectively (same for flows). In Soviet Australia we have 50 Hz power, so 16 l/min is the max you are going to get out of the pump with no restriction.

* Note that 3.6m head is often quoted, but for some reason I've assumed 2.4m (maybe it's written on my pump for a 50Hz supply).
 
For these pumps, max head = 2.4m* or 24 kPa. Hence the water will be pumped up to a height of 2.4m REGARDLESS of the diameter.

* Note that 3.6m head is often quoted, but for some reason I've assumed 2.4m (maybe it's written on my pump for a 50Hz supply).


OK, I was wrong. I misread the pump specs, I was going off a slightly fuzzy pic of the spec plate on a website. I thought 1.5 Bar sounded a litle optimistic, in my defence I'm a lot more used to pumps with delivery ratings in bar, when you work with fermenters that are 13 metres high you kind of need them.

At 50 Hz the pump is rated for 8 l/m at 1.5 metres head (not bar!), so it's 10 times lower than I said.
 
So in summary, KK pump is significantly under powered for my application?

Next question, are the March or Chugger pumps up to the task?

I appreciate the technical, well thought out responses too.
 
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