3 questions regarding march pumps....

I am about to buy a march pump model 809hs to pump my hot wort out of my morebeer kettle, through a counterflow chiller, through a venturi valve, and into my fermentor. My kettle is kind of low and this isnt a loop system so i have the following questions:

1) what is the net suction head pressure for this pump at boiling?

2) my chiller is 3/8" copper, do you think there would be a problem if i ran all 3/8" tubing upstream of the pump to the venturi valve?

3) in most march pump systems where the pump is below everything, is the beer that remains in the line after pumping just figured as a loss or does it usually siphon out?

Thanks for your help.
Dustin hickey

Here's my best guess at the answers to your questions:

1. Go here for info on this: http://www.engineeringtoolbox.com/boiling-point-water-d_926.html
When the liquid is at the boiling point, vapor bubbles will form in the kettle and when they reach the pump head it will lose prime. Just below the boiling point the pump can still cavitate, but at what point depends on the pressure head on the suction side of the pump among some other things such as the speed of the impeller, flow rate, restrictions in the suction line, etc IIRC. The bottom line is that you won't be able to pump boiling liquids at all and generally not until the temps fall somewhat below 200F with the common home brewing configurations we typically use. I'm not proficient enough with pump calcs to take it any further than that and I may not have this exactly right, but I think it's fairly close to the way it works.
2. The 3/8" tubing will work, but only marginally so. Assuming it's tubing that you are using, then that would be the outside diameter. The inside diameter would be something like 1/4" which is on the small side and quite restrictive. This will inhibit the flow rate considerably. Whether or not that could be a problem I cannot say without more information. I'm not clear on the purpose of the venturi valve. Is this for aeration or what?
3. Yes, in most systems this wort is just chalked up to a loss. In any case, the volume is likely very small and not worth worrying about or trying to recover. You can easily calculate the volume in the line and when you do so, you will realize that it is rather trivial. It will be much less than you think.

Hope this was of some help. I'll defer to others for refinement and corrections.

Thanks Catt22,
Further comments..

1) Understood. I will not be pumping boiling liquids since I am pumping from my kettle just to cool the wort. My main question is how much net suction head pressure is required at the pump inlet, or in other words ( how much lower than the kettle does the pump have to be? )

2) The tubing I will be using is 3/8" inside diameter on the upstream side of the pump. Sorry I should of specified.

3) Ok. sounds good.

Thanks
Dustin

1. A good rule of thumb for this is about 1 foot of drop to the pump head. You can get by with less, but it will be harder to prime the pump. So long as you can get a gravity flow to completely flood the pump volute, you will be good to go. A bleeder valve on the output side of the pump makes this a snap.
2. 3/8" ID is better. Still somewhat restrictive which will inhibit the flow, but as long as you are happy with the flow rate it's OK. Go to larger tube if you want to improve the flow rate, but that's really the only issue.

1) ok that should be no problem. I will be approximately 1'-0" below the bottom of the kettle.

2) It is only going to be about 3' of 3/8" tubing and then my 25'-0" counterflow chiller which is also 3/8" copper tube. If it wasnt for the chiller i would stay all 1/2" but at the moment I have no choice in the matter i guess.

Thanks for our help Catt22.

Have a good day.

Catt22 said:

The bottom line is that you won't be able to pump boiling liquids at all and generally not until the temps fall somewhat below 200F with the common home brewing configurations we typically use.

Click to expand...

Catt, I have no problems pumping boiling wort with my March. I circulate though my coil for sanitation before I turn off the burner.

arturo7 said:

Catt, I have no problems pumping boiling wort with my March. I circulate though my coil for sanitation before I turn off the burner.

Click to expand...

Then it ain't boiling. With enough positive head on the suction side, it's possible to mitigate the cavitation problem. If it's actually boiling and vapor pockets are forming, the pump will lose it's prime. At least that's what has happened in my experience. Perhaps you know a trick that I don't to overcome this problem. You can pump liquids that exceed the standard boiling temperature of 212F if it's a closed pressurized system, but there again, the liquid is not actually boiling due to the increased pressure. The hotter the liquid, the higher the pressure would need to be. A good example of this is the cooling system on a car. The radiator cap typically keeps the pressure at 15 psi above atmospheric so the coolant can be above 212F without actually boiling. We aren't dealing with a closed system, so our limit is the atmospheric pressure plus whatever minor positive suction head we have and that is usually only about 1 or maybe 2 psi depending on the liquid level above the pump head. I can pump through my chiller and back to the kettle at just under boiling temps, but I can't pump to any significant height, such as my elevated HLT (5-1/2 ft +) at anything above 200F. There are more than a few variables that can affect this such as the flow rate, hose sizes, fittings and restrictions on both sides of the pump, so as usual, YMMV as with most everything else brewing related.

My pump is about a foot below the kettle, after the pump there is 4' rise to the top of the coil. Maybe there's enough head pressure to make it work? Maybe it's not at boiling temp going through the coil?

Either way, I can maintain a boil in the kettle while I'm pumping through the coil. I'm supposing this is enough to sanitize the coil.

arturo7 said:

My pump is about a foot below the kettle, after the pump there is 4' rise to the top of the coil. Maybe there's enough head pressure to make it work? Maybe it's not at boiling temp going through the coil?

Either way, I can maintain a boil in the kettle while I'm pumping through the coil. I'm supposing this is enough to sanitize the coil.

Click to expand...

I'm confident that the hot wort will effectively sanitize your chiller coil (and mine too). It is important to flush it out with clean water immediately after use and then run some hot Oxyclean or PBW through it at the earliest opportunity to clean it well, but you already knew this I'm sure. That's my standard procedure and I have had zero contamination problems so far. I sure hope I never do.

Hey guys,
That brings up another good question. What is your procedure for cleaning your pump and lines? I am not running a loop so what do you think would be the best way to clean everything?

My system will be as follows.

More beer kettle w/ ball valve through high temp silicone beer line to pump. then from pump through silicone beer line to chiller. then from chiller directly to venturi valve and fermentor.

What i mean is that there will only be one pass through the pump and chiller. When you say hot PBW, what temperature would that be and do you think one pass through would be enough?

-Thanks,
Dustin Hickey

DustinHickey said:

Hey guys,
That brings up another good question. What is your procedure for cleaning your pump and lines? I am not running a loop so what do you think would be the best way to clean everything?

My system will be as follows.

More beer kettle w/ ball valve through high temp silicone beer line to pump. then from pump through silicone beer line to chiller. then from chiller directly to venturi valve and fermentor.

What i mean is that there will only be one pass through the pump and chiller. When you say hot PBW, what temperature would that be and do you think one pass through would be enough?

-Thanks,
Dustin Hickey

Click to expand...

I hook up my pump to the chiller and connect all of my hoses together then pump hot Oxyclean in a continuous loop back to the kettle. I like to keep it circulating for about an hour, but I'm sure everything would be well cleaned in only a few minutes doing this. I use the hottest tap water available, but I have also heated water in the kettle using the burner. I prefer the hot tap water in order to conserve propane. The hot Oxyclean solution is most effective for about the first 20 minutes, or so I've been told. It still has some cleaning power after that period, but it rapidly diminishes over time. This is not usually a problem as everything should be well cleaned in the 20 or 30 minute window.

Thanks Catt,
Thats a good idea, I can just circulate back to my kettle. Is it the same for PBW? thats what I normally use for cleaning.

DustinHickey said:

Thanks Catt,
Thats a good idea, I can just circulate back to my kettle. Is it the same for PBW? thats what I normally use for cleaning.

Click to expand...

Yes, it's the same procedure for PBW. PBW is somewhat stronger IMO and an excellent cleaner, but it's also on the expensive side. You can also use ordinary automatic dishwasher detergent, but be sure to rinse extra thoroughly if you do so. Rinse with lots of cold water. Rinsing only takes about five minutes or less. If in doubt, taste some of the rinse water to see if you can detect anything.

arturo7 said:

My pump is about a foot below the kettle, after the pump there is 4' rise to the top of the coil. Maybe there's enough head pressure to make it work? Maybe it's not at boiling temp going through the coil?

Either way, I can maintain a boil in the kettle while I'm pumping through the coil. I'm supposing this is enough to sanitize the coil.

Click to expand...

This is my experience tool. The wort is probably a couple of degrees below boiling temperature technically, but I recirc the last 10 minutes of the boil for sanitization as well.

Hey one more thing guys. Say I decided to hook up an extra line to recirculate back to my kettle after the coil for sanitizing and cleaning. When it comes time to hit the valve and drain the wort from the circ loop into the fermentor through the section of pipe that hasnt been in the circ loop, how is that unsanitized pipe that wasnt in the circ loop sanitized? How do you guys do it in your system?

DustinHickey said:

Hey one more thing guys. Say I decided to hook up an extra line to recirculate back to my kettle after the coil for sanitizing and cleaning. When it comes time to hit the valve and drain the wort from the circ loop into the fermentor through the section of pipe that hasnt been in the circ loop, how is that unsanitized pipe that wasnt in the circ loop sanitized? How do you guys do it in your system?

Click to expand...

I use a section of hose that I dedicate to just that use and nothing else. I take extra precautions to keep it clean and sanitized. I just soak it in Oxyclean taking care to be sure that it gets completely filled with the cleaning solution. Then I rinse it well and submerge it in a bucket of Star San until I'm ready to use it for pumping the wort into the fermenter. In your case I would just run some of the hot wort through the discharge pipe and collect it in a pitcher or something, then return it to the kettle. Do this a couple of times while the wort is still hot and you should be OK until it's time to shoot it into the fermenter.

I've always had to kill the flame to keep the wort pumping for sanitizing. It's not a big deal, I just kill the flame, start recirculating for 2 minutes, add flameout hops and start chilling.