Best choice

[batsofbedlam]

I'm torn between a 1 1/2 hp and a 3 hp airablo vane vacuum pump with the new radiator oil cooler feature. I'm going to use this to replace a 20 cfm oil-ring pump that i am disappointed with. In a 1000 tap sugarbush, the oil-ring pump would not make up for any vacuum leaks, so instead of the promised 25-28 inches of vacuum, I was getting 5 22 inches.
Supposedly the vane pumps will pull more cfm's than rated especially under low vac. I'd like to go with the 1 1/2 hp to save electricity costs, but not at expense of not having enough cfm's.
Which would you choose?

[DrTimPerkins]

Which would you choose?

You may not like this answer, but the best solution is probably to stick with your current pump, which sounds like it is probably adequate for that number of taps, but focus instead on fixing the leaks. That is especially the case as you pull higher vacuum. Putting a larger pump on will not solve your leak problem. You may end up with a higher vacuum level at the pump, but not in the woods where it is important. It'll make you feel better looking at the gauge, but won't improve your sap production substantially.

Putting a bigger pump on a tubing system with leaks is kind of like trying to solve the problem of a drafty house by putting a bigger furnace in your house but leaving the windows open. It'll help a little bit, at a substantial cost, but doesn't solve the real problem.

Either way, bottom like is that you'll definitely move more CFM with a vane pump of that size (with more electricity use and higher noise level), but you probably won't get a much higher vacuum level.

To understand the rating (cfm vs vacuum level) of pumps, you need to see the full curve. The maximum CFM ratings of many pumps are rated at 0" Hg, and can either slowly degrade (for a time) or steadily degrade in CFM with increasing vacuum level until they drop off near their maximum vacuum levels.

[sapman]

I might add that the Busch pumps I've priced are very competitive (or less money, even) than the vane pumps with the new radiators. Nicer setup, too, I'd say.

[Buffalo Creek Sugar Camp]

Has anybody seen a chart showing a performance curve on the Busch pumps? I wonder how they compare to a two stage SIHI as far as CFM's at high vacuum?

[220 maple]

Jeremey,
Have you talked to Henry lately? The big guys in Vermont are more concerned about the amount of Hertz the pump is pulling instead of Vacuum. The Vac. systems we seen were all dead headed. I'll try to explain. When they set the vacuum pump up they dead head the vacuum line then they see how many hertz is being pulled. One large producers pump was pulling 58 hertz, if they have as few as five leaks the pump will read less say 57.9 hertz. If they only looked at the vacuum guage it probably would not show that the system has leaks

Mark 220 Maple

[brookledge]

If you have a 3 phase pump with variable speed drive the Hz. is what controlls the speed. So you need a transducer to have the speed controled. As it detects the vacuum level that you have it set at it speeds up or down. It is sensitive enough that you can look at the Hz. like 220 maple said and tell if you have a leak. Compared to a big pump always running at full speed you might not know you have a leak because the pump overcomes the leak. Which isn't all that bad but one lateral open you will lose a fair amount if it is open for days with out knowing it.
Keith

[Teuchtar]

Another consideration (bigger vacuum pump and tolerate leaks versus small vacuum pump and leak-tight) is to remember the refrigeration effect of expanding air.
Consider a minor leak far from the pump. As that little package of air travels down the pipeline, it expands as the pressure drops from atmospheric to the pump vacuum. As it expands it cools.

The dicey part is when freezing is taking place in the evening. All the extra cold air is expanding and chilling your sap further. This can mean the pipeline is running several degrees cooler than the outside air and will freeze sooner.

Earlier freezeup, and later thaw tomorrow morning.

Another reason to hunt down those leaks and fix them even if you think you've got a beefy big pump. I fact, maybe the oversize pump is causing a reduction in sap production instead of increase.