Will/Can this work?

thp_7

Just imagine where the air is going to want to go in that system.

Steve Ebels_3

Will/Can this work?(SE)

Even the jolly old State of Michigan is looking to cut fuel costs. I received a set of prints today that call out the specs for installation of several outdoor wood heaters in a boys correctional/bootcamp facility. On the detail page of this print the engineer has spec'd 60 series B&G circulators on the wood heater side of the system, circulating water from the WH to a HX. These are large industrial sized wood heaters and the flow rate is 90GPM. The thing that caught my eye is that the circ is mounted in a second story mechanical room which has an elevation of approximately 5-7' above the water level of the outdoor unit. Bear in mind this is an open system. To me this would mean that there will be virtually no positive suction head available for the circ and that doesn't add up to me. So I called the engineering firm and spoke with the guy who did the drawing. I voiced my concern regarding cavitation issues to him and he replied that the wood heater company says they do it all the time. That was basically his explanation and rational for drawing it in that way. The B&G engineering manual that I have shows very little NPSH required for the circ but doesn't ANY circ need at least a LITTLE positive pressure on the suction side?

What do you think?

Steamhead (in transit)

I think you're right

stick to your guns. Cavitation can kill a pump.

Mike Reavis_2

we once used an indirect to heat the water

for a bottle-washing machine. This was an open system. It worked great, once we got the right boiler hooked up to the indirect (the owner did not order the make-up water heater that was on my spec's). I over-sized the pipe on the suction side of the pump, and located the pump below the water line of the reservoir. This was a bronze series 100--little chance of cavitation here, but I was not taking chances.
Mike

bob_50

Manual

Steve, B&G has a manual TEH 1075 Cooling Tower Pumping and Piping, that you will find useful on an application like this.

Steve Ebels_3

Mike

That's the thing that's bugging me about this print. The engineer has the circ located roughly 6-7 feet ABOVE the water line of the vessel. The part that really freaked me out was after while discussing this with him, he suggested installing valves on the outdoor wood burner to seal it off once it was filled. Now you have a closed system using a non-ASME rated appliance. I have no clue how he thinks this will pass inspection.

Constantin

... just goes to show...

... that some engineers ought to be taking more classes to understand the equipment they're specifying.

I ran across a large, brand-new Vitola the other day, one that was gas-fired and fitted with a super-size LLH. All specified by an engineering company that evidently felt better qualified to spec this install than to take the advice of the installer. What a colossal waste of resources.

In other words, you're not alone.