Vacuum Pump for Steam System

Gordo

Does anyone have a recommendation for a small, very quiet, motorized vacuum pump to induce low pressure in a dry return or a line from a Paul System vent?

Charlie from wmass

I will look up my old threads from Pumpguy. I have not seen anything that small yet. But I am always looking.

Charlie from wmass

http://forum.heatinghelp.com/discussion/149599/brown-vari-vac-system#latest

ttekushan_3

How low do you want to go on the vacuum, that is, do you have an idea how many inches of mercury and what kind of CFM?

"Quiet" and "Moderately Sized" are the problem.

I came up with a solution that is a loop with a small Grundfos cartridge circulator and a home made jet pump/eductor. I had a situation that involved a distant sub-header and about a 2' lift into a dry return that was several years away from being restored to vacuum. It serves about 410 square feet EDR. It's been in service for a number of years now and is silent and reliable. How much vacuum? Dunno. But it managed to take a 40 minute stall then hammerfest and provide nearly silent and quick heat.

If you give me a bit of time I can get back to my desktop computer and provide all the particulars, schematic and genuine eductors to choose from.

Charlie from wmass

I have been toying with that, just need a home for it. I think I just thought of a home for it as I typed.

nicholas bonham-carter

From an old thread here, I believe someone has used a shop vac for this purpose.
You are really only exhausting the dry returns, as the rest of the system has the steam pushing the air out.--NBC

ttekushan_3

Okay here we go.
First of all, for a large system, a nice liquid ring vacuum pump is a lovely idea. Just installed one in a larger project in October. Sourced from Oak Services to replace a defunct Nash/Jennings vacuum condensate unit from 1954. Excellent service from Dennis, by the way.

But the smallest is going to be about 1.5 HP and expensive. And not quiet. I searched high and low for something that would work including small regenerative blowers, but really, that's not quiet and won't tolerate moisture. So off to the jet pumps we go.

So out of desperation one day, I had to come up with some kind of a solution for a "lift" with some vacuum and didn't want to go with a typical condensate unit, since I wanted to eventually have it do double duty.

First, here's a picture of the impromptu vacuum pumping station. It was assembled with extension cords and an aquastat on a different main. Not long after, it was hard wired. Really!

Second is the diagram and working rationale for the boiler room files. If you can make sense of it, use it for the good health of small steam heating systems everywhere. Incidentally, it works with a main vacuum return restored. I feared seal problems but no such problems have occurred.

Third is a revised version for a job that was to have occurred last summer but got delayed and, well, winter started very early in Cleveland so we didn't break into a working system especially since all the leaking piping around the boiler has to be repiped anyway. This summer. Really!

When I find "The Eductor Files" I'll add them.

ttekushan_3

If there's any issue opening the second pdf from above, I've posted it again. I had trouble doing so on The Mobile Device so just in case:

BTW, it is extremely quiet, can run continuously, is tolerant of steam temperatures,etc.

nicholas bonham-carter

Here is the link to the shop vac method, with familiar names:--NBC

http://forum.heatinghelp.com/discussion/139813/Another-Look-at-Vapor-Vacuum

Maybe we need a vacuum section here on the wall!

vaporvac

I second that!

Gordo

@ttekushan, that is excellent! I am eager to try it out on a needy system. As to what cfm or inches of Hg, I just not sure. This is uncharted territory for me, and I'm a bit low on the learning curve.

The shop-vac idea, it seems to me, is a bit loud and really seems to be more of a proof-of-concept than something I want to leave running in someone's basement.

So far, there seems to be no "off-the-shelf" vacuum pump system that will handle moisture, be plug-n-play, quiet, and small enough to go on a residential system unless we make one.

Gordo

ttekushan said:

If there's any issue opening the second pdf from above, I've posted it again. I had trouble doing so on The Mobile Device so just in case:

BTW, it is extremely quiet, can run continuously, is tolerant of steam temperatures,etc.

This looks good! It seems like it should work well for evacuating air in a small two pipe system.

Is the circ bronze or stainless?

I would also ask if any measurements were taken as to vacuum level generated by your brilliant device?
Was a measurement done to see if the steam came up quicker?

ttekushan_3

Well, I'm certainly delighted that this little contraption has caught the imagination of the vapor-enlightened here.

As to your specific points, Gordo, I liken this specific small leg of this otherwise large steam heating system to a small two pipe system. I concur that there isn't anything out there of a diminutive size and noise level. The Grand Master liquid ring pumps or even the Giant Jet Pumps of the hurling chamber design are institutional devices. Us "lug the boiler down the stairs on an appliance dolly" are not served.

In a way, my little pumping station is a miniature jet pump/ hurling chamber design, but arranged vertically so as to make an inexpensive cartridge circulator work and allow the separation chamber (as I call it, rather than "hurling chamber") to be of low volume. It also eliminates switches, solenoid valves, etc.

I've found that it doesn't really take all that much suckage to iron out distribution trouble and really speed up the steam flow.

I have no doubt that my eductor is not very efficient at all, yet it really picks up the pace of things and, most importantly, drains the header and lifts into the dry return.

Several important points about this particular installation:
• -this was installed before the vacuum return was restored. I wanted the system to function on gravity return and evenly; very bad piping practices were abundant, with the faith that the vacuum return would take care of it.
• -the header in question is at the end of some very long undripped branches off the main. This part is a 3rd addition to the system and has a convoluted path. There's a LOT of start up condensate.
• -one boiler is equal to EDR, but the piping maze requires a substantial pickup factor. It could take over an hour for this leg to [noisily] clear. Two boiler operation allowed realistic heating cycles (55 minutes) but even with the oomph of two modulating boilers this still took 1/2 hr to heat up. I was getting to efficient operation but this darn area wouldn't heat up during most cycles. So they had no heat over there. Including the executive office! I knew they would be unimpressed with newfound "efficiency" if it meant no heat at all! Repiping into a quasi lift fitting brought the time down to 17 minutes. Not good enough. And noisy still. And thus the desperation and this brain storm.
• -measurements of improvements in steam circulation involved the clock on the wall.
• -the pumping station eliminates the delay and all but one "clank" at the beginning of the cycle (the center of the line has a transition that's pitched incorrectly. A project for another decade). So upstairs, steam gets everywhere about the same time, even before the restoration of vacuum. I was pumping into substantial back pressure. The new Nash Jennings Vacuum in the boiler room eliminates most of the back pressure in this remote area at start up, so the performance is completely seamless. The single clank reappears only on cold starts and if Total Dissolved Solids at the boilers start getting too high. I consider it an "audible alarm." And those offices are quite comfy now. It's safe to say that the steam comes up quicker. [I would only say that if installed in a system with a very oversized boiler, I'd install a check-valved relief vent on the dry return, in case the air still wants to outrun the jet pump a bit at beginning-of-cycle. I suppose this will vary depending on how much vacuum is retained between cycles. ]
• -this pumping station was made up of "found parts" in my salvage cache, including that Grundfos circulator. I wasn't sure how it would work out, so in it went. And there it still is. It's cast iron. It was old and crusty when it went in. It's had no problem. I don't recommend CI, but golly, the darn thing has been working silently and without complaint so far. It sits all summer with no exercise and starts fine in the fall. However, cracking a union revealed that the water is always crystal clear, and I presume the turbulence ejects sediment so that a minimal amount is all that ever remains there. Perhaps heavier dosing of Rhomar water treatment on the last run of the season sends enough carryover out there to preserve the pump. Dunno for sure.
• -I never measured vacuum other than taking the eductor assembly and shoving a garden hose on one end and put my hand on the suction line and saying, "That'll have to do." Very scientific.
• -The only sound is the subtle sound of water running through a valve. Rather pleasant, really.
• -The circulator has not cavitated under any circumstances.

Real eductors look attractive. I had settled on the LM model of eductor from Jacobi-Tarbox, since it seems the most forgiving of gasses and water in the mix. But I haven't tried one yet.

jumper

another approach is an air powered venturi jet. Perhaps an aquarium pump would suffice. Or a portable tire inflator. Possible improvement is to pull and exhaust the suction through condensers.
If I was setting up a Paul system I'd think about evacuating through a main vent first,then the radiators manifold.This subject has come up before.My opinion was and still is that you don't need radiator vents at all with mechanical suction.

Pumpguy

Sorry, late to this thread.

Smallest liquid ring vacuum pump I currently offer is 1 hp. I have been exploring recently discovered 3/4 hp LRVP's, but have not been successful in getting price quotes and other information from these vendors. If anyone is interested I will pursue this further.

Eductors, jets, venturis, whatever you want to call them, are quiet, that's for sure, but not as efficient in terms of cfm/hp as LRVP's. Whatever you use as the motive fluid, air, water, or steam, the volume required can be quite substantial, so the required motive fluid volume and pressure should be carefully researched before committing to using one of these. Also, you need to plan for where this motive fluid will come from, and where it will discharge to.

nicholas bonham-carter

Instead of using some pumping device to exhaust the air, a chamber which fills with steam, could develop enough vacuum on the off cycle to remove any remaining air from the returns.
Some sort of check-valving would keep the steam out of the returns, but allow any air to flow back into the chamber, which would then be exhausted by the steam in the next firing.
Tight valve stems, and unions would be a must.--NBC

Pumpguy

Sounds like an interesting concept. As NBC says, there would need to be no air leaks in the system.

The vacuum chamber would need to cool the steam quickly to get the needed condensation to provide the induced vacuum. Also would need a way to drain the condensate after the steam condensed.

Remember, all fluids flow from high pressure to low, so draining condensate from a vacuum chamber could be a problem.

SWEI

Combine that with gravity and you end up with something known as a Torricelli tower. Priming one typically requires a good vacuum pump, but I suspect you could "ladder up" with collapsing steam.

jumper

In my day Siemens sold a small close coupled LRVP with excellent performance. For a house though,the auxiliary water handling equipment is a bit much. Collapsing steam produces excellent vacuum but doesn't expel air any better than a steam vent or trap. That's why a venturii is simplest way to expel air. And the less air,the better steam heat works.One way to tighten a system is to smear vacuum grease around stems.

In olden days water was inexpensive. If the water is cold enough you can evacuate down to 28". Air powered vacuum jets can go down to 29". 28" leaves three times as much air in your system than 29".

ttekushan_3

Chamber that collapses steam. Sounds like a radiator to me!

vaporvac

@jumper , I need more info on the vacuum grease. Please.

nicholas bonham-carter

here is how the vacuum accumulator might work with a two-pipe vapor-vacuum system.
At rest on the first chilly day of heating season, the boiler and pipes are full of air. As the boiler fires, it will push the air out of an oversized header (vented with a Hoffman 76 vacuum vent).
Then as pressure continues, all the air in the supplies, and radiators will be replaced by steam. This leaves only the dry returns with air, as the radiator traps have closed.
At the end of the firing cycle, all the steam collapses, and the air in the returns will rush into the oversized header, through an equalizer pipe with a check valve.
On the subsequent firings, the air in the header is pushed out, leaving smaller and smaller amounts of air in the returns, as this goes on. As it may take several cycles to achieve a deep vacuum, leakage would have to be kept to a minimum.--NBC