Vacuum for one pipe Paul air line system

Pumpguy

I have been asked to provide a vacuum pump for a one pipe Paul air line system in a large residence. As part of renovations, which included a new boiler, the contractor scrapped the old vacuum pump and piped the air lines to atmosphere. This resulted in very poor and uneven steam distribution.

Fortunately, all the radiator Paul vent valves and air line piping is still there.

So the question is, how much vacuum should there be on the downstream side of the Paul valves? TLAOSH does not answer this question. I was thinking about running the vacuum pump start-stop, controlled by a vacuum switch, but not sure what the settings should be.

Any and all opinions on this matter will be greatly appreciated.

ChrisJ

In a perfect world this would be completely dictated by outdoor temperature, no?

But how cool can you run the boiler without risking problems?

Pumpguy

I suppose so, but in this case, to the best of my knowledge, there is no outdoor temp sensor. Also, I doubt there would have been one on Paul systems back in the day.

Pumpguy

Typical settings for low vacuum, 2 pipe vacuum return systems are off @ 8" Hg., and back on when vacuum bleeds down to 3" Hg. Am wondering if these settings are OK for Paul air line systems too?

ChrisJ

Pumpguy said:

I suppose so, but in this case, to the best of my knowledge, there is no outdoor temp sensor. Also, I doubt there would have been one on Paul systems back in the day.

I doubt there was a thermostat on it originally either, are you going to eliminate that too?

I believe @Steamhead is king when it comes to systems like this. Perhaps he can share some helpful info.

ChrisJ

By the way @Pumpguy please keep us updated with your progress.

I've been mulling the idea of converting my single pipe system into a Paul system for a while now.

Bio

Pumpguy said:

I have been asked to provide a vacuum pump for a one pipe Paul air line system in a large residence. As part of renovations, which included a new boiler, the contractor scrapped the old vacuum pump and piped the air lines to atmosphere. This resulted in very poor and uneven steam distribution.

Fortunately, all the radiator Paul vent valves and air line piping is still there.

So the question is, how much vacuum should there be on the downstream side of the Paul valves? TLAOSH does not answer this question. I was thinking about running the vacuum pump start-stop, controlled by a vacuum switch, but not sure what the settings should be.

Any and all opinions on this matter will be greatly appreciated.

Check out this thread:
http://forum.heatinghelp.com/discussion/155246/nextgen-vacuum-heating

http://www.airtechusa.com/products/hp120v.html

DanHolohan

And read this.

ChrisJ

DanHolohan said:

And read this.

I keep saying it but the wetheads keep sticking their noses up in the air..... Of course this has a pump, but we'll let that slide.

DanHolohan

LOL!

jumper

Don't know for certain but seems that the stronger the vacuum the better. Less air always improves circulation. Ideally there's be no air. Condensate should move by gravity not air somehow pushing it.

ChrisJ

jumper said:

Don't know for certain but seems that the stronger the vacuum the better. Less air always improves circulation. Ideally there's be no air. Condensate should move by gravity not air somehow pushing it.

That's why I want to build a silver soldered copper system and pull a deep vacuum on it and then fill it with a certain amount of water, or another liquid and then bring the pressure up with a gas like nitrogen or argon to get the proper boiling point.

That's my dream system if I'm ever in a position to actually build it. No vacuum pump, no vents.

jumper

No need to add gas to hermetic system.Problem is figuring out correct weight of water to add.Then your heating becomes like refrigeration using free cooling. That is your home is cooling your boiler.

ChrisJ said:

jumper said:

That's why I want to build a silver soldered copper system and pull a deep vacuum on it and then fill it with a certain amount of water, or another liquid and then bring the pressure up with a gas like nitrogen or argon to get the proper boiling point.

That's my dream system if I'm ever in a position to actually build it. No vacuum pump, no vents.

Pumpguy

Thanks for everybody's comments.

The system as a whole is not my design. Contractor tells me before renovations there was a vacuum pump that was sealed with city water, once through the vacuum pump and down the drain. This means almost certainly it was a liquid ring vacuum pump, and quite likely a Nash. I have been asked to furnish a replacement, since it's not there now, but appears to be needed.

This system is now fitted with pumped condensate return to the boiler. Not my idea, and not my place to comment to those that asked me for a vacuum pump on weather this should, or should not be there now. (I have seen reference drawings of Paul systems showing both pumped and gravity condensate return to the boiler.) It does provide an ideal source of seal water for the vacuum pump, which can be recirculated back to the condensate pump's receiver. This will eliminate the need to use once through city water.

I was also told this system has been fitted with a new boiler. I assume by the same contractor that removed the old vacuum pump. I know that has the possibility to open a whole new can of worms, but boilers are not my area of expertise, so will defer to others to deal with any problems with wrong near boiler, or system piping.

To apply maximum available vacuum on the air lines would mean the pump would have to run continuous, which is not practical. To apply less than maximum achievable vacuum, some sort of switch or controller would be needed to stop and start the vacuum at predetermined settings.

So, does anybody know, or can venture an opinion, as to what settings the dead men used to control an electrically driven vacuum pump on a Paul one pipe air line vacuum system?

So far, I have not seen this particular bit of information included in the write-ups on Paul systems I have seen. I could always use the standard low vacuum 2 pipe settings of off at 8" Hg., and back on at 3" Hg., and try increasing these settings to see if we get better results. I would rather rely on experience or opinion of others that know more about these sort of things than I do.

SWEI

Pumpguy said:

To apply less than maximum achievable vacuum, some sort of switch or controller would be needed to stop and start the vacuum at predetermined settings.

I'm going to try and leave this thread on track, but I'd love a chance to work on some options for controlling this. PM me if you're interested in exploring further at some point.

Steamhead

Pumpguy, my only comment is that you have to start somewhere, so use the usual settings and see how that works. And let us know how you make out.

PMJ

DanHolohan said:

And read this.

Thanks for this Dan.

I've been saying for some time that even the small amount of natural vacuum between cycles does really nice things on an old leaky 2 pipe system. It is so easy - more folks should give it a try.

nicholas bonham-carter

Maybe the steam could be fed into the Paul system vacuum airlines with condensate draining out the former supply of the radiator.
The steam could move quickly with a vacuum.--NBC

jumper

nicholas bonham-carter said:

Maybe the steam could be fed into the Paul system vacuum airlines with condensate draining out the former supply of the radiator.
The steam could move quickly with a vacuum.--NBC

Turning one pipe into two pipe? I think it's a very good idea. Many buildings have been modernized with tighter windows and insulation. Load is much less so the control that two pipe provides will be very beneficial.

Pumpguy

Thanks for everybody's replies.

I was supposed to meet with contractor and homeowner today, but a family emergency came up, so had to put this off till next week.

Hopefully a game plan can be put together, and I'll add posts about how this all develops as time goes along.

Hope everybody has a wonderful Christmas!

Dave in QCA

Pumpguy, it sounds like there is a mechanical contractor involved that does not fully understand what he's doing. Oh Well!
One solution of course is to restore the Paul system and there are many advantages to having I working properly. I think your idea of starting with the vacuum levels that you use on typical two-pipe systems makes complete sense. However, going to a deeper vacuum will produce a better modulation in the temperature of the vacuum and that will produce very desirable results.

In answer to some other thoughts on vacuum level and temperature, it is worth noting that while the boiler operation will begin under a vacuum and steam will begin to flow at lower temperatures than a system operating at atmospheric pressure. Once the radiators are filled with steam and the vents close, the pressure of the boiler, mains, and radiators will begin to rise as more heat is added, and the pressure and temperature will rise as long as the boiler fires. When firing ceases, boiling will slow and nearly stop, but steam will continue to flow and the boiler will boil lightly as the radiators emit heat, condense steam, and draw a vacuum. Thus, the temperature of the vapor will be determined by the length of time that the boiler fires, which will be in relation to the heating load. No outdoor sensor required, really.

It is interesting that the contractor has discovered that the system is very unbalanced. This would be expected if they left the Paul vents in place, as their venting rate is quite high, and are a recipe for producing an unbalanced system, UNLESS running in a vacuum. Of course, the other possible solution is to simply replace the vents with a slower vent, like a Hoffman #40. But, the Paul operation would be much better in my opinion.

Pumpguy

The way I understand things, this is an old contractor, new contractor situation.

I will be letting the customer use a temporary loaner vacuum pump, which will just run continuous. I will explain that they can vary the vacuum by throttling an atmospheric air bleed valve.

I hope to provide a loaner vacuum switch too, if I can find an old one that still works. It will be up to the customer to wire in the switch if he wants to operate start - stop, and maybe try different settings. My loaner pump just has a 3 prong 115 v power cord and plug, along with a 20 amp DPDT toggle switch.

Currently, visit is set for Tuesday, 12/29.

Merry Christmas everybody!

Pumpguy

Visited the job site this morning to drop off loaner vacuum pump, and look over installation. I would have loved to see the old vacuum pump and how it was connected and operated, but it's gone now.

It's definitely a Paul system for most of the house. Each cast iron radiator has a little Paul valve and air line on the opposite side of the steam inlet valve. Steam inlet valves are now thermostatic type, and I was told they do not modulate. Just full open or full closed. I believe that's a good thing with a one pipe system, correct?

Found the air line that used to be connected to the old vacuum pump. Was told when boiler was operating @ higher pressure there was saturated air & vapor being discharged. There was nothing discharging during my visit.

The boiler is new, didn't record model. No obvious piping errors, all in steel & iron. Has 2 steam outlet pipes, full size, connecting to an even bigger header. Only thing not there was a dropped header.

Earlier I was told system had a condensate pump, but it is a 30 gallon boiler feed pump, running start - stop on water level demand of the boiler.

Even though the boiler was on, controlled with a vaporstat @ around 8 oz. pressure, all the radiators that I felt were stone cold.

This system also has some vent coils that are piped in 2 pipe fashion.

I did notice some air vents on the one pipe return lines which I thought strange for a Paul system, but then I wasn't there to find fault with the system, just to provide and tell how to install and operate the vacuum pump.

I expect the loaner vacuum pump will be installed and running within the next few days, so we'll see how the system performs after that.

In the meantime, if anyone has any comments about the details above, please chime in.

Gordo

@Pumpguy, what make and model# vacuum pump did you use?

Abracadabra

Gordo said:

@Pumpguy, what make and model# vacuum pump did you use?

I'd be interested in that info too

Pumpguy

Typically we use our version of the now obsolete Nash MVF 15 vacuum pump. These are a vertical 1 hp, 3450 RPM liquid ring type available with either a 115/230 volt single or 208-230/460 volt 3 phase motor and an EPR elastomer mechanical shaft seal. Air capacity is around 13 ACFM and are capable of going out to around 22" Hg. vacuum, depending on condensate temperature and system air leakage.

For the small size systems usually discussed here, this ACFM capacity is overkill, but it's currently the smallest I have available.

For large 2 pipe systems like schools and office buildings, we have used vacuum pumps as large as 15 hp, 200 ACFM.

The pump can be sealed with domestic cold water, once through and down the drain, or recirculated condensate. I prefer to use recirculated condensate to seal the vacuum pump to avoid wasting water, and more importantly, to avoid bringing the dissolved solids out of solution from the domestic water and clogging up the pump's interior and discharge passages.

Pumpguy

Thinking more about and trying to understand this system.

The thermostatic steam inlet valves on each radiator are a pneumatic operated type. I don't have any brand or model information at this time.

Obviously they would open when the thermostat is calling for heat, and close when the heat setting is satisfied.

My question is, with no operating air pressure present, would these valves be normally open, needing air to close, or normally closed, needing air to open?

Thanks.

Dave in QCA

Normally open. In pneumatic controls, lack of control air always fails to full heat.

Pumpguy

Thanks Dave,

Pumpguy

End user has been using 1 hp liquid ring loaner vacuum pump since 12/29/15. Pump operated start-stop, controlled by a Square D vacuum switch set to shut off @ 8" Hg. and back on @ 3" Hg. vacuum.

Pump was sealed with 1/2 GPM city water, once through and down the drain.

Only problem occurred when vacuum pump pulled vacuum clear back to the boiler. This vacuum pulled water out of the boiler feed tank and flooded the system up to the first floor.

A water zone valve was installed in the boiler feed line, normally closed except when boiler calls for water and energizes the boiler feed pump.

After installation of the zone valve, Installing contractor was pleased with these settings and overall system performance. He ordered for permanent installation a rebuilt vacuum pump and motor assembly, along with a new vacuum switch (same settings as loaner), accessories to allow vacuum pump to be sealed with recirculated condensate from 30 gallon boiler feed tank, and a new vacuum gauge.

Vacuum pump will discharge air and seal water back into 30 gallon boiler feed tank. This tank will function as a discharge separator. The seal water will fall back into the tank, while the air will be discharged to atmosphere through the boiler feed tank's air vent pipe.

Contractor said he would would provide performance feedback and possibly pictures after these components have been installed and put into operation.

Hopefully more to follow.............

jumper

Don't understand.Where did air get into boiler to push water all the way through radiators to pumps? Is there a vent somewhere? My reply to your original question about how much vacuum is optimal in Paul system, no such thing as too much vacuum.

Pumpguy

@jumper, system was filled with air prior to initial startup after loaner vacuum pump was installed.

Boiler feed tank is vented to atmosphere. As vacuum pump removed air and lowered system pressure, atmospheric pressure pushed feed water into boiler, flooding the system.

Zone valve now acts as a positive barrier, opening only when boiler is calling for water and boiler feed pump is activated.

@SWEI, I think your post is for another thread.

jumper

Do you think feed tank can stand negative pressure without buckling?

Pumpguy

@jumper, Possibly, but this being a one pipe Paul air line system, the usual MO is to only use vacuum pump to evacuate the radiators. Once steam hits the Paul air valves on the rads, they close, and only open when cool below steam temperature. Condensate drains back to boiler feed tank by gravity through F & T traps.

In this particular case, I believe, but haven't been told, that this vacuum pump install is on the contractor since they didn't know what the old vacuum pump was for, so they removed and discarded it. I am sure they don't want to incur any more expense than necessary to restore system to "as designed".

SWEI

Would this be possible to retrofit on a conventional one-pipe system with standard vents?

If I ran soft copper to every radiator and added a vacuum pump and controls, what might I get?

ChrisJ

@SWEI I was pondering thermostat / temp switch controlled 1/4" solenoids on the radiators connected to plastic tubing going to a vacuum source. Shut the solenoid when the steam hits the second to last section at the top.

Pumpguy

@SWEI, See page 251 of TLAOSH. There you will find Dan has suggested this very idea. You will then have converted the system to a Paul system. Page 250 suggests a payback of one heating season!

Paul radiator vents with threaded air outlet connections are still available. Now the difficult part is choosing and installing a vacuum pump. These days of course, we don't see steam engines operating, and there isn't enough steam available to make vacuum with a steam ejector. Water could be fed through a venturi eductor, but that's expensive and wasteful of water. So some sort of motor driven vacuum pump is needed.

Liquid ring type vacuum pumps are the type I'm most familiar with. Being a "wet" pump, some water and vapor carryover doesn't hurt them. These use water like a piston, to pump air. They require a flow of water into them, and discharge water and air to atmosphere. Setting up an arrangement where the water can be recirculated through the vacuum pump, while at the same time air is drawn off the rads and discharges to atmosphere is the tricky part. In this particular example, the 30 gallon boiler feed tank served the purpose quite nicely.

jumper

Liquid ring pumps ideally have some sort of water recirculation so they're too complicated for non-industrial uses. Unless there's a vent or a significant leak somewhere allowing air back in, you don't need an efficient vacuum generator. That's why I suggest a compressed air power ejector. It's inexpensive and rugged in case it sucks liquid.

Supposedly one pipe radiator vents let air back in to expel condensate. But if air is mostly expelled from system the condensate should drain by gravity. You shouldn't even need Paul vents if whole system contains only water and water vapor.

Pumpguy

@jumper, Typically, liquid ring vacuum pumps are sealed with water, once through and down the drain. This arrangement was used for the trial. A water recirculation feature on a liquid ring vacuum pump is always an accessory. There are a number of arrangements that can be used depending on the application. Requirements are a reliable water supply and a way, if necessary, to deal with temperature rise.

As far as efficiency goes, they are quite good. The pump I used for this example is 1 HP, with an air pumping capacity of around 14 ACFM. It operates start-stop, controlled by a vacuum switch. This allows for a short run time, and a long off time.

When using a venturi device to produce vacuum, you need to take into account the power needed to move the motive fluid through the nozzle.

On this particular system, condensate originally flowed back to the boiler through the same pipes that fed the steam. Only the installation of a new (and with less water holding capacity) boiler necessitated the need for the boiler feed pump.

Just curious, what size air compressor do you think would be would be needed to power the air ejector? And what would that air ejector's air removal capacity be in terms of ACFM?

ChrisJ

How much do these pumps go for?

I can't think of a single air compressor I'd want running in my house for my heat except perhaps a screw type and those run $3-6K so that'd never be practical.

Pumpguy

@Chrisj, Price depends on many factors. It's best if we discuss your particular system offline. It's against the rules to discuss prices here on the wall.