purging air recycling existing water...

aperson

Has anyone heard of purging air from heating pipes by hooking up a pump or circulator with a hose and moving the existing water in the system in and out of a bucket of water, basically not purging with fresh water but running the old water through at a faster rate and into and out of a bucket? Thank you.

JDHW

I have heard of this method for purging the ground loops for a ground sourced heat pump. Needs a big powerful pump. Have a look at:

https://www.kensaheatpumps.com/filling-purging-a-kensa-ground-source-heat-pump/

BW John

HVACNUT

Yeah its called a pump purge. 3 hoses. Its typically used when adding antifreeze. 

aperson

How about using this method instead of a regular purge. What is the difference in effectiveness. And why 3 hoses? Thank you.

HVACNUT

You could do it for a regular purge. The benefit is visual. You'll see the air. But it's not necessary if it's done right and the air eliminator and PRV are doing their jobs. 
Fill a 5 gallon bucket half way.
One hose from the bucket and into the pump.
One hose out of the pump and into the boiler. 
One hose out of a purge valve and into the bucket.

SuperTech

I use the method described by @HVACNUT quite frequently because I work on a lot of homes that have hydro air units in the attic. Unfortunately glycol antifreeze is a necessity with these setups. 

I use a 18 volt Milwaukee transfer pump for this. I love that pump. I haven't used it on any boilers that dont have antifreeze in place of a standard purge.

 If the boiler is piped  correctly and the circulator is pumping away from the expansion tank and air eliminator very little fresh water needs to be added when the system is opened for servicing.  

aperson

I have never had problems with air in my system before. My tale of woe is I had someone come to purge air because there was hammering from basement pipes only. This person purged all 3 floors using well water, which I have not had problems with. They also cleaned the screen on the backflow preventer and half way through realized it was dripping from the seal so torqed it real hard. They also raised the cold psi from 12 to 20. When he left the backflow preventer was dripping from the gasket and out of the pipe, the thing leaked and dripped 2 quarts overnight. The guy came back the next day and replaced the backflow preventer but did not purge the system. I noticed the next day it was noisy as hell. I had another guy come and he did a "pump purge" recycling the same water in and out of a bucket. It took about an hour. To me this seems rediculous. Anyway his pump purge just seemed to spread the air bubbles around. I am asking if a lot of air is introduced into a system that has not had much trouble before, and you want it the hell out, would you do a pump purge or a a standard purge and why? Thank you.

neilc

either, done correctly, should work.
or,
there's no reason a proper pump purge should not do the trick,
maybe you need a better service vendor

aperson

Yes I am a single woman in a small town. It used to be I was so afraid of that mythical beast of fire and water and gas and electricity in my basement but I am starting to fear the HVAC repair men more. I am trying to decide if I should have this very young HVAC man do the purge or should I do it myself. I am making friends with the beast. How long does a good new water no pump purge take with 3 floors? Thank you.

neilc

if once you're set up each zone took 5 minutes , , ,
setting up and cleaning up would take more time,
that and being familiarized with the dragons downstairs,

is the very young guy cute ?

have you looked here for the better vendor?
https://heatinghelp.com/find-a-contractor/

aperson

What if the bubbles are stubborn. It's not like all the old water comes shooting out, it mixes and the longer you purge the more fresh water takes over. I just don't want the bubbles bubbling into the fresh water because they can't keep up with the flow. That would be the benefit of doing it myself because I know those bubbles are in there maybe even hiding and I would purge until they come out. HVAC guy comes on a tight schedule and thinks I'm probabley nuts anyway so the bubbles use that to their advantage. Yes he is nice looking and seems like a good kid. Thank you.

Alan Welch

There may be bleeders on your heat.  Is it baseboard or cast iron radiators?   If it is a monoflow system you can purge all day and not get all the air out. Pictures of the heat and boiler piping would help.

neilc

maybe post a picture of your typical rad, and any vent it has,
and another of the boiler, floor to ceiling, showing the circ, tank, and where the purgeing is being done,
and any vents down there also

aperson

Trying to add photos

aperson

Trying to add photos.

aperson

Photos?

aperson

?

aperson

There's my baby!

aperson

When I did try to bleed the radiator it seemed like a vicious mix of air water and antifreze came out. There should not be much antifreeze in there but when I purge I want it all out.

JDHW

I don't see a pump in any of you pictures - It may be on the right hand side of the boiler low down. Can you grab a picture of that area? On the dial on the front of the boiler what is the pressure reading?

aperson

The pump is on the opposite side of the boliler from the expansion tank and low down. Just imagine a nice quiet little pump. I believe it is on the return side pumping the opposite of away. So would you say it is pumping here. I'm going to order a copy of Pumping Away, I read some from a library copy I had special ordered from a tech library on the east coast. It is a book I need to read and set down and read again but I love figuring out how stuff works. Anyway thank you for your comment. The psi guage reads 20 but is off by five high so the actual cold (static) psi should be about 15. At this point I have decided to purge it myself. The young HVAC man never called back. And so for the best because I am going to do a great job. I am going to buy a psi guage to double check the actual psi. Where to get the best reading from the guage is a question because the service valve is on the return side which will have a lower psi than the supply side or is this only true when the circulator is running. And the supply and return psi both are equal when the boiler is off. This is what makes sence to me. I need a washing machine hose, and I need to find out how to set the pressure regulator. It is supposed to be preset at 12psi or 15psi. Any tips on how to purge will be appreciated. I have a pretty basic idea and have identified the supply and return valves and the order. I will start with the top floor. The instructions I am going off do not (isolate) the boiler, if that is the right word, so I will be being very watchfull of the psi. I would like to "isolate" the boiler but am not sure how. Thank you,

JDHW

I think you are on the right track with the book order. Dan Holohan did a blog on this (https://heatinghelp.com/systems-help-center/pumping-away-piping-webinar/). There is a discussion thread on here where one of the experienced guys was talking about venting air out of a system with multiple floors and the top floor vents were actually pulling air in rather than venting it out! The root cause was the pump location (the same as yours) and it had been like this for years.

I am based in the UK so some there are some bits of your installation that look a bit strange to me so better hope someone else will comment in detail on your setup. Your pump is not in the best location on the system and this could mean that air is continuously being pulled in through radiator valves/vents or other fittings. If this is the case no amount of purging the system will ever get the air out because it is continuously entering the system. Fresh water from the purge will contain air that will come out when it heats up. When the system is properly setup and running you should just need to fill it up and then go round the radiator vents once it is hot and that is it.

You have the right bits on you system to make it work properly they are just not in the right order! Looking where the feed water from the mains enters the system you will have to perform a lot gymnastics with valves you have to purge the system. Your question regarding the boiler pressure gauge changing when the pump is on is correct given the location of the cold feed into the system.

When the system is not running the pressure in all the pipes around the boiler will all be the same and indicated on the pressure gauge, this is known as the static fill pressure and since your boilers is in the basement this will be the highest pressure in the system. If you were to move up the house and measure the pressure in each radiator it would be lower as you go higher up - 30 feet of height is about 15 psi. So you need enough pressure when the system is filled to ensure that the pressure in all the radiators is above zero (above atmospheric pressure really).

The expansion tank on your system (grey cylinder just above the boiler) is the pressure reference point for the system and is connected to output of the pump (through the boiler). When the pump runs is will generate a pressure difference of up to 10 psi (depends on the model, flow rates and the resistance of your pipework). In unscientific terms your pump is trying to "suck" the water through the radiators rather than "blowing" into them. This means that the pressure in parts of your system, in the upper rooms, could drop below atmospheric pressure - bringing air into the system!

Hope that helps a bit.

aperson

I think a lot of people on this site try to complicate rather than simplify. This is a boiler that has performed beautifully for 30 years. So let's do everyone a favor and rule out what works.

hot_rod

The system has an auto air purger, check to see if the silver float vent is working, remove the plastic cap and see if you can push down the center stem. Air should come out. That small round vent can become plugged and not allow the system to take air out as it circulates.

If water, and air is moving through the pipes that vent should remove it within hours or a day. Open all zones of course.

neilc

3 floors, you might need more pressure than the 12-15, more like 20, especailly sinse the circ is before the expansion tank.

You don't see any of the auto air vents, like the one over your expansion tank, upstairs on rads, do you?
(especailly all the way up on the 3rd floor, where the air goes?)

turn the boiler and the circ off,
then try bleeding air where you show that open vent spraying,
and all the way up on the 3rd floor,
On the 3rd floor, you're still getting water out, after any air, correct?
Trying to establish you have enough static pressure (20 ?) to keep water up to the 3rd floor.

aperson

Thank you. I will check the air vent but it was just replaced and checked by a tech. It let out a hiss. The top floor is small like an attic and has the least amount of pipe noise and plenty of heat.There are no auto vents on any rads. When I bleed them water runs out. Except for the trouble spots where it is like an air pocket excerts pressure and it hisses and shoots out a mixture. I took videos of this where you can hear it. The mixture is of water antifreeze and air. The auto vent is on top of an air purger ontop of the expansion tank. The auto vent was replaced because it spewed out old antifreeze. The old, congealed antifreeze might have clogged the airpurger. But the auto vent did make a hiss when the tech checked it. The whole system was purged since the auto vent spewed antifreeze. But there is still antifreeze in there because I can smell it when I bleed the rads. But it does seem to be oddly concentrated with the air. I think this because of the smell. Anyway I am going to purge this thing Saturday to get out air and remaining antifreeze.Can someone please tell me the best way to do this. I have a good idea but I would feel more confident having feedback. Thank you.

neilc

there are purging threads here to search,
or thru youtube,

that auto vent on the air scoop at the boiler, that cap should be left loose, so air can vent out,
it might spit a little, but shouldn't be a floor wetting flood event,
if after a day or 2, and with a quieted system, the cap could get turned back down if three is leakage, but mostly they're left loose.

and I would try bleeding at the rads with the circulator(s) off,
bump the circ back on for a minute or two, then back off, and bleed at the rads again,
do this a couple / few times

aperson

Thank you. But what I am really worried about is the psi when purging. What is that large valve on the right when facing the boiler. It is on the opposite side of the boiler from the expansion tank. Should I have this valve open or closed when I purge the lines. I mean it is open now. But should I turn it off to purge. Does it somehow isolate the boiler what ever that means. 

neilc

the large green and red handles stay open,
manipulate the zones with the smaller red handles,
or you lock the zone actuator(s) open instead of disturbing the manual valves above,
you do have to manipulate the red handles under the purge valves also as you do each zone,
all closed except for the zone you're purging,
don't forget to release them,
the psi you want to keep below 25, so you don't get to 30 and a safety relief valve discharge,

aperson

Thank you. How are the tech guys using a pump to (power purge?)without  setting off the relief valve.

aperson

What do you mean "or". I planned on leaving the large red and green handles open AND moving the zone valve for the zone I am purging to manule which is open. Hellllloooo?!

neilc

aperson said:

What do you mean "or". I planned on leaving the large red and green handles open AND moving the zone valve for the zone I am purging to manule which is open. Hellllloooo?!

I think we're saying the same thing,

yes, leave the large red and green open,

"or" means you can use the red handles over the zone valves, "or" the the manuals on the zones, which you would need to open anyways , , ,

you got this, check back when you're done

neilc

aperson said:

Thank you. How are the tech guys using a pump to (power purge?)without  setting off the relief valve.

pump probably won't make 30,
and wouldn't be running against closed valves anyways,
you rig the hoses in the bucket of water, and then pump thru open valves,
circulate until bubbles cease in bucket,
shut off pump and close valves, done

aperson

This is an old fast fill, how do it work?

neilc

well? , , ,
did you swing that lever to its right, as the arrow shows?
and or tap on its bottom, sharply, but gently?

didn't the other techs use the fast fill ?

if the circ is off, do you have water pressure at the 3rd floor ?

aperson

Oh, I had a sweet time. What arrow? And this fast fill must be an old jallapy(spelling for sure wrong.)But, yeh, push the lever one way and more water rushes in. I had a friend keep an eye on the psi and work the fast fill while I took a video of all the bubbles and worked the open service valve. The main floor was by far the worst. We must have run fresh water through at 10psi for 2 hours.   Bubbles just kept pouring out, medium, and little and tiny, just spraying out under water. They even rose to the surface and danced and jumped over the water. Crazy! It got to the point we couldn't believe it and we shut it down and checked the water source by turning on a faucet with a short hose. The faucet just runs well water and we put that hose into a bucket under water and no bubbles so we kept purging. The first thing that threw me, after the fast fill, was the zone valves, I would move their levers to manule and they would, on their own, move back to auto! I figured it out. What a trip, by my third zone, I was timing the close, of the open return valve and the fast fill perfectly. YES!

neilc

aperson said:

What arrow?

the 3rd "L" in "fast fill" stamped on that lever, in that last picture, but you swung the lever , , , so good.

aperson said:

We must have run fresh water through at 10psi for 2 hours.   Bubbles just kept pouring out, medium, and little and tiny, just spraying out under water.

no, I said 25 ish psi, you want a higher pressure when purging to force air up high, back down to your hose.
At 10 psi, water may have been slipping under air pockets.
and,
you're only purging one zone at a time, the others are shut off so a solid water flow completes thru each of the purging zones.

aperson said:

The first thing that threw me, after the fast fill, was the zone valves, I would move their levers to manule and they would, on their own, move back to auto! I figured it out. What a trip, by my third zone, I was timing the close, of the open return valve and the fast fill perfectly.

those manual levers should have a little locking notch in the end plate, you swing the manual lever, and lift it and let it settle into that notch.

And I may have mislead you, I thought searching for purge would have been better than what I write here.
Latch all the zone valves open,
then shut/isolate all 3 zone with the red handles under the purge drain bibs,
as you purge thru each zone, cycle the valve under the purge hose open and shut a time or 2 to burp any air below the isolation also,
then shut / isolate the zone you're on, and move over to the next.
There's no way this should take hours unless the house is 1000 ft tall, or 10,000 sq ft, , , , even then , , ,

aperson

It took 4 hours for all 4 zones. I did get the psi up to 15 after we got more comfortable. Bubbles poured out of the main floor zone so we were just patient. The basement might have benefited from a higher psi. Then the 4th zone, which is the water heater was loaded with bubbles and it burpped out a lot of air. I'm going to upload pictures, not sure if I can upload a video. Definitely got out all the antifreeze.

aperson

Now... I see the arrow but it still doesn't explain a thing, it's like an arrow pointing down a dead end street.