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purging a system

dpframing
dpframing Member Posts: 25
2 serious questions from an amateur. I have a slant fin hot water system with no bleed valves at the baseboard heaters. I have tried to bleed the system at the boiler by letting the water runs for 5 minutes with the fast feed valve open, but I cannot get all the air out. And there is no air escape valve on the boiler.  When the boiler fires at night, I get 10-15 seconds of serious bubbling and gurgling sounds before it quiets down. Is this air in the system bad for the circulator pump?  AND if I purge the system totally, is there any trick to fill it back up?  Thanks

Comments

  • hot_rod
    hot_rod Member Posts: 15,004
    best to get all air outside

    the pipe. Does the system have any type of air eliminator near the boiler piping? It may be a large cast iron scoop type with a round float vent with a tire type stem on top. If you have an vent like this it may be plugged and need replacing.



    It's tough to get all the air out by power purging. As you heat that cold water additional; small bubbles and entrained air will be released. You really need some type of auto vent to keep removing the air as the system operates.



    Yes, the air will hamper heat transfer in the boiler and fin tube. it caused noise, as you know, and can cause internal erosion.



    If the air is making it's way back to the boiler that is good, so a working air eliminator will be able to eliminate it.



    I like the micro bubble eliminators. The work quickly and remove the smallest of bubbles that the old scoop type allow to pass through.



    Here is a link to Journal that show the how and whys of air and dirt elimination.



    www.caleffi.us/en_US/caleffi/Details/Magazines/pdf/idronics_2_usa.pdf





    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,292
    If you could....

    take a few pics of your near boiler piping, we can help you purge your system of air.  Judging by your questions, and with all due respect, it seems like you have no idea how your system works, or should work.  There should be a vent somewhere, and an air scoop of some kind, hopefully some boiler drains.  When done properly you should never hear any gurgling noises.  Yes it could be bad for your circulator.

    I hope you have someone, at the very least, who comes out and does an annual service to your system.  They should come out and walk you through your system, all it's components, and show you how to purge all the air.
    steve
  • dpframing
    dpframing Member Posts: 25
    Thanks

    Thanks for the quick replies. I don't have any air elimination system on my boiler. The only Schrader valve I see is on the top of the expansion tank. That's the problem. And all this air noise is driving me crazy.  
  • dpframing
    dpframing Member Posts: 25
    Air

    Also, I was looking for a Spirovent or something, but none are installed. Is this what you call a "microbubble" air eliminator, which would function as the system worked?
  • dpframing
    dpframing Member Posts: 25
    photos

    Here's a picture of my system
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,292
    Yes

    Spiro vent makes a micro bubble eliminator.

    Hate to be a pain, but could you back up a few feet and take a pic.  Want to see whats up higher, piping etc?  Maybe we can help you further.  But in all honesty, it appears youre going to have to find someone who really knows about hydronics to do a little repiping for you.
    steve
  • Slimpickins
    Slimpickins Member Posts: 323
    edited December 2011
    draft hood???

    While looking at the pics I noticed the condensation above the auto vent damper and something else didn't seem right. I think you're missing the draft hood. Usually if a boiler has an integral draft diverter build in to the boiler, it in the back so it can draw air. Hopefully you have a CO detector because this could be a dangerous situation. If you have the installation manual you can look and see if it requires a draft hood. If you don't have the manual you could post the model, model and serial number and someone could look it up for you. If indeed the draft hood is missing, you need to take quick action and get it resolved. From not being able to see the whole boiler in the pic, I may be missing something like a barometric damper control or power venter.
  • icesailor
    icesailor Member Posts: 7,265
    Purging Your System:

    I doubt seriously that you have been purging your system properly.

    First, there's no fast fill by-pass on that Taco pressure reducing valve. And the system pressure is probably set too low. It needs to be 15# to 18# if you have a second floor. and are having a problem.

    You are probably putting the hose on the bottom of the boiler and purging through the boiler and by-passing the system. If you are not, and using the drain above the circulator on the return, the ball valve below the drain needs to be closed so that you force the water being drained, and replaced by the fill valve, to run through the radiation and purge the system. I doubt that the valve will fill fast enough to give you a good purge. If the fill/PRV valve was fed into the bottom of the boiler, it would be purging hot water. When the water comes back from the system, and gets hot, you know you have come around and probably purged it. The way it is now, you will only get cold water back from the system.

    If you do not have enough pressure in the system, all the air vents in the world will not vent your system. In fact, they will let air in when you open them. And any air that is dissolved in the water will come out of suspension when it meets the vacuum of the top of the system.

    If you can figure this out, take a double hose connection/washing machine connection and connect it to the bottom drain on the boiler. Connect the other end to a cold water drain that has street pressure. Take another short hose and a 5 gallon bucket. Open the by-pass feed to the boiler watching that you do not over pressurize the system. Don't let it go over 25+#. Make sure that the yellow handled by-pass ball valve is closed. Open the drain and let the water flow into the bucket. Make sure that the end of the hose is in the bottom of the bucket. Within 30 seconds, you should hear an eruption in the pipes and the hose will dance. Hold your hand around the return pipe. After the bubbles come, the pipe will start to get hot. When all is quiet and the pipe is getting really hot, shut off the by-pass hose to the bottom of the boiler and the by-pass/purge hose. Shut off the drain/purge hose and open the by-pass ball valve. If the circulator is running, the pipe will get hotter and hotter. Leave the system at 18#-20#. It should be working.

    Replace the fill valve. If you try to adjust it, it will start leaking bye and will over pressurize the system.

    Drop the system pressure to zero and check the expansion/Extrol tank pressure. It should be at least 12#.

    I have never been able to purge a two story system with 12# pressure alone.

    I haven't opened a vent on a baseboard in so long, I can't remotely remember when it was.
  • dpframing
    dpframing Member Posts: 25
    Thanks ICE

    You're right. I purge the system not fron the boiler at the bottom but at the top. I shut the ball valve and open the spigot hose valve and let it flow WITH the fast fill valve lever open  at maximum flow to create pressure. BUT as you said, I only get cold water, so I'm not flushing the hot water from the boiler. Your instructions are thorough but past what I can do. I give up and  I have called in the pros who swear that replacing the fill valve will stop my pressure relief valve from drip leaking.  I hope they can remove the air as you said by the time they are finished. Here in Brooklyn the set price for that job is $350. You might think I lived in Alaska and the plumber had to be flown in - it is so expensive for a 2 hour job.

    Also I am thinking of getting the right model Spirovent air eliminator off of eBay and installing that after the season too even though I don't know how much that would cost for the install.  
  • JK_3
    JK_3 Member Posts: 240
    The "pros"

    The quote that you got was it from them coming and checking the system or was it over the phone. Most diagnostics can not be done over the phone. Just based on what I can see in the pictures I believe that you have several issues including no air elimination,not best pump location, inverted expansion tank and of course the safety issue of not seeing the draft hood. We don't discuss pricing on this site but I recommend that price not be the only concern. Knowing that the boiler is operating safely should be #1 priority, then comfort,efficiency and longevity should be considered in which ever order is important to you.
    Life is Good !! Enjoy it !!
  • dpframing
    dpframing Member Posts: 25
    Thanks JK

    The posters on this site are very professional. Thanks for your help. The corrosion someone noticed near the flue was old condensation that came down the duct because the draft was 95% clogged. Off of 4 fixtures too- 2 small biolers and 2 hot water heaters.  My co2 detector never went off though. This year I got the chimney guy over who took the duct out of the wall before it goes verticle and it was totally clogged with sand and bricks. I had no draw.  I need a stainless steel custom fitted 6 x9 oval sleeve liner to the tune of $2800 because the bricks inside my chimney are over 80 years old.

    The quote was over the phone from the supervisor who swore it was the fast feed valve that needed replacing, so much so that he said if it wasn't , he'd give me my $230 back. So they came over and replaced it. So far no drip from the pressure relief valve, and the pressure stays at 22 lbs. when the boiler is cranking at 170 degrees. So far so good. But the overnite test is the true test.  Thnaks again to everyone .
  • icesailor
    icesailor Member Posts: 7,265
    No flow:

    I don't see a fast fill feature on that Taco valve. Perhaps its that lever on the far side.

    Last February, did the heat work? Did it work the year before? If the answer to these two questions is "yes", and you purged it like you said you did, the circulator probably isn't working. Either the motor isn't drawing current (Amp Clamp, the rotor is jammed or the impeller is broken off.

    If the relief valve is dripping, is the pressure in the system going up before it drips? Check the pressure in the Extrol through the Schrader valve.

    I've NEVER purged a system like I suggested (and you said that you did it that way) that didn't start pumping unless the circulator was broken.
  • dpframing
    dpframing Member Posts: 25
    Hey Ice

    The system worked OK for 8 years but I had a tennant in the unit. This is the first season I lived there. The boiler was going on and off 10 times an hour when I got there and it was driving me crazy. So I raised the aquastat which was set at the lowest setting, 150 degrees.  This is the first year the aquastat was set at 190 degrees. The pressure on the boiler went up to 38 lbs. hot, and the relief valve did its job and dripped leaked. They came out yesterday and replaced the fill valve (which has an auto feed lever on it) and the pressure only maxxed out at 30 lbs at full heat. But this morning I checked the system ( it went down to 26 degrees last night) and I still had a half gallon of water in the bucket under the relief valve. I called the company, and the supervisor who GUARANTEED the work and  who said he'd give me my money back if the fill valve replacement didn't work, of course begged off. First he said he's have to send a guy for a FOURTH visit to adjust the set screw on the Taco fill valve. I said I lost confidence in his company and that the screw was factory set at 12 lbs, and that I didn't want it messed with since it was low already and it might allow air into the 2nd floor baseboards if it was set lower. Then he said he wanted one more chance to fix the problem and now he wants to replace the pressure relief valve ( a Conbraco 30 lb rated). I said he should replace the expansion tank at the same time too since these bozos didn't do a proper check on that part in four visits. They just pressed on the Schrader valve when the system was at full prressure and heard a little air come out and no water. If they purge the system to put the new relief valve in, I want them to check the bladder pressure in the tank then. If it's at zero, which I think will be the case, I am gonna insist they rreplace it ( a Watts ET-15). Very discouraging and time consuming. I'm sure you pros out there would have diagnosed the problem in one visit and charged me fairly. But not with these amateurs in Brooklyn. Keep you posted. 
  • dpframing
    dpframing Member Posts: 25
    Hey Ice

    Also, the circulator pump is fine , I think. I got alot of heat and even when the boiler goes off, I can still hear the pump circulating the still-hot water thru the system. So I think that it's ok.
  • icesailor
    icesailor Member Posts: 7,265
    System Pressure:

    The ONLY way to check the pre-charge pressure in an "Extrol" type tank is to drop the system pressure to zero and check the tank pressure with a gauge. If you check the tank with 25# PSI in the systrem, you would have 25# PSi pushinf on the bladder? Compressing the air in the tank? Someone (npot you) needs to read the instructions that came with the tank.

    If the tank is 10 years old, it may be shot. Amtrol "Extrols" seem to go for 15 years. The others seem to go anytime.

    If the pressure climbs rapidly when you start the burner, the tank isn't doing it job.

    I'd be embarrased if you called me back about something like this. If you put a hose on the boiler and put it into a 5 gallon bucket and you only get a small amount of water before the pressure goes to zero and stops, the extrol is shot. It needs air in the air chamber. But if the tank is over 10 years old, replace the tank. Ir's shot. The bladder is broken. Trust us, it's broken.
  • JK_3
    JK_3 Member Posts: 240
    edited December 2011
    Telephone diagnostics

    I am not sure what issue you are trying to address. The noise and gurgling, the dripping pressure relief valve or the whole system. I recommend that the first thing you do is get a copy of the installation manual and compare the pictures and drawings to what you have. The "pro" who guaranteed that a new pressure reducing valve was going to solve your problems (without testing) is either someone that really doesn't know or goes to the school of " if that's not the answer we can tell the customer that something else is also wrong and the charge will only be another $$$$". When a customer calls my company with a dripping pressure relief valve  I inform them that  we have to come and diagnose because it may be a defective pressure relief valve   or a defective pressure reducing valve or a defective expansion tank and that it may be that the  pressure reducing valve or the  expansion tank could have gone bad causing the pressure relief valve to over exercise and is now also opening below 30 psi. When given the fact that the is always air in the system it may be the piping drawing air into the system as the pump kicks on which could also over pressurize the system.
    Life is Good !! Enjoy it !!
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