I have looked all over the place and found very little specific information on bleeding air from a hot water baseboard system. Just a generic instruction to “bleed the system”
I recently did work on my system and afterward bleed the system (the best I know how) and I am getting heat out of all radiators, the outgoing pipes and most importantly, the return pipes all seem hot. The problem is that the system appears to be noisier than it was. I know some groans and creeks are par for the course but this seems like I still have air in the lines. I bleed the system by going to each bleed valve opening it until the air spits out and I get a steady stream of water (a total of about 30 seconds); I started at the top and worked my way down. I have done this 2 or 3 times. I got some air at the very top, none at the lower levels, but still the noise.
Am I bleeding the system correctly? Should I bleed each location longer each time or more often?
Any other suggestion?
I waited until mid day when there was no call for heat and the circulation pumps were not running to bleed the system.
Replies
Start with the highest radiator and work your way down,
Crack the bleeder open and wiat for a steady stream of water, Close, and move on
When the system has been freshly filled, it is entirely possible a few repeats might be needed as air comes out of solution.
What made the teaching of Jesus different and apparently so hard to accept then as now, was that it required a critical reassessment of the structures and values and attitudes of human society as his listeners and followers shared in it.
- Monika K. Hellwig
from Jesus: The Compassion of God (The Liturgical Press, 1983)
Does your system have an air scoop or air separator? Properly installed, this would be between the boiler and the suction of the main circulating pump.
What "work" did you do?
When the system is being filled originally or after any draining high points are vented, top down. If the system is closed, not leaking, and not setup or installed incorrectly, this is all that is required. Another thing to note is that as the water is heated, it will release dissolved gases that cooler water will hold. Run the system until its good and hot, shut it down and vent it afetr a few minutes, but while its still at operating temp.
I extended one of the heating zones into a formally unheated garage (now living space), on the other other zone replaced some badly corroded bleed valves and a badly damaged baseboard (tubing and fins).I don't touch the heating plant itself (I leave that to Keyspan) since I don't know enough about it except the very, very, very basics. I am learning though, each time the Keyspan people come in for their annual check, I quiz them as much as they will stand for, they are pretty patient too. I can now identify what the circulator is and that I have ones that "suck" rather than push (they are on the return side). It is amazing though that there is so much reading material out there on electrical, plumbing and the like and so little out there on helping one understanding the heating system. I do not see anything that resembles either an air scoop or an air separator. The pumps are on the return side, there is nothing between them and the baseboards and on the outgoing side just a flo-check valve (and a branch prior to the flo check for an expansion tank)The pipes at the boiler are hot (outgoing and return), the heat at the new base boards are very good, it is just that the system in general seems nosier than before (my father noted that too), not just at the new additions. I will bleed the system as you suggested, hopefully that will work. Thanks.
Waited until the system was hot, bleed each baseboard (a few times). Got some air at one or two baseboards. The system has quieted down a bit, except I am still hearing an occasional "popping" sound (for lack of a better word) when the circulator starts up in on of the pipes only in the basement about 10 -15 feet away from the boiler on the outbound pipes. So I'm thinking I still have air in there.
Edited 2/7/2007 9:57 pm ET by bobo66
If a vent is on the downslope end of a run that is not level, you may not be able to get out the air trapped in an upslope pocket. As long as the air pocket is small enough, water will flow and you'll get hot water at the return to the pump. What I have done on occassion, to flush out bulk air in a real hurry, is to attach an old washer hose to the drain valve on the return just upstream of the pump, turn off the valve inline between the drain and boiler, and open the drain. I usually open the bypass around the water makeup valve to help maintain system pressure while doing this (and the pumps are turned off). The rapid rush of water through that loop sweeps out the air quickly. With the end of the hose in a bucket, I can monitor the outflow for bubbles. It doesn't take long, and it is a lot easier than fiddling with the vents in awkward places. If your system of return lines and pumps is plumbed this way, you can try it.
It does seem odd not to have an air scoop in the system. Mine, going back into the 50s, is on the supply side coming out of the boiler, right above the boiler. The takeoff for the expansion tank comes from the top. Makeup water will contain more dissolved air than the heated water can hold, so formation of some bubbles initially can occur, thus the need for an air scoop.
You may have some trapped air as others have pointed out. However, you also may have disturbed the copper tubing just enough when you did your new work that some tube sections are either touching each other or are hitting studding, etc.
When the hot water - usually 160 min - starts flowing through the copper, there is some expansion of the tubing. And if the clearances for the copper tubing are tight, then you could be getting noise from the tubing itself. I've spent most of the winter "adjusting" my copper lines in 4 zones because some runs were moved slightly to accomodate a high volume ac system. It's amazing how much noise copper tubing can make when it is subjected to a close clearance from an adjacent tube or house structure.
Thanks guys,
I will try that with the bucket.
As far as the noise from the expansion the pipes, I found out quickly exactly what you mean.
The extended portion of the first zone extended through an old wall and then partially through a new one. As neither of these wall were support walls I was able to make ample sized holes through each stud, even with that, there was still rubbing a spots and lots of noise. I had left the wall board off to make sure there were no leaks, so I was able (with the blessing of the inspector) to gingerly enlarge those holes to end those noises.