Burnham Bleeding

BurnhamBoilerUser

Hello , I have a Burnham Boiler that is 27 years old with 2 Taco zone valves with of course to separate thermostats and one circular pump which is on return side and air scoop with high vent on supply side. My issue is that I had to replace my circular pump before fall of this year and the pump i replaced was a single speed with no check valve (gundfos 25 years old ) with a new gundfos 3 speed with a check valve in it ( they don't sell the old style single speed anymore that i just replaced ) Ever since I replaced this pump I have been having issues getting all the air out of each zone I have bleed each zone with the by pass from the auto fill on to increase the pressure without popping the PRV .I would let each zone bleed into 5 gallon buckets to where I would get at least 6 buckets of water to dump before i would switch to the next zone and repeat the same process after I feel that i have all the air out of the zones I would reverse the process as shut the by pass off reclose zone vales and reset taco zone vales back to auto then fire it back on again and would hear air coming through the pump which i thought my air scoop would remove what was left but i guess not. I'm wondering is the way I'm trying to bleed this unit is incorrect or I'm just not bleed this thing right ? Or could it be the check valve should not be in ?

hot_rod

What type of heat emitters? Any large piping, over 1"? Purge valves in a proper location tom force air around them loop?

You need quite a bit of flow to push air around in radiators or large pipe.

Some installers will connect a garden hose to the system to get a good power purge.

Check to make sure the auto vent on the air purger is not stuck or plugged.
The old technology ramp air scoops can take days, weeks to get all the microbubbles out.

Elevate the boiler to 180-190 will also drive out additional air.

Ideally the circ would be downstream of the expansion tank to use the delta P to aid in air removal.

BurnhamBoilerUser

Thanks Hot _Rod
Photo shows the two ball valves , 1st one is supply with the high vent attached to the air scoop with expansion tank which I do know the tank should be a 30 instead of 15 ( 15 was originally installed when unit was put in 27 years ago and had no pressure issues until last year then I replaced with a new 15 ) 2nd ball valve is the return This would be the valve that I close to bleed and leave the 1st ball valve open then I would hook a hose up to the return drain for zones as in picture 2 /5 then manually open the zone that the hose is draining from of the taco zone valve and run the auto fill by pass for force feed water making sure pressure doesn't exceed 25 then run until i see a steady stream of water and switch to next zone and repeat .I have baseboard heat closed loop with no bleeders at the baseboards ( copper pipe slant fin baseboards ) single story home. Expansion tank with bladder was replaced last year before winter started with no bleeding needed but pump replaced this fall but needing bleeding which didn't surprise me that it needed bleed, that's when the air issues started.

hot_rod

sounds like it still has some air moving around

That Honeywell air vent has a shutoff function.The black upper portion rotates from an off to open position , make sure it didn’t get turned off
Also the small 1/8” connections can plug with sludge. The vent should be removed, cleaned, and checked for float operation.

If you turn it off, you can remove the very top and see if it is working inside

If you are a risk taker, you could remove and replace the vent without another drain down.

try a service on the one you have😉

BurnhamBoilerUser

Thanks again Hot_Rod .The air vent is open but I will try what you suggested on cleaning it out .Other question is since the boiler is been running due to season and I feel that maybe I need to bleed more air out of this boiler ,do you have a recommended temperature that the boiler should be around before I start doing this or not ? Don't want to introduce cold water into this boiler if temperature is to high but not sure what would be in reason either .

BurnhamBoilerUser

Ok Hot_Rod again thanks for the tip. I just checked and clean the high vent but really didn't see anything out of the ordinary inside besides the float looking a little dirty. So i did a clean the unit down re assembled and returned it back to the open section for flow but I'm not hearing any air coming out of this high vent but still do hear the gurgling sound when the pump kicks in and starts feeding the zones Any other suggestions you might have that I could give a try ?

SuperTech

I've heard of a trick in a book I read once but I've never tried it myself. I read that if you add a little Dawn dishwashing detergent to the boiler it helps reduce the friction or something like that. 

Sometimes the location of the air scoop and automatic air vent is the problem. It's best to have 12-18" of straight pipe before the scoop for laminar flow. A scoop right by an elbow and too large a circulator can cause turbulent flow and work against the efficacy of the scoop and vent. 

BurnhamBoilerUser

Thanks Super-Tech but I never heard of the Dawn Dishwashing soap .As you can see I did post a pic of the pump and return / supply lines now I wondering about the pump I just put in in October now since it is a 3 speed but on the lowest speed that available for it .

hot_rod

You have done all the best things to get the air out. What is the fill pressure? Sometimes bumping it up 5 psi will help get air moving along better.

Those ramp scoops are just not great at getting the small microbubbles out. Even with the upstream piping you have.

Usually slow speed gives the scoop a better shot, may as well try bumping it up a speed, that is how the new electronic pumps do the "self purge" they just speed up for a few seconds. That works if the air is in the pump, once it is moving through the system you just need a good working air separator.

It may just take time, days, weeks.

There is a fine line with adding dishwashing soap. A small amount may work, too much actually forms more bubbles

BurnhamBoilerUser

Hot_Rod the fill pressure on is about 14/15 psi when heated it will go to 18/19 psi .So you don't recommend rebleeding the zones again or do you feel that I would reintroduce more air into the system ? I really appreciate your info and help on this matter. I also wondering what is a good temperature for the boiler to be at if it would help to be at if I was to re bleed the zones ?

SuperTech

If all of your zones are circulating I would avoid trying to purge it again. You will just end up introducing more air. Turn the high limit up to 190-200⁰ temporarily and let it run. If the air vent is functional you should be able to get the air out eventually.  I always install a new air vent on the boiler whenever I drain it for repair or service.  They don't last long and a new one is cheap enough. 

Any boiler that has continued air noise that I have encountered has always been able to be fixed by installing a microbubble resorber air eliminator in place of the old fashioned air scoop.