Shared Knowledge

 

 

“Hydronic Heating System - Getting Air Out”

 

11 September 2005

Updated 17 March 2006

Updated 12 April 2007

 

 

 

Several years ago, we renovated our home and as a part of the renovation, had new baseboard radiators installed in every room although we kept the existing furnace and utility room associated plumbing.

 

As we moved into the house in the spring, I had no need to check out the heating system until fall and when I switched on the system for the very first time, I could hear heated water gurgling, moving, through the radiators on the second of our 3 floor house. Having lived in a home with hydronic heat before, I knew there was air in the line that had to be removed. So I began checking the baseboard radiators in every room of the second floor and found now air bleed valves on any baseboard unit!What? Why would a heating\air conditioning company do such a thing? Not told to? Cost another $100 for the whole house?

 

At first, I attempted to try to get air out of the system by flushing all existing water out and refilling it but that did not work.  Then I actually adjusted the street water inlet valve to increase the water pressure in the system from the recommended 11-PSI to 15-PSI and at first, I thought this had solved the problem, but within a day or 2, the water gurgle noise was back again.

 

Finally, frustrated with what was not right, I actually hired heating companies to come and inspect my system and while they were in my home, I asked them how to solve my problem. Unfortunately, I quickly found out that normal furnace maintenance personal know nothing about hydronic plumbing and so I was back to solving the problem myself.

 

So install air bleed values on all my existing baseboard radiators? Thought about it but what a hassle and did not want to hire someone to do it either and in the end, did not want to have to go around each floor of our home and bleed air valves over and over again. There must be a better solution, but what?

 

Using the Internet, I began a search of the problem and all related to hydronic. Somewhere, at sometime, I came across the details of a Taco brand, whole house air bleed valve, which when inserted in the line coming directly out of the furnace before any of the zone valves or expansion tank would bleed any and all air in the system. (In my case since I had a 1.25" line coming out of my furnace, I order the model VRTX 125 Taco Vortech Microbubble Air Eliminator, $219 valve directly from Taco). (Note that Taco makes these valves in sizes from 3\4" all the way up to 2")

 

In my case, I installed the valve myself as I only had to drain the system of water, cut the pipe coming out of the furnace, take a hunk out of it, which would allow the insertion of the Taco valve, and solder the valve in place.  If you are not comfortable installing the valve yourself, it should only take a plumber or heating\air conditioning specialist an hour to install the valve.

 

 

 

Once the valve was installed, with the valve controlling flow to the expansion tank closed and yes I have a valve which shuts off water to the expansion tank, I refilled my entire 3-zone system with water. I then waited an hour or so for as much water to get into all lines as possible. I then shut the furnace supply valves for 2 of the 3 zones, unhooked the pilot light igniter system, turned off the gas supply valve, set the thermostat to “heat” and then used the master switch on the furnace to turn it on. With the thermostat calling for heat, the circulating pump began to pump water throughout the first zone and almost immediately, I could hear air hissing out of the Taco air bleed valve! I let the circulator pump, pump water through zone 1 for 15 minutes or so and when I checked, I could still heat air hissing out of the Taco now and then, so I left the pump circulate for another 30 minutes or so.  Then when I checked and listened, I could not hear any more air being taken out of the water in zone one, so I shut down the system using the furnace master switch, closed the water feed valve to zone 1 and opened the water feed valve to zone 2. I then turned the furnace system back on and let the circulator pump move water through zone 2. Again, the Taco hissed air for at least 30 minutes.

 

With zones 1 and 2 bled of air, I closed the water feed valve to zone 2 (zone 1 already closed) and opened the water feed valve to zone 3 and again switched on the system and allowed the circulator pump to move water through the pipes of zone 3.

 

Now with all zones bled of air, I shut down the system using the master switch and open the feed valves of all zones and again turned on the system and let the circulator pump run for another half hour to get the very last bit of air out of the complete system.

 

I was now ready. I opened the valve allowing water to expand into the expansion tank, if necessary, turned off the system, reconnected the pilot light igniter system, turned back on the gas supply valve, and turned on the switch to the system and let the furnace begin to heat water and circulate it throughout the entire system. Believe it or not, even after all my zone bleeding, I could still hear air hissing out of the Taco valve!

 

Bottom line? I no longer have air in the lines of my 3-zone hydronic heating system. 

 

Update. It has now been almost 3 years since I installed the Taco valve and not a minutes trouble with it and no more air noise in any of my home 's heating zones. I think a Taco whole house air bleed valve or something like it just should be a mandatory install on any new hydronic heating installations.

 

Update 15 April 2007. I have gotten and continue to get many emails related to trapped air in a hydronic heating system and questions as to why the Taco valve works. If you think about it, radiator bleed valves are only good for air trapped at the valve itself as the bleed valve has no special ability to filter air out as water moves past it. However, the Taco whole house bleed valve does have the ability to trap and remove embedded air in water as it moves past the valve and water is always moving past the valve. All I can tell you is that it works and "no" I am not a salesman for Taco valves. I will say that although the valve could have taken out all the air eventually by just installing and turning on the heat, my method of pumping cold water around each zone, hastened air removal or so I think.