HVAC question
 

I have a customer with a large house. (One of many) The basement has 3000 S.F. of in floor heat and 5 air handlers for the main and upper floors. The problem started last Tuesday. When I arrived the system was full of air, the auto air vent had gone bad. The system has some glycol in it. I used the system pump to purge out the air in each loop. The next day I had to go back to replace other parts and again found it FULL of air. Replaced the parts and bled it again figuring I had missed a pocket of air. Got a call Friday and she has a bad smell in the house and no hot water. The system had not discharged any solution to cause the smell but you can see where the air vent had been putting out a LOT of air. The water looks brown and stinks. I figured that the system had a bacterial bloom so I flushed the entire system with fresh water. I plan on going back Monday and injecting an algaecide and letting that circulate for a day then flush and refill with the right mixture of glycol.
Have you ever seen this?
What did you do?
Is there a brand of glycol that isn't prone to this condition?

Have you pressure checked the system. We are talking Radiant in a concrete floor. If so is it a loop or manifold layout?

Pressure is not a problem. It gained pressure with the feed turned off and I tested the indirect for a bad coil. The pressure is from air. When I originally got there the relief valve was stuck closed and the system pressure was at 40 PSI. I guess out in UTAH they have a real problem with this because the water has phosphates in it.

There are multiple manifolds. WIRSBO

The only thing that comes to mind if there is a partial blockage and the system cycles to flow and starts to siphon. Are there any air check valves that could be drawing air in reverse. As in a expansion tank or a air bleed at a line end or high spot loop?

Nope - very hard to draw in air at 40 PSI on a two story building. I talked to a friend that has heard of this before but never seen it himself. ( owns a large plumbing and hydronic company here ) And the air production almost stopped after I flushed the system. Before I flushed the system when I was purging the air with the auto air vent by circulating one loop at a time it acted like the air never ended. It acted like it was producing air almost as fast as I could vent it. ( it probably was )

I'd like to hear the results

I will let you know of the results.

What kind of piping was used on the job ?

What kind of expansion tank is being used ?

Not my field here but you mentioned she had no hot water on friday is there a common boiler with heat exchanger for the home? did the city have apipe problem causing brown airiated water.

It is an indirect heater - just a stainless steel tank with a cupronickel coil inside it that boiler water is pumped through. AND I pressure tested the coil. The Air is coming from the bloom.

Man, whats going on with the water over there?:fear:

you may not be anywhere near flint, but...

I have a low pressure hot water system using radiators and had something similar this year. When I bled it the air coming out smelled like acetylene.

The air coming out of a NORMAL boiler system tends to stink especially what comes out of an expansion tank. This was FAR over and above that.