Expansion tank install

scatgo · January 4

I am going to be installing a new furnace that will include a new expansion tank and air scoop as in the diagram. Obviously, I am going to have to drain down the whole system beforehand. Now the water side of the blader type expansion tank is going to have a lot of air in it. Is there a fast and easy way to get all of the air out of the tank when I fill the system back up with water? And from what i recall there must be a minimum length of pipe between the furnace and the air scoop and expansion tank. is that right?

109A_5 · January 4

" Now the water side of the blader type expansion tank is going to have a lot of air in it. "

Gravity.

Jamie Hall · January 4

When you pressurizejthe expansion tank to system pressure before you attach it to the system, that will drive all the water out of it.

hot_rod · January 4

consider upgrading to a micribubble type air purger. The work faster and better than the scoop type, with no dimension limitations

HVACNUT · January 4

The system will need to be purged of air. And your diagram is not showing a purge station.

hot_rod · January 4

A Webstone valve here allows you to isolate the components, pump, expansion tank. And also drain pressure off the expansion tank if it ever needs replacement, since the purge port can work on either side of the ball shut off valve.

Intplm. · January 4

@scatgo If you use a air scoop as pictured, you need an eighteen inch nipple before the air scoop. If you use a micro bubble air separator, (in my opinion a better product) an eighteen inch nipple/length of pipe is not required. I would use a micro bubble air separator, a much better air eliminator than an air scoop as in your drawing.

The bladder type expansion tank is commonly pre-charged to the system pressure requirements. On a Hot water boiler that pressure would be 12-15 psi, the same as your automatic feed valve. I like that you have the feed valve at the point of no pressure change.

One thing I like to do is add a valve between the expansion tank and the tee. This helps tremendously when the expansion tank needs to be replaced (and it will need replacement).

The way to purge a new system requires a purge tee set up preferably on each zone. Here is a picture one example a purge tee. There are others you can use too.