Where to locate Spirovent for hyrdonic boiler.

JZETTY84 · 2:02PM

Hey everyone,

Im doing some maintenance to my hydronic boiler, mainly repiping the hook up for the expansion tank which was done poorly. The way the boiler is set up, it has 5 zone valves, and one circulator pump that is located on the return side just above the inlet of the boiler. The expansion tank is currently connected to a T just below the pump, so on the "blow" side of the pump, not the "suction" side. Additionally, the expansion tank is mounted upside down, with the full weight only being supported by the 1/2 copper pipe its sitting on, so its kind of a mess. Also, there's currently no air vents on the system at all, so i am constantly repurging the system. I want to run some thoughts by just to confirm Im putting things in the right spot.

In the photo below, right above the expansion tank, you can see a hose bib, ball valve, and BP valve. Thats the boiler feed line. Im going to remove the hose bib and ball valve (already have a shut off further downstream that you cant see), 90 over to the right, install a Pro-Pal full port ball valve, to which I will hang the expansion tank, and put a 3/4 Spirovent jr eliminator on top that,
Then from there, T into the main return loop just above the circulator pump. That way, the expansion tank and spiro are now on the suction side of the pump, and mounted correctly as well.
If you're wondering, the reducing valve is located behind the BP, so you cant really see it in the photo, but its there. Next year I will swap those so that the BP is behind the reducing valve, but not going to mess with it at the moment.
Lastly, I dont have a photo, but one of the 5 zones covers two rooms: my master bed and bath (2nd floor) and play room directly below it. Its by far the biggest single zone, and the radiator in my master bath is the highest point in the loop. One of the baseboards in my master bath has a 1/4 turn valve with nothing attached to it. Not sure if there was ever a purge valve there or not, but would it be wise to add a purge valve there? This is the zone this has always given me issues with losing pressure and having to repurge. Im hoping the first two steps mentioned above will help a lot with that, but im just curious if adding a second air valve at the highest point in that loop would further help or not?

EdTheHeaterMan · 2:25PM

If you have not already purchased the Spirovent, there is another company that makes a microbubble air vent that you can place on a vertical riser. more info to follow

EdTheHeaterMan · 2:25PM

Depending on the BTU output needed (that would be the I=B=R NET on older boilers or AHRI Net output on newer boilers) you can use the Caleffi Discal 551706A on a vertical pipe. You will need to reduce to 1" copper, since that is the largest vertical air vent available. That will handle up to about 90,000 BTU NET output. What size is your boiler?

You could then place the air vent on the supply vertical then the circulator pump as shown in this illustration to follow

JZETTY84 · 2:50PM

thanks so much! I dont know the BTU's off the top of my head. Ill get the details when I go home for lunch in a few hours. Stand by!

hot_rod · 2:55PM

You do have a good purge assembly on the return above the pump.

I would rebuild this return piping from the ball valve down to the boiler, get rid of the dielectric union, add an isolation valve under the circ..

You could tee in the expansion tank here also, then you are pumping away but with the pump where it is. The added valve under the pump isolates the pump, exp tank, fill; assembly

A ECM delta P zone valve circ would bve a nice upgrade while you are in the neighborhood!

EdTheHeaterMan · 3:13PM

This rendering puts the air seperator at the best location to remove air from the system. where the water is the hottest and just before the circulator pump where the pressure is the lowest. by using my x-ray vision you can see thru the return pipe to the supply pipe where the boiler supply has the air separator then the circulator then the branches to the zones.

From the bottom of the Discal Air vent you can use the 1/2" opening for the water feed assembly and expansion tank be sure to support the 1/2" copper so it supports the expansion tank if and when it fails and gets waterlogged. That can be quite heavy.

JZETTY84 · 6:11PM

ok here is the tag. based on the CP number, it was made in 1998…

JZETTY84 · 7:32PM

geez, thanks Ed! Thats an awesome drawing! I get what you're suggesting, the only problem is there's about a foot, maybe 18inches of vertical pipe on the supply side from boiler before it hits the manifold for all the zone valves. Dont think Ill have enough room to squeeze the pump in there along with the vent, pretty sure thats why they have the pump on the return side. Additionally, i just happened to look at it yesterday, the vertical supply line, where it connects to the top of boiler is cast iron and its SUPER crusty, i flaked a big chunk of rust off of it yesterday, im actually concerned that could break if I start messing around with it. Thats actually going on my list next summer when I dont need heat, to get that first pipe replaced. So i know its not ideal, but given that, can i keep the expansion tank, air vent and pump on the return side?

HVACNUT · 9:12PM

You're getting very invasive, @JZETTY84 .

That newish 3/4" piping with the blue tape goes down into the block near the supply? If so, the block has a built in air scoop, and there should be an air eliminator in that location.

If you're repiping everything for pumping away or something, then yes, a micro bubble smasher is better than the factory air scoop. But if you're only looking to get rid of air, use the 3/4" tap. It works.

Where to locate Spirovent for hyrdonic boiler.

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