Where to locate Spirovent for hydronic boiler

JZETTY84 · October 12

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 · October 12

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 · October 12

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 · October 12

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 · October 12

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 · October 12

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 · October 12

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

JZETTY84 · October 12

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 · October 12

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.

hot_rod · October 12

I would use this multiple use type sep above the boiler. Larger size, press available.

No harm, and some value with the tank and circ on the return piping.

The expansion tank does not need to be below the air purger.

But you are correct the the circ pumps away from the tank.

JimP · October 12

Here’s a thought while you’re doing all these improvements and if you return water temp is often below 140 degrees install this mixing valve.
https://www.supplyhouse.com/Caleffi-280975A-1-1-4-Sweat-ThermoMix-Thermostatic-Mixing-Valve-130F

You can do it pretty simply between your return and hot side. I wish I’d discovered this valve sooner. They’re often difficult to add because current best practices recommend pumping away from the hot side of the boiler and in that case this mixing valve won’t work. You’re not stuck with that configuration so yo could easily add it.

JimP · October 12

Here’s the 140 degree

https://www.supplyhouse.com/Caleffi-280976A-1-1-4-Sweat-ThermoMix-Thermostatic-Mixing-Valve-140F

JimP · October 12

oh I mistakenly saw the pump on return side. Sorry you’d need to move the pump which I guess you can do with zone valves. Anyway, just a thought. The mixing valve works great!

hot_rod · October 12

I think he mentioned baseboard heat emitters?

I would add up the total footage of finned or cast baseboard.

That x 500 (btu/ft)

Compare that to the boiler output, looks like somewhere between 125 and 145,000 out, depending on which number you like.

So at 125,000 divided by 500, you could, or should have 250’ of baseboard.

More often than not boilers are oversized, sometimes grossly so.

If it is it probably heats quickly and would not need return protection. Typically low mass fin tube doesn’t need return protection either. Even with a properly sized boiler.

The biggest downside to an oversized ci boiler is the run cycle time. Short, under 10 minute run times and often cycles drags efficiency down into the 70’s % range. 5 zones is another concern for short cycling.

It looks like maybe 1” zones off that large header? If so you could flow 8 gpm or so. If the emitters are 1”?

EdTheHeaterMan · October 13

looks like that is a bigger heater than the 1" can handle. You may need to do a little extra piping to get the maximum benefit if the Discal that must be installed on a horizontal pipe. The NET AHRI output is 126,000 BTU. too much more than the 90,000 the 1" can handle.

@hot_rod has shown the Spirotherm VDR125, which will work for you. It also includes a dirt separator with a magnet to capture metal particles until they can be cleaned out.

JZETTY84 · October 13

The zones are 3/4" off the header. I have about 100-110ft of baseboard radiator, however, one of those zones goes to a room with radiant floor heating, that room is about 15x20 in size. Not sure how much that translates to equivalent baseboard but im sure its probably still oversized. Again just trying to address two problems right now. One, redo the expansion tank so that its on the suction side of the pump and in a hanging position. Two, reduce air in the system. But also trying to keep things simple in the process, boiler is nearly 30 years old and dont know how much she has left in her, so I dont really want to go crazy in the process. I can definitely go with the Spiro on the 3/4" vertical next to the supply vertical on the boiler. Then just T the expansion tank on to the return just above the pump. Just hope I can fit it in there, they really dont give you much room between those two pipes. Might have to elbow it over then up just to get clearance….

JZETTY84 · October 13

So with the spirocombi, should I remove and cap off the existing auto air vent?

hot_rod · October 13

The new Spiro goes in the 1-1/4 or 1-1/2 riser of the boiler supply, the hottest point. Where Ed showed it.

If you want to leave the pump where it is on the return, a 1/2" tee above the pump for the expansion tank and fill connection.

I think this may be easier than trying to get a purger pump and iso valves above the boiler. I think it would be too tight?

Correcting the pump to expansion tank relationship will make a huge differance in air removal. Within hours of start up with all zoes calling you should be air-free.

Yes cap off the old vent.

So 110 ft baseboard= 55,000. Maybe another 6- 7,000 for the radiant= 62,000 btu/hr on the coldest day.

When you are ready to replace 'er, a 80,000 mod con would be a good match.

JZETTY84 · October 13

Thank you hotrod! Im hoping to get 10 more years out of this boiler. Our house was built in the 30's, but had two big additions in the 70's and 80's and they just added systems each time. So it currently has a steam boiler, hydronic boiler, 24" whole house exhaust fan, a gas insert to heat the kitchen and then forced air ac in the attic for the second floor. So im constantly maintaining one system or another. Point is, if I can squeeze ten more years out this boiler, im hoping I have enough cash at that point to ditch both boilers and add duct work and forced air in the basement to heat and cool the first floor to go with the forced air system on the second floor. Thats why I dont want to get crazy with it, just want to get her running healthy and not have to constantly purge the air out.

hot_rod · October 13

https://forum.heatinghelp.com/discussion/comment/1906321#Comment_1906321

Understood. With the proper tools and some piping knowledge a press type air purger and expansion tank move could be a hours job. Some addition time for fill and re-purge. A few 300 bucks or so in parts.

If you hire someone labor rates could be $100/ hr. - to the moon.

EdTheHeaterMan · 5:35PM

If all you have is 62,000 BTU of emitters, then a 1" us more than enough for your system. All that should fit nicely on the supply riser.

hot_rod · 8:05PM

12D, 12 pipe diameters of straight pipe after a circulator is the best practices recommendation

Iso flanges would be nice, if you have zone valves on the supply branches, those isolate one side,

A valve below the sep give you isolation for all the components

ScottSecor · 9:05PM

@hot_rod is it twelve pipe diameters of straight pipe on the "inlet" or the "outlet" of the circulator?

Dave Carpentier · 10:18PM

Somewhere I read that 12" of straight pipe on the inlet side of a circ is appropriate. Maybe it was 12D, but as im using 1" pipe..

Where to locate Spirovent for hydronic boiler

Comments

Categories