Air Scoop with Injection System

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Old 01-08-07, 07:19 PM
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Air Scoop with Injection System

I'm planning on changing my 2 zone (pump) hot water baseboard system over to a 4 zone primary-secondary with injection (and outdoor reset, obviously!).
Thanks to all the information on this site and at the manufacturers sites it looks fairly easy. I started thinking about how the air scoop on the primary loop would remove the air from the system and then I realized that air could easily be trapped in the secondary piping. The flow between the 2 loops will only be some 3-5 gpm under design load. In addition, the injection piping will be in the vertical runs. Think about it- on ititial fill all that air laden water will enter the secondary loop. Do I need to have an air scoop in the secondary loop as well as in the primary loop?
 
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Old 01-08-07, 08:11 PM
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Just make sure you have a way to purge or bleed the secondary. Have you thought about using a microbubbler like a Spirovent or one of the many similar designs out there?

If the secondary is a loop, it will be purgable. If it has branches, you'll need to leave bleeders wherever there is a higher branch.
 
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Old 01-08-07, 09:33 PM
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Originally Posted by bikerbob View Post
the injection piping will be in the vertical runs. Think about it- on ititial fill all that air laden water will enter the secondary loop. Do I need to have an air scoop in the secondary loop as well as in the primary loop?
How about a horizontal P/S layout ? The injection loop will be the vertical piping with the injection tees in the horizontal runs. This way you don't need the heat trap in the injection loop either. I can't find the URL I found this diagram at ... try googling it...

I've seen P/S "purge tees" on the web. (not used them so can't attest to the quality, maybe someone else has ???? anyone ???) They are made by WEBSTONE, and I've seen them at www.houseneeds.com . It's a complete P/S TEE with a ball valve smack between the two injection tees. This allows you to close that valve and force ALL of the flow down the long road, out of the boiler, through the injection loop, through the secondary loop, and all the way home again.

check it out:

http://www.houseneeds.com/shop/HeatingProducts/HydronicHeating/webstone/webstonepropal.asp

I kinda like the ball with drain valves too.

It couldn't hurt to put a scoop in both loops I don't think...
 
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Old 01-09-07, 03:59 AM
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One air scoop on the primary is all you'll need. I would definitely go with a microbubble resorber type like a Spirovent or Taco 4900 for better air elimination.

That webstone p/s looks cool. They make good stuff.

You might also check out http://www.ravenproducts.us/hydronics.htm and see if they make a p/s unit as well. Their standard headers are pretty cool and look like a time-saver.
 
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Old 01-09-07, 05:39 PM
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Wow, thanks for all the good info.

I checked out the Webstone valves and was amazed to also find the combination ball valve with drain combination in addition to the P-S purge tee. (but I guess you said that NJ) Then I went over to the raven products and found the manifolds. In all my trips to plumbing stores I have not seen these. I guess they keep them behind the counter? :-) I was just thinking how much easier it would be to use a welded together manifold instead of screwing some 11 parts together.

Are the fancy air purgers really worth it? Besides Spirovent, Taco makes one too. But Taco makes another one as well called the VorTech. But the standard ones are dirt cheap like $20. Oh wait let me check the Taco site- oh I see, the 4900 uses PALL rings to seperate air from the water. Cool stuff.

Also, NJ, I was originally thinking of trying a horizontal section for the injection lines. If you do this I believe it needs to be high up in the secondary loop or else it can still thermosiphon. In my case I need to keep that area clear for servicing the top and side of the heat exchanger (cleaning out the soot). Which involves removing the flue. Ah, the joys of burning oil !
 
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Old 01-09-07, 09:35 PM
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Cool Webstones

I almost always use Webstones, and have been thrilled with them. I've used B&G and Raven ones too, and was happy there too. My regular supplier just didn't carry the other ones. I would definitely spend the extra $80+/- for a spirovent or similar air separator. Air scoops are old technology. Sounds like you have a Burnham boiler. If you had a Buderus, the cleanout would only be in the front and all the piping in the back. The Logomatic outdoor reset control is really nice too.
 
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Old 01-09-07, 10:13 PM
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Talking Spirovents just look cool!

Spirovents just look cool!

My old system had a B&G series 100 pumping in the boiler with a tee off the riser leading to a simple expansion tank (no airtrol). No purging options for a diverter tee so twice a heating season, I'd have enough air messing up the system that I'd have to do a full bleed and then drain the tank to restore air there... or else do it a month later. Anyway, one day I just decided to buy a modern compression tank. I also bought a Spirovent.

When I got home I started thinking that putting the tank on would be easy enough. On the 3/4" tee that used to go across and feed the old tank, I'd just put on a 6" mipple a 3/4" to 1/2" reducing elbow and then a foot long 1/2" nipple and a ball valve and then hang the tank. The tough part was adding the Spirovent. I'd have to add it before the circ...

My piping came through the wall at a 4' height ran about 4 ' like that and dropped drown through the circ and then across into the boiler. The feed was above this 4' section of pipe. The tee for the feed rose vertically and then 90'd itself back to where the feed and swing check were. I took the elbow out and added a tee going vertical. The feed valve teed in at the 1' high mark and at the top I put a cheap auto air vent.

I never had air problems again. I wasn't pumping away, no Spirovent, no air scoop, just a captive tank and an auto air vent on a riser. The Spirovent sat in my shop for years until mid-December when it finally got a home. I look at the the little air vent on top of the new wall hung and I can't help but think that would actually probably suffice...

But damn my Spirovent looks cool!!!
 
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Old 01-10-07, 06:28 AM
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thoughts on air eliminators

There is a difference in air elimination approach between the standard scoop/hyvent and the "microbubble resorbers" like the Honeywell, Spirovent, and the new Taco 4900 (replacing the Vortech). The standard scoop creates a pressure differential much like an airplane wing, and more or less hopes the air goes up and over to be captured by the vent. Eventually, most of it does. The resorbers use an "increased surface area" approach to collect microbubbles. Over time the microbubbles coalesce to become macrobubbles and float up to the venting point. To collect the microbubbles, the Spirovent uses a piece of their (Spirotherm Co.) baseboard heating element (a circular wire mesh around a piece of copper tubing). The Honeywell literally uses a section of wire brush. The Taco uses fancy-schmancy "PALL rings."

The traditional scoop needs 18" or so of straight approach piping because it wants the flow to stabilize a bit to get the air to the top half of the pipe before it enters the scoop/wing. Not necessarily laminar flow, but at least somewhat less turbulent. That improves the efficacy of the scoop. The resorbers don't need the straight approach (but some straight length probably doesn't hurt) because the method of removing air is different. They don't care if the flow is turbulent, they're relying on the bubbles to stick to their presented collection surface.

Of all of them, I'm most impressed with the Taco 4900. Not the "PALL rings" so much as the conical vent head. A rep showed me a cutaway. Compared to an old Spirovent I disassembled, it had much better engineering inside. IMHO.

Bottom line is I would definitely go for the better eliminator, consistent with HVAC-EMT.

And don't get a Vortech. The rep told me they will be phased out. Apparently the "well" in which the hyvent seats could fill with water and corrode if they hyvent starts to leak.
 
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Old 01-10-07, 08:35 AM
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Thanks xiphias!

Now my Spirovent has lost its coolness. ;-)

Do those pall mall fall stall gall ball things make any noise? On a Spirovent you can hear the cage spin, although you have to be pretty close. It would be interesting to compare the Cv of each in a given size, but I can't find the Spirovent ratings.

I still think that they're superfluous. A big riser loop branch and 2 AAVs up top. Whenever I look at Viessmann piping diagrams I always note that they just use AAVs. Either on the boiler, LLH or both. I fear the day I have to untwist the piping to get back to the Spirovent, but not quite enough to risk another union.
 
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Old 01-10-07, 07:35 PM
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HVAC-EMT: how'd you know I have a Burnham? It's only 2 years old now in my 9 year old house. Yes it cracked, 2 out of 3 sections. Replaced the block for no charge, except labor. $1200 !!! That's when I decided to start doing stuff myself. My neighbor, who is a oil burner/heating tech told me yea, it looks like Burnham may have done something about the casting but now they have problems with the slip nipples leaking... ha ha ha (but I was not amused).

Burnahm units have a return in the back, but they ship it with a plug installed. As long as they didn't seal it in there with some kind of super sealer I should be able to get it out and change my return piping.

After my own horror show and stories from others I don't want to risk using reset on this Boiler. That's why I decided to do a P-S loop, better protection for the boiler and I can use full reset temps in the secondary loop. Also control the wild hi and low temp settings with this goofy Honeywell control.

XIPHIAS: thanks for the info on how the new tech seperators work as well as the skinny on the Taco offerings. Funny I looked at the Vortech and thought "gosh that well in the top looks like a problem waiting to happen" I guess this was one of those "form over function" type of designs.

I just ordered a bunch of Webstones valves for this project. Also picked up a pair of Raven manifolds at the plumbing supply. After I left I discovered that the handle of a ball valve hits the manifold. I'm thinking "what the he....?" and then I got another email from Ravenproducts. Did you guys know that they make two versions of the manifolds? One has 3" long branches spaced 6" apart and the other has 4.5" long branches at 7" apart. You need the longer branches for handle clearance.

I was planning on using a Tekmar 356 along with a regular old Taco SR506 relay box. Tekmar makes some fancier stuff but usually includes perishable items like relays on the main board and they are not field servicable. So, in doing one of these systems you always have to think of a plan B if/when the fancy control craps out (usually when it's -10F outside) how to run the system.
 
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