# Where To Install Automatic Air Vents



## velvetfoot (Oct 28, 2014)

I'm having a devil of a time getting air out of the zones. There two floors and no bleed valves now in the baseboards.  I want to put some automatic air vents on my zone piping.  I want to limit to one to a floor because of the hassle.  Where is the best place in the circuit to put them?  

I'm not even certain how the pipe runs upstairs, but if it's like I suspect, the last baseboard on the circuit is in a walk-in closet that wouldn't exactly be closely monitored for leaks, as well as more of a hassle to install.  The place I'm thinking of is in a bathroom, but I 
THINK it's the first in the circuit.

I'm trying to think this through as well as not burn the house down, etc.  Removing the old baseboard fitting might not be too easy, nevermind removing all the water first as well.

Or I could wait for weeks and see if the air scoop removes the air eventually.  I've tried a lot of fill/venting with no luck but still can't seem to get the air out.  It's not like there is no heat, the gravely sound coming from the pumps as well as the bubbling in the baseboards (more upon initial startup because they get broken up by the moving water, I imagine.) are driving me crazy, and can't be helping the pumps either.

I don't know why they don't put vents in as a rule.  When the house water is turned off and a fixture is used or something like that, the air sputters out of an upstairs faucet until it is purged.  Seems to make sense.  

Ideas?


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## maple1 (Oct 28, 2014)

The installers put little bleed valves in my upstairs zones 18 years ago - but I don't use them & don't want to touch them as they had problems with a couple of them leaking then. If I have issues with air in the pipes up there, I can get it out in the basement with the shut offs & drains on each zone down there. My air vents are at high spots in the near boiler & manifold piping down there. Up high in an upstairs zone might be the logical place, but I would be reluctant to cut something in in a place where a leak might go undetected and do damage below.


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## velvetfoot (Oct 28, 2014)

maple1 said:


> I would be reluctant to cut something in in a place where a leak might go undetected and do damage below.



Me too, but I'm just not getting the air out.  This is on the second floor. 
I have a vent at the air separator and at the top of the buffer tank.  I thought that'd be enough in the basement.  The boiler pumps seem to clear themselves out, but not so the zones, esp. the second flor zone.

I'm not super confident, but I'll think I'll give it a whirl.  I plan to blow out the line from a drain valve I have at the top of the buffer tank, make a couple of hacksaw cuts on a coupling, put protection around joints, heat up and remove old coupling, install new Tee with 1/8" stub, install Taco Hy-Vent, refill zone - of course that'll be easy because of the new vent (yeah, right).


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## Bob Rohr (Oct 28, 2014)

velvetfoot said:


> I'm having a devil of a time getting air out of the zones. There two floors and no bleed valves now in the baseboards.  I want to put some automatic air vents on my zone piping.  I want to limit to one to a floor because of the hassle.  Where is the best place in the circuit to put them?
> 
> I'm not even certain how the pipe runs upstairs, but if it's like I suspect, the last baseboard on the circuit is in a walk-in closet that wouldn't exactly be closely monitored for leaks, as well as more of a hassle to install.  The place I'm thinking of is in a bathroom, but I
> THINK it's the first in the circuit.
> ...




Every auto vent you install is a potential leak.  Vents installed in living spaces, over finished floors and ceilings are the most prone to leak.  With float type auto vents at high points it is good insurance to a a hygroscopic cap for a second shut off mechanism.

At this point, unless you can define all the high points I would not start cutting into baseboards to add vents.

With a quality air separator at the hottest point in the system, IF all the loops are circulating at 2- 4 fps the air should disappear.  Bumping the pressure for a day or two may help, keep an eye on pressures if you have an expansion vessel that is sized tightly.

When we installed float type vents in sensitive areas we used a cap with an adapter to 1/4" copper tube and ran it down to the mechanical room or an area safe for any leak or discharge.

Sorry about the pic, my computer must be giving up on me?


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## jebatty (Oct 29, 2014)

> Vents installed in living spaces, over finished floors and ceilings are the most prone to leak.


 Murphy's Law proves true again.


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## velvetfoot (Oct 29, 2014)

Bob Rohr said:


> With float type auto vents at high points it is good insurance to a a hygroscopic cap for a second shut off mechanism.


My plan is to screw down the caps if not necessary.  I've read that Taco had an adapter for a tube.
I just feel I've tried a lot of filling/venting and thought I'd give this a whirl.  The Taco air scoop seemed to get rid of the air in the basement loop.  I might add another air separator closer to the pellet boiler at some point-the current one serves both.


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## maple1 (Oct 29, 2014)

I have always been able to get the air out of my second floor zones, from the basement. If you can blow the line out from down there as you were planning to do before cutting per post 3, it should be possible to blow the air out with water from down there also.

The caps on my auto vents all went to pieces also - but they are plastic. I could likely replace them with metal if I wanted.

I think if I had to resort to cutting something into my baseboard on the second floor, it wouldn't be an air vent per se, but rather just a stub with a small ball valve on it that I could manually open when I felt there was a need to let air out - and that I could take the handle off of & put a plug in the opening of for the rest of the time.


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## leon (Oct 29, 2014)

velvetfoot said:


> I'm having a devil of a time getting air out of the zones. There two floors and no bleed valves now in the baseboards.  I want to put some automatic air vents on my zone piping.  I want to limit to one to a floor because of the hassle.  Where is the best place in the circuit to put them?
> 
> I'm not even certain how the pipe runs upstairs, but if it's like I suspect, the last baseboard on the circuit is in a walk-in closet that wouldn't exactly be closely monitored for leaks, as well as more of a hassle to install.  The place I'm thinking of is in a bathroom, but I
> THINK it's the first in the circuit.
> ...


========================================================================================================

Its more like avoiding rather than risking the leaking of the dreaded corner elbow
of a baseboard heating menagerie(I have it and hate it) It will be safer for you to
install a half inch spirovent in the top of your airscoop(s) rather than the $10.00 automatic vents.
The water has to be very hot to vent any entrained air inthe system properly you can
always turn the the boiler temp up and force it to dump the heat in your dump circuit
(assuming you have one).


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## velvetfoot (Oct 29, 2014)

Waiting for second fitting to cool off.  Did the second floor first.  Cutting removing the old elbows went remarkably smoothly, knock on wood.  I got a one-handed recip saw at HD that made the cutting way easy.  It has a .5" stroke that made it easy to cut through the elbow that it pretty close to the wall.  The air purge went well:  it was Boilerman that recommended that, but I've been doing that for winterizing for a number of years.
Will report progress, lol.
Here is the saw.  It's pretty nice.





http://www.homedepot.com/p/RIDGID-T...Orbital-Reciprocating-Saw-Kit-R3031/100646504


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## maple1 (Oct 29, 2014)

Well now, the truth finally comes out.

New tool = ulterior motive.

(That's nice looking.)


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## velvetfoot (Oct 29, 2014)

maple1 said:


> Well now, the truth finally comes out.
> 
> New tool = ulterior motive.
> 
> (That's nice looking.)


Now, that's not me of course.  I'd be using TWO hands.

Update:  Pumps on.  The sound of hissing air is music to my ears.  
Will update on further results.  (Hey, I'm just going up and down the stairs.)


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## velvetfoot (Oct 29, 2014)

Didn't get rid of all gravelly noise, yet.  What seems to happen, so far, is that air is expelled after the pumps rest for a little while.  This mirrors what was happening the unending turn on pump/turn off pump/drain cycles, which is not only tedious, but probably not good for the equipment either.  

Time to listen for the hiss, and no, it isn't directed at the Giants in KC.


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## velvetfoot (Oct 29, 2014)

No hiss.  Maybe it needs a longer rest.  The zones are not gurgly now while the pumps are running, but the pumps still sound gravelly, like small air bubbles. 
I'm going to turn on the boiler and let it run, and listen for hissing, part time, lol.  Did I put the one vent on each floor in the optimum position?: who knows, but hopefully it did some good.  It's not leaking, and...I got a new tool.


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## velvetfoot (Oct 29, 2014)

I can't resist.  Second floor pump almost quiet.  I forgot to do something today and will have to break open the buffer tank to extend the vent/drain valve stub;can isolate is and drain it down a little.

The thing with the vents method, new oxygenated water isn't being injected.  If air gets up to the upper two levels in the house, it stands a better chance of making its way to one of the vents on that floor.  That's my hope anyway.  Hey, I'm just tickled it's not leaking.


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## leon (Oct 29, 2014)

What brand of vent did you use?

What ever you do, do not tighten down the caps as they will not release the trapped air.


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## chken (Oct 29, 2014)

Okay, I'm no expert, I put little air vents at the high points of my zones. Also, it's not clear to me, but if you're getting lots of gurgling, repeatedly, are you sure the auto water fill is working? Mine can get sticky after a year, so I just wiggle it. You'll know if your water pressure in your system is low. If I'm completely off base on what you're talking about, feel free to ignore me!


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## velvetfoot (Oct 29, 2014)

Okay, wife said, why 66 and not 68, as set?  Turned out the zones were airbound!  I isolated boilers, and flushed at 40-50 psi (well tank) pressure.  Incredible amount of air, pretty long time to flush out air.  I left the autofill on fast fill and opened a valve part way and just waited; it took a while.  Did similar for boilers, headers and tank.  Made sure to bleed down to 12 psi autofill pressure before I got them involved.  Rediscovered what a siphon was with a hose carelessly left in a 5 gallon bucket; quality time with a mop-need to get a better one.  About to start pumps.  Fingers crossed.

I'm still thinking the vents might do some good.  We'll see.


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## Bob Rohr (Oct 29, 2014)

velvetfoot said:


> Okay, wife said, why 66 and not 68, as set?  Turned out the zones were airbound!  I isolated boilers, and flushed at 40-50 psi (well tank) pressure.  Incredible amount of air, pretty long time to flush out air.  I left the autofill on fast fill and opened a valve part way and just waited; it took a while.  Did similar for boilers, headers and tank.  Made sure to bleed down to 12 psi autofill pressure before I got them involved.  Rediscovered what a siphon was with a hose carelessly left in a 5 gallon bucket; quality time with a mop-need to get a better one.  About to start pumps.  Fingers crossed.
> 
> I'm still thinking the vents might do some good.  We'll see.




Time and patience to do a proper purge.  I helped a local plumber start a system today that had 40 radiant loops.  It took almost 3 hours to get every loop purged enough so we had flow to allow the air separator to finish off the job.

Volume and pressure is what you need to purge quickly, hence that Autofill with it's 5 gpm flow rate   On large pipe systems, like GEO loop fields often times a 1-1/2- 2 hp swimming pool pump is what you need to flush out the loops!

You should be fine now.  If the gravely sound in the circ doesn't disappear, we will talk more about cavitation and it's cause and effect.


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## velvetfoot (Oct 29, 2014)

Bob Rohr said:


> Time and patience to do a proper purge.


Things were quiet til the pumps stirred things up. They were totally quiet at first, then the bubbles from the second floor.   I repeated the fast purge on both zones again a couple of times (didn't take as long this time) and got some quiet pumps.  The pellet boiler pumps didn't seem to have an effect.  Started up the boiler.

I didn't put myself ahead of the curve by blowing out the zones, for sure.  

I think the key was the high pressure/flow.

As I said somewhere else, my Air Scoop is on the supply header past the bypass for the Thermomix, so the scoop isn't seeing any flow until 130, and after that, it's mostly going to the tank unless the boiler and zones are on at the same time.  I'm thinking maybe another separator, or replace and relocate the current one to the buffer tank supply pipe near the tank.  That way the separator will see the flow of the boiler to the tank, as well as flow from the tank to the zones.    What do you think?


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## leon (Oct 29, 2014)

Why not high above the boilers where they normally are?


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## velvetfoot (Oct 30, 2014)

This would also be above the boilers. The tankis like 7' high or so and the pipe comes in the top.


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## velvetfoot (Oct 30, 2014)

Bob,
Woke up to the sound of water running in pipe.  Heat, yes.

Do you think that spot would be good?  The Sirovent and I( think Caleffi work in both directions and requires no minimum length.
I kinda thought the buffer tank with the vent on top would act as an air eliminator.  

Maybe I should be more patient.


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## leon (Oct 30, 2014)

One more reason to like steam heat IMO.

The spirotops would be a better choice with an air scoop.


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## velvetfoot (Oct 30, 2014)

Now that I think about it, I should be able to get a quiet system when there is no heat. 
I wonder if a vertical air eliminator just upstream from each pump would do the trick?
I get what appears to be a solid fill, and then when the pump comes on, bubbles.  
I think I have the first floor solid now with the pump running.
Oh well, back to it.


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## leon (Oct 30, 2014)

If you look at the spirovent/spirotop brochures you will see
how they or other vent types should be plumbed in a heating system.

Pumps are usually flood filled from the boiler base outlet which is
the best way to reduce cavitation to near zero and eliminate any
chance of pump damage and improve pump life span.


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## velvetfoot (Oct 30, 2014)

leon said:


> Pumps are usually flood filled from the boiler base outlet which is
> the best way to reduce cavitation to near zero and eliminate any
> chance of pump damage and improve pump life span.


I'm pumping to the return and I don't think I can fill upstream (check valves).  Anyway, the boiler pumps don't seem to be a problem, just the zones.


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## velvetfoot (Oct 30, 2014)

Well, I think I got a good part of the air out.  Starting up boiler now with zones still isolated.  I figure it'll run through the air scoop a few times that way as it heats up.  Who knows.


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## BoilerMan (Oct 30, 2014)

velvetfoot said:


> I'm pumping to the return and I don't think I can fill upstream (check valves).  Anyway, the boiler pumps don't seem to be a problem, just the zones.


Are these weighted flow checks?  If so, you can open them with the handle on the top which will help get flow up and move more air to the elimination point.  

You can try putting about a tablespoon of Liquid Dawn, yes the dish soap, into the system.  It will cut the surface tension in the water allowing it to carry air bubbles down a pipe more efficiently.  

TS


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## velvetfoot (Oct 30, 2014)

Thanks.  The zone checks are flo checks and there are a couple spring checks.  Makes sense about the soap.

I just spent an entire boiler cycle down in the basement with it heating the tank to 176 and also providing some zone heat.  It turns out there is indeed noise coming from the boiler pump plenty also from the zone circs.  It was pretty darn quiet when cold.  I went around with my stethoscope and could hear the bubbles in the pipe all the way from a short distance from the pellet boiler, past the air scoop, and then finally as they burped their way into the tank.  I bet if that air scoop was a Spirovent or Caleffi, or like that, it'd be gone sooner rather than later.  Right now, I'm hoping for eventually.  Or, I might bust a move and install a new air eliminator.  Then again, I busted a move with the auto air vents, duh.


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## arbutus (Oct 30, 2014)

I put in a single Spirovent, right near the lowest part of the system (basement), at the expansion tank connection, and had very little trouble with air.  After the initial fill and bleed for the radiators (second floor) and staple up loops (in basement ceiling) I had occasional air gurgles for a couple weeks, and darn near nothing after that. 

There were some other discussions about air eliminators, with the Spirovent or Caleffi type solving similar issues for other folks here.


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## velvetfoot (Oct 30, 2014)

arbutus said:


> I put in a single Spirovent, right near the lowest part of the system (basement), at the expansion tank connection


I wonder if you could be more specific.  My current air scoop is just past the boiler protection recirc line and therefore sees flow from both boilers.  The flow then goes to the tank and/or zones if they are running. I had thought that the zone pumps running from the buffer only and bypassing the existing air scoop would be a factor, but I'm currently thinking that just replacing the current air scoop with a Spirovent would do the trick.  I had originally thought about putting a Spirovent close to the pellet boiler, but I was concerned about head loss and figured the existing air scoop would handle both boilers.


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## arbutus (Oct 31, 2014)

It is very close to the PS setup in the sticky at the top of the boiler room.  Rotate the picture 90 degrees and it will show the primary loop is at the bottom of the house, and all the zones are higher.


The odd bubble or two that have gotten into the radiators after the initial fill and bleed have been absorbed into the water and separated by the Spirovent.  No gurgling like when I was filling and bleeding, and I have had various small portions of the system drained and refilled over the last year.  Each time a few bubbles to the upper levels, but not enough to worry about, and no gurgling in the radiators.  Tried bleeding the radiators again this fall and they were full.

I was able to isolate the boiler and pressure relief valve, use fast fill on the pressure reducer, and drain air from the zones with a garden hose during initial filling.


The Spirovent does a good job.  I'm sure the Caleffi product is quality as well.  I can't compare to an air scoop, because I don't have one.


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## velvetfoot (Oct 31, 2014)

I might try to replace the air scoop tomorrow.  Oh, wait, it's tomorrow already.


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## Bob Rohr (Oct 31, 2014)

Are you sure you are not cavitating one of the pumps?  Any flow restrictions upstream of the circs?

Cavitation forms, and will continue to form vapor pockets, not to be confused with air bubbles.  Vapor pockets can form even in a system that has been purger 100% air free.

Vapor pockets form when you drop the fluid pressure below the vapor pressure, this can happen at the eye, or inlet to the circ under some conditions.    So the key is to make sure the SUCTION side of the circ has enough static pressure to prevent this condition.

And the hotter the fluid the more apt to create or cause cavitation.  Vapor pressure of water at 140F is 2.9 psia, at 200F it around 10psi.  So be sure you have at least 10 psi at the circ inlet.  This is the key to why so many OWF destroy their pumps frequently, not enough pressure in an open vessel to provide the vapor pressure to prevent cavitation.

Idronics 16 will be about pump sizing, selection, and troubleshootring.

Did you use a Caleffi 281 ThermoBloc?  It has a gravity gate (check valve) inside.  it ships with a screw locking it closed that needs to be removed for gravity circulation function.

Tips for avoiding cavitation

Run system pressure as high as possible (practical)
fluid temperature as low as possible
expansion tank at the suction of the circ pumps ALWAYS
mount circ pump as low as possible in piping, maximizes static pressure at the suction
no flow restriction devices on the suction side, valves, checks, mixers, etc
12" of straight pipe is ideal, not always possible on the suction side
Microbubble type air separators, the iron, scoop type vents are best for light boat anchors


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## ewdudley (Oct 31, 2014)

Bob Rohr said:


> And the hotter the fluid the more apt to create or cause cavitation. Vapor pressure of water at 140F is 2.9 psia, at 200F it around 10psi. So be sure you have at least 10 psi at the circ inlet. This is the key to why so many OWF destroy their pumps frequently, not enough pressure in an open vessel to provide the vapor pressure to prevent cavitation.



Vapor pressure of water at 200 degF is more like 11.5 psia, which equates to 6.5 inches of mercury vacuum or 3.2 psi below atmospheric pressure.  So if your OWB pump has a static head of 2 psig at the bottom of the boiler, and the pump develops a pressure drop of 10 or 12 ft (~4.75 psi) you could easily be in trouble, especially considering that pressures within the impeller turbulence can be significantly lower that the pressure entering the volute.

But in a sealed system with 10 *psig *(as opposed to the '10 psi' mentioned above) you would need a hell of a pump to cause cavitation.


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## Bob Rohr (Oct 31, 2014)

ewdudley said:


> Vapor pressure of water at 200 degF is more like 11.5 psia, which equates to 6.5 inches of mercury vacuum or 3.2 psi below atmospheric pressure.  So if your OWB pump has a static head of 2 psig at the bottom of the boiler, and the pump develops a pressure drop of 10 or 12 ft (~4.75 psi) you could easily be in trouble, especially considering that pressures within the impeller turbulence can be significantly lower that the pressure entering the volute.
> 
> But in a sealed system with 10 *psig *(as opposed to the '10 psi' mentioned above) you would need a hell of a pump to cause cavitation.




Thanks for catching and clearing that up, I need to be careful with my psi, psia and psig. 

 I believe Grundfos recommends 4 psi, suction side at 190F operating condition.

It is certainly easy to establish problem  conditions with improper component placement.

From some old B&G training regarding expansion tank placement.


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## velvetfoot (Oct 31, 2014)

Thanks guys.
I'm about to turn on the Bernzomatic to sweat on the Spirovent.  One of those slip couplings sure came in handy.
I will buy a gauge I can thread onto the hose connection on the valve right before the pump.  I should look for at least 4 psi at 190-190 won't happen?  How about cold?

Bob, I have model 280975A.  Does this have the capability you mentioned?

Gotta go.  Have to also plug those darn air vents as well (long term leak concern) after sweating in the Spriovent.


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## velvetfoot (Oct 31, 2014)

Used 50/50 solder. I had forgotten how easy it was.


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## velvetfoot (Oct 31, 2014)

Did indeed plug the 1/8" adapter tees where the two autovents were;  at least I got that nice one handed recip saw out of it.
I put the new Spirovent where the original air scoop was located.
The vertical pipe with the insulation,the supply riser from the oil boiler, is blocking the recirc line to the Thermomix (only a 280, no easy way to defeat it, far as I can tell).

I'll get a pressure gauge to attach to a hose connection tomorrow.  It'd be a handy thing to have.

I wonder where I should set the pumps' speeds?  First floor, second floor, boiler pump all have same Ecocirc Vario pump.  I slowed them down some.
There's still pump noise, but I still think its air that has to get out.  Time will tell; must be patient.  At least there's warmth.


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## Bob Rohr (Oct 31, 2014)

A heads up on that T&P valve in the tank.  The probe needs to reach into the tank, by code, so it can sense the temperature.  They do make extended probe types for use thru a fitting like that.  Technically the valve should be right into the tank port, top or within 6" of the top if side mounted.  If I'm not mistaken.

That should be plenty of "air scrubber".  Not my favorite brand , but a nice quality 90% plus efficiency device.


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## velvetfoot (Nov 1, 2014)

Bob Rohr said:


> A heads up on that T&P valve in the tank.  The probe needs to reach into the tank, by code, so it can sense the temperature.  They do make extended probe types for use thru a fitting like that.  Technically the valve should be right into the tank port, top or within 6" of the top if side mounted.  If I'm not mistaken.



I believe it has an 8" long probe, but I still am not sure if it gets all the way past the 4" of insulation.  Still, the valve is going into the 1.25" stainless dhw coil inside the buffer tank, perhaps a "tank within a tank, which snakes around inside it and goes in at the bottom and out at the top, so it is sensing the temperature.  The tank side is protected by the boiler pressure relief valve.  I'm not sure why the "T" part of T&P is even necessary, but this is what the distributor told me to do.




Bob Rohr said:


> That should be plenty of "air scrubber".  Not my favorite brand , but a nice quality 90% plus efficiency device.


Yeah, I know, but that's all the local place had, but it does seem nice.  Was quite active when filling, Interesting that they gave me the contractor's price over the phone (even though I told them I wasn't a contractor) and I had to argue a little for it.  The regular schmo price was $40 more!  Although I got a lot of stuff on line for this project, I spent plenty at that place at the schmo rate.

Trying to figure out which valve to open for a complete fill as possible depending on the temperature of the boiler protection is a pain.  Maybe I should have piped in a bypass.  Perhaps some boiler vents as well:  I burped them a little with the pressure relief valves.  I inadvertanly left the oil boiler pump running with no heat on when we left the house for dinner and when we came back it was totally quiet.  I'm hoping the zones clears up with time-I think the downstairs one is already on its way, but will check the pressures at the zone pump inlets tomorrow.

Any ideas on the pump speeds?


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## BoilerMan (Nov 1, 2014)

Personally I'd leave the circs on "high" speed for a few weeks to move the air out.  After that turn them on the lowest setting that will deliver the comfort to the zone.  

From personal experience that is generally the "low" setting for the majority of residential setups.  With the circs on the return it could be "med" but try low first for a few cold days, if the last BB in the loop is heating well then leave it on "low".  

TS


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## velvetfoot (Nov 1, 2014)

Thanks.  

I am thinking of moving the separator to the outlet side of the buffer tank (see photo, above).  That way the Spirovent will still see flow when the boiler pump is on and the zone circs will see flow even when the boiler pump is not on,  but it may not see flow when the boiler pump is on and the zone circs are on.  I could turn on the zone circs and let them run.


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## velvetfoot (Nov 1, 2014)

Well, I relocated it.  We'll see.  Maybe should've just added it instead and have too.  Or, be patient.  
Also bumped up the pressure, cold, to 15 in the system and 17 in the expansion tank.
Couldn't see any hose bib pressure gauges around here with a scale of less than 0-100.


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## velvetfoot (Nov 1, 2014)

BoilerMan said:


> Personally I'd leave the circs on "high" speed for a few weeks to move the air out.  After that turn them on the lowest setting that will deliver the comfort to the zone.
> 
> From personal experience that is generally the "low" setting for the majority of residential setups.  With the circs on the return it could be "med" but try low first for a few cold days, if the last BB in the loop is heating well then leave it on "low".


Would you have an opinion as to where I should set the boiler pump?  All the pumps are the same and they pump to return and are infinitely adjustable..  Thanks.


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## velvetfoot (Nov 1, 2014)

The Spirovent seems to be doing the trick.  Very little noise from upstairs zone on high.  Hope I didn't jinx it.


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## Bob Rohr (Nov 1, 2014)

velvetfoot said:


> The Spirovent seems to be doing the trick.  Very little noise from upstairs zone on high.  Hope I didn't jinx it.




Run the pump on the lowest speed that will cover the load, start low, maybe bump up in design conditions if needed. 

 Air eliminators work best at flow velocities under 5 fps.  Above that their efficiency starts to suffer.  And above 4 fps you will start to hear "water flowing" when the system runs, and it can start eroding fittings and ells.  The hotter the water the more aggressive, so keep the flow rates low.

Also flow rates below 2 fps will make it tough to get the air pushed back to the air eliminator, so 2- 4 or 5 fps is what you should design and size everything to.

Step one, determine the flow rate you need to run, step two, use a pipe sizing chart or software to select the correct size pipe to assure 2- 4 fps.


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## leon (Nov 2, 2014)

I can tell you that in my case the B+G dumb as dirt three speed pumps are t'eed from the sump
outlet of my oil fired hot water Buderus boiler.

Water pumps work best when the installed with flooded suction just like hydraulic pumps. The water is always feeding the pumps at all times and the air scoop and vents are higher than
the pumps.

My pumps are at the numbe rone setting with zero problems except when I installed them as I had a large amount of air to bleed out at temperature with one zone of almost 250 feet of continuous base board(home perimeter including non living space/storage)


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## BoilerMan (Nov 2, 2014)

leon said:


> Water pumps work best when the installed with flooded suction just like hydraulic pumps. The water is always feeding the pumps at all times and the air scoop and vents are higher than
> the pumps.



In a closed loop system this is not the same.  If you were pumping _out _of the bottom of a boiler like in a hydraulic tank it would be similar, like open systems such as OWF.   The key is where the expansion tank is connected, most efficient tank location is as the air elimination device, which is most efficient at the hottest point of the system, which is at the boiler supply.  Most efficient circulator (not a pump) location is closely after the point of no pressure change, which is the expansion tank, so on the supply.  

Many book have been written on this, bottom line is all will work in an over-sized resi system, but when things are engineered in a large commercial system this comes into play.  When we are talking about 10+ HP circulators capable of moving 100+ GPM and expansion tanks of hundreds of gallons.  

TS


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## velvetfoot (Nov 5, 2014)

To close the loop, I did slow the pumps down as well.  Totally silent-like you can't hear them.  I'm going to give most of the credit to the Spirovent, and of course, my advisors.


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