repeated air problem in hot water baseboard

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Old 11-29-05, 08:18 AM
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repeated air problem in hot water baseboard

Greetings. After finding this forum yesterday and spending a few hours rummaging through it, I must say great job to the moderators and regulars. This is a really terrific resource.

But to the point.

We just added a bed/bath on our second floor (modified shed/dormer deal). We added this new space onto the existing second floor heating zone. The supply for this zone comes up out of the basement, T's into a Beacon/Morris K42 toekick unit under a (yet to be installed) vanity, then through a ~3 ft baseboard in the bathroom, then through the bedroom proper with about a 14 ft baseboard run, and on through the rest of the second floor.

The second floor zone is controlled by a programmable thermostat that sets down at night to 63F and turns up to 68F around 5am. Lately it has not been too cold at night here (southern New England) so the system is generally not calling for heat during the night. But, when the system starts calling for heat in the morning, we start to hear a ping/drip type sound from the toekick unit, and shortly thereafter start hearing air in the bath and bedroom baseboards, and I can go down to the boiler and hear the air bubbles in the basement return. This persists through the morning heating cycle and actually seems to worsen with time. Then the heat is pretty much done for the morning and we're out of the house so I don't have any data after that. Haven't observed the problem in the evenings, but then again it's been warm here and we're also allowing the evening temp to begin its drop to nighttime level. This problem has been ongoing for about a month.

The boiler is a two-year old Burnham Series 2, gas-fired. System has a Spirovent on the supply side just before the zone valves, set-up exactly like the spirovent installation guide suggests relative to the other parts of the system. My initial thought was that the spirovent had somehow clogged (e.g., gunk/junk from construction) or failed, so I replaced the vent head. No effect on the problem. Thinking that maybe the boiler temp was too high for some reason, I checked the aquastat and it's set at 180F. I have not as yet checked in detail for a waterlogged expansion tank (it's a new State that was installed with the boiler), but just twanging the side of the tank with my finger suggests that it is not full. Doesn't sound or feel like a tank full of water in there. System pressure as measured by the gauge on the boiler is about 15#.

Now I'm looking at the toekick heater and associated plumbing as somehow being the source of the problem. The installation for this unit appears to be totally by the book -- standard T on supply, monoflow T on return, T's spaced about 14-16" coming off the main hot water run, B/M hose kit coming from stubs to unit. However, looking at the piping chart on the installation guide, I see there is supposed to be an air vent on the return side. Would that be something like a mini-spirovent, or does it simply mean an elbow with a purge valve? We have the latter but not the former.

Could it be that the placement of the toekick unit as first in the loop (it's maybe 35 linear feet of pipe from the boiler to the unit), or more specifically the T's coming off the main run that are somehow causing bubble formation?

I'm at a loss. We never had a problem like this prior to the remodel; the system worked flawlessly. Suggestions? Many thanks.
 

Last edited by xiphias; 11-29-05 at 08:36 AM.
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Old 11-29-05, 04:27 PM
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Air problem

If you have the mono-flo tees on the return side, do not install an automatic air vent on the discharge side of the toe kick heater. You can actually draw in air in such an arrangement. A manual bleeder would be preferable. If the mono-flow tee is on the supply, an auto vent on the return should be ok.

Edit/Add: Toe kick heaters create a lot of friction loss. You may have to increase the boiler pressure by a few psig.
 

Last edited by Grady; 11-29-05 at 04:29 PM. Reason: More info
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Old 11-30-05, 11:13 AM
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thanks and need to follow-up please

Thanks Grady. You have saved me at least one potential screw-up -- I had been thinking about an auto-vent on the return side. Nice to know that would have been a mistake. I kept the system off last night and this morning tried to bleed on the manual bleed at the toekick return elbow before running the circulator. Got only a nice stream of water, no air. Checked pressure at the expansion tank = 16.5 psi, and the boiler gauge is about 17psi while system is off. Assume that's sufficient to overcome frictional loss of pressure, especially so early in the heat run (toekick is first in series on this zone). But still we've got bubbles running through the system.

Also turned off downstairs zone last night and this morning there was a noticeable amount of air in the downstairs zone as well.

I just don't get why this system would have so much air in it if the spirovent is working. I did replace the head after first having the trouble upstairs. Shouldn't the spirovent take care of it over a few days? This problem shows zero sign of improvement.

Thanks for any followup you (or others) can provide.
 

Last edited by xiphias; 12-01-05 at 06:48 AM. Reason: 17 psi on boiler gauge when system off, not running as previously stated. Not sleeping enough....
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Old 11-30-05, 02:34 PM
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Heating Problem

xiphias:

I'm not completely convinced yet that you actually have an air problem; you describe the sound you hear as a "ping/drip"; an air problem in the supply/return piping sounds a lot more like water flowing, like the sound you would hear from a main plumbing drain with the tollet flushed; I've had air-problem customers actually state that it sounded like "water was running inside the walls".

A "ping" sound is a more often the result of boiler water that is too hot (~200 degrees or above); this drives any residual air out of solution to give the characteristic sound of marbles or BB pellets against the inner pipe walls as the water is pumped by the circulator.

You state you checked the aquastat to read 180 degrees, but what is the boiler temp gauge saying, especially at mid to late-cycle when the water is at its hottest??

Then again, it's not that uncommon for the temp gauge or high limit control to be off by 10 degrees or more.

; There is always a certain amount of temp override due to the differential control & before the "high limit" kicks in to shut down the boiler.

Check the boiler temp; try turning down the high limit on the aquastat to ~170 degrees to see if that produces any improvement.

That said, any addition to a zone during remodel often creates a pesky problem in hot water systems (assuming the piping install was done correctly) by sometimes causing a misbalance between the two zones, or as Grady mentioned, the possiblility of a convector auto bleeder sucking in air.

Also recheck the manual & auto bleeders on the convectors & bleed them if you haven't done so already.
 
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Old 12-01-05, 06:45 AM
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Thanks Chimney Cricket. I probably mis-characterized the ping/drip noise. What that really appears to be is the toekick normal metal expansion as the heat cycles on in the morning, combined with the air bubbles in the system working through it.

We let the system run as normal last night, and when it first cycled on this morning we heard a big gurgle work its way through the upstairs, at one point creating a fairly loud banging noise farther along that zone. Successive calls for heat through the first hour showed some improvement -- toekick stopped its metal expansion tick/click, and bubbles/gurgling in the system were becoming less with each cycle. Just when I thought things were improving, however, on the next cycle there's a big gurgle when the circulator comes on. My guess is that the air I noticed in the downstairs zone yesterday was now getting mixed into the system and coming upstairs. Perhaps this would happen if both zones were open at the same time? By this time the house is already up to temperature and we're on the way out the door, so have no idea what it's doing after that, if anything.

I did have time to check various parameters this morning while the system was running. Aquastat is at 180. FWIW, it's a Honeywell L4080D original to the boiler. (I can't actually see a model number on it, though. I'm basing that on the parts list in the boiler manual.) During operation, the temp gauge on the boiler gets to 170F, the burn cycle ceases, and the temp continues to rise for another minute or two, peaking just below 180F before slowly starting to fall. The pressure on the boiler gauge during operation was 22 psi, and I confirmed that pressure using a tire gauge on the expansion tank. The pressures I reported yesterday were obtained after leaving the system completely off for about 18 hours.

The only auto-bleeder in this system is the spirovent down at the boiler. Did a purge of the manual bleed yesterday with the system cold and got only a nice stream of water (pretty sure there's only one bleed upstairs and that's on the toekick return elbow-- prior to the remodel the whole system had no manual bleeders anywhere in either zone).

So, still have a problem. Chimney Cricket, I am intrigued by your mention of "pesky" and "misbalance." Can you elaborate on what kind of misbalance, how to evaluate for that, and if that's the problem, how to fix it?

Again, thanks.
 
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Old 12-01-05, 05:54 PM
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Air

I certainly hope there are manual bleeders on each peice of heating element. You cannot purge the air out of a mono-flo tee system any other way.
 
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Old 12-02-05, 04:42 AM
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it's a series loop

Thanks Grady. I was unclear or misinterpreted. The overall system is a series loop, one loop for each zone. The only T’s are for the toekick heater. The main line (3/4”) comes up out of the basement starts running under the subfloor. There’s a standard T for the toekick supply that comes off the main line and up through the floor as 1/2”. The toekick return is 1/2” and has a manual bleed at the elbow where it goes back into the floor. Then it rejoins the main line with a monoflow T. Set up is just like the "one-line up-feed" shown on page 6 of the Beacon/Morris manual at http://www.beacon-morris.com/litlibrary/TFII-10.pdf including the spacing (12-18") between supply T and return T.

It was finally cold enough last night for the upstairs heat to cycle during the night. First cycle had a big gurgle. Successive cycles had less until the system finally ran totally quietly. Then around 5:45am when the downstairs started calling for heat and the upstairs was also calling to come up to the morning temp, we get huge bubbling/gurgling/swishing upstairs (not sure what was going on downstairs), like you’re standing on a rocky beach with waves lapping up. Just a ton of gurgling. Which now a couple hours later seems to have subsided to a few periodic gurgles.

Is this the “misbalance” that Chimney Cricket alluded to? Is the colder water/air from downstairs finding its way upstairs when both zone valves are open?

If the system is circulating all this water/air, why isn’t the spirovent down by the boiler catching it? It’s on the supply right before the zone valves.

Again, thanks for the help.
 

Last edited by xiphias; 12-02-05 at 09:56 AM.
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Old 12-02-05, 04:55 PM
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Flow restriction

I think your mix of zone valve, mono-flo tee, & toe kick heater is creating so much restriction (especially the zone valve) your circulator cannot provide adequate flow. The only zone valve I would even think of using on your system is the Honeywell V8043E-1061. This valve has far less flow restriction than most.
 
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Old 12-02-05, 09:34 PM
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Air Problem

Xiphias:

The sounds you're now describing are DEFINITELY air problems; air inside the pipes is the most common bugaboo of hydronic systems; it's pesky because of the noise, but be persistent; it won't harm anything, & it's just a matter of time until it's solved.

If you hired a contractor that did the recent install, he should be called back to resolve it; he's the one that introduced the air problem; most will honor a 30 to 90 day guarantee on their jobs; when he opened the system he introduced air, & installed the additional piping & the toe-kick unit; any one or all 3 of these factors can affect the subsequent performance of the system; another possibility is that pinhole leaks were created by the install of the toe-kick & the baseboard in the remodel; these could be introducing some air into the system..

Unfortunately, there are probably 7 different possible reasons why the air problem persists; adding additional piping to a system that "worked perfectly before" can sometimes throw the 2 zones out of balance, this is especially true if you have a single circulator serving both zones, because the water resistance can increase considerably with added pipe/water volume, especially if you have "long runs of about 35 ft".

In a case where both zones are calling for heat at the same time, the water will tend to flow more easily thru the downstairs, shorter zone, & more sluggishely in the longer zone; sometimes balancing valves are installed in this case at the return manifold to make the water resistance in both zones more equitable.

When only the upstairs zone is calling for heat, as Grady noted, the higher water resistance may be too much for a circulator that worked fine before, but now is unable to keep up; sometimes a circulator with a higher head rating has to be installed; this could explain why the Spirovent is not expelling the air; the flow in the longer zone may be so sluggish that the air & water are "sliding over each other" so that the air doesn't stay in the water solution (entrained) so that it can be carried back to the Spirovent & be expelled.

It should also be noted that when there's a lot of air in the piping, the pump is going to perform very poorly because it's designed to pump liquid, not air, and also that unlike a water without air fluid, the air/water mix is compressable, cutting down flow efficiency thru the pipes greatly; when the air is finally eliminated the circ is now pumping all liquid & quickly & efficiently moves it thru the zone & back to the boiler, as it was intended to do.

The fact that you have no bleeder valves at the convectors infers that the house's original install had a non-bladder expansion tank (air collecting system), it was subsequently changed to a bladder expansion tank (air elimination system), but nobody ever put in the required bleeders at the baseboards when the expansion tanks were changed, especially at the high points where air usually collects, on the 2nd floor.

Thus, if a contractor was involved, call him back to see if he will do the fix; if not, consider calling an expert on hot water systems; if you decide to tackle the problem yourself, the least expensive & easiest starting point would be to add manual bleeders to at least all the 2nd floor, then add them to the 1st if the problem persists.

Other points to check would be a) that the circulator is "pumping away" from the expansion tank; some installs have the discharge side of the pump flowing directly into the expansion tank; this can create a negative psi in some parts of the system that can suck in air; b) if the problem still can't be found, the system can be tested for leaks by being shut down, drained, & 20 psi of air pumped in using a test jig with a psi gauge attached; any psi drop on the gauge indicates an air/ water leak; these can often be heard as air escaping during the test, or the use of soapy water on all pipe fittings to detect air escapes.

I repeat, be persistant; all hydronic systems occasionally have air problems & it takes a while to get it expelled so you have a quiet-running system.; each hot water heat piping arrangement is unique & it thus takes time to learn each one's particular quirks; many times piping is installed with loops, bends, or hooks to go around an obstacle that ends up being an air trap & creates future problems later on.
 

Last edited by Chimney Cricket; 12-02-05 at 10:24 PM.
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Old 12-03-05, 09:38 AM
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great stuff

Grady and Chimney Cricket, thank you. Looks like I have a bunch of things to pursue now. Will be at least a week as heading out of town shortly for work. Will let you know how this all works out. Thanks again.
 
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Old 12-03-05, 04:52 PM
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xiphias

Please keep us up to speed on your progress.
 
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Old 12-16-05, 09:15 AM
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while I was out...

The requested update.

While I was out of town last week, it was decided to drain and refill the system and see what happens. Nothing changed. Still lots of gurgling, etc.

Yesterday, raised system pressure (while running) from 22psi to 24psi.

This appears to have done the trick. Through last night, only a very small periodic burble and I assume that is on its way out as the spirovent would appear to be doing its job now that there is sufficient pressure in the system to move things along.

One observation is that the pressure relief on the boiler (standard 30psi relief) did spit some water/air a few times yesterday. Over the course of the day it filled a 32oz cup approximately twice. Will check tonight and see is there's any more. Am I correct in assuming that this is probably just overpressure from the pre-existing air working it's way through the system and now that nearly all the air is out of the system that will not be an issue? Which leads to perhaps my final question:

Is this system ok to run at 24psi? Don't know what kind of tolerance there ought to be between the the actual system pressure, reading on the pressure gauge, the boiler pressure relief valve, the pressure reducing valve, etc.

Again, many thanks.
 
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Old 12-16-05, 05:31 PM
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24 Psig

Twenty four pounds is really pushing the limits. Once you get the air out, I think you will be able to drop the pressure to around 20#. Sometimes that air is stubborn & needs a real kick to get it out but after it is gone pressure can often returned to normal.
 
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Old 12-19-05, 06:22 AM
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ok

Thanks Grady. Left the system at 24psi over the weekend just to make sure all the air is out. Plan to reduce to 20# this evening.

What's the downside to having pressure so high?
 
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Old 12-19-05, 04:05 PM
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24 Psig boiler pressure

Your relief valve is a 30# valve. Most will start to open before reaching 30# & be wide open at 30#. If for some reason, your pressure crept up 2-3 psig, I would not be surprised to see the relief valve open to some degree.
 
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Old 12-21-05, 07:17 AM
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there's no going back down (!?)

So I get home last evening and go down to the basement to see how things are with the boiler. Pressure has been hanging steady at 24# since Saturday when the air issue seemed to have resolved. Pressure relief never kicked, things seemed fine.

The original goal of the trip to the basement was to try dropping the pressure back down to 20-22# per Grady's suggestion so we're not pushing any limits. But, first thing I hear (one of the zones is calling for heatso circulator is running and boiler is firing) is lots of bubbling in the return manifold just above the circulator (Taco 007). One circulator drives both heating zones and the indirect water heater and is set up down at the boiler return inlet. I can even hear the pump cavitating a bit as air appears to be getting into the pump rotor. Never do hear air exiting the boiler up the supply line, though.

Now I'm thinking this is not how things are supposed to be after 3-4 days of no bubbling/gurgling upstairs. Air should have been kicked out by now, right?

Well air is still in there and appears (at the moment) to be concentrated/trapped in the return manifold. Manifold basically consists of 1st floor zone return coming through basement ceiling, elbows downward toward boiler with coupling from 3/4" to 1" (pretty sure it's 1"), then the 2nd floor zone enters the 1" via a tee a few inches down from that, then the indirect heater tee's into the 1" as well, then 1" goes into the circulator with output into boiler. Very straightforward; looks quite clean.

Well, I figured, there's air in here and probably I don't want to mess with the pressure. But curiosity won out so I dropped the pressure down to 20-21# anyway to see what would happen. [insert "you dummy" here...] Immediately the upstairs zone starts it's gurgling/sloshing like the old days. So I bump the pressure up to 22#. Less gurgling/burbling, but still quite a bit. Back up to 24#, and things quiet down.

What on earth is going on here? Feel like I'm pretty much chasing my tail. Do I concede to forever running this system at 24-25# and probably having air down in the return manifold (not sure if it would ever get purged?)? Cavitation in the pump rotor can't possibly be good over an extended period of time.

Has this system, with the added friction of additional piping, baseboard and toekick upstairs, overwhelmed the ability of this circulator pump to push everything through? Re-reading some of Chimney Cricket's earlier comments makes me think this may be the problem.

Many thanks for input.
 
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Old 12-21-05, 04:11 PM
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Pressure

It, I guess, is possible the circulator has met it's match with the additional friction loss. Until we can figure out a way to get this air out, I suggest you crank the pressure back up if that is what it takes to make this thing quiet.
I hate to suggest jacking the pressure up another pound or two to try forcing that air thru the circulator but if you feel froggy.....
 
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Old 12-22-05, 06:36 AM
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circulator math?

Thanks Grady, for sticking with this. I'm going to let things chug along for another couple days at 24-25# and see what happens.

Meanwhile, I'm wondering if there's a straightforward way to determine circulator requirements for a given system (e.g., head, flow rate, etc.). For my house figure about 200 lin ft of pipe/baseboard per zone (175 1st floor, 225 2nd floor), rounding up to include the small loop for the indirect water heater.

thanks.
 

Last edited by xiphias; 01-11-06 at 11:53 AM. Reason: math included earlier was wrong.
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Old 12-22-05, 07:03 PM
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Pipe length

Are you telling me you have +/- 200 ft. of pipe (not counting baseboard) per zone? That is a lot of pipe.
 
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Old 12-23-05, 03:24 PM
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~175 and ~225 are approximate total loop lengths, including baseboard. I just ballbparked those numbers from sketching each floor on notebook paper at work. Will try to get a better measurement over the weekend that separates out baseboard, etc.
 
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Old 12-23-05, 05:16 PM
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Friction loss & pump head

Somewhere I have some information on calculating friction loss & pump head. As soon as I figure out where that "somewhere" is, I'll post a link or attach the chart(s).
 
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Old 12-29-05, 08:05 AM
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Thanks. Good luck finding it and will be interested to see. Hopefully it's not in the same "somewhere" as my studfinder and that nifty gizmo for making haywire twists in wire leader. I've given up on them....
 
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Old 01-04-06, 01:06 PM
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Today we had a plumber over to look at the system. Second-generation plumber, 45 years of experience, known and respected around here. He liked the overall setup as described in earlier posts. Said the system is set up right. The system has been gurgling along at 24-26# since my last post. So far as we can tell, it's only gurgling on the second floor zone. Haven't heard a problem on the first floor. He purged the second floor, never seeing any bubbles issuing from the drain hose. Then he did the first floor for good measure. No air. He confirmed what Grady said about the pressure (24-26# is too high), and set both the system pressure and the fill valve to 18#. He cycled on the upstairs heat and there was no gurgling. Maybe that was it, he said, just had some stubborn air, and see how it goes. He did say that if there continues to be a problem, perhaps installing a T with a Taco Hy-Vent on the boiler pressure relief would fix the problem, or perhaps adding mini hy-vents in the upstairs farther along in the loop (even though he said in theory with our kind of closed series loop + spirovent system they shouldn't be needed).

Within the hour after he left, however, there's quite a bit of gurgling and sloshing throughout the whole upstairs. Sounds similar to the last time I dropped the pressure.

Why when the system is theoretically air-free are we hearing lots of air?

What are possibilities here? Is the new spirovent not working? It's rather simple technology and I wouldn't think a new one would be defective. Is there a way to test it? My initial knee-jerk reaction (way back in my first post) was that the existing spirovent had clogged or something due to construction debris or whatever. So this problem spans two spirovents, both the existing and the new one. What are the odds of having the existing one fail and installing a defective new one?

One observation is that at higher system pressure, the air/gurgling problem is lessened but not eliminated. I assume that means the spirovent is working with what air is getting to it in the first place. In other words, upping the pressure is getting most but apparently not all of the air to move through the system. The gurgling sound is most apparent right when the circulator comes on. It then dissipates through that heating cycle. Then repeats the next time the circulator comes on. I assume that dissipation of noise is the air/water becoming mixed and behaving more as a coherent fluid (albeit an air-rich fluid).

Another observation is that after several days of being quiet in the first part of the second floor zone, in the past couple days we are hearing air in there again. Recall that this is downstream of the toekick heater and not all that far away from the spirovent in terms of linear feet of pipe (maybe 35 feet of supply pipe from spirovent, across basement ceiling, up to second floor, and then on its way around the upstairs).

Note: I recently re-looked at some of my photos from the framing and rough plumbing phase of the remodel and, contrary to what I posted previously, it looks like there are monoflow T's on both supply and return sides of the toekick loop. The gentleman who did that part of the plumbing recalls using two monoflows as well. Is that relevant to this problem? I saw in the Beacon-Morris install manual they call for a standard T on the supply side of the toekick loop. Big deal or no?

So do we have a bad spirovent? Do we have some weird physics problem involving system pressure, gravity, water flow restriction/drag, or what?

Is overwhelmed circulator still a possibility?

Perhaps the real question here is what is the logical way to think through this problem and what is the proper course of action to get things working properly? i.e., what are the possible sources of the problem and how do we most effectively, logically, proceed to eliminate them until the system is working properly?

Should add that I don't think the system has a leak. For one, the pressure seems to stay wherever it's set. For another, I would think by now if there was a leak we'd see a wet spot on the floor or ceiling somewhere.

Many thanks again for any insight.
 
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Old 01-04-06, 04:54 PM
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xiphias

Well, that somewhere must be the same place as yours. So far, no luck in finding the information I've been looking for.
I hate to admit it but I am just plain stumped. I do however suggest you call the plumber back & at least see what he has to say.
The two monoflow tees MIGHT be causing part of the problem especially if there is no air vent on the toe kick heater.
I don't know if any of the guys on heating help.com might be able to help or not but many of them have forgotten more that I ever knew. Here is a link: http://www.heatinghelp.com/
Please let me know if they can bail us out.
 
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Old 01-05-06, 07:49 AM
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thanks

Grady, thank you. Have posted over there. Will see what happens.
 
  #26  
Old 01-05-06, 12:12 PM
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I doubt the two monoflows are causing the problem. I have put in two separate toe kick systems and used monoflow tees on both the supply and return sides. Just make sure the monoflow tees are installed in the proper direction. If they are in the wrong direction, I can see this being an issue, but not sure if it would be what you are seeing.

Also, the toe kick units typically have a bleeder. Make sure that that is closed tight and that it is not partially clogged with debris. Going along the weird physics route, maybe air can enter through this bleeder but water can not exit.

The other thing you may want to try is closing off the water supply to the boiler. If there is a leak, the water level/pressure in the boiler should start dropping. I hate to say it, but there could be a leak which is draining in such a way/spot where it is not apparent. I have seen that as well.

Good luck
 
  #27  
Old 01-06-06, 06:44 PM
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on the road to recovery, I hope!

Alright, now feel I'm moving forward.

Many many thanks to Grady for finding some info on how to calculate pump head and flow rate. The "rules of thumb" are apparently:

Head (ft) = (Total length of longest loop in system) * 1.5 * 0.04

The 1.5 multiplier is adding 50% for elbows, fittings, etc. The 0.04 I can't explain.

Flow rate (gpm) = boiler BTUh rating / 10,000

So for the pre-remodel system, the longest loop was about 175 ft. Head requirement was thus 175 * 1.5 * 0.04 = 10.5 ft

That is within the spec for the existing Taco 007 circulator (0-11 ft), barely... but hey we never had a problem before, either.

For the post-remodel system, about 30 ft of pipe/baseboard, plus a short toekick loop, were added to this loop. So now at a minimum we're at 210 ft. Do the math and 210 * 1.5 * 0.04 = 12.6 ft.

Guess what? Circulator would appear to have met its match. I'm guessing that's why we're not pushing the air out of the system.

Now, about the flow rate. Which BTUh do I use to figure that out? Input BTUh? I=B=R Net? There's about a 25-30% difference between them that will affect my new circulator selection. Speaking of which, brand suggestions? Taco? B&G? Grundfos? Other?

And, what kind of cushion should I have on these numbers? 5%? 15%?

Almost there! Thanks.
 

Last edited by xiphias; 01-06-06 at 06:58 PM.
  #28  
Old 01-06-06, 07:21 PM
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BTU/hr & circulator

For the BTU/hr part, use the I=B=R rating. As for the circulator, you might want to check out Grundfos 3 speed circulators. The one problem with them, and it may not be a problem for your application, is the flanges are rotated 90º as compared to the Taco 007. Here is their web site:
http://www.grundfos.com/web/HomeUs.n...ag/PAVA-53CT8Y
 
  #29  
Old 01-10-06, 08:52 PM
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Smile Hydronic system pressure; Positioning circulator pump

To: xiphias

Each foot of rise effectively takes away/ e.g. reduces the pressure in the system above it by .434 psi, which results in 1.0 psi less pressure for each 2.3 feet of height. You can easily see that a two story house with approximately 8' of rise per floor, loses about 7 psi on the way to the baseboard radiators on the second story of a house with basement furnace location; so you can see that flow rate & efficiency drops drastically with
rather small increases of height and low system pressure.

Another link to the same website addresses the issue of circulator pump positioning that is excellent. I note the fact that, as mentioned there the circulator that comes with furnaces is where it is for convenience of the shipper, and installers seem to always leave it/them there in the same place - most often right over the burner assembly, which is not only bad practice for pump efficiency, but also subjects the BURNER to becoming drowned when the circulator pump seal gives-up and springs a leak. That, of course ruins the burner motor and any controls nearby that do not like baths.

The problem of burner drowning is rather easily solved, though, by simply installing a shield of heavy duty aluminum foil (temporarily, then better material when you have more time), to direct the drip away to a bucket, floor drain, scupper, or other safe place until the furnace can be shut down to move the circulator assembly.

Also included is a link addressing when to replace Air Vents. I had experience with one sticking open. Temporary fix was to rap it smartly on the side with a short stick, which dislodged whatever piece of scale or other foreign matter that was causing it to stick in the open position, and it stopped leaking. Worked for me. Then I replaced it with a new one.

Link below addresses circulator positioning:
http://techtips.remichel.com/ShowIns...stallItemID=40

Link below has flow rates for closed hydronic systems based upon 20
degree F. drop & one gpm flow rate per 110k BTUH:

http://techtips.remichel.com/ShowSer...rviceItemID=92

Link below is titled, "Replace Air Vents". which recommends new vents
when replacing boiler:

http://techtips.remichel.com/ShowSer...rviceItemID=92

Good Luck.


Yours truly,

arksdad
 

Last edited by arksdad; 01-10-06 at 09:58 PM. Reason: MISSPELLING
  #30  
Old 01-11-06, 11:38 AM
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update...

Had the hydronic systems design guy from a local plumbing supply house over this morning. Nice guy, seemed very competent. He had some interesting comments on how the existing system is set up, and what he might have done differently, such as put a separate circulator on the indirect and make it priority-zoned. But then he said "but that's just me, and I'm a circulator-oriented guy, and there's other ways to do just about anything with these systems." Nicely put, recognizing different philosophies of plumbing, etc. And I should add that the supply house offers this service gratis (wow), although typically it's used by contractors spec-ing jobs.

Anyway, his assessment is that the existing Taco 007 circulator is inadequate for the flow/head requirements of the newly-lengthened system, hence the air problems we're having. His recommendation is to replace the 007 with the Taco 0010. So that's what we're gonna do. Looks like this will be a simple swap job as we have just enough clearance between boiler, wall, etc. to fit the slightly larger pump.

Nice to see that my amateur observations and calculations, using forum input, research, and resources gained from the education I've had here, agreed with an on-site pro. However, I had concluded that the new circulator should be the Taco 008 in order to meet the much higher head requirements. He said that the 0010 could still meet the demands of the system and would be a better choice than the 008 due to its flatter performance curve. Pumps with steeper curves apparently have the potential to be noisy, particularly in zone valve systems (ours). Check out http://www.taco-hvac.com/uploads/Fil...CurveChart.pdf and you can see the difference in the curves for our existing 007, what would have been my choice (008) and his recommendation (0010).

So we'll see how it goes and post back here with results.

Thanks to all, especially Grady.
 

Last edited by xiphias; 01-11-06 at 12:41 PM. Reason: flat pump curves better for systems that use zone valves because the flat curve minimizes changes in flow as zones open and close.
  #31  
Old 01-11-06, 05:09 PM
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Pump curves

The folks at that supply house really do offer a very valuable service. I certainly hope you deal with them. He is right about pumps with steep curves.
BTW, I totally agree with him on the use of circulators vs zone valves. Honeywell does make some zone valves with a larger than normal port which helps flow substantially.
 
  #32  
Old 02-06-06, 08:03 AM
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ugh! tale of woe continues...

OK, here's a summary of the past couple weeks:

1) installed new Taco 0010 circulator per design guy's recommendation. Not only did it not fix the air problem, but it was really loud. Vibration feeding back up the heating pipes, made the living room feel like the inside of an electrical transformer. No good.

2) Using some excellent on-line resources at Taco's website, I developed my own set of piping diagrams and figured out head requirements at various flow rates for the whole house. Determined that the toekick loop was adding 2-3 ft of head to the second floor zone, and that eliminating it would drop the head requirement at the minimum flow rate to remove air (about 3.2 gpm in 3/4" copper) to within a half foot of the pre-addition zone. We can go back to our old 007 pump and theoretically be pumping about 4 gpm.

3) ran all my calculations by the design guy, who concurred with my numbers. One of his suggestions was to put each zone on its own circulator, sized appropriately (would have put an 007 on the first floor zone, a 009 on the second, and an 005 on the indirect water heater). Well, given the bad experience with noise/vibe from the 0010, and the time/expense of doing all that, we opted to simply cut out the toekick loop. Turns out we don't need the heat in that part of the room anyway, and getting at it was very simple.

4) So, toekick loop is out. Cut out monoflow diverters, replace with straight 3/4" pipe. Reinstall 007 pump.

5) All should be well, right? Wrong! Same old tons of air, although it is obvious now that getting rid of the toekick loop significantly reduced the flow restriction. What used to sound like a high-pitched garden hose of water/air now sounds like a lower-pitched wave running up the beach.

6) In comes a new guy: boiler installer, system designer. Said "I heard your pump cavitating before I even walked through the basement door." This guy applies a super-purge the likes of which I've never seen. First he purges the system running forward through the zone valves to the drain valves, then he closes the zone valves and blows a bunch of air backwards out the boiler. COOL! Puts brass caps on all the drain valve spigots, just in case they're admitting air. No more cavitating. Would appear that the system was simply never really full of water, and had so much air the pump couldn't push the air through.

7) That was Friday. Saturday morning, the upstairs zone starts calling for heat. First couple cycles, the system is totally quiet. Hooray! After a few cycles, hear a small bubble. Same deal Sunday morning. Best data from this morning. System calls for heat around 3am. Totally quiet. Hooray! Maybe it just took a day or so to get the last of the air out. Wrong! After a few calls for heat, hear a small bubble during one call. Then it just progresses from there: the air gets worse with each heating call and now can hear it throughout the piping upstairs, and the pump is cavitating again.

What on earth is going on? How can the system be tight and quiet then develop so much air? The system temp is 175-180 F. Pressure is 18-20#. I can't imagine we're really boiling water and making bubbles, are we?

The new boiler guy is in town tomorrow and we'll ask him, but other opinions would be most welcome. Thanks.
 
  #33  
Old 02-06-06, 04:13 PM
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Unhappy Wow

The only thing I can think of is air is working its way out of solution as it heats. I've seen it lots of times, especially if the water being fed to the boiler goes thru an in home treatment system. The prefered way to purge is to discharge the purged water into a bucket or drum containing a submersible pump to pump this same water back into the boiler. This way the introduction of fresh water is minimized. I understand I am grasping at straws but that's about all that's left of the life raft.
 
  #34  
Old 02-17-06, 08:06 AM
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pressure, solution, etc.

OK, we did another super-purge on Tuesday this week. Also raised the system pressure so that cold it's around 21-22#. Full-on running it's up around 25#. So far (though it's been warm here this week), we've heard nary a burble. Should know more as we heat through the coming cold spell.

Obviously, we'd like to get the pressure back down to 18# or so, but frankly, I'm almost afraid to try.

Is it reasonable to assume that at this higher pressure we're keeping the air from coming out of solution? Based on the results of the previous super-purge, I think Grady has hit the mark -- even at 170-180F we're driving air out of solution and for whatever reason it's just not getting removed down at the spirovent, perhaps due to inadequate circulation oomph (e.g., upstairs zone so long now it's really marginal).

Alternatively, maybe this is the purge that finally flushed the air out and dropping the pressure won't result in the return of air problems.

One thing I'm considering is raising the high limit to around 200-210F for a day or two, figuring that if we can drive the air out under this higher pressure, then it will work through the spirovent. Then I have a bunch of de-oxygenated water and can safely reduce both temp and pressure to normal working values.

Sensible, stupid, dangerous?

Probably a more reasonable course would be to slooooowly bring down the pressure, maybe over a week or so, draining just a bit of water at a time and not mess with the high limit. In which case, where and how to drain? Use the boiler pressure relief valve? The valve/bib at the boiler return (under the circulator, which is mounted on the return -- I know I know we should be pumping away but way back when I didn't know all that...).

Suggestions? Thanks.
 
  #35  
Old 02-17-06, 09:22 AM
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I would think that the only way you could be driving air out of solution would be if you had a conventional style expansion tank (no bladder) that would allow the air to go into suspension. How much air can there be in your water, especially with a spirovent in the circuit.

On a normal basis are you adding any make-up water or is your feed regularly closed?

Can you easily put the spiro and extrol tank on the return before the circ? Then you'd be pumping away at least...
 
  #36  
Old 02-17-06, 02:04 PM
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Not sure if we're adding any make-up water. I have been pondering the possibility of a leak for some time, but haven't been home long enough at one stretch to feel comfortable shutting off the supply to see if system pressure drops. No LWCO on this system that I know of.... However, the fill valve was set to 16# two years ago. We ran the system at 20+# for a week or so a few weeks ago. It held pressure just fine. I would have expected that a leak (or other need for make-up water) would have allowed the system pressure to drop back down to the fill valve setting, then add make-up water to compensate for a leak at the fill-valve pressure. And we would probably see a leak given the apparent magnitude of the air in the system. More recently the fill valve was set to 18# (during which time we verified that it appears to be working properly in auto-mode), and now we're running at 20+# again. So far, again, system pressure is holding.

Expansion tank is fine, so we're not adding make-up water to waterlog the tank.

Spiro and expansion tank need to stay where they are due to piping layout constraints. Also it's set up where spirotherm says it should be (on supply where water temps highest). Have thought about maybe putting a Hy-Vent on the second floor if it'll fit in the convector housing.
 
  #37  
Old 02-17-06, 02:14 PM
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Pressure & Temperature

As reluctant as I am to run a system with 25# of pressure, my gut feeling is to let sleepping dogs lie.
 
  #38  
Old 02-17-06, 02:35 PM
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Me too! Thanks.
 
  #39  
Old 02-17-06, 03:15 PM
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Why don't you turn off your feed for a while, monitor the pressure closely and see if it drops? If you have a leak and it goes undetected it'll kill your system.

Good luck...
 
  #40  
Old 02-18-06, 09:14 AM
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Pinhole Leak! Pinhole Leak!

I think.

Turns out the sleeping dog was perhaps playing possum. Started to hear some air this morning.

Possibly the exchange with Who got me thinking hard enough about a leak that for about the third time (but the first time in at least two months) I went around to all the baseboard end caps and pulled them off to look at all the piping I could see. Got to the end cap just upstream from where on the past two occasions the air problem seems to get started. (When we've had a good purge, it appears that the air problem begins to manifest itself early in the circuit, but that might be biased somewhat because it's right near the bed.) Found a thin but pervasive white-and-green crust on the riser. Seems to cover most of the vertical section of the pipe, at least down through the subfloor. I'm guessing that this is what copper pipe and our local water residue look like in a small, evaporating leak.

In getting the baseboard end cap off, I may have put my thumb on the elbow joint and might have removed some crust at the leak source (the joint). If not, then there must be a pinhole(s) about 1/2" below the joint as that's where the crust starts.

Am I correct in assuming that a very small leak like this will introduce air, but not measurably affect system pressure over say, 7-10 days (about the time period between the many corrective actions we've attempted, which have involved purging, draining, etc. and essentially resetting the system)? Also that when it is leaking, this early in the circuit the water is being evaporated fairly quickly by the ~180F surface temp of the pipe?
 
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