Radiant heat - have air bubbles - need advice

[UpstateNY]

Guys,

Solve the puzzle, win a prize.

I just fired up a closed radiant heat system, with 50/50 antifreeze made for radiant systems. The in-floor Pex and all other associated fittings are leak free. When I first filled the system with oxygenated tap water, then drained out half the water and pumped anti-freeze, I used the fill/purge valve to rid the system of bubbles. Then I left it running overnight and came back to more bubbles. A friend suggested that suspended micro-bubbles in the water had simply gathered together to form larger bubbles. So I purged it again until there were no more bubbles. Left it running overnight again, yep, bubbles have returned. So that means bubbles are created while the system is running. And as far as I know, that’s the only time they’re created.

Attached is a pic. I’ll take a better one, but since the floor got poured today (the radiant system was running during the pour), I couldn’t get any closer. And yes, the tank and "system" are level, it's a crooked pic .

From top to bottom I have the following: Out of the top of the water heater, hot side, there's a tee into the Air expansion tank (you can’t see the tank, it’s out of the pic over the top of the heater), the other side of the tee goes to the pump (pumping downwards), then the pressure-relief valve, then the pressure gauge, then the fill /purge valve, then turning right leading into the hot manifold, down into the in-floor Pex, up from the Pex into the cold manifold, up and back into the top of the water heater into the cold side. The air eliminator cannot be seen, it is screwed into the right side of the hot manifold.

I have never used shark-bites in my life, but used them for all connections. They don’t leak and all they grip onto is to 3/4 " Pex plastic pipe (no copper pipe in the system).

My one thought is: could air be leaking into the system on the inlet side of the pump ? It does use a Sharkbite there. I assume there is suction at that point, vs pressure on the other side of the pump ? Assuming there is suction at that point, would a Sharkbite let in air ? Do Sharkbites crave pressure but not do well with vacuum, assuming there is vacuum at that point ?

The thing I find overall confusing is that the system is under-pressure, by virtue of the pump in operation (although maybe not over the entire circuit, maybe there is a vacuum at some point(s)), so how could air get into a positively-charged system ?

You would think if the system is above atmospheric pressure, all’s it could do is leak, how could it **** in air ?

Or might it be because I initially used tap water, there's a fair amount of oxygen captured in the water and I might have to purge it multiple times ?

Any thoughts ?

 

[anthony666]

you got no air eliminator, you got no expansion tank .. it looks like you're using the same water to supply your domestic hot ?? so you're gonna be filling the tank regularly with fresh cold oxygenated water ??? you could work at it for ever and it will always be full of air


whats my prize ???

 

[UpstateNY]

whats my prize ???

None, you didn't read the post, you just looked at the pic .

Closed system, with air eliminator and expansion tank -they're just out of the pic until I can take a better one.

 

[anthony666]

there's no 'suction' in a circ pump either bud .. they work by creating a pressure differential, the system always flows to low pressure in order to equalize itself and thereby gives you circulation

 

[anthony666]

None, you didn't read the post, you just looked at the pic .

lol you're right .. i read it over and .... yea yea

 

[anthony666]

did you win the sharkbite lottery ???

 

[anthony666]

k .. lemme start over .. if you fart in the tub, where do the bubbles go ?? up, ergo, where should your vent be ?? next .. the spot right behind your pump is where the point of most constant system pressure is, that's where you tee in the expansion tank .. again, fart in the tub, bubbles go up, so teeing the expansion tank up is a bad idea

redo the system in copper, soldering is easy, check youtube for some how-tos and maybe your local home depot has a guy that can show ya (do they do that still ??)

how did you get the glycol in ?? how did you purge it and still keep the mixture right ??

 

[pstnbly]

Since the system is filled with glycol you could try closing all but one loop at a time, run the pump at high speed for an hour each loop and see if that purges the air.

The accepted purge method would be to have a purge valve on each loop manifold (supply and return) (can't see manifold ends in pic) close all but one loop valve, place a return hose from one purge valve in a bucket, place the suction line from a purge pump in the bucket attach the discharge line from the pump to the other manifold, put some glycol mix in the bucket, begin purging, watch for bubbles to cease, close loop valve, move on to next loop, kapisch?

I'll take mine in cash

 

[UpstateNY]

k .. lemme start over .. if you fart in the tub, where do the bubbles go ?? up, ergo, where should your vent be ?? next .. the spot right behind your pump is where the point of most constant system pressure is, that's where you tee in the expansion tank .. again, fart in the tub, bubbles go up, so teeing the expansion tank up is a bad idea

redo the system in copper, soldering is easy, check youtube for some how-tos and maybe your local home depot has a guy that can show ya (do they do that still ??)

how did you get the glycol in ?? how did you purge it and still keep the mixture right ??

i've soldered a lot, thought I'd use SB's for their ease of use. So you're suggesting that Sharkbites are the cause of the air infiltration ?

Radiantec Inc designs these systems for a living, they show the air expansion tank teeing off the top of the hot water heater in their designs, just saying. Same for the air vent, they're designs show it "in-line' on the horizontal piping system where all the guages, purge/fill valves, gauges, relief valves etc are, mounted horizontally, halfway down tank.

Here's the radiant install manual: http://www.radiantec.com/pdf/Direct_Radiant_Heating_System.pdf

I appreciate your critique of the design as regards the location of the air eliminator and expansion tank, but their placement or mis-placement (and Radaintec would say they're in the correct place) will not explain the air issue ?

Lastly, initially I charged the system with 100 % tap water, then drained about half of the water out of the system, then added the anti-freeze via the purge/fill system to obtain a roughly 50/50 bubble-free mixture.

 

[UpstateNY]

Since the system is filled with glycol you could try closing all but one loop at a time, run the pump at high speed for an hour each loop and see if that purges the air.

The accepted purge method would be to have a purge valve on each loop manifold (supply and return) (can't see manifold ends in pic) close all but one loop valve, place a return hose from one purge valve in a bucket, place the suction line from a purge pump in the bucket attach the discharge line from the pump to the other manifold, put some glycol mix in the bucket, begin purging, watch for bubbles to cease, close loop valve, move on to next loop, kapisch?

I'll take mine in cash

No prize for you either ! Before I purge, you can see all the air bubbles running around inside the Pex. I use the method you describe (use bucket with glycol, watch for air bubbles to cease etc) but I purge all 5 loops at once as I don't have valves to do each loop individually, and when I'm done, ALL air bubbles are gone in ALL loops - guaranteed. I button the system up, let it run for 12 hours, and come back to more bubbles. It's not my purging method, there are NO visible air bubbles when I am done purging .

Maybe what I'm asking here from folks that have built radiant systems, if one uses oxygentated tap water (with anti-freeze), did you have to purge more than twice due to trapped oxygen in the system ? I purged twice so far, and there are no VISIBLE circulating air bubbles after each purge, but might the pump still be "frothing" air out of the tap water and it might take multiple purges to clear that out ?

 

[Highbeam]

Are you pressuring the system? As in, when the pump is not running you still have 15 psi? Does the static pressure change after running it? Trying to discover if you are introducing more air into the system or just getting it out.

We can't see it but are you using a real air scrubber or just one of those tiny bleeders?

 

[UpstateNY]

Are you pressuring the system? As in, when the pump is not running you still have 15 psi? Does the static pressure change after running it? Trying to discover if you are introducing more air into the system or just getting it out.

We can't see it but are you using a real air scrubber or just one of those tiny bleeders?

HB,

You might be on to something. Here's pic of the of the manifold that you can't totally see in the pic. I'm not sure if that's a bleeder or a scrubber. The manifolds is/are made by IMSA, and Italian company .

Let me ask a real stupid question, how do I pressurize the system ? Via the air nozzle on the top of the expansion tank ? The tank supposedly comes pre-presurrized, 12 PSI sticks in my mind, but I never checked it .What should the running and static pressure be in PSI ? Should they be the same value, or when the water heats does the pressure in the system increase ? Since the concrete is still wet, I can't say for certain, but I do think the running pressure is more than the static pressure.

 

[anthony666]

. So you're suggesting that Sharkbites are the cause of the air infiltration ?

no .. i'm suggesting that a lot of them in one build kinda makes the whole thing loose .. say for arguments sake you had 10 of them and they each had a degree of deflection by the time you add them all together there's ten dgrees of deflection and the sum of them might possibly cause a leak, but i doubt it

I appreciate your critique of the design as regards the location of the air eliminator and expansion tank, but their placement or mis-placement (and Radaintec would say they're in the correct place) will not explain the air issue ?

pockets of air get reabsorbed into water as it circulates .. no disrespect to radiantec, but it's physics .. bubbles go up, the end. if they have no way to escape they are trapped .. again, no disrespect to the wonderful folks at radiantec, but if you want a real authorative voice on hydronic systems, go to the library and get 'modern hydronic heating' by john seigenthaler

and really, if radiantec had their **** down cold you wouldn't be asking why it's full of air .. yea ??

 

[UpstateNY]

and really, if radiantec had their **** down cold you wouldn't be asking why it's full of air .. yea ??

Not necessarily. The design might be fine, it could be the SB's etc etc I can't say the design is right, the issue is, if it IS wrong, how does the wrong design account for air getting in ? A bad design might in some deficiency in the system, but what design error would cause air to enter the system ? Or maybe you're saying, that bad design might prevent me from properly purging the system ?

I'm not arguing, I want to figure this out, I'l redesign it if I have to, and eliminate the SB's with soldered copper, but rather than shotgun it, I'm trying to see if someone definitely knows what could be causing this. Again, when I purge the system, ALL air bubbles are gone.

P.S. My local library has that book, gonna get it, thanks for that info

 

[anthony666]

when you filled the system you introduced dissolved oxygen in your tap water .. there are microscopic bubbles in there, they coalesce into bigger and bigger bubbles .. it takes days of heating and circulation for these bubbles to escape

meanwhile you gotta do your part by giving them an out .. at the highest spots in the system where they naturally accumulate

in your case you would pressurize the system by shutting off the 'out' valve before you shut the 'in' valve while you're purging .. that lets you well pump or city water pressurize the system .. don't go too crazy, a good rule of thumb is if the valves are fully open by the time you wind them shut is a good baseline

 

[anthony666]

not arguing either brother, trying to help you stay warm

 

[UpstateNY]

when you filled the system you introduced dissolved oxygen in your tap water .. there are microscopic bubbles in there, they coalesce into bigger and bigger bubbles .. it takes days of heating and circulation for these bubbles to escape

meanwhile you gotta do your part by giving them an out .. at the highest spots in the system where they naturally accumulate

in your case you would pressurize the system by shutting off the 'out' valve before you shut the 'in' valve while you're purging .. that lets you well pump or city water pressurize the system .. don't go too crazy, a good rule of thumb is if the valves are fully open by the time you wind them shut is a good baseline

Ooooh, there's a germ of idea there. As written, I have my expansion tank on a tee, on the hot output of the water heater, and mounted above the water heater. I have some "clear" Pex from the tee up into the expansion tank. There is an air bubble in that clear pex that goes up into the expansion tank when the system heats up, when the pump is first turned on, the air bubble bounces up and down inside the clear Pex.


How do those expansion tanks work ? If they are a rubber bladder, that air and water can go into, right now, by virtue of the presence of the air bubble on the inlet side of the tank, that bladder is full of air. When the systems heats up, I can see the air bubble go up into the expansion tank (and the water below the air bubble then begins to enter the tank). But more importantly, when the system cools, the air bubble moves down and "into" the tee, thereby adding air into the system.

How and/or should I "drain" the air out of that bladder ? Should the air bladder been filled with liquid before installing ?

 

[brewchief]

A real microbubble eliminator would help matters a bunch, spirovent is one brand but there are plenty others that are pretty much the same.

Pex laid out for a floor has a lot of very small ups and downs and always seems to hold air bubbles even after you think they are all gone.

That style of manifold will allow you to turn off each zone if need be, the white caps turn one way or the other to shut off flow.

I don't care for the sharkbites but I'm not sure if they are a problem for sure or not.

Mount your bladder tank to the bottom of the spirovent.

Is the pex you used oxygen barrier?

 

[Ron Lombardo]

in order to solve your dilemma you need to remove the pipe covering and take a picture of the entire piping system around the water heater ... the order the components are piped is very important for example ... did you use a SPIROVENT ... it needs to be the first component on the supply off ..in your case the water heater ... also the mixture of antifreeze is not 50/50 ... its more like 70 / 30 should take you down to zero degrees ... too much antifreeze will require a larger pump ... it decreases the gpm.

 

[anthony666]

yea, it's a bladder with air pressure on one side and your system water on the other side .. as the water heats up it expands and pushes against the bladder

all you gotta do to kill that bubble is let it escape upwards by flipping the tee down

if you don't wanna spend loot on an air eliminator solder in 3 feet of vertical pipe at the highest point of the system with a boiler drain (hose bib) on the end .. the air will collect up there and you can bleed it off through a hose into a bucket .. it's gonna take you days and days to get all that air out mate .. what do you have in the system ?? 70 gallons ?? if you had 10% dissolved oxygen in the system, and managed to get 90 % of that out during your purges you still have over a half a gallon of air in there that's gonna come out slow

patience .. be this guy

 

[Ron Lombardo]

if you don't wanna spend loot on an air eliminator ???? Instead spend it on gas .... LOL

 

[pstnbly]

Dear upstate, look on your pic, see where it says "manual control knobs with provisions for Thermal Actuators"? You can isolate the loops using these they are VALVES! Look again at the pic " manifold shut-off Drain Valves" these are PURGE VALVES.

Lots of good advice here between the BS, Tony6 is a little snarky but he knows his stuff, but obviously you are not hearing what we're saying. I personally have many full radiant systems up and running on wood, condensing and conventional boilers. Systems with multiple zones and multiple heat sources combined, using conventional and delta P circs, sophisticated control schemes, outdoor reset and all the toys.

If you can't be open minded about what we are saying then good luck to you, you may never purge this system. Each loop must have a confirmed purge first! Only then can you move on to purge the system completely. Good luck to you.

If I knew then what I know now, I would have bought Sharkbite stock.

 

[anthony666]

Tony6 is a little snarky but he knows his stuff

hey !!!





lol

 

[acmikee]

install a auto vent at the highest point like a Hoffman #79 or something simular

 

[Highbeam]

install a auto vent at the highest point like a Hoffman #79 or something simular

and for crying out loud flip the expansion tank so that the water inlet is on top, AKA so the fart bubbles can rise out. Easy to do, sharkbites have a wonderful feature of swivel/rotation. Flip that ***** down.

Sorry, 15% hard cider talking.

A real spirovent is not expensive and at the high point of the system will let out the bubbles. Your water heater will do a pretty good job of allowing a zillion fine bubbles to form into a few big ones.

You presurize the system with the fill water.

 

[UpstateNY]

in order to solve your dilemma you need to remove the pipe covering and take a picture of the entire piping system around the water heater ... the order the components are piped is very important for example ... did you use a SPIROVENT ... it needs to be the first component on the supply off ..in your case the water heater ... also the mixture of antifreeze is not 50/50 ... its more like 70 / 30 should take you down to zero degrees ... too much antifreeze will require a larger pump ... it decreases the gpm.

Ron,

I will remove the pipe covering and take another picture today.

The actual mixture ratio is 60/40, understood it makes the pump work harder and reduces the GPM. But I've got loads of flow, it's a 3-speed pump, and the mixture ratio doesn't account for my problem - air bubbles .

No, I did not use a Spirovent (but I know it's a good product), the manifold pictured above came with it's own air eliminator, and I acknowledge that vent may ****. I can buy a spirovent and easily remove the existing vent and cap it off. Thanks for your response, good idea about the Spirovent and its placement in the system.

 

[UpstateNY]

A real microbubble eliminator would help matters a bunch, spirovent is one brand but there are plenty others that are pretty much the same.

Pex laid out for a floor has a lot of very small ups and downs and always seems to hold air bubbles even after you think they are all gone.

That style of manifold will allow you to turn off each zone if need be, the white caps turn one way or the other to shut off flow.

I don't care for the sharkbites but I'm not sure if they are a problem for sure or not.

Mount your bladder tank to the bottom of the spirovent.

Is the pex you used oxygen barrier?

Chief,

The white caps don't control flow, but the ones on the top manifold do, so I can turn off each zone if need be. I'm not concerned the pex is leaking as before the pour the system was runs for days, no leaks.

Pex is oxygen barrier.

"Mount your bladder tank to the bottom of the spirovent" - the vent is an in and out device I think, so you mean plumb the bladder on the output side of the vent ?

 

[UpstateNY]

I've ordered a Spirovent for the system and will install it on the output side (hot side) of the water heater. So it'll be up high where it most likely will "see" the air bubbles. I'm not sure that POS air eliminator that came with the manifold is doing a damn thing.

I did some research, Sharkbite is "certified" for use with Radaint Hydronic systems. Makes sense if the things can sustain domestic hot water with city water pressure, they can take a lower temp, lower pressue system such as this.

 

[anthony666]

spirovents are three port .. in, out, and a 1/2" NPT port on the bottom that you plumb in the expansion tank and system make up water via a pressure regulator and a back flow preventer .. put it about 6 inches upstream from your system pump, that's the point of most constant system pressure where both the spirovent and the expansion tank are designed to work optimally

don't remove the vent from the end of your manifold .. the more points of egress available for system air the better

seriously the shark bites are ghetto .. you could probably build a garage with zip ties and duct tape, but it's just not the right way to do it, is it ??

check your manifold picture again .. 'manual control knobs with provision for thermal actuators' .. take the cap off, and watch the opposing flow meter .. see it change ?? now take a look at what the cap was covering, there's a little *** there .. that's a valve, ergo, adjustable .. el chiefy was right

 

[jlckmj]

I think you will be set once you put the spirovent up top, I have one there and as I fill my tank with water I can actually hear the air escaping from it. I also have a vents like yours on both of my manifolds and I don't think they ever eliminated any air.

jim

 

[UpstateNY]

spirovents are three port .. in, out, and a 1/2" NPT port on the bottom that you plumb in the expansion tank and system make up water via a pressure regulator and a back flow preventer .. put it about 6 inches upstream from your system pump, that's the point of most constant system pressure where both the spirovent and the expansion tank are designed to work optimally

don't remove the vent from the end of your manifold .. the more points of egress available for system air the better

seriously the shark bites are ghetto .. you could probably build a garage with zip ties and duct tape, but it's just not the right way to do it, is it ??

check your manifold picture again .. 'manual control knobs with provision for thermal actuators' .. take the cap off, and watch the opposing flow meter .. see it change ?? now take a look at what the cap was covering, there's a little *** there .. that's a valve, ergo, adjustable .. el chiefy was right

Ok, spirovent has been ordered and I'll plumb it the way you suggest. I leave the existing POS vent as well.

Sharkbites are the nuts. I've soldered enough in my life, these things are sweet, as is Pex pipe. I don't give a rats *** what they cost. Time is money .

Both manifolds have control valves, the orange ones are easy to actuate, the white ones are not.