Air in system-is my boiler plumbed correctly?

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Old 07-13-20, 10:25 AM
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Air in system-is my boiler plumbed correctly?

Weil McLain HE4 series 3, Nat. gas boiler. This is an older cast iron boiler that has had every component replaced over the years except the boiler sections. Single story house with 3 zones, one circulator. Baseboard copper with aluminum fined radiation.


SYSTEM OVERVIEW:
  • The zone vales are old style Automag electromagnet type. They are on the system return.
  • There is no air scoop in the system, just a high vent, and manual key vents in various locations.
  • Circulator is on the return mounted on boiler inlet (factory location)
  • The expansion tank is located on the return zone manifold on suction side of circulator.
  • The cold water inlet from pressure valve is also on the return manifold
  • There is no Backflow preventer
  • Both supply and return manifolds have dead end stubs for possible future zones
ISSUES, AND CONCERNS:
  1. System makes noise, and has air in piping, Auto vents don't work well. Been difficult to remove air
  2. I always wonder if system was originally plumbed correctly with zone valves, circulator , expansion tank, and cold water inlet on the return.
  3. The dead end stubs on the manifolds make me wonder is they are trapping air?
Proposed possible changes to system:
  1. Install Vertical Spirovent on vertical Supply line from boiler before supply manifold. There is no room for a scoop without a lot of plumbing.
  2. Move expansion tank, and cold water inlet closer to the circulator inlet (per Weil McLain directions).
  3. Install back flow preventer and replace the pressure reducing/fill valve.

Please look at the attached photos of my system and the layout. Any suggestion greatly appreciated.




ORIGINAL WM BOILER INSTALL INSTRUCTIONS. NOTE LOCATION OF EXPANSION TANK, AFTER CIRCULATOR?


CURRENT WM INSTALL INSTRUCTIONS: NOTE LOCATION OF EXPANSION TANK BEFORE CIRCULATOR?








DEAD END STUBS ON MANIFOLDS, POSSIBLE AIR TRAP?

 
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  #2  
Old 07-13-20, 12:59 PM
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Have you tried bleeding the air out of the system? Once, of course, the system must have worked OK? And any air was eliminated? What is the system pressure? If it is maintained at, say, 15 psig cold, which is above atmospheric, the question is how did the air get into the system? There are several possible ways for that to happen, but that question needs be answered before making your proposed wholesale changes.
 
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Old 07-13-20, 02:18 PM
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Thanks for your input! I have tried bleeding the system several times over the years. I have battled this issue for a long time. The air vents have always been problematic for me which is the reason for wanting to try the Spirovent for air elimination. If I turn the cold water supply off, isolating the system, it has gone to zero pressure indicating a leak, but none are found. The air vent has a mini 1/8" ball valve for quick change. If I shut the valve eliminating the vent, the system holds pressure which is 12 psi. Simple solution, replace the vent (that is not visibly leaking). However, I want to sort out whether the plumbing is correct prior to the heating season, so wholesale changes are something I am prepared to do even if it's just to increase efficiency of the system after I sort out the air issues.

Looking at the system, how would you suggest I correctly bleed it with the way the system is currently plumbed. zone returns are plumbed: zone valve on each zone>drain valve>isolation ball valve>return manifold. On supply side: hot water piping from boiler>supply manifold>isolation ball valve on each zone>supply to zones.

Again, thanks for the help......
 
  #4  
Old 07-13-20, 04:44 PM
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L,
These are a couple thoughts I have about your system. It really isn't piped that bad. The first thing I would do is put a Spirovent on the supply pipe but you need a special design made for verticle operation which I will put a link for so you can see what is available.

Another thing that I don't agree with are those auto vents. They have their purpose but not on a residential loop system. First off once the pump comes on the water flow by so fast no air gets removed anyway. Next, the vent can fail in 2 ways. The first by leaking water and the 2nd is by letting air get sucked into the system when the pump runs. You can solve this issue by just tightening the cap down to eliminate the use of the vent altogether.

On a Weil Mc-lain you need that auto vent on the boiler. As I said if it is no good you can replace it or at least unscrew the top and check for debris. That is a good Taco vent I believe. That vent should be operational at all times which means leaving the ball valve open. If the pressure goes down with the valve open it could be because you are releasing air and with the main shut off there is no water coming in to replace it. I would leave the ball vale open to the vent and leave the main ball valve to the boiler open to make sure you have water and then you will be able to check for water leaks.

Another possible place you could be getting air and not see water is if your pump gaskets get bad. They will not be bad enough to leak water but worn enough to suck air in when the puymp runs.

According to what your feed valve pic shows I cannot see any fast fill feature on it which is a lever that bypasses the factory setting used to manually increase the boiler pressure.


The way I bleed a system is to isolate all zones except the one being bled and then shut off the return ball valveto that zone and in your case manually open the zone valve so the water can circulate through the zone.

Put a hose on the drain valve on the zone to be bled. Increase and maintain the boiler pressure to between 25-28 psi to force the water and air through the zone and bleed until you get a steady stream of water then close the feeder and drain at the same time and you should be good to go on that zone. Close the return valve and zone valve and repeat with the other zones the same way.

When all done you should have roughly 25 psi in the boiler. Drain off about 5 psi and run your boiler between 18-20 psi. With wet rotor pumps like yours the higher pressure helps with cavitation.

When you bleed your system it should always be done with the boiler and pump off or just shut the power off. One final thought. Have you checked the charge in your extrol tank. You shut the valve off above the tank to isolate from the system and with an air presure gauge after removing the blue cap on the bottom attach the gauge to the schrader valve. It should be be between 12-15 psi. If not you may have a leak in the bladder and should be replaced or try to reinflate first..

https://www.supplyhouse.com/Air-Eliminators-310000


https://www.supplyhouse.com/Spirothe...aded-9310000-p

Hope this helps a little.
 

Last edited by spott; 07-13-20 at 05:25 PM.
  #5  
Old 07-14-20, 08:59 AM
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Spott,
Thanks for detailed suggestions, and yes it's helpful. The vertical Spirovent is what Is had in mind. If I use that, does that eliminate the need for the auto vent? BTW/ I disassembled the auto vent, and it was clean inside. no debris.

The pump gaskets look fine, no sign of water, and I checked the flange bolts for tightness, but as you indicate they could be deteriorated, allowing air to enter. Maybe when I drain the system to install the spirovent, I will get new gaskets, maybe a new circulator as I don't have a back-up if my current one fails.

The feed valve does have a bypass lever though it doesn't work very well which is one of the reasons I was going to replace it when I add the backflow preventer.

The expansion tank bladder is not leaking and is set at 12psi with no pressure in system.

Do you think the location of the expansion tank is ok or while the system is down, should I move it? Also, should I do anything about the dead end stubs on the supply and return manifolds theorizing they may trap air?

So if I understand you correctly - on my system to bleed air out I do the following:
  1. Turn off all return ball valves
  2. Turn off all supply ball valves except the zone being bled
  3. Open the zone valve of zone being bled, and leave others closed
  4. Open drain valve with hose attached run to sink or bucket
  5. increase pressure at fill valve with override lever (not sure about this)
  6. After air is bled, shut supply ball valve off, and set fill valve override lever back to normal pressure (not sure about this)
  7. repeat for rest of zones
The water will flow through the return piping the pump, the boiler, into the open supply zone, and out the drain valve. All other zones are isolated, and pump is not running. Is that correct?

I am kind of fuzzy on your paragraph (below) of your reply in regards to 5 & 6 of my proposed bleed method. Are you indicating to increase and maintain pressure by adjusting the screw on the fill valve to increase pressure or to use the bypass lever?? Also, Not sure what you mean"close the feeder"

"Put a hose on the drain valve on the zone to be bled. Increase and maintain the boiler pressure to between 25-28 psi to force the water and air through the zone and bleed until you get a steady stream of water then close the feeder and drain at the same time and you should be good to go on that zone. Close the return valve and zone valve and repeat with the other zones the same way."



 
  #6  
Old 07-14-20, 10:19 AM
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Air accumulation in hydronic systems is on-going. Air bubbles rise to highest points of system when circulator is not active. Feel air scoops at boiler and periodic venting at lowest system level, is wishful thinking.

After reading the various complex ways to manually vent here is this DIYer's approach air removal.

Have 60 year old boiler, 8 zone system, heating elements 18” above main line are fed from
below with diverter / monoflow tee's. Each element is guaranteed air trap and low flow rate does not remove air.

Installed Watts auto-air-vents at high point of each element/zone. Never go through multi step hassle of manually venting, hoses or changing 12 psi system pressure.

https://www.supplyhouse.com/Watts-05...Vent-3679000-p

Watts auto vents can be opened for cleaning and servicing. Years ago one developed a leak. I keep $9.00 spares just in case. Installed ball shut off valve on expansion tank to easy depressurization for servicing.

Over the years have tried many types of vents and many leaked, failed and had to be replaced. Sealed can types like JACOBUS-MAID-O-MIST were the worst. On DIY.com see many pictures of them that leaked with cap shut off.

https://www.supplyhouse.com/Jacobus-...-1-8-Auto-Vent

In picture lacro46 auto vent located 12" above boiler looks nice, but does little to vent air elsewhere in system.

Spirovents sell for $90+ https://www.supplyhouse.com/Spirothe...inators-311000

It might be more effective for lacro46 to buy and installed 10 Watts auto vents for $8.29 at high points, rather than one Spirovent at boiler level.
 

Last edited by doughess; 07-14-20 at 11:55 AM.
  #7  
Old 07-14-20, 12:50 PM
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Actually I have been down that route many times with the auto vents. I had them on all high points of system plumbing including at radiation points where manual key vents were originally. Nothing but trouble! they leaked or let air enter the system. I removed them all except the one at the boiler which the manufacturer states is where it should go.
 
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Old 07-14-20, 03:00 PM
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Watts auto vents are very reliable. Been using them for years, only one had issue. Most other brands of auto vents have issues. Seems like I tried many that failed.

Have isolation valves on all zones and circulators. Never pull vacuum on systems. Auto vents would release any air that got there.

From picture do not see how auto vent on boiler is going to remove air from extensive pipe system above.

Manufactures instructions are focused on boiler and not system. Air bubbles rise to highest point in systems which typically is not at boiler.

Bottom line is Watts auto vents work great here.
https://www.supplyhouse.com/Watts-05...Vent-3679000-p
 

Last edited by doughess; 07-14-20 at 04:27 PM.
  #9  
Old 07-14-20, 03:46 PM
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L,
No need to go into my disapproval of auto vents on most occasions such as yours because you have had first hand experience with their uselessness on loop systems.

As was previously stated by doughess they do not work with the pump running which is defeating the purpose since pumps are on most of the winter. The Spirovent is an excellent choice and does work with or without the pump being on, in fact better with the pump running.

As far as the statement made about air constantly entering system is false. The forced hot water system is a closed system. Once the air is bled properly and no fresh water is introduced and you have no leaks either from bad vents of degraded pump gaskets or bad solder joints there is no way for air to enter the system again.

Think of it as filling a piece of pipe and capping both ends with a means of getting the initial air out. Once the air is out and the ends capped no air will ever get into that pipe again. This is the same thing with your closed heating system. It is impossible for air to enter a closed system on its own.


I installed my boiler in 1984 and have not had to bleed it since and I have a monoflo system just like the previous poster does only instead of auto vents I went another way and also have 8 rooms with every room having its own zone.

Since I had the means at the time I used this job as a project goiung against all the socalled rules of micro zoning and only 2 way ZV's instead of 3 because when monoflo zoning they said that when 1 zone valve closes it effects the rest of the system.

All I can say is that no matter what room you;'re in it's the temp you set it at.Eight zones, 8 stats, 8 zone valves, 36 years and no problems, air or otherwise against all advice from people in the industry that said it wouldn't work.
 
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Old 07-14-20, 04:41 PM
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Doughess never wrote: As was previously stated by doughess they do not work with the pump running”

Again have been misquoted by that poster. Maybe he can site the post referenced.

Watts auto vents release air in their tank body, whether or not the pump is running. When that air is released, then water and maybe air replaces it. Endless cycle, independent of pump status.

Have never heard of perfect hydronic system with no air. Do not speculate on where air might come from. Just assume it will come and install Watts-Automatic-Vent-Valves
 

Last edited by doughess; 07-14-20 at 05:01 PM.
  #11  
Old 07-14-20, 06:30 PM
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Air accumulation in hydronic systems is on-going. Air bubbles rise to highest points of system when circulator is not active. Feel air scoops at boiler and periodic venting at lowest system level, is wishful thinking.

This is where I got the quote. Possibly read it wrong? Post #6

 
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Old 07-15-20, 05:39 AM
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Spoot,
Would you please see post 4. I have a couple questions about bleeding my specific system.
 
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Old 07-15-20, 01:39 PM
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L,
What specifically would you like to know. I reread my post 6 and realized that I neglected to mention to open all the isolation valves and return the zone valves to the auto position and open valves between extrol and vent on top of boiler then test system for proper operation.
 
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Old 07-17-20, 05:41 PM
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I just now have realized that doughess has a monoflo system. They can be difficult to bleed air - for some loops or devices, more than others. My best luck is installing power-purge valving for each difficult device or loop - such as, for my system, kickspace heaters or first-floor heating loops. For power purge, shut a supply or return valve and open a drain valve. Works every time. Once the air is removed, it never re-appears, even after years. I have no automatic air-eliminator devices installed - they are forbidden on a system like mine with an old-style, conventional expansion tank (as opposed to a bladder-type expansion tank). (An air eliminator will quickly deplete the air cushion in a conventional tank.)
 
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Old 07-21-20, 12:39 PM
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If you are tearing down the system for any reason move the circulator to the supply after the expansion tank connection and add an air seperator after the circulator.
Forget any system vents, if manual vents not a problem to leave them.
The circulator changed about 1958 to the one piece style (wet rotor) circulators and were suggested at that time to move them to the supply to help eliminate air.They do this by adding pressure to the system thus breaking the air bubbles into smaller bubbles so they can move down a vertical pipe and get back into he boiler. The hot water passes through the air seperator and eliminates the air.
When the circulator pumps towards the expansion tank pressure is removed from the system and pumping away from the tank pressure is added to the system, thus assisting in air elimination.
When this is changed there is no need to change it all again when it is time to change the boiler to a new boiler.
 
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Old 07-27-20, 06:12 AM
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For me, the location of the circulator is the single most confusing thing about Hydronic heating. One boiler mfg. states it should be on the supply and another states it should be on the return???? My Weill Mclain boiler is circa 1985 or so, and came with circulator mounted on the return (suction) side right at the boiler. The current version of this boiler from WM has instructions stating the circulator can be either on the supply or return.

From the current WM installation manual:
"The circulator is shipped loose (wiring pre-attached to boiler) to allow you to locate it either in the return or supply piping, as desired. See page 3 for a typical installation. Pipe the expansion tank to the suction side of the circulator whenever possible. Install an air separator in the supply piping.Connect the expansion tank to the air separator only if the separator is on the suction side of the circulator. Always install the system fill connection at the same point as the expansion tank connection to the system."


"Diaphragm-type or bladder type expansion tank (Figure 16) 1. Ensure expansion tank size will handle boiler and system water volume and temperature. Tank must be located in boiler return piping as close to boiler as possible, before inlet side of circulator. See tank manufacturer’s instructions for details."


What is really confusing to me is where does the supply (pressure side) become the return (suction side). In a loop with circulator, it seems the supply is delivering pressure all the way to the suction side of the circulator, so it seems the whole loop is the supply? conversley, the suction side is sucking all the way from the supply side of the loop which seems the whole loop is the suction side. So, where does one stop and the other start?
 
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Old 07-27-20, 12:34 PM
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As a practical matter pump location, in or out, makes little difference on typical 12 psi pressure, low flow rate hydronic system that cycles frequently. If for any reason air bubbles develop in my system Watts-Automatic-Vent-Valves remove it.

I do not obsess with potential problem, just remedy it and move on to other issues in today's life.

Pascal's law / principle of transmission of fluid-pressure is a principle in fluid mechanics that states that a pressure change at any point in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere.
 

Last edited by doughess; 07-27-20 at 02:39 PM.
  #18  
Old 08-06-20, 10:16 AM
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Contrary to belief of some there is a huge difference with air problems and location of circulator to expansion tank. The circulator should always pump away from the expansion tank whether on the supply or return side of the boiler.
With multiple zones the location of the tank and circulator can be harder to get into a common pipe area.
After 41 years in the heating business this was the way to resolve any and all air problems in the hydronic systems.
Believe th pump manufacturers not the boiler manufacturers.
 
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Old 08-06-20, 07:34 PM
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Have zero years in plumbing business. Heard that air is problem in hydronic heating systems. Have no idea on how air gets into water. Read many DIY posts about venting issues.

My system has 12 elements fed with diverter tee's 18” below. All elements were guaranteed air traps that water flow would not remove bubbles from.

Occasionally had an element that did not get hot apparently because of air.

Starting 50 years ago tried all kinds of air vents.

Eventually found Watts-Automatic-Vent-Valves for $9.00 were very effective, reliable, and can be opened for service.

Do not waste any time on how item location or plumbing might contribute to air accumulation.

For $9.00 each, it was a very easy, simple solution to a common problem. Keep spares but have used only one in many years.

https://www.supplyhouse.com/Watts-05...Vent-3679000-p
 

Last edited by doughess; 08-06-20 at 07:52 PM.
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