Air entering system

DougK

With a little help from a friend, I designed and built a HWsystem for my garage shop. It works fine all but one little problem, when the system sits for awhile air locks in the pump and of course no heat due the pump cavetating. I do not have makeup water as this is in an otherwise unheated garage in NW Pa. although I did modify a 2 gal pump sprayer to serve this purpose but have not yet connected it. I've read where the auto vent on you of the scoop can sometimes allow air in. Could this be it...the system works fine once I get the air out of the pump.

DougK

Jamie Hall

It could be. If the pressure at the separator is less than atmospheric, it will suck air in.

mattmia2

It is more likely to be air that never was removed from the system collecting at that point since your air elimination isn't great and you have no system to replace the air with fluid as it works its way out.

DougK

So what can i do to eliminate air better?

mattmia2

Put the air elimination device between the hot outlet and the pump. Have the pump set up so it pumps away from the tank. Use a microbuble resorber type air eliminator instead of an air scoop. You want the air elimination at the point of hottest water and lowest pressure, that is where the most air will come out of solution.

hot_rod

Actually a tank can be an excellent air removal device. I'll bet there is an anode rod in the top of that tank? If so, remove it and add a 3/4 auto air vent.

Also, to work best the circulator wants to be just downstream of of the expansion tank. A 6" nipple out of that air purger, then the circ would be sweet and probably resolve you air issues.

With a spare expansion tank you can make a portable, temporary fill/ pressurization system.
A tank and boiler fill valve., called a PIG

mattmia2

hot_rod said:

Actually a tank can be an excellent air removal device. I'll bet there is an anode rod in the top of that tank? If so, remove it and add a 3/4 auto air vent.

That's what i was thinking was happening, when the water slowed down in the tank it had a chance for the air to settle out, but i didn't make the last leap to actually make it the air elimination device.

hot_rod

Looks like you have a fill valve attached to the bottom of the tank? It should maintain pressure and allow you to purge.

I think you are one valve short of a good purge method, unless the upper right has a hose bib? Hard to tell what is in the upper right.

Here is a pic. A hose bib added to the right of the upper valve.
Turn off that valve and water is pushed around the loop and back to the purge valve near the valve that is off. It can take 10 minutes or more to purge a long loop.
Is the loop 3/4 fin tube?

After air stops coming out, open upper valve snd it should run.

Looks like the flow arrow on the circulator is pointing down? if so the tank and air purger will work fine.

DougK

So the easiest is to remove the anode and install an air eliminator there as that is obviously where the air is coming from. I will try that and get back to all of you.
This has been frustrating....THANK YOU!

DougK

hot_rod said:

Looks like you have a fill valve attached to the bottom of the tank?  YES w/backflow.

Hard to tell what is in the upper right. An air scoop and auto vent.

Is the loop 3/4 fin tube? Yes

DougK

Installed a 1/2" auto vent between the tank and the pump. If this doesn't work, I'll put one at the anode rod.

hot_rod

Better, but...,
The vent really would like to be in the tank. The tank becomes a low velocity zone, so water moves very slowly in a wide open container. That slowing down, in some cases stopping of flow in a large, domed top tank is what allows air to rise and exitn via the auto vent.

That is the concept behind the cast air purger you have not, creating a "wide spot" in the piping to lower velocity, allowing air to rise to the vent.

I did a clear demo of this if you click on the Hot Topics, episode 1 link in the menu to the left.

I had a small air pump constantly pumping air in the nbottom of that clear plastic tank as I ran the various circulators, between the clear tank, and clear auto vent I built, you get a clear pic of how well a tank doubles as an air separator, or air removal device.

If you can, get the vent in the tank and you will too be pleasantly surprised on how well it works.

Larry Weingarten

Hi, I’m liking hot rods approach. A few more thoughts; the existing anode could be the source of the “air”, but I like to keep an anode in the tank if possible. A way to do this is to replace what you have with a combination anode. It is both an outlet and anode suspended underneath. That way you get gas or air elimination and tank protection.

Yours, Larry

DougK

The new vent has helped immensely. 
I did not know that a combo anode was available. I will look into this...
How do you like my "pig"? 

Larry Weingarten

Hi @DougK , Here's a source for anodes: https://www.waterheaterrescue.com/OrderPages/sacrificial-anodes-sales-page.html Now, please tell us about the pig! It looks like it used to be involved in spraying paint, or cooking things.

Yours, Larry

DougK

I worked 33 years for a hospital in their carpenter shop where we sprayed contact adhesive for countertops. When they decided to do away with the shop, I was able to buy 95% of the equipment...this pot was included. For almost a decade it's been sitting in my garage with me not knowing what to do with it...I KNEW I SAVED IT FOR A REASON...👍😎🇺🇲

DougK

Ok, I've gotten rid of 99% of the air...now onto a secondary concern...pressure.
(see 3 pics) The pic with the red knob set at approximately 12-13 lbs is the make up water pressure. This valve also, I believe,  has a backflow preventor on it. The guage w/temp on top is on the tank...other guage is located before h2o goes into the fin tube.
I get the increased pressure from heating but if the inlet is set at 13lbs, why are the other pressures over 20lbs?...is this a concern?
Also expansion tank pressure is 12lbs...