Plain steel tanks and Spirovents

nick z.

I thought somone hear once said you shouldn't use the two together.I would like to,as the boiler doesn't appear to have a internal baffle.(old Utica)
H.O. says they have constant air problem which i think was coming from make water due to leak in old radiant loop in the basement.While I have to drain the system down to isolate the rad. I wanted to add a air elimantor as now there is none.
Thanx, Nick

ChrisL

Spirovent

You can't use a spirovent on a plain steel expansion tank because it will slowly remove the air out of the expansion tank. This will continue until there is no air left in the system. That is why you need to use a bladder type expansion tank.

DanHolohan

How can it do that?

I've heard this before, but how can the Spirovent call the air from the tank if there's a device on the tank such as an Airtrol tank fitting to stop gravity circulation between the tank and the system.

heatboy

I may be way off here.

If there is no thermal loop established between the boiler and tank, the air should never leave the tank, allowing the use of a Spirovent. At least, it makes sense to my dimly burning bulb. Although, in all of my days, I have only seen a dozen or so steel tanks piped correctly, and to fix them would cost more than a diaphragm compression tank.

hb

zeb_3

Spirovent & steel tank

I have installed this combo a few times w/ no problems whatsoever. My fathers house,he is "OLD SCHOOL" & had to keep his steel tank, I added the "SPIROVENT" 5 years ago.

Boilerpro_3

There is always going to be some water moving in and out...

of the tank, since as the system water is heated it expands and enters the tank. When it cools it reenters the system piping, carrying some air with it. I posted about this a week or two ago. Systems with conventional tanks are air control systems, while systems with diaphragm tanks are air elimination systems. Air control systems are constantly working to keep and put the air back in the tank. In air elimination systems, air is vented by an automatic vent at the air separator. Automatic vents should never be used with conventional tanks because eventually they may remove air that was once in the tank, causing it to waterlog. I've fixed some troublesome systems just by closing the automatic vent. B& G has some real nice explanations of this in their engineering manual... may have even been written by Gil.

Boilerpro

Larry (from OSHA)

what about

Larry (from OSHA)

what about

Larry (from OSHA)

what about

using a B&G EAS air eliminator? Or if there is something similar. This will work with the steel tank to grab air and send it to the tank. Does anyone have any experience with this device? I am looking at using one on my system but I am wondering if it will be effective if the boiler is not pumping away. Currently I have what I believe you would consider a low mass system. Boiler has about 2.7 gallons water. 3/4" copper baseboard loops with 120 feet of emitter on 3 zones and maybe another couple hundred feet of pipe.

Any thoughts are certainly appreciated.

Larry

Larry (from OSHA)

correct piping?

could you please describe what correct piping would be? and would i be correct in assuming that when using an air eliminator (spirovent or similar), after some period of time when all entrained air and oxygen has been removed/driven off, the eliminator would be mostly decoration on the piping? thanks for your perspective.

Larry

Boilerpro_3

That would be the ticket

Or if you want something less expensive you may be able to still find the IAS model with a 3/4 inch tapping on top. It's first pass efficiency is not as effective as the EAS, but given time they work well. I have found them to be more efficient than the air scoop models out there. The IAS -400 has only a 1/4 inch tapping on top making it useless for your application.

Boilerpro

ChrisL

Lab vs. real world

This is probably a situation where Lab findings and real world lead to different conclusions. While I would agree that it is possible for air to be slowly removed from a plain steel expansion tank, how long does this take? Is it significant? In this situation, I figure its better to err on the safe side.

Chris