Spirovent with Old steel expansion tank???

Glenn Harrison

Was watching This Old House today and watched Rich Trethewey (sp?) installing a Spirovent for a customer with a 1950's baseboard system, that had to have the baseboard bled every year. The thing I noticed is he just put a boiler drain on the bottom of the Spirovent, and left the old steel tank connected to the boiler. I have been taught that you shouldn't have any auto air elimination in the vacinity of the boiler when using steel tanks, unless the air elimination vents into the expansion tank. Also noticed no pumping away, of course. My feeling is he probably just created another and possibly bigger problem for this customer. Any opinions on this?

Mike Kraft

ding ding ding ding

I saw the same thing Glen!I couldnt believe me eyes.I was looking for an airtrol fitting but the camera didnt focus on the tank very much.Richard certainly knows his stuff without a doubt.But that program was more than confusing.

That compression tank is now destined to fill with water!If automatic venting devices are installed all the air will be removed,the compression tank being void of air will fill with H2O!The call may have been for an obstructed airtrol or a bad dip tube.

cheese

Mark J Strawcutter

email

asktoh@thisoldhouse.com and ask them to clarify?

Mark

GAverill_2

Problems

We actually did this by mistake in our old building, replacing an old manual air vent with a Spirovent. It successfully removed all the air in the system in a few days-including all that in the old B&G compression tank.
I watched the same show and could not believe what I was watching. If they would have continued on to replace the compression tank with a bladder type tank I would have considered the problem solved, but now fear that the homeowner is probably having the relief valve popping off as a result.

kev

steel tank

If you pipe the steel compression tank off the bottom of spirovent, and then pipe up to tank that is tapped in the bottom. I would think the tank would stay charged with air at the top? Please help me to understand if I am not correct.

Mike Kraft

KF

I see what your seeing.But it wont work.The spirovent is a very useful air removing tool in forced circulation systems.But the system that Richard serviced was not a 100% a air removal system.It is an air management system.The "old style" steel tank that has been refered to has no diaphram with a factory air charge in it.It is a vessel that is available in different sizes.

The air is directed to this tank via several fittings.The link I attach should help.But in this type of system on initial start up the air is manually vented at the higest points of the system.In this case on each HWBB loop.The design of the airtrol fitting and the boiler tube will then allow heated water and gases(air) to be collected in the tank.Take a close look at the cut away of the fittings.

A spiro vent piped from the bottom to a steel compression tank would merely allow water to flow into the tank and the excessive air to be "scrubbed" out and leaving no captive air to be collected for expansion.And leaving no choice but for the relief valve to blow as the water is heated and a very vicious and dangerous cycle is begun.

Hope this helps.

cheese link: http://fhaspapp.ittind.com/literature/files/7.pdf