Piping two boilers

Terry_3

I am looking for advise on how to pipe two boilers using pumps for zoning. Thanks for the help!

jim f

Charlie_2

connections

How can two residential steam boilers be twin in successfully?

Mark A. Custis

I like

This. Did you take out the Tacos in the air handlers? What did you use to control? I like the controls in the airhandlers, but ended up not needing what they could do for us.

Good job, Jim.

Mark

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hot_rod

Depend on what

you are doing with the boilers, distribution wise. This arrangment allows flow only through the boiler that is fired. (check valves or check pumps are needed)

A good way to do it if you are staging the boilers. Primary secondary takeoff for the distribution would allow different loads and pumps to be used without effecting the boiler flow.

Lots of ways to tie 'em together based on the system you are building.

hot rod

Steamhead

Here are a couple of ways

from Columbia.

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JohnNY1

this way

Here are three with domestic water heaters.
Two works also. Of course, the drawing is simplified.

Boilerpro_3

Potential problem with that lay out, HR, is

severe and repetitive thermal shock. This can occur when the system is already hot from one boiler firing and then the second boiler is fired. The 180F system water hits the 65F boiler and OUCH!!!. If you pipe cast iron this way you are going to want to provide individual boiler protection, like a return mixing valve (ala ESBE Thermix) or make sure the off boiler is at some minimum temp due to a standing pilot with damper or drilling a small hole in the check valves to allow a little water from he hot boiler to backflow through the off boiler.
also got to watch out for cold return shock with this layout...seen that problem too.
I think I read recently that Burnham just added a control to help deal with these problems on some of thier boilers.

Boilerpro

hot_rod

Good points BP

A tekmar 262 stage control will run the boilers. It has,among other features a soft start feature to help handle this. Also boiler #2 should not fire until #1 drops to 140 degrees. They will also post purge to remove excess heat and dump it into the slab. There should never be a 180 start up potential on the second stage. The rotate feature will also help by adjusting the firing order based on accumulated run times on the boilers. As you know the PID logic constantly monitors the boiler temperature and target temperature and fires the boilers accordingly.

From what I read the tekmar has built many protection features and adjustments into this control for this application. Guess I'll find out

I admit this is my first 262 install, so I need to play with it some to make all the protection features "click"
I'm thinking the time and effort to make this piping/ control logic work easily overcomes the energy dollars lost by allowing flow through an unfired (cooling tower) second boiler. I won't know if I don't go!

hot rod

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Boilerpro_3

HR, those 262's are Real Nice!

Have a couple in use and they run the boilers much nicer than the older 252's. You'll be really satisfied. The soft start feature is for start up of the system after setback. It gradually brings the zones supply water temps up. I don't think this will help the shock the the second boiler on start up, unless you are running a lower temp system. Hope to see you at Wetstock!

Boilerpro