Indirect on Steam
Hey Guys,
looking to add an Indirect to a steam Boiler system. Does anyone have a good piping diagram to make this work?
Comments
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No magic to it. What is the boiler make and modle #. I could give you a more accurate diagram if we know what boiler it is and what available tapings there are.
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There are several ways to do it. Can also do it with a tanlkess coil, nonferrous circulator, and a storage tank or using an electric water heater as a storage tank.
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Weill McLain SGO4
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Assuming the near boiler piping is as the I/O manual diagram shows. There are 2 options one is easier that the other. but you may find that using an inexpensive circulator pump might preent a problem.
This diagram illustrates how to use the hot water in the boiler to make hot water in the indirect. when ever there is a call from the DHW tank the burner operates to heat the boilre water to 180° max. and you use the boiler water below the water line to heat the heat Heat eXchanger in the DHW tank.
The problem with this design is that this essentially an open system and you should use a stainless steel, or bronze circulator since a cast iron body will rust over a short time and you will be replacing circulators regularly. Also the wet rotor circulators tend to get fouled by the dirty water so many who do this on occasion prefer the B&G 100 design. This type pump may be less expensibe from Taco or Armstrong.
The other design is more complicated but is less of a problem that an open system above. Basically you get the tankless coil made for the SGO boiler (if you have the blank plate to remove) and install the tankless coil. (some SGO Boilers can not accept a tankless coil). Then you install a closed system using the Coil as the heat source. That closed system needs a standard pump, expansion tank, relief valve, and all the other accessories to fill the system with water and vent the air form the system.
If you boiler can not accept the tankless coil, than you are probably going to use the first option.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Here is the boiler manual. Weil McLain wants you to use tapping U1 for the indirect supply. I would put the return from the indirect into B1. The piping between the boiler and the indirect should be 1" although some will use 3/4" 1" will give you maximum output from the indirect. I would use copper tubing and you should use a bronze pump. I would put full port ball valves at the boiler connections.
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That would make a better design for the open system idea
If all the piping is below the water line, then this is what you might do. If any of the water in the Tank HX is above the water line than you will need to add some purge valves that are not shown.
Just more proof that two Ed's are better than one
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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the other way to do option 2 is to just use a storage tank and run the potable water through the tankless coil. a noferrous wet rotor circulator will do better in potable water than the water in a steam boiler. probably can nearly buy the wet rotor circulator and tank for what a nonferrous 100 series costs.
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@EdTheHeaterMan I question which would be the better pump location. Pumping the hot water out of the top tapping might cavate the pump which doesn't have much "Head" on it although I prefer the restrictive coil in the indirect on the pump discharge as you have shown.
I would prefer the pump on the return line where it would have more head but that puts the restrictive coil on the suction.
What do you think.?
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the top tapping won’t have head on it if the pump is floating in space like in the photo, but the pump should preferably be close to the floor, then either tapping would provide the same head to it, right?
NJ Steam Homeowner.
Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
That just might work… either way you are going to want to minimize restrictions between the pump inlet and the boiler, but with the pump set as low as possible you do have a fighting chance at avoiding cavitation in the pump. Maybe.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
Fixed it
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Lets say there is 24" height difference between the two tappings on the boiler. If so the bottom tapping will be about 1 psi more than the top. 2.31 feet/psi
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Make sure check the pressure drop in the indirect. Makes a major difference when using a steam boiler, where you're starting with extraordinary low pressure as it is. Not all indirect are the same. And the coil type of indirect, not the tank in tank.
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I think that is why most folks that do this like the B&G 100 becuse of the flat pump curve. Less chance of cavitation at that low pressure across most of the GPH of different systems you might use it on.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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For what it's worth, I always give the customer the choice. Without fail, they all choose the 007. Some will choose to stainless steel. And I have that pretty good results. Close to flawless. The main issue with the pressure drop, is the potentially not having enough heat transferred to the indirect. The greater the pressure drop, the slower the water in the coil will move. Slow enough, it will not heat properly. Not an issue on a standard hot water boiler, where you are starting with 12 PSI or something like that. Take a steam boiler where you are starting with close to zero, and hopefully not getting above 2, and you can have issues.
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Yes at the tapping, but not at the pump, if the pump is at the same height in either case.
that’s why you put the pump as low as you can regardless of where the tapping is—the vertical distance adds to the pressure the same
NJ Steam Homeowner.
Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
See my sight glass boiler videos: https://bit.ly/3sZW1el
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Also..coolest condensate is at the bottom..pumps will last longer. Mad Dog
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