Pressurized Storage Pipeing

[jimdeq]

I have a question in regards to my pressurized storage pipeing. I have three tanks, pressure vessels in my basement directly below my attached garage. The tarm solo 60 is located in the garage above the tanks. The tanks have two threaded fittings on the top of the tank to support 1.25" pipeing. They also have a threaded fitting on the bottom 16" to support 1.25" pipeing. I had my plumber over today and was explaining to him that I wanted hot water coming in at the top and hot water going out at the top. Return water would then be from the bottom fitting. I wanted to do parrallel plumbing of the three tanks. I was planning on seperate parrallels for the hot in and hot out. He stated that it is very difficult to do parrallel with three tanks because its difficult to keep all the same lengths in 3 tanks vs 2 tanks being easy. He wants to plumb in Reverse Return in which first tank in hot is last in return cold. This method would eliminate a full row of pipeing , valves, fittings, etc. The Solo 60 is bigger than I need. My storage equals 1140 gallons. I have three zones, one high temp fan coil, one DHW, and ond low temp radiant. Can I assume the double top piping is strictly for BTU transfer when a zone is calling for heat, or should I do what he is saying and just do one row of pipeing. I already have the fittings, I just want to do it right can anyone help?

 

[ewdudley]

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I have three tanks, pressure vessels in my basement directly below my attached garage.

...

The tanks have two threaded fittings on the top of the tank to support 1.25" pipeing. They also have a threaded fitting on the bottom 16" to support 1.25" pipeing.

...

I [want] to do parrallel plumbing of the three tanks.

...

[Plumber] stated that it is very difficult to do parrallel with three tanks because its difficult to keep all the same lengths in 3 tanks vs 2 tanks being easy. He wants to plumb in Reverse Return in which first tank in hot is last in return cold.

...

Can I assume the double top piping is strictly for BTU transfer when a zone is calling for heat, or should I do what he is saying and just do one row of pipeing. I already have the fittings, I just want to do it right can anyone help?

The installation guides I've reviewed that talk about three or more tanks all agree that piping parallel tanks is just a matter of using symmetrical connections.

Here's a typical example:

http://www.newhorizoncorp.com/PDF/Laddomat 21 Manual.pdf

There's a few variations. Many show two hot end manifolds at different elevations so that a priority buffer zone can be maintained for DHW.

But the simplest is just one manifold at the top and one at the bottom.

For three tanks most of the diagrams show a tee in the top manifold between the two tanks on one side, and a symmetrically placed tee in the bottom manifold between the two tanks on the other side.

Some show oppositely placed tees for boiler and load circuits while others show the boiler and load circuits entering/leaving and leaving/entering the manifolds with pairs of tees next to each other.

Some show boiler supply going in one end of the top manifold and boiler return going in the opposite end of the bottom manifold, with load connections using the opposite end of each manifold.

From all this what I gather is that all that matters is the symmetry.

Also there's an install here on hearth.com com where the guy fans-out multiple equal length pex lines to the top and likewise to the bottom, which looks like great solution.

Others have plumbed multiple tanks with no special attention to symmetry and have reported that the tops of the tanks are hot and the bottom of the tanks are cool, end of story.

Cheers --ewd

 

[jimdeq]

Thanks EW, I think one manifold on the top would be easiest. I assumed I was going to build 2 manifolds. I have all the fittings,including thermometers,bushings and valves. Being that the boiler is oversized would the double top manifold benefit by being more efficient. In other words, if the boiler is pushing out 150,000 btus at a rapid burn and my high temp zone calls for heat will I get more BTUs transfered to the tank with the extra set of lines while the high temp zone is also being satisfied. Tell me if Im crazy,Im not a plumber.

 

[ewdudley]

Thanks EW, I think one manifold on the top would be easiest. I assumed I was going to build 2 manifolds. I have all the fittings,including thermometers,bushings and valves. Being that the boiler is oversized would the double top manifold benefit by being more efficient. In other words, if the boiler is pushing out 150,000 btus at a rapid burn and my high temp zone calls for heat will I get more BTUs transfered to the tank with the extra set of lines while the high temp zone is also being satisfied. Tell me if Im crazy,Im not a plumber.

Your btus per hour going anywhere is going to be the rate leaving the boiler. Using 1.25 inch pipe, a free flowing Danfoss or similar mixer, at Taco 007 or similar, and a straight shot to the tanks, you should be able to push 12 gpm or more. 1.25 inch pipe at 4 feet per second is about 15 gpm, so you could use a bigger pump even.

12 gpm with a 25 degF deltaT through the boiler would be 150000 btu / hour, so a single 1.25 inch manifold should be about right, I'd say. However if your tanks get heated up over 150F or so you might have a problem maintaining a 25 degF deltaT and the boiler would have to idle some. Some of us have a second pump in parallel (or series depending on the piping resistance) to deal with this situation, but it might be simpler just to load the boiler with approximately the right amount of fuel such that the fire burns out when the tanks get hot.

 

[jimdeq]

I will have a grundfos 26-99 for my boiler /storage loop. I hope that pump will move alot of btus out of the boiler.