Siegenthaler's Mini-tube System

Paul Rohrs

Has any one installed the Mini-tube systems described in the RPA's Precision Hydronics book that Mr.Siegenthaler wrote?

It looks like a hybrid primarysecondary and relatively simple. I have an application coming up that I am going to design around and wondered if there were any Wetheads with a few jobs under their belt.

PR

Boilerpro_3

I've used versions of it...

It's really no more than standard injection piping that's been extended out longer. I believe I first saw it in B&G enginnering manuals from the 60's or just came up with it on my own a couple years ago and later discovered it was the same thing as a minitube system. Since all it is a longer injection system, the same rules apply. If you go from a high temp source loop to a low temp load loop the flow rate and pipe size goes down accordingly. If the source and load are the same temp, I don't think there is a pipe size or flow savings. I've used the concept in two configurations. In one I used one circulator to pump high temp water continuously to manifolds that supplied slab radiant. The high temp water flow balance was set by circuit setters and the slab manifolds were pumped as called for thermostatic control. In the second, the minitubes were set up primary secondary to a constantly pumped high temp source with a circuit setter to limit the amount of hot water available through that circuit. The minitubes were also piped P/S to the two zone sysem loop with one change.... A valve was used to restrict flow through the middle of the tees so some flow was diverted through the minitubes. As each zone called for heat the flow rate through the minitubes varied according to that zones injection need. Both work real slick and made the installation less expensive. Nothing like running 1/2 inch copper runs instead of 1 1/4 inch to serve large slab zones!

Boilerpro

Paul Rohrs

How about.....

That sounds exactly like what I am planning. I have 1 zone of 10,800 linear feet of 58 pex. (36 loops of 300 ft) 4 manifolds of 9 loops supply and return. I am thinking about feeding the secondary loop with a single high gpm high head circulator (B&G PL-55) and using flow setters on each supply manifold to regulate and balance to each manifold location. I am also piping the 1" manifolds as reverse return. I am searching for flaws in my logic but I think the mini-tube is a great way to only run 34" to feed my 1-12 secondary loop.

PR

Boilerpro_3

Sounds good to me....

One improvement I might suggest is instead of using one large PL-55 for the supply, use two smaller pumps in parallel, with each pump carrying half the load. Install outlet checks and you have automatic back up if either pump fails. Another nice thing about this setup is that the load the slab can place on the heating plant is inherently limited, so the sysetm tends to be more stable. Also, if you reset the heating plant supply water temp, you will also reset the water temp to all the zones. One outdoor reset is all that is needed to reset all the slab zones. Talk about saving some change!

Boilerpro

hot_rod

Check your numbers, Paul

maybe I'm reading you wrong. 36 loops on a 1" manifold? What is the total BTU/hr load for the space? The secondary pump needs to be sized to the load and pressure drop. The design calcs should give you the exact spec (gpm at ft. of head) for that pump.

hot rod



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Paul Rohrs

HR

> maybe I'm reading you wrong. 36 loops on a 1"

> manifold? What is the total BTU/hr load for the

> space? The secondary pump needs to be sized to

> the load and pressure drop. The design calcs

> should give you the exact spec (gpm at ft. of

> head) for that pump.

>

> hot rod

>

>

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 144&Step=30"_To Learn More About This Contractor,

> Click Here to Visit Their Ad in "Find A

> Contractor"_/A_

Paul Rohrs

4 pairs of supply\return

I have 4 sets of supplyreturn manifolds with 9 loops on each. My total flow is 34.2GPM and each loop is at .95GPM
You're right though, I would wake up in a cold sweat if I tried to get away with 36 loops on 1 1" manifold. Yikes!

PR