Monoflow loop sizing

SteveMac

Thank you both for your help. The key words that I missed in the IBR literature was "available head". By selecting a circulator and looking at the flow at different heads I was able to properly size the loops.

Dawn finally struck on Marblehead.

Too much stress, I need a vacation.

Thank You,
Steve

SteveMac

Monoflow loop sizing

I'm currently doing a job on which the homeowners insisted on cast iron radiators. I will be using a monoflow (diverter tee) system. I have sized all the zones except for one. The problem I'm having is that it is a large house with one zone being located guite a distance from the boiler.
The load of the zone is 27,000 BTU. The loop will be split with one circuit being 260' long with a 1.22 GPM flow and the head is 15.6 feet. The other circuit is 290' long with a 1.55 GPM flow and the head is 17.4 feet. The allowance for the tees is included.
The problem that I'm having is that the IBR table I have (my fathers) for a "one pipe system" only covers "head" up to 14 feet.
Is there a newer table that takes into account modern circulators? Could someone post or send me a link if there is a table available. If not what am I doing wrong?
The urgency is I need this information yesterday through no ones fault but my own (I didn't anticipate this problem).
I will be purchasing the new IBR manual from this site within the hour but that will not help me in ordering my stock for tomorrow.

Thank you in advance for you help.

Steve

Dave_4

You will be dissapointed.

The new I=B=R manual also stops at 14' of head. Both the old Guide 200, as well as the new Guide 2000.

Your best bet might be to split the "off the chart" circuit into one more "split" or, extrapolate the data using common sense as to where the chart would be, if the area you fall into isn't there.

Better yet, you may need to simply increase the trunk (or circuit) diamater.

Did you consider this option? It is the correct one IMO.

BTW, I did teach the I=B=R schools for a few years and know the tables well enough to help. The speed of the water (and the ensuing noise potential) once we get over 14' of head at the flow rates you need becomes a major reason why the tables do NOT go any higher than 14' of head. Cost of big pumps, noise and circuit temperature drop are inter-related.

I'd change something else, not the circ./pump.



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SteveMac

Ken,

Thanks for the response.
Common sense tells me the trunk should be 1" and each circuit 3/4". That is probably the route I will go in conjunction with a Taco 009 circulator. However, you mentioned increasing the trunk size. I'm not opposed to this, but I am puzzeled how this is going to reduce the head, as the length of the trunk and circuits would remain the same. I'm not questioning your ability, I'm just trying to get it straight in my own mind.

Thank you,
Steve

scrook_2

You will experience less head drop in the larger trunk (about 2/3rd's the drop for a 1 1/4" vs. a 1"), and though the drop in the two 3/4" sections will stay the same, the reduction in drop in the trunk section alone may get you below 14' of head.

Dave_4

Re-think that.

No one designs a trunk with 1" and mono-flo tees at 3/4" You end up in a squirrely array that gets you in trouble.

You may be mis-reading the I=B=R tables for a "one-pipe" design. The relationship of the branches and the trunk is based on the tables in the I=B=R book because the math always works out - unless the house is a castle.

Head is a function of friction. 1" pipe has lots of friction - and results in head requirements that has you thinking 009. Think 1-1/4" and perhaps only 1/2" branches. That gets you into a real nice warm and fuzzy place near the center of the tables, not outside them.


GPM is a function of dividing the BTU load by 10,000 - resulting in a 20 degree dT for that circuit. Head is a function of flow resistence, and overcoming that resitance so the 20 dT is possible.

You're almost there, but not quite. Re-read the manual 200 you have and read ALL the parts about the use of the tables for a one-pipe system. The tables are read from the bottom up - sort of. Then, do the trunk sizing last.

Makes all the difference in the world.

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SteveMac

Thank you both for your help. The key words that I missed in the IBR literature was "available head". By selecting a circulator and looking at the flow at different heads I was able to properly size the loops.

Dawn finally struck on Marblehead.

Too much stress, I need a vacation.

Thank You,
Steve