1/2" pex homerun to iron rads

spacoli

Can I use 1/2" standard oxygen barrier pex ( vs. PAP) home run from a manifold? I have a mod/con boiler that very rarely sees 130-140 degrees supply temps and it would have to be very cold (below 15*) to see over 140 degrees.   My longest single run would be around 50'. Thanks

Rich_49

Certainly

As long as the 1/2" will provide enough flow to each particular radiator . 

spacoli

largest rad

My largest radiator is 19" high x 7" wide 6 tube across 37 sections and 19" high x 7" wide 6 tube across 30 sections this happens to be the one around 50' run away.

jonny88

works beautiful

i use this system a lot,works just fine

Robert_H

spacoli

Who is the manufacturer of those rads? 

Tinman

37 sections for 1/2"...

may be too big for 1/2". This chart is easy to follow and will let you know for sure.

Tinman

Bad image

Sorry about the poor quality of that chart image. I'll try to attach a PDF. On "File Attachments", can you attach anything other than a photo? Would I need to copy and paste a PDF file? Thanks.

Robert_H

The numbers dont match up...

You say your rads are 7" wide x 6 tubes which seems like a miss-match .   For example 4 tube Gurey Copley's are 7" wide and 6 tubes are 10 5/8" wide.  (similar to Tinman's pic) That's why I was asking about the manufacturer. Knowing your water temp we just need to determine the EDR per section x number of sections from there BTUH and correct tube size.



I just want to clarify, with the generic tables we can pick 7" or 6 tubes and get two significantly different EDRs per section.  If your measurements are correct, your rads fall outside the nominal tube count/width/EDR slope. If we know your manufacturer we can get the right data from their catalogs or the "EDR" book.

spacoli

weil mclain rads

They are indeed 7" wide and 6 tube. Well Mclain manufacture. Thanks

spacoli

Picture

Picture

Robert_H

Rad info

Should be 3 sqft per section for 6 tube WM Cameos (picture matches catalog) that are 20" tall. I ran into the same 1" difference in catalog and real life on my Gurneys.

comes to:

30sections, EDR = 90, 8100 BTUH @ 140 degrees

37sections, EDR = 111 , 9990 BTUH @ 140 degrees



With the BTU someone should be able to help with determining if 1/2 will handle that length.



BTW, Im not a pro, just a homeowner and radiator nut. Im in the process of installing a Modcon with old rads and a radiant ceiling. I oversized my rads to keep the down below 140 on design day.



Good luck.

Robert

SWEI

10,000 BTU/hr

requires 1 GPM at a 20º∆T.  No problem for 1/2" PEX (1.81 FPS, less than 4' of head per 100'.)  I'd probably run them at a 25º - 30º∆T.

spacoli

Thanks

Thanks for all the replies.. Robert, my rads I'm sure will be over sized too, as I gut, remodel and insulated the walls. Long process, I'm doing one room at a time.



SWEI, How do you regulate the delta T?

Rich_49

Add

all of your GPM requirements , figure out the highest head circuit including all piping and devices .  You can install a single speed circ that closely matches your GPM and flow or you can use a variable speed pump . These methods will get you close to your desired Delta T .  All the pump factories make variable speed pumps , Taco offers the 00VDT series and the Bumble Bee , both are capable of closely monitoring and controlling Delta T. 00 series are not ECM circs and come standard in 008 , 0012 , 0013 .  Bumble Bee is an ECM circ that operates between 9 and 42 watts and can be set up for Delta T operation , constant or setpoint .   Swei is right on point with his Delta recommendations

10kREDLINE

home runs

I ran home runs to all of the cast iron rads in my home last summer. the system works great, some big old cast iron rads, some smaller. but none the less, i feel heat almost immediately from the radiators, due to the home runs and not having to wait for mass amounts of water to make its way around the whole system.  i didnt use a smart pump, but probobly should have or could have.  i used a grundfos 15-58 on speed 2, and a taco differential pressure bypass, and have 3 zones using zone valves. multiple zones open at once is not a problem, and i plumber my pex manifold from a 1 1/4 header. good luck,

radmix

Home Runs

To make it easier you only need to run 3/8" pex to each radiator