Steel,copper or plastic pex, for 30 ft run between oil & coa

Hi, I am going to be hooking them up parrael, There is about a 30 FT run between the 2 boilers so there will be about 60 ft of pipe, should I use steel "Black pipe",copper or pex? what size? I was thinking 1 1/4 in.
The run of pipe is going to be in the basement under neith 2 of my childrens rooms, how can I keep the heat from the pipes cooking there room and the basement in the summer? Thanks

Everything else feed wise on my oil system is 1 1/4 in if that matters, what diffrence is there between teh 1 in and the 1 1/4 in?
My house has the old big cast iron radiators and we take lots of long showers if that matters. Thanks

what temp do you run your boiler at now with those big cast iron raditors?
If your aboue 200 degrees use copper or black iron and fiberglall pipe insulation.
BDD

The best choice for water flow would be copper pipe. Compared to PEX-AL-PEX copper has much less internal resistance for the circulator to overcome. Steel pipe would be better than PEX but not as good as copper. If your coal boiler is going to have it's own circulator a Taco 007 with 1 inch copper will work fine. With PEX it might limit the Btu's you can get out of the coal boiler. If you are going to use your existing circulator that also have the additional resistance of the heating distribution system you should use 1-1/4 copper. I've attached a graph that compares 1 inch PEX-AL-PEX and copper. Note the superior flows with copper. You can make PEX work but you need a larger pump. I'm assuming 30' is one way. The lengths shown on the graph are one way lengths. The equivalent length of fittings and valves need to be added to get a piping resistance length.

Any pipe you use should be insulated.

Suggest you take the advice of Yanche on this one

Short cut rules dictate you can move (trouble free) 10,000 of btu load per gallon of flow with a 20 degree temperature drop

trouble free flow in 1 inch steel or copper is 8gpm

14gpm in 1-1/4 copper

16gpm in 1-1/4 black iron threaded pipe

25gpm in 1-1/2 steel pipe

if you have a boiler of any significance - 1 inch just isn't enough to carry the design load.

Now that said - if your heat loss calculation of the load is less that 80K - one inch is fine - you simply cannot carry the potential of the boiler away with 1 inch - but you will never need to - unless you over fire!

I have always been and forever will be - a threaded pipe sort of guy!

I'm a copper guy.If something goes wrong and temps go to 200 or higher what happens to pex?Copper will laugh at thoes temps and will last for a few lifetimes.I've been doing plumbing my whole life and don't even own a pex crimping tool.I'll tell you the way I think of it,Pex is a solution to a perceived problem.Yes copper is costly but in the long run It lasts.How many plastic heating tubings have they made in the last 30 years?I'm just not a plastic guy on water or heat lines.Now DWV thats a different story.SCH 40 if it's supported well is great.
old school DON

With cast iron radiators water temps are in the 140-160 range
If it's steam black mal pipe is best.Galv pipe on steam tends to "peel" on the inside.
Just my .02

I agree with sting about iron pipe.I like to use i.p. to the circulator and to the flo valve.But then again I still like circulators on the return in a residential system.
DON

Yeah it is 30 ft one way with its own circulator, I run the oil boiler at 180 hi and 160 lo that is what I will put my K6 at when I get it. SO you guys are saying I should run 1 1/4 inch copper? if I run 1 1/4 in pex with a grundflow 3 speed and all it is doing is circulating though the 2 boilers at a 60 ft round trip I would still have to much resitance? and the pex also can not handle heat above 200? thanks

I might look at this problem from a checkbook view. If you need larger than one inch flow the Pex is out. Either copper or iron will do the job, so look at price. I think you'll find the copper is quite a bit more expensive than the iron. I'd have no fear of using either. If they were the same price I'd use copper.

Joe G., Please post the exact model of your pump. Knowing the BTU capability of your boiler I'll do an analysis. I'm on travel and can't post the results until Sunday.

I was just at HD and was looking at their prices for copper, I believe a 1 inch ten foot section was going for $39 and something cents. Price does add up quickly, but the piece of mind in knowing you did it right the first time and never have to think about it again is priceless.

Sting wrote:
14gpm in 1-1/4 copper

16gpm in 1-1/4 black iron threaded pipe

I saw this in Dan Holohan's book also. How come you can move a higher GPM through steel than through copper.

Yanche,

Doesn't this contradict what you've been saying that you can move more GPM's through copper than steel?
For the record, what you said makes sense since copper does seem smoother and less rough than steel pipe.....

I have a taco 007 right now, the pump I was going to put between the 2 boilers to run constant was grundflo 3 speed that is suppose to be equal to the 007 accordiny to teh plumbing supply guy.

beatle78 wrote:

Sting wrote:
14gpm in 1-1/4 copper

16gpm in 1-1/4 black iron threaded pipe

I saw this in Dan Holohan's book also. How come you can move a higher GPM through steel than through copper.

Yanche,

Doesn't this contradict what you've been saying that you can move more GPM's through copper than steel?
For the record, what you said makes sense since copper does seem smoother and less rough than steel pipe.....

The details of heated water flow through pipe is rather complex. My data for PEX-AL-PEX and copper comes from the published work of John Siegenthaler, P.E. He's an expert in hydronic heating. Unfortunately he does not favor steel pipe and has not published the resistance factors for steel pipe. Looking at his analysis methods for copper pipe might give a way to derive the data. He points out that the flow characteristics published by pipe manufactures or are ASME specs all assume cold water, 60 deg F I think. The flow characteristics of water are a function of temperature. So, one would have to look at the flow data for piping at the same temperature to make valid comparisons. I'm still trying to educate myself as to how to do it for hydronic heating fluid temperatures. My gut feeling is that while flow in schedule 40 steel piping might be superior to flow in copper piping when you consider the resistance of el's, tee's, etc. the total resistance in copper will be less. If you compare flow in an elbow for example. In copper especially type M, there isn't much of a blunt edge of the pipe end for fluid to run into. But with schedule 40 pipe you have the much thicker pipe wall thickness.

Engineers talk about the operating costs of piping. If you look at my pump graph curves above you can see that at a given flow rate PEX or copper will work, if you use the right size pump. But the pump for PEX is much larger, more expensive to buy and consumes more electricity. So in a sense there is an operating cost for the piping you choose. In the end it's all a trade off, pay now or pay later.