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

Life is a compromise !
DON

Lowes sells 1 1/4" black iron for $1.76 a foot by the 10 foot lengths. That's cheaper than I can buy it at the wholesale place! They'll even cut & thread it for free.

So 1 1/4 in Copper sounds about right? I know some say to use 1 in, but is there a neg to useing the bigger pipe? thanks

Just the price and the cost of fittings,, and soldering larger fittings requires a bit more skill than the smaller ones.. I solder a 1/2 or 3/4" fitting almost without thinking about it.. but a 1 1/4" that I pay attention to what I'm doing,, I DON'T want to take it apart and re-do it.

Greg >

Soldering: heat the fitting, not the pipe. Soldering 1 1/4" copper to a copper elbow isn't bad, but when soldering to a brass fitting like a valve you do want to make sure the heat is proper. You can't just put the heat to the bottom and hope it'll work. By the time the top is hot, the bottom will be too hot and will boil the solder out of the fitting. Work the flame around the fitting keeping it deep into the fitting, that is, away from the pipe a bit. The edge and pipe heat easily, you need to apply the heat where most of the mass is. Most of the heat on the bottom, but give the sides a good shot too, even the top a little. You need to make sure the inner part is hot enough so the solder wicks deep into the fitting. Ball valves should be shut when soldering, boiler drain valves and zone valves should be open. (so the rubber seals don't melt).

When you get to 1 1/2" it's common to use two torches at once.

You cannot solder a pipe that has water in it. If there's any chance of water in the pipe, like, when you drained & the dribbling has stopped but water still laying in it, that water has to be boiled off. It's common for a miserable leak if water was still in the pipe or worse yet, a drippy valves leaks as you're trying to solder. Normally when I solder I get it up to heat & just add solder to the top. On stuff larger than 3/4" I'll go from the top around each side til I can see it's made the trip to the bottom. BUT... is there's been water in the pipe, or any chance that water may be slowly dripping during the solder, I always melt the solder at the very bottom first. Remove the flame for a second and see if solder will melt right at the bottom. If it will not, it's not hot enough, or it's not hot enough because it has water in it. More heat! Once it takes solder at the bottom I know it won't leak and go from there to the top & sides. If you just can't get it to melt at the bottom you're going to have to stop the dribbling! They make plugs that go through a fitting and plug the pipe internally so you can solder. Best thing is just to stick to new stuff with no water.

Yeah don't be bashful with the heat and spread it around.
DON

Yanche wrote: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.

I wonder why he doesn't talk much about steel pipe? I saw a chart in "Pumping Away" and the GPM specs that Dan put in for Steel was always slightly higher then the specs for the same size copper.... hmmmmm

I suspect Dan's numbers are wrong. If you look at the Hazen-Williams formula for calculating pipe pressure loss and the suggested friction loss coefficient it shows copper had less friction loss than steel. The pressure drop is a strong function of pipe diameter and perhaps the steel pipe diameter is greater than the equivalent copper nominal size. I haven't had a need to work the calculations through to get an definitive answer.

See: http://en.wikipedia.org/wiki/Hazen-Williams_equation

If all the circulator had tto do is circulate water from coal boiler 30 ft though oil boiler and 30 ft back useing pex would still be to much fricton for it? I would lose efficey and heat? Just wondering

Many, many folks circulate water from a remote boiler much farther than 30',, I have my remote boiler halfway between my house and my shop, it is 150' to either building.. so my circulator pumps move the water out 150' and back 150', a 300' round trip,, not a problem.. I know of outdoor wood boiler users that have more than 500' round trip.

Greg L.'

Using pex? Pex is also only avaialbe in 1 in or can you find bigger? I have mostly Black pipe and copper in my home now, 2 RM in the house (New part ) use pex to the radiators.

I run 1" Pex Al Pex. 1" id.

Greg L.

JOE.G wrote:If all the circulator had tto do is circulate water from coal boiler 30 ft though oil boiler and 30 ft back useing pex would still be to much fricton for it? I would lose efficey and heat? Just wondering

The longer a pipe is and/or the smaller it's diameter is the more resistance to flow it will have. Look at the graph in my previous post:

about5812.html#p56971

It compares the flow resistance curve of various lengths of one inch PEX-AP-PEX and copper. It also has three pump curves plotted. The intersection of the piping flow resistance curve and the pump curve is the operation point. It's where the pump pressure heat equals the piping head resistance. Draw a vertical line down the the flow and read the number. For example 100 ft of PEX-AL-PEX and a Taco 007 would allow 4 gallons per minute to flow. Is that enough? Well it depends on how much heat in BTU's you want to move, the supply temperature and the return temperature.

Look at the graph below. It shows flow rate vs. BTU (in thousands) for various temperature differences. Let's assume you have all copper tube baseboard. The amount of baseboard needed for your house frequently used as 20 deg temperature drop as a design criteria. So look at your 4 gallons per minute flow rate and read up and to the left on the 20 deg line. You will move 40,000 BTU. No more, unless you change the pump to a more capable pump or change to a heat emitter that can work with a larger temperature differential. If you bought a 130,000 BTU boiler like a AHS S130 Coalgun or A-A 130 Anthratube your piping system CANNOT move the capability of the boiler. Your boiler will be working approximately 1/3 of the time.



On the other hand if your piping system was 100 ft of copper pipe the piping resistance is much lower. You could flow about 12.5 gallons per minute. That point is off the graph but it's more than 100,000 BTU a closer match to the referenced boiler.

The point I'm trying to make here is you need a balanced system design, the right sized boiler to your heat load, the right piping design and suitable heat emitters. Understanding BTU heat transfer principles will allow you to buy and install what's needed.

There is that much of a diffreence between teh 2. black pipe and copper I guess are alot closer.

All the outside boilers use the Pex for long runs and it works. Why wouldent it work for a 30' run?