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