Boiler to Forced air plumbing help/suggestions needed

There are Di-Electric unions available that have a plastic separator to cut down or eliminate the galvanic action of the dissimilar metals. They don't cost that much, and you should only need two. I used them on my water/water heat exchangers.

My propane boiler has a low water cut off, it is in the output side of the boiler in the middle of a 3' vertical run. So in theory it should shut off the flame even while the boiler is full of water. I asked a plumber about it, and he said it is code. In my previous houses, the boiler did not have a cut-off. Just more parts to go bad and need replacement.

Greg L

Copper pipe expands at a faster rate than carbon steel or cast iron pipe at the temperature is increased. By analogy the same will be true for copper vs. steel or cast pipe fittings. So ... design your piping so a male copper threaded fitting always mates with a female steel or cast fitting. As both are heated by the hot water the thread joint will get tighter. Use an American made Teflon tape. It's much better than the China made stuff. On threads over 3/4 inch I use high temperature RTV silicone applied to both the male and female threads. Sparingly to the female threads. Remember a thread is just a leak with a spiral path. You stop the leak with a plug, the pipe tape or sealant. Ideally you apply either in such a way that the inside water pressure pushes against the sealant to make the seal tighter.

I like to have a minimum of metal type transitions. So I get to copper with male adapters at the boiler and pipe everything with copper. I use copper unions where needed. My feed water piping is a threaded male PVC adapter to a female copper or brass fitting. I avoid threads where possible.

I don't have a low-water cutoff because I have a hot water boiler. I went and ordered a 19x20", 3 row water/air coil and I think it will be fine. The coil is rated at ~160k BTU, my existing furnace is 144k BTU or 114,500 NET output. The TACO 007 is rated at 20gpm, my blower fan is 3/4HP so all together I think I'll have a warm basement and the house will at least be as warm as last year and my pockets will be stuffed with the cash that I'd ordinarily give the Propane company. The only downside is I'll never use the full capacity of the EFM boiler with my current setup, 25 pounds of coal per hour will make more heat than I can ever hope to dissipate through a 20x22" plenum. It's also 2 tons of coal a week if I need to burn that much to keep warm I'm buying a winter house in Jamaica mon. I didn't test my water but my HW heater is 15 years old and still good so I imagine it's OK. There is the option of running separate zones to baseboards or radiators but not this year.

My company has used copper to black iron fittting and stainless fittings quite often for over 30 yrs. with theses coils and have had no leak problems or problems with dissimilar metals. As Yanche said use a good US made commercial duty teflon tape and apply a good pipe dope paste like "LA-CO slick tight". The threads themselves are what seals the joint. The threads are cut on a taper and the dope and tape are mostly a lubricant to allow the joint to tighten properly. I use a boiler treatment called 4 in one which treats the Ph of the water prevent foaming ,an removes the oxygen from the water in a closed system. It also has a color indicator that tells you when your boiler ph is correct.

It appears there are numerous ways to install your boiler that will work. Maybe the most practical way is to talk to others in your area and/or look at some jobs done by local plumbers and do it in a way they would be familiar with. The time may come when a repair is needed and you are not able, for whatever reason, to fix it. Some older guys may not have kept up on newer methods and if confronted with something new and they know the homeowner did it they may not want to work on it. The old "Don't expect me to fix your mess ups for you" excuse. They may even want to re-plumb it their way and blame whatever problem you had on incorrect plumbing.

Just something to consider. There are a lot of good plumbers out there and a few that are not above robbing you without a gun.