Pump size

[heaterman]

I am getting to this thread late, so pardon my ignorance.

Everyone seems to be talking about only the distance from the OWB to the inside boiler, isn't it also necessary to figure out how much piping is in the house? and how would you do that? I have six zones in my 3000sf house, all mostly 3/4 or 1" copper, and 80% of the piping is all in the walls or otherwise inaccessible. How could one possible add up all the lengths, T's and elbows to figure out the required pump size? Yes, you can accurately add up the new run, but that only seems to be 1/2 or even just 1/3 of the problem...

My current boiler has one large circ, and zone vales. I figure new pump needs to be at least that big because if only the wood boiler is running, then the new circ needs to do all the work of the old circ, plus the added distance from tarm to the oil boiler.

Does larger pipe always mean smaller pump? I was planning on 1 1/4" pipe from the tarm to the oil boiler in the cellar, if I upsize to 1 1/2" pipe, and eat the cost now, does that mean for the next 20 years I can use a smaller, more energy efficient circ and save electricity costs?

Is there any downsize to the larger pipes?

The house is not a concern because the system presently runs on it's own circ. Correct? The zone and boiler piping currently in the house does not enter into the equation unless you are going to do a direct run out to the wood boiler with no additional circ. The existing controls and zone valves will still operate as normal. You're just providing the heat from a different "burner" thereby eliminating the need for the fossil boiler to fire. All it knows is that when there is a call for heat from one of your zones, it doesn't have to fire the burner if it's already hot enough.

Typically one would tie the wood boiler into the existing piping via primary secondary tees which are closely spaced (no more than 4 pipe diameters apart) and use a separate circ to move the water from the wood boiler into the existing piping.

When it comes to piping long distances, it's always better err on the larger rather than smaller side of things. A samller circ costs less to operate and less to buy when it comes time to replace it. A 15-58 or 007 runs for less than half the cost of a 26-99 or a 0011.

What is the total distance from the wood boiler to the point where the pex would tie into your existing piping? What is the heat loss of your house? In other words how much heat do you need to transfer?

 

[MrEd]

The distance from my Tarm to my oil burner is only about 50 feet (100 feet total and was plannong on 1 1/4 black iron), but in my design, I didn't have the oil burner circ running when the wood boiler was firing. My plan was that the wood boiler circ wood run when the wood boiler was firing, and the oil burner circ would run when the oil burner was running - a parallel setup based on nofossils 'simplest pressure storage" design.

I don't see how I could make use of the oil burner circ without circulating water thru the oil burner (and all the losses that go along with that).