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[Gunpowder]

Working on plumbing the inside of a 50K BTU furnace application (not a house but an office). I am plumbing with 2 T valves prior to accessing the heat exchanger so I can install to a small water heater if I decide to later. The hot watter is not used much in this building so not a priority.

Question is size. I am running copper. I had planned on 1" since my heat exchanger is also 1" but since the thermostatic valve included with the boiler is 3/4 and the two T valves are also 3/4"  I am questioning my thought to use 1" copper. Especially since the Rahau I installed from the OWNB is 1" (so therefore 3/4 ID).

There will eventually be a second run from the OWB to my residence but that comes later this year. Not a factor here I assume.

1. I could just use 3/4 since everything is 3/4 already and only serving a 50BTU force air furnace.
2. I could plumb 1" to 3/4 adapters at each valve which enables me to use 1" 90 elbows to reduce flow drag overall.
3. 3/4 copper is comparable to 1" PEX (3/4 ID) so no difference
4. 3/4 is cheaper

Thoughts?

[RSI]

1" pex is 7/8" ID.
Depending on how much pipe you have, it might be ok with 3/4". If there is a lot of pipe, you will probably need to use a larger pump if you use the 3/4"
It makes a big difference if you have long small pipes compared to a few small fittings.

[Gunpowder]

1" pex is 7/8" ID.
Depending on how much pipe you have, it might be ok with 3/4". If there is a lot of pipe, you will probably need to use a larger pump if you use the 3/4"
It makes a big difference if you have long small pipes compared to a few small fittings.

Approx 95' from OWB to furnace room. Then maybe 10' to furnace. Like I stated, the Thermostatic valve is 3/4 (CB only sells a 3/4 or 1 1/4).

The valves around the Thermostatic valve would all be 3/4 according to the CB kit specs. I may be able to switch my current 3/4" 3-way valves to 1" but not available at local box stores. These valves are used to divert to water heater and then back to the main line and then on to the furnace.

[RSI]

3/4" will probably be fine if it is that short.