3/4" pex

[AIM]

Well I screwed up a couple years ago and ran some 1" pex underground that does a fantastic job of melting snow and keeping worms warm. Anyways I am moving my boiler and rerouting the lines a different way to fix this but I'm wondering about using 3/4" vs 1".
My house run will be approx 70' long and my shop run will be about 30'.

3/4" is a bit cheaper and the fittings are way more abundant. Plus 3/4" is a ton easier to work with than 1". If 3/4" will work just fine then I'd like to go this route but if not, then I guess I'll stay with 1".

Any thoughts?

 

[Butch(OH)]

First thing you need to realize is that in fluid carrying capacity 3/4 is NOT "just a bit" smaller than 1" For rough and ready calculating purposes you can use one half, yes 1/2 of the capacity of 1" pipe. The term that all fluid engineering uses to measure resistance to flow in a piping system is "head" and it is measured in feet. It is pretty easy once you get the basics, probably on line somewhere. Anyway using those calcs you can figure out exactly how much your heat carrying capacity will suffer when going to 3/4 pipe, again for rough and ready "calculating" you can use one half. I have had my OWB for going on 4 years and my GUESS is that I don't push the heat carrying abilities of my system at all and my runs are very close to yours, 65 to the house and maybe 20 to the shop.

 

[outbackrider]

Here are my thoughts.
Do it right the second time....
I have done too many things once, incorrectly, trying to save a buck.
Well it costs you more at end.
I am in my 5th year of burning, and first year, I laid insulated hard pipe above ground, it worked, not too bad, but each year I had to take the pipe up, reconnect, etc. The hard pipe was too difficult to work with. I didn't want to spend the money for the flexible insulated pipe. Like a friend, I made some up last year, used 6" pipe, pipe insulation wrapped around the pex, and then wrapped in insulated foil. It worked, but, I lost between 7-8 degrees of water temp by time it made it to my house. I have finally decided this year to spend the money, and get the good stuff. I just dug up all my hard work from last year and will use it to heat our swimming pool in the early spring.
Do it right the first time, use the correct size and insulated pipe......:bang:

 

[ericjeeper]

I agree with most..

Not the time or place to cheap out.. Only so many btus can be delivered in any size tubing.. How many btus do you need?

 

[welder15725]

My central boiler has 3/4 inlet and outlet. So I ran my pex in 3/4. Seems to work in my house. The house is 80' away. I need to install some thermometers in my system so I can see what my temp lose is. But I know it's only a few degrees.

 

[Mac B.]

I have 2 friends that both ran 3/4 from the boiler to the house with no problems at all. One ran his with insulated pipe under ground and the other ran his in just corrugated drain pipe underground. Both work very well but we are also in NC so it doesn't get as cold as it does for some of you. Their boilers are both about 110' from their house. I just ran mine uninsulated in corrugated drain pipe 20" deep.

Thanks Mac

 

[AIM]

Not the time or place to cheap out.. Only so many btus can be delivered in any size tubing.. How many btus do you need?

Not looking to cheap out. I just would rather run 3/4" than 1" if it will do the job. Of course I want it to do the job with BTU's to spare as well.
I don't know how many BTU's I need. I think I've seen the way to figure it out here on AS so I will see if I can dig that up and do some math.

1080 sq ft + basement = 2160 sq ft w/ 8' ceilings = 17280 cubic ft. Well insulated w/ good windows. (15 year old house that I built myself)

768 sq ft garage/ shop. poorly insulated. Leaky and drafty. (I've been insulating little by little but can't seem to get the ambition to finish it) I'm not to concerned with the garage. It will heat it however well it heats it. Until I get it sealed up it's pretty much a losing battle.

 

[Paul61]

You messed up on the 1st install, it's not the fault of the 1" pex.
Jeep is right...don't cheap out on the insulated lines & run 1", not 3/4.
Here's my setup:
250' run to house (approx 5000 sq.ft.), 150' run to shop (2000 sq.ft.), only a couple of deg. max heat loss over these distances.
My OWB is 500,000 btu, burns 1/3 cord per week to heat both buildings.

Paul

 

[Penguins87]

Go with 1". Don't be sorry. Too much is better than too little. That way if you need to add something in the future your set.

 

[AIM]

Paul61
Look at the difference in numbers between you and I. I'm heating 2160 and your heating 5000. (and 768 compared to 2000)
Your distances are over 3 1/2X and 5X that of mine. In your situation I wouldn't think twice about using 1"

I'm just not one to overkill when it's not needed.

That's why I installed a little bitty 65,000 btu gas furnace when I built my house and it does a great job of heating my place. (now it's just a place to gather dust)

 

[ericjeeper]

I think you have made up your mind

Kind of goes like my dad used always tell me.. "Do whatever you want, you are going to anyway"lol
Ok if you are replacing a 65 k furnace you know you need about 65k of BTUs

 

[welder15725]

are you putting a coil in your furnace?? or heated floors??