# Pex size and flow?



## Sawyer (May 31, 2008)

I will be plumbing from a Garn 2000 located in a shed 175” to a plate to plate heat exchanger in the boiler room in the house (The max demand will be 92,000 Btu/hr.). Another line will run 70" to a 32,000btu boiler in my shop. I have not been able to locate charts for flow/distance. If someone would like to send to charts I am willing to do my homework also. Can this be done with 1” or will 1 ¼” be required. I was told that it is expensive to locate the pex tools to work with the 1 ¼” fittings for one application. 1” would also be easier to work with. I have also seen mentioned where two size X have been used instead of the original design size to be more economical. I have a AIC LA14-50X  heat exchanger available but the hose connections are only ¾” and is rated at max 110gpm. I will be digging a trench within the frost line as it is under a driveway and foaming in place with closed cell as recommended.  After spending the money on the Garn it would be foolish to mess the installation up being cheap but on the other hand the Garn did use up a lot of my available resources.


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## Fredman (May 31, 2008)

I used 1 inch from my boiler to my house and my house is 150 feet away. A guy in the shop where I work is going to dig up his pipe this year and put his pipe in a trough and foam it this year. I think it is the way to go, more foam the better.


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## Sawyer (Jun 1, 2008)

Fredman said:
			
		

> I used 1 inch from my boiler to my house and my house is 150 feet away. A guy in the shop where I work is going to dig up his pipe this year and put his pipe in a trough and foam it this year. I think it is the way to go, more foam the better.



Thanks Fredman, are you East or West UP? 

What is the heat demand on the 1" you ran? What size circulating pump if I may ask?


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## Fredman (Jun 1, 2008)

I run about 180 but it goes up past that in the 190's. I just switched to T-11 pump and don't forget a filter on the return side (which I am putting in this year). Central is what we are considered, south central to be exact.


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## deerefanatic (Jun 1, 2008)

I might add that running two pipes in parrallel is not a free lunch... Cross section alone is not everything......

For instance, According to Dan Holohan (author of some of the best Hydronic books any DIY person could read) you size the pipe diameter to the flow you need, then size your circulator head for the lenght of pipe you need...... So, if you need to flow 4 gpm, use 3/4 inch or larger... REGARDLESS of how far you have to go.... 10 feet or 100, use 3/4 as a minimum..... so, to flow 12 gpm, you can use 1 1/4 inch, OR a run of 1" and 3/4" together... The 1 + 3/4 route gives you more cross section than the 1 1/4" single pipe route... Why then can it not flow more? Well, there is more pipe wall incurred with multiple pipes, so you have more friction......

All in all, I ran a dual run for my house heat exchanger. I shudder to think of the cost of 1 1/4" fittings and tools... Not to mention how much of a pain it would be to deal with that stuff........


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## heaterman (Jun 1, 2008)

From another thread here............




Here’s the reason for the 1-1/4” pex.

Figuring 300’ round trip and not even adding any additional restriction caused by elbows, valves, tees, heat exchangers or other piping, the flow numbers look like this. (my guess is that your actual flow rate will be somewhat lower because of additional piping and fittings)

with 1” tube with 1-1/4 tube

007 Taco = 4.9 gpm 007 Taco = 7.9 gpm .85 amps
009 Taco = 6.2 gpm 009 Taco = 7.4 gpm 1.3 amps
0011 Taco = 8.3 gpm 0011 Taco = 12.7 gpm 2.2 amps

*To figure the heat carrying capacity of those flow rates multiply the gpm by 10,000. That’s figuring a 20 degree drop supply to return*

So to get 80,000 btu’s through the 1” tube you have to use the 0011 circ which uses 3 times the current of the 007. To get the same 80,000 btu’s through 1-1/4” tube you only need the small circ which operates for nearly 1/3 the cost of the 0011.  That really adds up over a period of years. Given that oil and gas will never be $2.00 / gallon again, how long do you plan to burn wood?  10 years? 20?

To put it simply the 007 will run for about 10 hours on a dime’s worth of electricity. The 0011 will only run for a tad over 3 hours. I know you’re smart enough to figure that out over the course of a year because you’re here asking questions. You’ll be surprised at how quickly the larger diameter tube pays for itself in electrical savings. Not to mention the smaller, low head circ will last longer on an open system 9 times out of 10.
Those 009’s and 0011’s need a fair bit more pressure on the inlet side of the impeller and it’s just not there in that type of a system.


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## Sawyer (Jun 2, 2008)

deerefanatic said:
			
		

> I might add that running two pipes in parrallel is not a free lunch... Cross section alone is not everything......
> 
> For instance, According to Dan Holohan (author of some of the best Hydronic books any DIY person could read) you size the pipe diameter to the flow you need, then size your circulator head for the lenght of pipe you need...... So, if you need to flow 4 gpm, use 3/4 inch or larger... REGARDLESS of how far you have to go.... 10 feet or 100, use 3/4 as a minimum..... so, to flow 12 gpm, you can use 1 1/4 inch, OR a run of 1" and 3/4" together... The 1 + 3/4 route gives you more cross section than the 1 1/4" single pipe route... Why then can it not flow more? Well, there is more pipe wall incurred with multiple pipes, so you have more friction......
> 
> All in all, I ran a dual run for my house heat exchanger. I shudder to think of the cost of 1 1/4" fittings and tools... Not to mention how much of a pain it would be to deal with that stuff........



Did you terminate the dual run supply/return lines into a 1 1/4" manifold at both ends?


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## Sawyer (Jun 2, 2008)

heaterman said:
			
		

> From another thread here............
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Following this thought and the fact that I need 92,000 btu would I be better off with a dual line system as deerfanatic, increasing my pipe size to 1 1/2", or running the more costly to operate 0011 Taco with 1 1/4". I would think the handling of the dual smaller diameters would be easier and the fittings more accessable. I am getting ready to dig the trench and prepare for the insulators.


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## heaterman (Jun 2, 2008)

Sawyer said:
			
		

> heaterman said:
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Here's the tricky part of design work. Note the line that's bold faced. The last statement refers to a 20* temp drop supply to return. If you can size your heat emitters to provide a 30* drop you can provide the same btu's with less gpm. In Europe it's not uncommon to see design temp differentials of 40 or even 50 * supply to return. Less flow required = smaller circ and tubing. 

As an example, using the 007 with the 1-1/4 tube and a 30* drop you can deliver 118,500 btu's. A slab radiant floor, a well designed panel rad system or even a baseboard system can deliver those kinds of drops. Tough to do with a fan coil type HX.

If you think about this you can begin to see the beauty of the new variable speed circ's coming on the market. You just dial in you desired parameters and the circ matches them.


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## Sawyer (Jun 2, 2008)

heaterman said:
			
		

> Sawyer said:
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## Willman (Jun 3, 2008)

> If you think about this you can begin to see the beauty of the new variable speed circ’s coming on the market. You just dial in you desired parameters and the circ matches them.


With the variable circs  how is the tubing sized ? Still 1/2" for supply to zones ? How about the P/S loop ? 
Will


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## beavah (Jun 4, 2008)

Hey Sawyer, I am new to this website but I have been in the heating industry for years and heatman is dead nut acurate. Using 1 1/4 pex will be harder and the fittings will be more expensive HOWEVER trying to find a 0011 pump at 10:00 o'clock at night, forget it.  Everyone has a 007 pump. Plus if you ever upgrade the system (addition to house) the ability to pump more btus will be much easier with that size pipe. Go through the pain in the ass now to make your life easier in the future.


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## deerefanatic (Jun 4, 2008)

Or, run multiple parrallel pipes manifolded together... This has an additional advantage of if he decides to put in radiant, etc, he already has the extra pipes that he can use (as the air coil would no longer need as much flow..) and have all his pumps and stuff in his boiler room.

I have mine manifolded to 1 1/4 in the boiler shed, but only 1" in the house because my fan coil only has 1" inlets anyway........ But it's also only for a few inches of pipe.......


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## heaterman (Jun 4, 2008)

Willman said:
			
		

> > If you think about this you can begin to see the beauty of the new variable speed circ’s coming on the market. You just dial in you desired parameters and the circ matches them.
> 
> 
> With the variable circs  how is the tubing sized ? Still 1/2" for supply to zones ? How about the P/S loop ?
> Will



The btu's required and the temp drop you can achieve will tell you the gpm you need. The flow requirement can be varied based on the available temp drop in your loop, whether it be an in floor loop or the main primary secondary. The gpm always dictates the tubing size. 

You see.........it depends   sizing the tube and the circ is kind of a backwards calculation from a known point which is the btu's required.


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## heaterman (Jun 4, 2008)

beavah said:
			
		

> Hey Sawyer, I am new to this website but I have been in the heating industry for years and heatman is dead nut acurate. Using 1 1/4 pex will be harder and the fittings will be more expensive HOWEVER trying to find a 0011 pump at 10:00 o'clock at night, forget it.  Everyone has a 007 pump. Plus if you ever upgrade the system (addition to house) the ability to pump more btus will be much easier with that size pipe. Go through the pain in the ass now to make your life easier in the future.



Thanks for the compliment Beavah. Your kindness is exceeded only by your good looks.


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## Sawyer (Jun 4, 2008)

Thanks for all the input, I will definately go to the larger volume with the smaller head pressure so I can use a lower amperage pump. This is a great site for help and advice.

Thank You!


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