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1" pex question

milkie62

milkie62

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I do not have any problem since I only have 2 zones.But how does a 3 or 4 zone system work when the only insulated pex I seen is 1" from the boiler to the house ? If there is a manifold how is there enough flow if say you have 3 zones in the house.
 
ericjeeper

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different types of Zones. I have radiant heat in my home. Tubing in the slab. I have 15 zones within my house. But they are all 1/2 inch pex. Every room in the house has its own stat. Works like a dream.
 
blackdogon57

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I have 3 zones for house/garage plus DHW loop all with 1" pex. Manifold is located where lines come through basement wall. Works very well. All lines have ball valves for supply and return at the manifold. Very handy when I shut down the 3 heat zones in the summer. Only the DHW loop runs then.
 
coyotencuttin

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the 1 inch pex is only the main supply to a manifold in most situations.from a manifold you would have 1/2 inch pex going to the individual zones.1 inck pex should be good for abot 80000 btu(from what i found this morning so far) which is fine for most applications. if you zone the house chance are that you won't have all the zones calling at once so it would be plenty to heat most any home.
 
tibikedad

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1 inch pipe can carry 8 gallons per minute, which equals 80000 BTUs per hour.
1/2 inch pipe is rated for 1.5 gal/min, which is 15000 BTUs per hour. If you aren't drawing this much, you are ok
 
Steveguy

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1" pipe will carry alot more than 8 gallons per minute. You can pull enough heat off of a 1" loop with the right system to pull down a boiler capable of 500,000 btu's . It depends on the circulator pumps you use, heat exchangers etc. I don't think 1" pex is a limiting factor in most any residential application. My nephew uses a Central boiler 60-48 on a firewood drying kiln being fed with 1" with several HX's hooked to it and when he loads the kiln with a fresh batch of cold wood it will pull on the boiler hard enough that it will burn constantly for most of the first day to get the chamber and the wet wood heated up and still not gain temp in the boiler. Thats making around 400-500 thousand BTU on a steady basis.
 
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blackdogon57

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2 taco 009's. 1 to house 1 to out building. 3 zones in house 2 in out building. Hot water side arms in both buldings. CB 6048. Goes through quite a bit of wood ( mostly waste from firewood operaton) but saves me lots of $$$ and gives me a place to get rid of my junk wood.
 
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milkie62

milkie62

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Well I have the old style 1" pex with the blue foam duct taped around it.It is 10 yrs old.The ground will eventually melt the snow even though the pipe is down 18".Boy that insulation must have deteriorated over that time.Well I am going to build a 3 car garage that I will also be heating with it.Does anybody have any rough ideas what radiant floor heat is per sq ft in concrete ? Getting back to my original question on the manifold issue.My zones are 3/4" copper coming off the main 1" line.Now being a volunteer fireman I know that I can only suck so many feeders off the main and then it is useless.So at what point do you stop getting sufficient heat at zero degrees outside and most of your zones are calling for heat ????
 
trialanderror

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1" pipe will carry alot more than 8 gallons per minute. You can pull enough heat off of a 1" loop with the right system to pull down a boiler capable of 500,000 btu's . It depends on the circulator pumps you use, heat exchangers etc. I don't think 1" pex is a limiting factor in most any residential application. My nephew uses a Central boiler 60-48 on a firewood drying kiln being fed with 1" with several HX's hooked to it and when he loads the kiln with a fresh batch of cold wood it will pull on the boiler hard enough that it will burn constantly for most of the first day to get the chamber and the wet wood heated up and still not gain temp in the boiler. Thats making around 400-500 thousand BTU on a steady basis.
true that. my home made conversion was rated dfor 500k, to heat my garage i used a huge radiator from a kenworth road truck. enough surface area to hold 4 20" box fans, and when they're all on, within 5 minutes 400 gallons of water drops 20*...... and holy the heat roaring from it is intense!! best exchanger you can use! i think radiators are better, they need to work extremely efficient, otherwise serious engine problems....
 
twofer

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1" pipe will carry alot more than 8 gallons per minute. You can pull enough heat off of a 1" loop with the right system to pull down a boiler capable of 500,000 btu's . It depends on the circulator pumps you use, heat exchangers etc. I don't think 1" pex is a limiting factor in most any residential application. My nephew uses a Central boiler 60-48 on a firewood drying kiln being fed with 1" with several HX's hooked to it and when he loads the kiln with a fresh batch of cold wood it will pull on the boiler hard enough that it will burn constantly for most of the first day to get the chamber and the wet wood heated up and still not gain temp in the boiler. Thats making around 400-500 thousand BTU on a steady basis.
If my calculations are correct even with a system designed for a temperature drop of 40 degrees (normal is 20 degrees) you're still talking about about velocities of 20-25 ft/sec. If I'm not mistaken this could lead to erosion of the PEX due to the water traveling so fast.

I could be wrong as I don't know what the allowable range of velocities are for PEX.
 
Steveguy

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"If my calculations are correct even with a system designed for a temperature drop of 40 degrees (normal is 20 degrees) you're still talking about about velocities of 20-25 ft/sec. If I'm not mistaken this could lead to erosion of the PEX due to the water traveling so fast."



Yeah I realize that the nephews system may not be quite right, I was mostly trying to illustrate that for most residential use 1" pex is plenty. most times you can get by with a 007 size pump and if you need more a 009 or equivalant will do it.
 
Marklambert61

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wrong .....

1" pipe will carry alot more than 8 gallons per minute. You can pull enough heat off of a 1" loop with the right system to pull down a boiler capable of 500,000 btu's . It depends on the circulator pumps you use, heat exchangers etc. I don't think 1" pex is a limiting factor in most any residential application. My nephew uses a Central boiler 60-48 on a firewood drying kiln being fed with 1" with several HX's hooked to it and when he loads the kiln with a fresh batch of cold wood it will pull on the boiler hard enough that it will burn constantly for most of the first day to get the chamber and the wet wood heated up and still not gain temp in the boiler. Thats making around 400-500 thousand BTU on a steady basis.
Sorry but your wrong 8-10 gals max in a 1" pipe
 
Steveguy

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Sorry but your wrong 8-10 gals max in a 1" pipe
Does any of this change my statement that 1" pex flow enough water to satisfy almost any residential need? That was the original question wasn't it.

I'm not going to argue the point any further, but the fact remains that discounting the proper numbers for feet per minute... turbulent vs. laminar flow... pipe erosion blah blah blah. 1" pipe will move more water than that. I know that 8-10 is recommended numbers but if you apply pressure, the flow will increase. Hold on to a 1" forestry hose fighting brush fire and you will get what i mean. DISCLAIMER: I do not recommend or condone the use of forestry hose, fire trucks or brush fires in home heating applications.
 
mtfallsmikey

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Does any of this change my statement that 1" pex flow enough water to satisfy almost any residential need? That was the original question wasn't it.

I'm not going to argue the point any further, but the fact remains that discounting the proper numbers for feet per minute... turbulent vs. laminar flow... pipe erosion blah blah blah. 1" pipe will move more water than that. I know that 8-10 is recommended numbers but if you apply pressure, the flow will increase. Hold on to a 1" forestry hose fighting brush fire and you will get what i mean. DISCLAIMER: I do not recommend or condone the use of forestry hose, fire trucks or brush fires in home heating applications.

It sure can, but not when HX's, zone valves, fittings are added to the mix. 1" is good for 90% of apps. Most OWB's do not have tappings larger than 1" anyway....Using primary/secondary piping and zoning techniques allow virtually undisturbed flow in the primary loop, makes the system more responsive.
 
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