3/4" to 1 1/4"

If you need three 600' loops of 3/4" pipe for a horizontal loop how much pipe would you need if you use 1 1/4'? Would hdpe with SDR# 13.5 be sufficient?

 

SDR of 13.5 would be OK.

However you can only reduce the amount of pipe by 5% according to the LoopLink design program.

With 3/4" pipe 2.5 gpm gives you 1.25 feet/sec of flow.

If you use 1 1/4" pipe you will need 6.5 gpm to maintain 1.25 feet/sec of flow.

 

With a three ton system needing 12 GPM would that give the flow rate you need?

 

Most 3 ton systems only need 9 gpm.

are you wanting to use the 1.25" pipe instead of .75"?

If so, you probably should do two loops of 900'

 

I want to use the 1.25" because I can get a real deal on it. Thanks for the heads up on two loops instead of three. With two 900' loops I should have more than enough loop length.

 

This "real deal" will be way tougher to work with!

 

I know the larger pipe will be harder to work but I have thirty acres in the back yard to work with. I have a basement that the floor is four feet under the top of the ground so there should be no problem coming in from the loop. In my location which is Greenville SC which is the best antifreeze to use? The frostline is around two feet so would five feet be deep enough to put the loops?

 

Ready to install my loops, just bring them up in the basement and cap them as I don't have the pump yet. Would I be better off back filling the loops a couple of feet at the time letting it rain on it helping it settle as it won't be used maybe for a while?

 

if you have the time, it might help a little

 

In needing two 900' loops how critical is it to have both loops exactly 900'? How much of a variance can you have between the two?

 

10%

 

Bill you need to meet Flo,

it is all about Flo, or flow. The flow controls the heat transfer.

Even flow is not just for babies any more. Water is lazy, it takes the easy way back and forth to the heat transfer points. In a geothermal heat pump system there are three points of heat transfer and you MUST INCLUDE all three for the system to work as designed.

Heat goes to cold, every time.

Refrigerant machines can concentrate heat to make humans feel comfortable.

All this time and money we spend is about whether the people living in the conditioned space are comfortable. People do not know when they are comfortable they only know when they are uncomfortable. That makes comfort a moving target. If you want to really get confused look at what Mr. Carrier did when he funded the psychrometric chart work. he added relative humidity to the temperature mix and invented air conditioning.

So, if you install two loops of unequal length and do not know how to balance the flow. Flo will file for divorce and you have wasted time and money. To get the most heat transfer out of a set of pipes buried in the ground the water should flow the same through the length of pipe. So if one pipe is 10 feet long and the other is 30 feet long and you use these pipes to feed the second heat transfer point, ie the heat pump, and do not balance the flow, what happens? The water goes through the ten foot section and misses the entire 30 foot section because water is lazy. It is going to take the easy way home. So to gain the same heat transfer for the heat pump you could have not buried the thirty foot loop at all. That said, how does one fix this error.

The easy way is to keep the installation balanced. It is too late we now have a 10 and a 30. To get water to flow through the 30 we need to restrict the flow through the 10. We do that, and now have 40 feet of pipe involved with the heat transfer. Good job. The heat pump is unhappy still. because it does not see enough flo, and Flow is still unhappy,too. We need a bigger pump, that uses more energy to push the water through the uneven loops to get enough heat transfer to the heat pump.

Design engineering is everything, (I am an HVAC contractor by choice and have a Journalism thingy on the wall so I did not have to take college level French), I am not an engineer but I have folks that I like who are same, and we all know we need to plan and do the math.

The perfect project is balanced. Buy and build just enough to do the job. That matches cost to operate with costs to build. Flow will be happy, Flo will be happy and you will be happy.

 

With a three ton heat pump needing nine gallons per minute and two loops of 900' each on closed loop horizontal what would be sufficient size pump on a QT flow center? Loops being 1 1/4" pipe.

 

SDR 13.5 transfer lesser heat than SDR 11, which is pretty much the geo standard. With SDR11, 1.25" pipe, in my area, with my ground conductivity, with my ground temps, 1800 ft of straight pipe, 6-8 ft deep, should support a 3 ton system. You loose velocity in the pipe, so your Reynolds numbers are going to be ugly. Not sure what impact that has. The problem is that you changed so many variables that I really don't know the best answer. My gut tells me that a single 26-99 will do fine, since you need only 9 gpm here, but could get bye with 7.5 gpm. The entire system pressure drop should be very low, but again, your Reynolds will look ugly. But than, you will have twice as much volume of circulating water as a buffer. Nothing a "standard" loop program would account for.

Like Mark said, now you don't get the flow balanced, all bets are off again.

 

I am up and running since November of 2014. Tranquility 30 two stage unit with a two pump QT flow center with one pump removed and capped, and two 1000 foot loops of one inch SDR poly pipe. During cold weather did well at 72 degrees with plenty of hot water from Desuperheater. When I switched from heat to cool it is not producing any hot water. I wonder if anybody can tell me what I need to do? Thanks Bill

 

How is your hot water piping arranged? Do you have an unpowered storage tank upstream of your powered hot water tank?

 

your loops might not be warm enough to allow much desuperheat, thus the circulation pump for the DHW is not turning on. Standard control logic since then you might pump hot water from your hot water tank through the refrigerant circuit into the loop field. Thus manufacturers disable the DSH circulation pump at colder source loop temps. This is in cooling only, not heating, and only with R410a units.
Sounds all normal, just wait until the weather gets warmer and you reject more heat into the loop, then the DSH pump will turn on.

 

I do have a buffer tank upstream of my powered hot water tank and being that it worked in heating mode piping must have been correct. I guess I will wait until the loops heat up and see if I get hot water. Thanks for the replies. Bill

 

What is your Entering Water Temp (EWT) and Leaving Water Temp (LWT) in cooling mode?