pex distance challenges

[farmer brown]

Hi, new on the board but have been lurking for awhile.

I dug a ditch yesterday for my pex pipe but the distance is longer than I thought. 225 feet one way with an elevation rise of approximately 30 feet, than into the basement with a drop of 9 feet. I live on a hillside. Do I need a bigger pump and >1" pex pipe or is this simply unworkable?

Anyone with any advice?

 

[Duetech]

Welcome to the forum. Everything I have read here would say >1” pex . But I think you will get some questions on your heat load, current pump size and plumbing set up.

 

[Gooserider]

Hi, new on the board but have been lurking for awhile.

I dug a ditch yesterday for my pex pipe but the distance is longer than I thought. 225 feet one way with an elevation rise of approximately 30 feet, than into the basement with a drop of 9 feet. I live on a hillside. Do I need a bigger pump and >1" pex pipe or is this simply unworkable?

Anyone with any advice?

Welcome, and I agree, you will probably want to either go bigger than 1" or consider multiple runs. I agree with Cave, you will get questions about your current setup, plumbing layout, and heat loads, so you might want to start thinking about those things now.

The elevation changes aren't a big factor, when the system is working as when you have a closed loop they basically cancel each other out - the extra work to go up hill is cancelled by the siphon action pulling it back down hill. The only things you may need to worry about is making sure that you can push the water all the way through the loop when initially filling it, and if using an OWB or other open system at the bottom of the hill, that you don't have air leaks at the top that would let the system drain down and overflow the boiler. If you are going through a heat exchanger and / or using a pressurized system then this is less of an issue.

If you look back through some of the many previous posts on the subject you will find the formulas that you need to punch your setups numbers through - figure out your heat load, and from that how many BTU's you need to push through the pipes, which will then let you figure out the gallons per minute you need to move, and from there figure out the size pipe you need to get your flow rate into the 2-4 feet per second range...

Good luck,

Gooserider

 

[farmer brown]

This is way more complicated than i figured. I have a three thousand sq ft house and tons of wood. However, I want to maximize efficiencies for a reasonable return on investment. The dealer figures it will work with 1' pipe and a standard pump but I am not convinced plus I don't want to lose gained efficiencies to my electric bill. I am concerned about head pressure, friction loss, and whether or not I will be able to draw enough heat through the heat exchanger to draw as much heat as possible. From what I have read the water needs to flow at an optimum rate and I don't know how to figure that out. Help!

Thanks again.

 

[flyingcow]

What are you planning on installing for a boiler? And why so far away?

 

[farmer brown]

I am looking at an outside gassifer. Was pretty much sold on the new portage and main optimizer but still not sure.

So far away since the house is on a hill side and I don't want to move the wood three times before i load the stove.

 

[heaterman]

Hi, new on the board but have been lurking for awhile.

I dug a ditch yesterday for my pex pipe but the distance is longer than I thought. 225 feet one way with an elevation rise of approximately 30 feet, than into the basement with a drop of 9 feet. I live on a hillside. Do I need a bigger pump and >1" pex pipe or is this simply unworkable?

Anyone with any advice?

Knee jerk reaction........you need 1-1/4" tube or a pair of 1" if your flow rate is needs to be over 5-6 GPM.

That being said, a heat loss calculation will tell you what flow rate you need along with circ size, heat exchanger size and all that other good stuff. Everything hinges on what the heat loss says.

 

[Gooserider]

This is way more complicated than i figured. I have a three thousand sq ft house and tons of wood. However, I want to maximize efficiencies for a reasonable return on investment. The dealer figures it will work with 1' pipe and a standard pump but I am not convinced plus I don't want to lose gained efficiencies to my electric bill. I am concerned about head pressure, friction loss, and whether or not I will be able to draw enough heat through the heat exchanger to draw as much heat as possible. From what I have read the water needs to flow at an optimum rate and I don't know how to figure that out. Help!

Thanks again.

It seems overwhelming at first, but if you break it down, it isn't as bad as it seems because each step feeds into the next one... This is why we keep asking the same questions over and over - as it is what you need to break down in order to find the answers. I think you are right to be nervous about the dealer's assumption that 1" will do the job, some of our pro's report that they see LOTS of OWB problems because of pipe that is too small, where the dealer (who often isn't a hydronic pro) seemed to think pex only comes in 1"...

This paper from Taco will walk you through most of what you need to figure out - (broken link removed to http://www.taco-hvac.com/uploads/FileLibrary/SelectingCirculators.pdf)

Note the first two things it asks you about are your heat load and the temperature difference between your supply and return lines - without those numbers you CAN'T calculate anything else in a meaningful way. Once you have those numbers, it is pretty much a case of following the instructions in that paper to get the tube size you need, and an idea on the pump performance you need - obviously that paper will try to sell you a Taco pump, but you can use the numbers it gives you to pick whatever brand you prefer...

Gooserider

 

[MyOutdoors]

Farmer, I made the mistake of listening:"The dealer figures it will work with 1’ pipe and a standard pump", I'm currently in the process of digging up my 1" pipe and replacing it with 2-1" lines. I listened to heaterman and others and did a heat load calculation for my home and it's amazing once you plug in the #'s how everything is spelled out for you on paper. Do it right now or spend thousands later. I thought I could dig up my existing pipe and reuse it...not that easy! I nicked the corrugated tubing with the back hoe a few times and now that some dirt has worked it's way into the pipe, I don't trust it for the long haul. The mistake of assuming a dealer/plumber/etc. knows what their talking about has cost me approximately $2,000 for being undersized. I am partially to blame since I did not listen to some of the people on this site at first. Lesson learned...let it be mine not yours!

 

[MNBobcat]

1 1/.4 inch Thermoxpex is only a $1.50 a foot more than the cost of 1". I'd recommend going with the 1 1/4 to be safe. Its not that big a difference in cost.

 

[stee6043]

Didn't we have a guy here in the boiler room not long ago that was having big fits with his OWB because his boiler was below the elevation of his house by a fair amount???

If you're running an OWB 30 feet below your house I'd double check with the manufacturer on whether or not this is kosher. Although, Gooserider mentions that without leaks you should be "okay". I guess you'd be fine as long as your pump is always running but I have to believe that eventually (perhaps hours, days, weeks) after that pump turns off some or all of the water in the system is going to find it's way back to the lowest point. Maybe it's just me. What do I know...I run pressurized...

 

[heaterman]

Didn't we have a guy here in the boiler room not long ago that was having big fits with his OWB because his boiler was below the elevation of his house by a fair amount???

If you're running an OWB 30 feet below your house I'd double check with the manufacturer on whether or not this is kosher. Although, Gooserider mentions that without leaks you should be "okay". I guess you'd be fine as long as your pump is always running but I have to believe that eventually (perhaps hours, days, weeks) after that pump turns off some or all of the water in the system is going to find it's way back to the lowest point. Maybe it's just me. What do I know...I run pressurized...

If a person is dealing with that much elevation difference the main concerned is getting all the lines and heat exchangers (of what ever type) purged out. Typically a normal hydronic circulating pump will not develop the kind of flow velocity needed to do that if you're looking at 30' difference. The answer in that case is to connect a "purge" pump that will blow the water and entrained air through the system and back to your purge point. Once that is accomplished the regular circ will handle the chore. We use a 3/4HP shallow well jet pump mounted on a 55 gallon barrel to make things whistle through.

 

[700renegade]

I doubt the net elevation rise of 21' will cause much of a problem, as you'll probably be running a high-head pump like a Taco 011 or B&G;PL-55. If the high point in the piping is out in the yard you might have some issues bleeding the air off of that point. You can probably flush the bubble thru by filling with a garden hose at the boiler and forcing all the GPM thru the lines ( close the valve between the hose and the boiler ). Even with a low head pump if you run 1.25" the elevation change is no factor to the pump as stated earlier ( after the initial fill that is ).

I wouldn't worry about what happens down the hill at the boiler if you open up the line system in the house - the capacity of the line set and HX is probably only a few gallons and it probably will easily fit in the top of your boiler tank if it is an open system.

Ideally the lines between the boiler and house are lower in the middle so at rest the bubbles naturally go to either end - yours is inverted which can give problems. A bubble filling the top half of the pex pipe is functionally the same as having a gate valve in the line turned 1/2 way closed.

Watch your ID data - for example a 1" pex-al-pex is much bigger than 1" pex

 

[farmer brown]

Thanks everyone for the advice. I am starting to think about relocating if I can. The problems identified have basically confirmed what my thoughts were and are now reinforced. I don't want to make this kind of investment and than find that the system always needs tweaking to make sure it is running at it's best. I will be running a closed loop through a heat exchanger was skeptical about the pumping ability from the boiler. Guess I will have to cover in my ditch. At least i didn't spend all that money on that length of pipe. Thanks again.

 

[flyingcow]

Pex pipe can have different ID from brand to brand. Some are true and some are not.

 

[Gooserider]

Thanks everyone for the advice. I am starting to think about relocating if I can. The problems identified have basically confirmed what my thoughts were and are now reinforced. I don't want to make this kind of investment and than find that the system always needs tweaking to make sure it is running at it's best. I will be running a closed loop through a heat exchanger was skeptical about the pumping ability from the boiler. Guess I will have to cover in my ditch. At least i didn't spend all that money on that length of pipe. Thanks again.

Where are you putting the heat exchanger - at the boiler or the house? If it is at the boiler, with a closed system between the house and boiler, then the elevation change is a non-issue once you have the system purged initially, and it should be able to eliminate small bubbles in the lines as well if you have gotten the flow velocity in the 2-4 fps range.

If you are running the open boiler to the heat exchanger in the house, there is a little more of an issue.

IMHO I would put the HX at the boiler and keep the current location unless there are other good reasons to change it.

Gooserider

 

[farmer brown]

The heat exchanger is at the house. It is a forced air system and the HX was installed in the plenum of the existing heat system.

 

[Tony H]

With what we know it appears that relocating to a spot closer would be a good idea. Besides the issues with pipe and pump size, elevation and so on there is the other factor of heat loss in the buried pipe no matter what there will be some loss but with good insulation and a reasonable distance it is minimal. I have my boiler
75' away with a well insulated pipe and the loss is very low but I sure would be concerned with a distance like you were considering. You may even find that going out to fill the boiler several times a day at 200' feet down the hill might be even less fun than moving the wood piles around at least you can move it on your time frame.
It is a very good idea to think ahead on where and how you will do your wood prep alot of the folks around here have put much thought and years of practice into that. I have two places to cut, split and stack with one being the area next to the boiler and the other up the drive about 200' away. I keep the early season wood at the far location and bring a trailer load every couple of days to stack in the boiler shed and when we start to get snow and ice I switch to the stack next to the boiler shed where I have about 6 cords and use that for most of the winter bringing down some loads from the far stack in spring again . Then during the summer I restock the 6 cords near the boiler with good seasoned stuff and start all over.

 

[rowerwet]

Didn't we have a guy here in the boiler room not long ago that was having big fits with his OWB because his boiler was below the elevation of his house by a fair amount???

His problem was that he had two return pumps and only one supply (from the boiler) pump, it wasn't the elevation, but he repositioned his OPB closer anyway trying to find the problem.

Thermopex will only loose 1*/ 100 ft according to CB, I found the ground frozen over my thermopex while the snow was completely melted over my septic tank, I think what they say is close to accurate.

 

[mwk1000]

I saw a nice chart of pipe material vs flow rate that charted the head pressure per 10 ft. I could swear it was on cozy heats site last year. It will help you see why 1" pipe 220 feet might not be a good idea. It will also show you that Pex/Al/Pex does a much better job than strait pex in the same size. I can't remember the number exactly but 220 both ways = 440 / 10 feet = 44 look on the chart and see that 1" pex @ 4 GPM is ?? ( .5 .6 ??? Whatever it really is I am not sure ) and you have 22 feet of head and you have not even used a fitting yet. That puts you clear out of the small pump range. Go to grundfos 's site and pick a pump and look at the flow curve. It will show you how many gal/min at what head it can deliver. Much better to have 1 - 1/4 pex/al/pex or maybe more.

if your like me I always need to know WHY something wont work. Here is my non-physics version.

Smaller pipes = more surface area per volume of water. More surface area = more turbulence. More turbulence = more resistance to flow. More resistance = bigger pump = more money now more money every electric bill

Can't find the chart any more but these folks are helping their customers well. It They have hit the situation spot on and even show you the electricity cost estimates of the different pumps. They deserve credit for the posing when most of the practical information seems to be getting harder to find on the net. They would recommend 1 1/2 inch for your original run as I suspected.

(broken link removed)

I put this in the sticky posts for future installers to have a look at