Help - plumbing design - radiant floor+ storage

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eriesigtau

Member
Jun 15, 2010
75
Titusville, PA
Hi, I just bought an Econoburn 150 but have not done any plumbing in the house yet. The boiler will sit outside under a sheltered uninsulated lean-to. I need a system that will supply 3 zones that each have 4 branches that are 250-300 ft coils. I would also like to provide plumbing for a 500 gal storage tank, 2 radiators, heat exchanger for a domestic hot water tank, and possibly might hook up my hot tub in the future. My econcoburn has an output of 150kbtu's and came with a grundfos 3 speed pump. I have 3000ft of 1/2 pex coming in the mail. I would like to do this piping myself to save money. I understand the primary/secondary loop design is best for my boiler. Can someone help me design this system?

I need to know things like:

What diameter should the supply/return lines be. should I use circulators or solinoid valves for the zones and what size should they be. how many and how large should the expansion tank be. should I use glycol or run the primary loop all the time or both? how many manafolds and what size. Suggestions for the heat exchanger for the hot water tank. Maybe someone knows of or has a pre-made diagram that has exactly what I need?
 
I'm not going to be a lot of help but you might get some idea on your pump requirement from this. My system is super simple, the floor loops are 1/2" pex and total slightly over 800' which is split into 5 loops. A Taco 009 pump pushes about 5 GPM if the flow valves are reasonably accurate. Pushing 3000' of 1/2" pex seems like it might be a fairly serious pumping load.
 
Hi eriesigtau-

Do you have a room by room heat loss calculation? If not this is really where you need to start.

Professional design and/or consultation can really help you make sure your on the right track.

Also I would highly recommend this book:

http://store.hydronicpros.com/product.php?qcp=1002

I believe this is the authors site.

Good luck,
Noah
 
The Taco site has free software to design a one pipe system.
 
Congratulations! And you are asking some excellent questions. Those questions show, however, that you might consider some serious homework on your own to understand hot water systems, flows, pump head, pressure loss, and many other system design points. Some of this gets very technical and, while expertise to answer most if not all of these questions exists on this forum, a few pieces of advice here and there often do not add up to all the advice you need, and you could find some serious and expensive errors to correct simply because something was missed.

I'm an amateur, do-it-yourself, kind of person willing to take on big challenges. I installed the Tarm myself, but my initial system was incredibly simple: boiler, expansion tank, storage tank, two circulators, and a couple of aquastats. Yet I made serious mistakes because I did not understand flow; how change in flow affects head; how pipe size and fittings affect flow and head; sizing of a plate hx and impact of a plate hx on pressure drop, flow and head; expansion factors, air venting, and the list goes on. My "simple" system got re-done twice before I was close to right, and even then I satisfied myself with some compromises that I didn't want to spend the money to really do it right.

I've learned a lot since the start, but when I decided to build my new 1500 sf shop, and while I'm almost certain I could have done the in-floor pex, 6 loops of 250' each, with the manifold, circulator, expansion tank, heat exchanger, temperature/pressure gauge, and mixing valve, as well as the anti-freeze, purging the system, and miscellaneous, I decided for my new shop to hire a local professional to do this for me. Pex in-floor when covered with concrete is too expensive to fix if a mistake is made. I don't regret for a minute hiring this work out.

One point simply is, if you can afford to fix potentially serious design and installation errors, go ahead as a neophyte and tackle the challenge. Alternatively, really do your homework to learn info you never even knew to ask about, and then do the work and hopefully avoid the really expensive mistakes. Or, still do your homework and hire key parts of the work out, using your knowledge to ask questions of the pro, satisfy yourself that the pro is doing it right, and learning from the pro so you can do other parts of the work yourself the right way.

I'm sure you will have success on your project.
 
You mention the pex is in the mail. Is this new construction or a retrofit application? Concrete? Staple up? Compact efficient building envelope or all chopped up with windows everywhere?

If you have a bare lot right now, I'd put your time into learning cutting edge building methods, then you could heat the place with one $30 electric radiator and forget about this stuff. Or you could build a reasonably efficient building and not need to worry as much about getting the zones right.

Here's my one and a half cents worth, I'd seal up the lean to for starters. Glycol is too much maintenence and moves less heat than water. The primary loop is usually running 24/7 during the heating season, isn't it? not that I'd like to rely on that.
 
jebatty said:
Congratulations! And you are asking some excellent questions. Those questions show, however, that you might consider some serious homework on your own to understand hot water systems, flows, pump head, pressure loss, and many other system design points. Some of this gets very technical and, while expertise to answer most if not all of these questions exists on this forum, a few pieces of advice here and there often do not add up to all the advice you need, and you could find some serious and expensive errors to correct simply because something was missed.

I'm an amateur, do-it-yourself, kind of person willing to take on big challenges. I installed the Tarm myself, but my initial system was incredibly simple: boiler, expansion tank, storage tank, two circulators, and a couple of aquastats. Yet I made serious mistakes because I did not understand flow; how change in flow affects head; how pipe size and fittings affect flow and head; sizing of a plate hx and impact of a plate hx on pressure drop, flow and head; expansion factors, air venting, and the list goes on. My "simple" system got re-done twice before I was close to right, and even then I satisfied myself with some compromises that I didn't want to spend the money to really do it right.

I've learned a lot since the start, but when I decided to build my new 1500 sf shop, and while I'm almost certain I could have done the in-floor pex, 6 loops of 250' each, with the manifold, circulator, expansion tank, heat exchanger, temperature/pressure gauge, and mixing valve, as well as the anti-freeze, purging the system, and miscellaneous, I decided for my new shop to hire a local professional to do this for me. Pex in-floor when covered with concrete is too expensive to fix if a mistake is made. I don't regret for a minute hiring this work out.

One point simply is, if you can afford to fix potentially serious design and installation errors, go ahead as a neophyte and tackle the challenge. Alternatively, really do your homework to learn info you never even knew to ask about, and then do the work and hopefully avoid the really expensive mistakes. Or, still do your homework and hire key parts of the work out, using your knowledge to ask questions of the pro, satisfy yourself that the pro is doing it right, and learning from the pro so you can do other parts of the work yourself the right way.

I'm sure you will have success on your project.
Click to expand...


I Am a perpetual do it yourselfer as well, I installed 2500 ft. of pex in my house and close to 800 in my shop . I knew absolutly nothing about it before I started ,I asked a lot of questions did a lot of research online. In the end everything worked out great with no leaks. I was very nervous about leaks after I poured the cement because the cement guys were not very gentle. The pex is very durable. just make the best effort to get the loops close in length,even then most manifolds have balancing v/v's. I thought it was the simplest part of the whole install. The hard part was laying 900 square ft of china multi on top of some of it.

Cheers Huff
 
ok, let say i have a circulator pump that feeds a zone from my manafold. Out of the pump i run 3/4" pex 40ft back to a location where i branch off into 4 loops that are 270ft long each and are 1/2 pex. what size taco pump should i use to maximze the btu output of this zone?
 
The RPA rule of thumb is .6 gpm for 1/2 pex. With 4 loops you need to move 2.4 gpm. At .6 GPM flow in 1/2" pex the pressure drop through 270 feet is about 3.5 ft., not including any other pressure drop in that circuit.

So chose a pump that moves 2.4 gpm at 3.5 feet of head, ideally in the mid range of the pump curve. The smallest 3 speed wet rotor pump you can find, maybe a Grundfos 15-58 on speed 1.

If the tube is 12" on center in concrete with no floor covering expect around 23 btu/ sq ft of output. Is that in line with what the zone requires?

The best way to design radiant is get the room or zone load calc, then you match the tube, spacing, flow rate and supply temperature to the actual design. With the info you have provided that should be a real close estimate on what to expect.

hr
 
I haven't been checking this forum lately but my state (IN) is preparing to place some pretty severe limits on OWBs, so I've been looking to check on alternatives.

About designing your system you should check the sticky thread on helpful bits of info. After reading the above post I checked the Taco site and found they recommended a min. flow of 1.2gpm and a max flow of 2.3gpm for 1/2" pex. The charts don't seem to agree with what my system is telling me, my loops must have some serious head considering the pump and flow rate.

My observations after 5+ years of having in floor radiant which isn't a "designed system", it was retrofitted to an older home. Comfort is better even at lower room temperatures. Don't expect to have the system warm up the house in a hurry. What has surprised me the most is how the floor loops hold the indoor temp. so steady relative to outdoor temp swings. I don't even have a thermostat on the floor system, once the outdoor temps get near freezing the floor pump is turned on for the winter. I have a water to air HX which picks up the extra load during colder weather. I think you'll really like the heat in the floor.

I've never been a great OWB fan but a gasser with storage really has me considering a geothermal system.
 
atlarge54 said:
I haven't been checking this forum lately but my state (IN) is preparing to place some pretty severe limits on OWBs, so I've been looking to check on alternatives.

About designing your system you should check the sticky thread on helpful bits of info. After reading the above post I checked the Taco site and found they recommended a min. flow of 1.2gpm and a max flow of 2.3gpm for 1/2" pex. The charts don't seem to agree with what my system is telling me, my loops must have some serious head considering the pump and flow rate.

My observations after 5+ years of having in floor radiant which isn't a "designed system", it was retrofitted to an older home. Comfort is better even at lower room temperatures. Don't expect to have the system warm up the house in a hurry. What has surprised me the most is how the floor loops hold the indoor temp. so steady relative to outdoor temp swings. I don't even have a thermostat on the floor system, once the outdoor temps get near freezing the floor pump is turned on for the winter. I have a water to air HX which picks up the extra load during colder weather. I think you'll really like the heat in the floor.

I've never been a great OWB fan but a gasser with storage really has me considering a geothermal system.
Click to expand...

2.3 gpm of 120F water flowing through 1/2" pex would be a pressure drop of 15.2 feet for a 100 foot loop.

At a .6 gpm flow rate the pressure drop through a 300 foot loop would be @ 4 feet from the Uponor sizing table.17.8
At 2.3 gpm the pressure drop would be 45.96 feet of head! That would be a tough circ to find :)

Yes 1/2 pex can flow up to that 2.3 gpm but you would not want to design your radiant loops with that pressure drop.
 
so I should keep my loops at 250ft? does that solve the head issue?

Atlarge54 - I do have a gaser not a OWB. Its an indoor gaser that I put in a lean-to behend my garage which is exposed to outdoor temps.
 
250, even 300' is fine for 1/2 pex radiant loops, just keep the flow rate down to the Radiant Panel Association suggested .6 gpm per loop. Pressure drop(resistance to flow) goes up as you try to shove more volume (gpm) through a pipe.

Some designers push 500' loops of 1/2 pex for radiant. The problem is you run out of fizz (aka heat) before you get the water to the end of those long loops. Long loops up to 600' are fine if you increase the diameter to 3/4". Larger diameters allow more gpm , and the pressure drop is lessened. That's why they make pipe is so many different diameters :)

In some cases like domestic water piping that is not an issue as it is an intermittent flow, so high velocity, even up to 8 fps (feet per second) is often acceptable. But for a heating loop you want to stay between 2- 4 fps, and there is no reason to use a high head 200W pump when a small 70 W pump will move sufficient energy.

hr
 
At 2.3 gpm the pressure drop would be 45.96 feet of head! That would be a tough circ to find. Yes 1/2 pex can flow up to that 2.3 gpm but you would not want to design your radiant loops with that pressure drop.
Click to expand...

Not quite! Flow isn't 2.3 gpm through 1/2" pex. Flow is 0.6 gpm through 1/2" pex in each of 4 loops, or 2.4 gpm total. The main line needs to the manifold needs to handle 2.4 gpm, which could be 3/4" but 1" would be much better, depending on length.
 
ok, your saying i should use 3/4 or 1" to feed 4 -270ft loops in one zone that are 1/2 pex. a grudfos 15-58 3 speed should do the trick for each zone. now we have one zone covered. i have three zones so what size supply line should I bring to the 3 zone manafold from the boiler? 1-1/4?
 
As best as I know, all lines are sized based on flow requirement and resulting pump head, and pump head also is related to length of lines and types and numbers of the various fittings. Flow and pump head are inextricably related. With these two determined you then can determine what circulator you need. Now you should be able to see right away that your question cannot be answered because there is not enough information. Use the Taco guide that has been recommended to you and you will go a long way in getting your questions answered.

I need to go back to my first post where I suggested you need to do some real homework. Your questions are leading to answers which may result in major and expensive design flaws because so much is missing. Even my last post, "The main line to the manifold needs to handle 2.4 gpm ..." and then my suggestion of 3/4" or 1" could be in error. Note that only gpm is known in making that recommendation. Without knowing the length of the line and the number and types of fittings there is no assurance that 3/4" or 1" in fact would work. Again, use the Taco guide and then when you have real problems or design issues, ask questions.
 
eriesigtau said:
so I should keep my loops at 250ft? does that solve the head issue?

Atlarge54 - I do have a gaser not a OWB. Its an indoor gaser that I put in a lean-to behend my garage which is exposed to outdoor temps.
Click to expand...


You might want to add power outages to your list of concerns. A boiler exposed to outdoor temps and no electricity can rapidly become a major problem. Real life experience let me know in a hurry----it'll happen on the coldest windy night and probably at 3AM when nothing is open. Electrical backup is a MUST.
 
... and I need to add that flow is related to BTU requirements and delta-T. The starting point is heat loss and determining BTUH needs based on heat loss. And then you need to consider your emitters and their temperature requirements.
 
Hmm, i dont know how to calculate the heat loss. The floor I am trying to heat with the radient floor heat is 1600 sq feet with 5 anderson 3x3 windows, 3 well insulated doors. Im not sure what the insulation is but its currently an all electric home and i didnt feel any drafts last winter. the house was built is 1982. The house also has a 800 sq ft upstairs that i plan to heat with a radiator plus electric baseboard if needed. The upstairs has 4 3x3 anderson windows. The finished basement will be heated with 1 or 2 radiators and is the same size as the main floor. the basement is completly underground with a bifold door exit. I will assume the boiler to the manafold length will be 125ft. the storage tank will sit about half the distance between the boiler and manafold. i will likely use glycol since the boiler is outside. i will also use a battery with an inverter as a power backup. like mentioned before, i expect to have 3 zones with 4 loops of 1/2 pex per zone measureing 270ft each. Is this enough info to size the supply line, manafold, and circs?
 
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