Hydronics: 400ft 1/2" pex 1-loop for radiant?

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Solar+Wood

Member
Feb 11, 2009
37
CO
Has anyone ever used a fella that designs radiant systems using 400 to 500 ft lengths of 1/2" pex in a single loop? 500 is his max.

Got a 5,600sq ft slab install and he's saying I can push 11 loops with one Taco 0011 pump and eleven loops at 12" on-center.... all loops 450 to 490ft.

Using closed cell spray foam insulation; so, it should be tight and high R.

Called Taco and from talking to them, the math actually works for the pump, lengths and number of loops (all eleven on that pump). Of course they give me the full lawyer disclaimer ---and that they are not designers. I can't recall if that was for a 80,000 BTU loss/design or a 150,000 BTU loss/design.

20*F delta. Can't recall, but think 0 or 10*F outside and 70*F inside. Tight house w/high R and U values.

I'm looking for feedback on the fella and the design he pushes. Was hoping to pour by the end of next week!

FWIW, I'm going w/closed loop. Talk boiler and other heat sources later.. just interested in the odd/unique design.

Any comments on this guy, his design and/or reputation? Looking for anyone that has dealt with him or his designs. Seems like a nice fella, but I'm trying to make sure before I make the ultimate commitment... concrete.

Thanks in advance!
S+W​
 

BoilerMan

Minister of Fire
Apr 16, 2012
1,717
Northern Maine
I've seen 1/2" loops of that length that flow with no problem. As you stated, you need a bigger (0011) to push the water. 0011 will eat 211 watts, if used 24/7 it will cost alot to run through it's lifetime, in the thousands of dollars. If you use shorter runs of 1/2" you could step down to a 008 for 300' runs. I have a 008 that pushes .75GPM through five 375' runs. It needs to be weighed from the cost savings of the tubing vs. the pump cost and operating costs. A few extra loops fo the same size tubing like 300-350' will save $$$$$ for the rest of the life of the building. The wattage used costs alot more than people consider, if I knew the Kwh rate of your electric company I could tell you the monthly costs to run the different pumps.
Taylor
 
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wood thing

Member
May 20, 2010
91
potter co. pa.
The rule of thumb where I live is no more than 300 ft runs. Once you have the floor poured, theres no going back. Good luck.
I've seen 1/2" loops of that length that flow with no problem. As you stated, you need a bigger (0011) to push the water. 0011 will eat 211 watts, if used 24/7 it will cost alot to run through it's lifetime, in the thousands of dollars. If you use shorter runs of 1/2" you could step down to a 008 for 300' runs. I have a 008 that pushes .75GPM through five 375' runs. It needs to be weighed from the cost savings of the tubing vs. the pump cost and operating costs. A few extra loops fo the same size tubing like 300-350' will save $$$$$ for the rest of the life of the building. The wattage used costs alot more than people consider, if I knew the Kwh rate of your electric company I could tell you the monthly costs to run the different pumps.
Taylor[/quohe
 

Bob Rohr

Minister of Fire
Jan 9, 2008
1,265
SW Missouri
Limit them to 300 footers. Longer lengths require more pumping power and may also end up with cool temperatures and lower output at the ends of the loop. In a commercial slab long loop lengths are not that big of a deal, and long loop lengths help you reach remote manifolds in large rooms. In residential radiant applications many suggest a 10- 15 degree delta T across the loop for consistent floor temperature.

Lower operating temperatures make it easier to use solar and GEO heat sources. One of the regrets I have with my own shop and office is not installing 6" on center loops, "it's poured in stone" The graph below shows the difference in 6 to 12".

hr.
 

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heaterman

Minister of Fire
Oct 16, 2007
3,374
Falmouth, Michigan
We never, and I do mean never, go over 300 with 1/2". It's not that it can't be done but why would anyone in their right mind want to live with the energy consumption of a high head pump on the system for the rest of its life.

So. Two suggestions, A: If you want or have to go with longer loops due to the layout, use 5/8" tube to keep the head down and also have a little temp left at the end of the loop. B: Use more/shorter 1/2" loops.

Just a thought............Tell your installer he can do anything he wants with his design as long as power consumption is limited to 100 watts..... :)
 

BoilerMan

Minister of Fire
Apr 16, 2012
1,717
Northern Maine
[quote="heaterman, post:

Just a thought............Tell your installer he can do anything he wants with his design as long as power consumption is limited to 100 watts..... :)[/quote]

Now that is where the money is!!! It's true that no one ever and I mean EVER thinks of power consumption when designing hydronic systems. The only ones I've ever seen is when it's for an off grid system with an inverter/generator setup. No one ever thinks of the thousands of dollars wasted in Kwh day after day, "oh it only costs 75 cents a day........... umm thats $5,475 if you run that way for 20 years". Hear it all the time in my line of work.

Taylor
 

Solar+Wood

Member
Feb 11, 2009
37
CO
Thanks folks.

I guess I need to re-evaluate all of this but the clock is ticking.

I am still a little confused... like always.

If you reduced to even 350ft runs and use a 008 Taco for each, you end up burning more power than the one 0011 for about the same number of total feet.
Am I getting it wrong?

I'm basing it on this assumption:
One section and one thermostat in that area. It calls for heat and you have two choices... 1) three pumps running three loops at the same time to heat roughly 1,000sq ft or 2)one pump running two loops same sq ft.

uh oh... battery dying and no cord... yikes.

More tomorrow. Again.... I know nothing here other than reading and talking to a TACO eng

Thanks!
 

Bob Rohr

Minister of Fire
Jan 9, 2008
1,265
SW Missouri
Back up a few steps. How much heat energy are you trying to move? What is the heat load? If you run a heat load calulation it will spell out how many BTU/ hr. required. With that number you size the loops, supply temperature needed, and the pump size. The key number for sizing the loop output, and required pump size is the BTU/ square foot required. Do all you can to the building to keep the number below 20 BTU/ sq. ft :)

If you use a load calc from one of the radiant manufacturers it will spell out total load in btu/ ft. required, flow rate needed, supply temperature, and feet of head. Usually the amount of tube, and tie downs required is also provided.

The RPA guidelines suggest

1/2 pex, max. flow .6 GPM, loop length 300 feet, 9-12" on center

So 11 loops at .6 GPM each = 6.6 gpm at a 20 degree delta T.

From the Uponor Design Guide 1/2 pex flowing 100% water at 120F supply, multiply 300 feet (loop length) X .0137 = 4.1 feet of head. So you need a pump to move 6 gpm at 4-5 feet of head.

Many installers got to 330' loops as you can get 3 loops from a 1000' coil of pex. Borrow or rent an uncoiler if you go with 1000' coils :)

A Grundfos Alpha circ, for example could power that system, 7 gpm at 6 feet of head, with about 45W of electrical consumptiuon. Or a 007 Taco or 15-58 Grundfos @ 80W.

IF your load is 20 BTU/ sq. ft. or under I would consider 300- 330 foot loops at 9" on center.

For your 5600 square feet of building X 1.40 (factor for 9" on center) = 7800 feet of tube. Add a bit for leader lengths to get to the manifold location, and you need to buy 8000 feet of tube.

At 12" on center = 5660 feet of tube required round to 6000 for leader length.

So you are talking the price difference between 6000 or 8000 feet of tube, at $.30/ ft. (online prices) $600.00 more to go to 9". I would highly reccomend spending the extra $$ to tube it at 9" on center, maybe 6" if the load is great than my assumptions?

hr
 

Solar+Wood

Member
Feb 11, 2009
37
CO
Back up a few steps. How much heat energy are you trying to move? What is the heat load? If you run a heat load calulation it will spell out how many BTU/ hr. required. With that number you size the loops, supply temperature needed, and the pump size. The key number for sizing the loop output, and required pump size is the BTU/ square foot required. Do all you can to the building to keep the number below 20 BTU/ sq. ft :)

If you use a load calc from one of the radiant manufacturers it will spell out total load in btu/ ft. required, flow rate needed, supply temperature, and feet of head. Usually the amount of tube, and tie downs required is also provided.

The RPA guidelines suggest

1/2 pex, max. flow .6 GPM, loop length 300 feet, 9-12" on center

So 11 loops at .6 GPM each = 6.6 gpm at a 20 degree delta T.

From the Uponor Design Guide 1/2 pex flowing 100% water at 120F supply, multiply 300 feet (loop length) X .0137 = 4.1 feet of head. So you need a pump to move 6 gpm at 4-5 feet of head.

Many installers got to 330' loops as you can get 3 loops from a 1000' coil of pex. Borrow or rent an uncoiler if you go with 1000' coils :)

A Grundfos Alpha circ, for example could power that system, 7 gpm at 6 feet of head, with about 45W of electrical consumptiuon. Or a 007 Taco or 15-58 Grundfos @ 80W.

IF your load is 20 BTU/ sq. ft. or under I would consider 300- 330 foot loops at 9" on center.

For your 5600 square feet of building X 1.40 (factor for 9" on center) = 7800 feet of tube. Add a bit for leader lengths to get to the manifold location, and you need to buy 8000 feet of tube.

At 12" on center = 5660 feet of tube required round to 6000 for leader length.

So you are talking the price difference between 6000 or 8000 feet of tube, at $.30/ ft. (online prices) $600.00 more to go to 9". I would highly reccomend spending the extra $$ to tube it at 9" on center, maybe 6" if the load is great than my assumptions?

hr
Thanks.

The house will be very well insulated and very tight/low air infiltration.

Attached is what was sent to me by the designer of the 500ft loop system. He says the loss will only be 80,000 BTUs while others have calculated it at 147,000 to 169,000 BTUs. All of them received the same info... (House info pasted below). The variation in BTU loss is making me bonkers and I'm about out of cash as it is earmarked for everything else... DOH!

I told them the closest place to base outside temps and HDD was Alamosa, CO. HDD of between 7500 and 8700 per year.

Either way, when I asked him about the difference in BTU requirements, he wrote back :
"Your spray foam insulation will give you a heat loss of about 12 Btu's per Sq. Ft., 12" spacing in concrete will put out over 30 Btu's per Sq. Ft. if needed."

I already bought 15 rolls of Pex-B. They are 500ft rolls. Bought an extra 4 rolls than his design required...just in case.

So I'm in a little pickle. Do I continue with his design which he says he has done thousands of... or cut the rolls in half and go with a much larger number of smaller pumps.

I AM off-grid, but "should" have adequate power w/my set-up.... either way I thought one bigger pump would be better than a hand full of smaller pumps. I would assume two zones will call heat at bout the same time engaging more smaller pumps which add up to be more than the one single pump.

Taco says the one big pump can push the number of loops he is suggesting for my design including his claim of 16 loops under the gpm load he has suggested would be needed. It's just so far outside the box from what I've been reading that I'm a nervous nellie now. If that one Taco dude said it was impossible this all would be a moot point, but he has said it could be done... BUT he/they were not designers, etc... add more lawyer-ease...yadda yadda yadda.

Anyone ever run across this system; and if so, how did it work?

At a loss and running out of time,
S+W
----start of paste for house info/rough info----


NOTE/UPDATE of below.... Going with all wood framing with ICF stem walls now. Galvalume exterior and still foam insulation. There will only be one garage door now... the 16x12.

Structures:
50x100 building (half living space and other half garage)
12x54 adjoining building (breezeway/pseudo greenhouse)
14ft eves
4:12 pitch to create 22 ft peak.
Living area ceilings 8’
Garage avg ceiling 16ft’? (UPDATE... will prob be 14ft)
Breezeway ceiling 13’
Manifold option to upgrade another building in future (add 3 zones later.. maybe 4?)

Floor:
All slab… 3 slabs all three 5” thick with 4” DOW under it. Perimeter will have 4” also… Closed Cell 2# spray foam prob…… or DOW??? Each slab thermally separate from each other. [UPDATE: ICF stem wall will have a total of 3 to 5 inches between wall and slab inside the building]


Thermostats:
In slab type
4 zones?
1 in garage, 2 in house, 1 in breezeway… open to suggestions.


Windows:
Roughly 272 sq ft of windows. Fiberglass framed Serious 725 series w/total window perf of supposedly .16U… 6.3R
· Four 4x6 windows in living area… all picture frame facing south (High SHGC, etc for solar gain)
· Four 4x6 windows in breezeway… all picture frame facing south (High SHGC, etc for solar gain)
· Two 3x6 casement. One east and one west
· One 6x2 picture window in bathroom close to ceiling for natural light
· One 6x4 picture in garage
· Garage door has four lights… 2x1… supposed to be R19.9 Amar door???

Doors
· Living area… 60 sq ft between two doors (not picked yet)… but will be fiberglass and mid grade R… Not much glass… R11? To R19? Both doors will NOT lead to outdoors. One will go into breezeway and the other into the garage.
· Breezeway…. 40sq ft of steel door. 6.5R? 2 3x6
· Garage door… 16wx12h… R19.9
· Garage man door 1 4x7 steel door.. 6,5R?

Insulation:
2LB Closed Cell spray foam… 4” walls and 6” ceiling on all.
May add fiberglass batts on top of foam in living area?

Building exterior:
Right now it’s all steel construction… may go with 2x6 framed conventional wood but w/same galvalume metal exterior and roof
[update: all wood building w/metal exterior]
 

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Bob Rohr

Minister of Fire
Jan 9, 2008
1,265
SW Missouri
Sounds like you are committed to that design. 250 foot loops are also an option but you need twice as many manifold ports.

I wonder why the tube is held back 18" from all outside walls? The greatest heat loss is at the exterior wall and that reduces the amount of tube (warmed floor) to meet the load.

Better pray that the actual load is 80,000 not the higher numbers :( But tight, well insulated homes can fall in that range.

The amount of heat output you get depends on the slab surface temperature, period. It's your radiator. Experts suggest staying below 82F surface or it becomes uncomfortable to stand on, too hot.

If your intended indoor design temperature is 70F, your floor temperature would need to be 85F to output 30 btu/ ft. So it is possible, but not practical.

If the large pump is a concern a Grundfos Magna (mini Magna) or the Wilo ECO could move that load with about 65 W or less. These are both pumps with ECM motors that have auto adapt features that "learn" your system. The pump speed, and power consumption drops as the heat load, or zones start turning off. Only on the coldest (design day) would the require full power. At partial load it might be running around 20- 40W.

Don't mean to rain on your parade, the whole concept behind radiant is the ideal, most comfortable heating system. Cold spots or elevated slab temperatures to compensate for lack of tube or square footage draws from the concept. If the system under-performs or can't keep up on design days, the only option is to crank up the supply temperature, and raise the surface temperature.

Floor coverings now or added in the future also reduce the btu output stick to hard surfaces, tile, colored slabs. Thin engineered hardwood if you must. Skip the carpet and pad over radiant slabs.

hr
 
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ewdudley

Minister of Fire
Nov 17, 2009
1,987
Cayuga County NY
I wonder why the tube is held back 18" from all outside walls? The greatest heat loss is at the exterior wall and that reduces the amount of tube (warmed floor) to meet the load.
I was curious about this also. I was advised to lay tube on 6" centers in the 18 " area near the outside walls, and to route the flow to the outside first so it hotter temperature were necessary the water would have a chance to cool off on the outside first. As was it explained to me, nobody stands a foot from the wall and as always dumping heat underneath cold glass works well.
 

Solar+Wood

Member
Feb 11, 2009
37
CO
Appreciate the feedback from all. No one can really rain on the parade... I'll just adjust and bring an extra umbrella <g>

I was looking at Grundfos pumps but have not looked at Wilo Eco. I like the "learning" mode of Grundfos.

Going to see if going 6" OC with more pex is an option. I guess that means one more pump tho, more manifold and more $ all the way around...but may be my only good solution now. See... an extra umbrella :)

Now where are my galoshes? :)
S+W
 

heaterman

Minister of Fire
Oct 16, 2007
3,374
Falmouth, Michigan
Speaking of "rain", this might be a thunderstorm at this point of your design process, but I would sure think strongly about doing multiple zones in your layout. Pumping everything from one manifold will put the entire structure at (supposedly) one temperature. Not sure you need the garage area at the same temp as the house. Realize also that different areas of the house have different heating demands. Bedrooms are usually run a few degrees cooler than the rest of the house and kitchens rarely need as much heat as say the living room for instance. The only way you can do this using one manifold is via actuators on each loop. Not a big fan of that due to added complexity.....(runs contrary to my simple brain)..... and higher maintenance/repair costs down the road.Multiple manifolds would probably work out great with 250' loops.
I would really take a hard look at using a couple more manifolds that are easily zoned with their own (very small) circulator. That gives you a little redundancy as opposed to a single circ running everything. I don't know what causes it but they never quit when you're around and always find a way to seize up on a holiday weekend. ;)
Off the cuff, I would recommend a manifold/zone for the garage, a second one for the main areas of the house and a third for the kitchen and bedrooms .

If your installer did a heat loss ask him for a copy of it. If it's a real live heat loss calc, it will break your structure down room by room. Take the heat loss for each room and divide it by the number of square feet in that particular room. The variation will become apparent very quickly and show you what rooms should be grouped together.
I have never run a residential structure on a single zone. Pole barns and workshops maybe but never a house someone is going to live in.

Keep in mind that you only have one chance to do a poured radiant system correctly. After the cement is down you live with your "I shoulda's" for the rest of your life. :confused:
 

Bob Rohr

Minister of Fire
Jan 9, 2008
1,265
SW Missouri
Speaking of "rain", this might be a thunderstorm at this point of your design process, but I would sure think strongly about doing multiple zones in your layout. Pumping everything from one manifold will put the entire structure at (supposedly) one temperature. Not sure you need the garage area at the same temp as the house. Realize also that different areas of the house have different heating demands. Bedrooms are usually run a few degrees cooler than the rest of the house and kitchens rarely need as much heat as say the living room for instance. The only way you can do this using one manifold is via actuators on each loop. Not a big fan of that due to added complexity.....(runs contrary to my simple brain)..... and higher maintenance/repair costs down the road.Multiple manifolds would probably work out great with 250' loops.
I would really take a hard look at using a couple more manifolds that are easily zoned with their own (very small) circulator. That gives you a little redundancy as opposed to a single circ running everything. I don't know what causes it but they never quit when you're around and always find a way to seize up on a holiday weekend. ;)
Off the cuff, I would recommend a manifold/zone for the garage, a second one for the main areas of the house and a third for the kitchen and bedrooms .

If your installer did a heat loss ask him for a copy of it. If it's a real live heat loss calc, it will break your structure down room by room. Take the heat loss for each room and divide it by the number of square feet in that particular room. The variation will become apparent very quickly and show you what rooms should be grouped together.
I have never run a residential structure on a single zone. Pole barns and workshops maybe but never a house someone is going to live in.

Keep in mind that you only have one chance to do a poured radiant system correctly. After the cement is down you live with your "I shoulda's" for the rest of your life. :confused:
 

Bob Rohr

Minister of Fire
Jan 9, 2008
1,265
SW Missouri
I understand the designers intent to make a simple user friendly installation. With one manifold you are burning 100 feet of tube just to reach the great room. That small 12X16 room will be toasty with all those loops going thru it. Leave the one manifold just for them garage. Consider removing one loop from the garage and putting it into the great room. I'd start 6" oc in them great room and bedroom with the first loop. An L shape layout puts all them energy on them outside walls first, that's where the load is.

A second manifold located on the common wall between the bath and 12X16 room would help with zoning and using the tube better where it is needed.
 

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Solar+Wood

Member
Feb 11, 2009
37
CO
Speaking of "rain", this might be a thunderstorm at this point of your design process, but I would sure think strongly about doing multiple zones in your layout. Pumping everything from one manifold will put the entire structure at (supposedly) one temperature. Not sure you need the garage area at the same temp as the house. Realize also that different areas of the house have different heating demands. Bedrooms are usually run a few degrees cooler than the rest of the house and kitchens rarely need as much heat as say the living room for instance. The only way you can do this using one manifold is via actuators on each loop. Not a big fan of that due to added complexity.....(runs contrary to my simple brain)..... and higher maintenance/repair costs down the road.Multiple manifolds would probably work out great with 250' loops.
I would really take a hard look at using a couple more manifolds that are easily zoned with their own (very small) circulator. That gives you a little redundancy as opposed to a single circ running everything. I don't know what causes it but they never quit when you're around and always find a way to seize up on a holiday weekend. ;)
Off the cuff, I would recommend a manifold/zone for the garage, a second one for the main areas of the house and a third for the kitchen and bedrooms .

If your installer did a heat loss ask him for a copy of it. If it's a real live heat loss calc, it will break your structure down room by room. Take the heat loss for each room and divide it by the number of square feet in that particular room. The variation will become apparent very quickly and show you what rooms should be grouped together.
I have never run a residential structure on a single zone. Pole barns and workshops maybe but never a house someone is going to live in.

Keep in mind that you only have one chance to do a poured radiant system correctly. After the cement is down you live with your "I shoulda's" for the rest of your life. :confused:
His design uses three stats; so, I'm guessing that means three zones.
One for the bedroom, one for the great room/everything else in living area, and one for the garage.
Has 12 port and 12 actuator manifold listed.

Got a headache now/still and my feet are getting wet! :(
 

Bob Rohr

Minister of Fire
Jan 9, 2008
1,265
SW Missouri
His design uses three stats; so, I'm guessing that means three zones.
One for the bedroom, one for the great room/everything else in living area, and one for the garage.
Has 12 port and 12 actuator manifold listed.

Got a headache now/still and my feet are getting wet! :(

One pump, three manifolds, and 3 zone valves would do it. No need to put 12 or more acuators on the one manifold. Those small thermal acuators on the manifolds draw 5 w each when they power on, and would require a large transformer or multiple 40Va to power all 12. 3 acuators per 40Va transformer, generally.

One small transformer 40Va could power all three motorized type zone valves. If electrical energy consumption is a concern 3 zone valves and a ECM pump would be nice way to go.

hr
 

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Solar+Wood

Member
Feb 11, 2009
37
CO
Gents,

Thanks again. Got some rain on my parade of health. Been sick.... my throat is killing me.

I think I'm going to add more pex and keep the 500ft runs since I have it already. GO 6" on center or 9" OC as suggested before. Stick with three zones for the living area and add a 4th zone for the breezeway... which I may just leave 12" OC...??? It has big windows and will suck in the heat. Hope to drape all windows at night to trap/slow down the heat transfer back outside.

The flooring will prob end up being tile in the living area and plain concrete in the garage and breezeway.

Please feel free to drop me a PM or a note here on any of it.

I'm guessing I have pushed things back until next week now with me being sick and some logistical nightmares from a vendor.

You guys are great!
S+W
 

BoilerMan

Minister of Fire
Apr 16, 2012
1,717
Northern Maine
One pump, three manifolds, and 3 zone valves would do it. No need to put 12 or more acuators on the one manifold. Those small thermal acuators on the manifolds draw 5 w each when they power on, and would require a large transformer or multiple 40Va to power all 12. 3 acuators per 40Va transformer, generally.

One small transformer 40Va could power all three motorized type zone valves. If electrical energy consumption is a concern 3 zone valves and a ECM pump would be nice way to go.

hr
I agree with this 100%! You can even go with EBV (electric ball valves) if you want to keep the power to a minimum. But 3 syncronus motor zone valves are not much of a draw either. I do like zone valves. Since you are off grid all of the watts you can save are going to = smaller inverter/ fewer batteries to keep it all running. I've installed off the grid systems and you'd be suprised at the parisitic draw of things, and how they eat up watts not even doing anything. Off topic, but watch out for gas ovens with glow bar igniters...... they draw 7 amps at 120v!!!!!

Taylor
 

711mhw

Feeling the Heat
Dec 7, 2010
479
Western ME
Gents,

Thanks again. Got some rain on my parade of health. Been sick.... my throat is killing me.

I think I'm going to add more pex and keep the 500ft runs since I have it already. GO 6" on center or 9" OC as suggested before. Stick with three zones for the living area and add a 4th zone for the breezeway... which I may just leave 12" OC...??? It has big windows and will suck in the heat. Hope to drape all windows at night to trap/slow down the heat transfer back outside.

The flooring will prob end up being tile in the living area and plain concrete in the garage and breezeway.

Please feel free to drop me a PM or a note here on any of it.

I'm guessing I have pushed things back until next week now with me being sick and some logistical nightmares from a vendor.

You guys are great!
S+W
I have a similar bldg. (40X80) with 16' eave. The house is within this footprint and it's got 2 floors 14' wide. I paid a radiant disign Co. and glad I did. My tube spacing varies from 18" in the shop to 12" & 6" in the living space. I have 3 thermostats and 2 manifolds and none of my loops are over 300'. It sounds like you have some guys in the biz. responding and I only am a radiant user, but after living with my system, it sounds like my designer is in line with what they are suggesting. We may have similar heating conditions but I have 3 large, insulated but leaky (12x14) garage doors. I insulated very well, but you have more. Watching my ret. temps. I think that at 500' you'll have a cold area towards the loop end as well as some pretty cold water to get back to temp.
After reading this, I'm just rambling. But what is the down side of an additional manifold and shorter loops? You only get one shot at this. I love my radiant floors. Good luck and remember to "daisey chain" all of your loops together and pressurise before pouring and monitor during the pour.
 

Mark Holden

New Member
Jun 6, 2012
49
Portugal
www.aljezurfarm.com
A central heating guy I know advised me to lay my tubes in a spiral loop; more even heat distribution and [I think] less total bends. Anyway, I did it [see attached photo].
I got a pallet of 20mm [3/4"] pex at an auction. loops are about 100 meters each, the tubing came in 120 meter rolls. I used the leftovers for my domestic plumbing [it's what they're using here these days anyway].
 

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woodsmaster

Minister of Fire
Jan 25, 2010
2,878
N.W. Ohio
Cool or should I say warm ? 100 meters is about 400 foot ? I was also thinking of using some left over oxygen barrior pex for domestic plumbing and was wondering if there was any reason not to ?
 

Mark Holden

New Member
Jun 6, 2012
49
Portugal
www.aljezurfarm.com
I think it will depend on the code where you live. I'm in Portugal; common practice here is solid masonry walls. they set large section tubing in during construction, then when the plumbers come they pull 16mm [5/8"] pex through. There's a system for the ends to fit neatly.
In other areas of Europe they use "uni-pipe". I don't know if they have that on other continents yet. It's a plastic/aluminum/plastic composite, and is rated for hot or cold potable water , domestic gas, and heating loops. It comes in coils [rolls] but you can't snake it through.
Copper is way too expensive now, but is still available here for repair work.
They used to use thick wall rigid PVC pipe that came in "pipe" sizes like old steel pipe. They threaded it and used metal couplings.
In my house, the builder used galvanized couplings that were all rusted closed 20 years later when I got the place [which is why I had to change it all].

The bigger rigid PVC, say 1-1/2" would be perfect for long underground runs from the wood boiler and/or solar collector array. It's fairly cheap and will stay put while blowing insulation around it. With brass or bronze couplings of course!
 
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nate379

Guest
What is normal flow through the pex? I have mine set wide open at over 2gpm.
 

Mark Holden

New Member
Jun 6, 2012
49
Portugal
www.aljezurfarm.com
I don't know what the flow through mine is; I hooked it to a standard manifold and keep the valves open.
So far it's been connected to an old oil burner I took out of another place [to replace it with an efficient gas boiler].
House is under insulted, but it doesn't get very cold here.
 
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