Hopefully simple system design questions

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Flying Dutchman

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Dec 1, 2013
16
Galena, IL
Good evening folks...

I'm running short on funds and want to know if this system design will work...

and ArboristSite looks like its gone for good... (topic for another place though). Glad to find this forum.

Current setup:
Natures Comfort NCB250 wood boiler
Taco 00 circulator pump
18x24 water to air heat exchanger
Standard 24volt thermostat kicks on furnace blower... Heats house.

Tore down half the house, rebuilt. 24 x 24.

Basement garage: 2 300 foot 1/2 inch pex runs in concrete pad.
Planning for 3 300 foot runs in the cieling joists. I have 18 cavities @ 24 feet, down and back loops in each one equals 864 feet (works out rough guesstimate I guess. I'd use a parralel header and, manual valves for the inlet side of each loop to balance things (if needed)

Pricing out the expansion tanks, relief valve, water to water heat exchanger and pump controllers I was like WOW super expensive while pricing it out with my boiler sales place ($1500 ish, Menards "panels" similarly priced.)

My "side job helper guy" who has "installed many of these systems" said I don't need that stuff. Just run two tees off of my main line, a mixing valve, and a pump for each zone. His setup is this way and several other people in the area also say theirs is similar and isn't isolated.

My brother in law who is an apprentice electrician (3 years) feels I should be able to use line level (120V AC) thermostats instead of pump controllers. The Taco 00 pumps have a low enough amp draw to be able to use these thermostats... Based on the rated amperage.

First question: Do you need to have an "isolated" system to run in floor heat? Or can I use the boiler circuit to pull from to heat the loops?

Second question: Will the line level thermostats work to control the pumps?

Thanks in advance! Also, please feel free to throw in any and all advice/links.
 
Don't have much to offer on your questions, but FYI AS is up & going good, has been for a little while.

Hopefully someone will authoritatively answer your questions - my seat of pants is that you'd want to isolate, for the long term. I don't think mixing valves & pumps were designed to run open - they might work OK for a while but eventually fail earlier than if they were on a closed system. How much earlier, I have no idea. Also have no experience with the stats, mine are all 24v.
 
I have an open boiler, heat exchanger, and pressurized system in the house.

Water to water hx I got from New Horizons. GEA Flatplate has a good online calculator for sizing and calculating pressure drop, temperature rise and flow rates. I think you had to register to use it but I haven't gotten any spam from them or anything.

Pexsupply.com seems to have decent pricing on many things, but my local plumbing supplier comes close on most, and beats them soundly on radiators.

I used Sioux Chief copper manifolds with valves from pex supply and Menards. The local supplier was a lot higher on these.

Search for your bigger items like pump and hx and tank and manifold on ebay to make sure you are close on price.


There is nothing cheap about this, but unlike forced air, a minute leak will cause big problems in a hurry.





You can use line voltage thermostats if you pay attention to the pump amperage. A transformer, relay, and enclosure aren't that expensive if you are using a 24v thermostat. For my infloor zone I have a Grundfos alpha pump and a mixing valve with outdoor reset and they just run all the time when the switch on the wall is turned on.
 
thanks for the replies guys.
Maple is this accelerated rate of pump failure due to cavitation or something?​
The thermostats are rated for 22 amps and can run electric baseboard heaters. The pump is less than 1 amp. .74 amp I believe. I think it will work. I am planning on pulling thermostat wire along with when or if I upgrade. My bro in law electrician says these systems are dirt simple to troubleshoot and they replace more complex systems in commercial and industrial settings with this type when the customers get tired of a complex system keeps breaking.
My plumbing helper guy said that over the last decade they have installed twenty plus systems without isolating it from the boiler circuit and have had no complaints. I guess its a cheap way to get started. I would really like to isolate the system and put antifreeze in it for the garage floor. Just in case. If dumb stuff is going to happen it will happen to me.

Arbutus why would I need a water to water if I'm running open? I'm talking a mixing valve and two pumps.
 
Possibly, yes. Also increased corrosion potential.

How much higher is the OWB than your house and the highest part of the heating system?

You could try it 'to get started', as you say, and change things later, if you want. But you need the height difference to even get started.
 
On the line voltage thermostats.
Menards carries a line voltage thermostat that simply plugs into a standard wall outlet.You then just plug your pump into it.
I have been using one with a Taco 007 for 4 or 5 years with no issues.
 
Maple, I would have to check but I am pretty sure my boiler will be higher than any point in the system.... but not by much only 2-4 feet. Last year I shelled three Broeder (Chinese Gundfos knockoffs that my boiler dealer swears up and down on his life that are bulletproof) 1/4 HP pumps. Now my Taco is making noise... I have screens in the lines and purge the air have plenty of boiler treatment only running 140 degrees... not sure what's up there or if this problem will cross over into the in floor system...Mr Fix it I hadn't seen those. Good to know. But this is new construction so I'll spring for the wall mounts.
 
Circulators have minimum specd inlet pressure. My 15-58 is 4psi at 190° and 1.3psi at 140. I would find it hard to see that boilers would spend all their time at 140, and quite regularly see above 160-170. This is one thing I didn't quite understand - how OWBs could have much pump life with their open [no pressure] nature, given what seems like big cavitation potential. Assuming pump at the bottom of the boiler, and 4-5' to the top of the water in it, that's only around 2psi water column. I have no OWB experience though.
 
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Flying Dutchman said:
ArboristSite looks like its gone for good...
Click to expand...

If you are trying to get on AS with a shortcut that you had from before, they don't work anymore. You will have to do an internet search for AS, then make a new shortcut to the new rebuilt site.
 
Thanks guys, I think for now I'm going to go with the non pressurized system. My stove is higher than my ground floor. Worth a shot.

Maple, good to know about the inlet pressures. i will watch that.

Arbutus, i see was just curious about why you had the presurized system.

Brennda, thanks for the tip!

Next questions...

I have read and read and read until I am blue in the face... I have a joist cavity install to do.

16" OC I beam joists. I'll be covering the bottom with plyboard as a cieling cover. Some kind of insulation will go in the cavity. Be it spray foam or fiberglass.

Do I need heat transfer plates? There seem to be two schools of thought, heat the floor (with the plates) or heat the cavity and subsequently the heat will rise into the floor. I think contact to the subfloor is a good idea...

I am going to have 900ft of pex (3 300ft loops) under this 24x24 floor, (8" on center ish) I am thinking that I don't need a huge amount of transfer plate coverage. I was going to take Aluminum roof flashing and bend it around the tubing to make up small square plates just to hold the pex to the bottom of the floor every 2ft or so and staple it with 1/2" staples.

Will this work?

Also, because of the joist cavity issue, you cant get those nice flowing loops like I was able to get in the concrete floor... how did you get it to all meet up at the manifold or did you use header pipes instead of manifolds?
 
What water temperature do you want to use in your underfloor retrofit?
This will provide the answer to your question.

Staple up tubing with no plates requires much higher water temperature to deliver the same btus through the floor compared to heavy extruded aluminum plates such as Joist Trak or Thermofin C. Staple up tubing is much less expensive than the heavy aluminum plates.

Lightweight aluminum plates are somewhere in the middle. In doing my research, I looked into making a jig but decided not to. There were plenty of vendors selling these, with various profiles. Some had a very pronounced omega shape, some had a u shape, some were a lazy u shape.

Both Uponor and Zurn have pdf radiant heat design guides available for free download with charts that give the btu delivered for various water temperatures in various types of installations with various floor R values. I encourage you to look them up.

Installation methods can make or break the system, with considerations like good contact with the subfloor (think nails or hardwood flooring staples) secure installation of plates or tubing (helps prevent expansion noise), etc

I have 16" oc floor joists and installed Thermofin C. Installing the 1/2" pex was tedious, but not too awfully difficult. I drilled 1 inch holes in the joists near the wall and was able to pull the tubing through just fine.
 
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Flying Dutchman said:
Thanks guys, I think for now I'm going to go with the non pressurized system. My stove is higher than my ground floor. Worth a shot.

Maple, good to know about the inlet pressures. i will watch that.

Arbutus, i see was just curious about why you had the presurized system.

Brennda, thanks for the tip!

Next questions...

I have read and read and read until I am blue in the face... I have a joist cavity install to do.

16" OC I beam joists. I'll be covering the bottom with plyboard as a cieling cover. Some kind of insulation will go in the cavity. Be it spray foam or fiberglass.

Do I need heat transfer plates? There seem to be two schools of thought, heat the floor (with the plates) or heat the cavity and subsequently the heat will rise into the floor. I think contact to the subfloor is a good idea...

I am going to have 900ft of pex (3 300ft loops) under this 24x24 floor, (8" on center ish) I am thinking that I don't need a huge amount of transfer plate coverage. I was going to take Aluminum roof flashing and bend it around the tubing to make up small square plates just to hold the pex to the bottom of the floor every 2ft or so and staple it with 1/2" staples.

Will this work?

Also, because of the joist cavity issue, you cant get those nice flowing loops like I was able to get in the concrete floor... how did you get it to all meet up at the manifold or did you use header pipes instead of manifolds?
Click to expand...


A heat load calc will tell you how many btu you need to deliver to the space. Once you have that BTU/ sq ft number you can determine if suspended tube, staple up, or transfer plates will work.

No question that plates transfer the energy best and allow fast response and low supply temperatures.

But in many cases radiant floor will not cover the load without supplemental emitters. Do your homework and run the numbers.

Floor coverings make a huge difference in floor output, as does any furnishings that cover the radiant, like cabinets or furniture without air space underneath. Throw rugs, especially with pads underneath can throw you a curve, and really shut down the heat output.

With I joists be mindfull of where you drill holes. Generally an 1-1/2" hole can be drilled anywhere in the web, larger holes for multiple pex runs need to be a certain distance from ends or bearing points. Use the hole drilling chart from the manufacturer.
 
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My system runs at 140F. Any hotter and the pumps seem to suffer.

It is/was hard to do those calcs because nothing is set in stone building wise. I am a lot farther along now though might be able to get some numbers.

Lets put it this way... if the floor heat works too well, I can just dial it back with the blend valve right? There is a general agreement is that the heat transfer plates are worth the money?

I like this Thermofin C stuff....
 
Heavy plates are $$$.
Use the charts in the Uponor and Zurn guides.
Floor R value, and BTU/hr at design temperature will tell you what temperature is required with various tubing methods.
 
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Flying Dutchman said:
My system runs at 140F. Any hotter and the pumps seem to suffer.

It is/was hard to do those calcs because nothing is set in stone building wise. I am a lot farther along now though might be able to get some numbers.

Lets put it this way... if the floor heat works too well, I can just dial it back with the blend valve right? There is a general agreement is that the heat transfer plates are worth the money?

I like this Thermofin C stuff....
Click to expand...
 
Yes it is much easier to simmer down, then fire up a floor output. You have one chance to install it properly if it is above a finished ceiling.

The limiting factor to any floor radiant output is the floor surface temperature. In a residential setting you do not want to run much above 80- 85 degree floor surface temperature. Above this the floor becomes un-comfortably warm to stand on, even with socks on :)

In some cases with good transfer you can get the floor surface to 85F with 120 supply. As the building load increases (colder or windier outside) the floor needs higher supply. Outdoor reset controls sense this and adjust to that increasing load. Or do it manually with and adjustable valve like a thermostatic mix valve.

In some cases like suspended tube installations, you need to run 180F to get the floor output. Poor heat transfer with conductive air currents.

Now with wood floors and transfer plates you really don't want to run above 140F against the wood with aluminum. The Wood Resources folks squirm when you talk above 140F against wood. Especially wood with glues like plywood, OSB, Adventech, etc, etc.

Even solid wood plank floors tend to become un-happy with elevated temperatures. if nothing else it drives moisture out and even dried wood will shrink down some more at high temperatures. This can lead to squeaky subfloor, if the fasteners cannot take the movement.

Do everything possible to keep low temperatures against wood floors both subfloors and finished wood flooring.
 
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Design Temperature: -4
Temperature Differential @ 65: 69 degrees
Walls 576-130= 446 @69deg/R13= 2314 BTUH
Windows 130 @69deg/R2= 4485 BTUH
Cielings 594 @69deg/R38=1078 BTUH
Total: 7877
Air exchange heat loss:
69x(.5x4500)x.0183=2841 BTUH
Total heat loss: 10718 BTUH
10718/(23x23=529)=20.25 BTU per SQ ft.
EFF (Guess 90% useable, kitchen island/peninsula) 20.25/.9=22.5
FSF @65= 76.25
FSF @70= 81.25

Resistance of floor coverings
3/4 OSB 1.05
Float pad: .2
Laminate MDF flooring: .5
Total R Value of floor coverings: 1.75.

Ok... So according to the Zurn table for joist cavity with aluminum plates (see attached)... And my value of 22.5

They calculate their chart with 3/4" Plywood as a subfloor. I dont know if their R-Values they say are floor coverings IN ADDITION to the plywood or the plywood is part of that figure... Seems like... Worst case, 180 degrees, best case 160 degrees. And what kind of plates are these, and how many???

Those seem like unacceptable numbers and I need to look at something above the subfloor??? Thanks for making me do this thing guys... Puts it into a better perspective...

I am getting R18 in the walls, that might help my numbers some and my windows may be better than R2... Will check on these tomorrow.
 

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Excellent work.

I came to the conclusion that this chart is for the thin double U aluminum sheets, and I base that on the much lower water temperature required in the Uponor design guide for Joist Trak which is a heavy extruded plate. That is for pex 8 inches on center, and assumes that you have covered every joist space with these plates.

Also, as best I can tell, your supply temperature should be based on an R value of approximately 0.7 because the subfloor is taken into account. So your lower estimate of 155 - 160 supply water temperature is probably close.

I wound up with about 75% of my floor area useful for heating after stairs cabinets, and joist bay ends were taken into account.

I don't have it handy, but recommend that you check the Uponor design guide for joist trak on 9 inch centers.
Another alternative includes panel radiators, or just a couple of plug in electric space heaters for the few days a year when it gets super cold.
 
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Thanks Arbutus ill check it out. I'll also have the forced air ductwork to make up the difference on the cold days... and this room will be open ie 8x8 type opening...to other rooms which will also have heat zones installed later but forced air until then. Also the garage below will also be heated... Based on the possibility that my Rvalue calcs are off...140 seems more feasible but...

To get the full 140 would depend on whether I put the system inlet tee before or after the water to air heat exchanger and whether or not the furnace blower is running if the tee is after the h.e. for the most part I think it will be fine until I gets real cold... at which point I can bump the whole system temp. 10 to 20 deg. If needed.


How would i select the correct transfer plates to make the most out of the under joist system? It seems to me I'm going to want as much transfer as I can get... And therefore need to spend the money up front to make this work right... I am installing roughly 900 ft of pipe and am looking at at least 800 linear feet 22ft x 18 bays times t2 runs per bay... even with cheaper thin ones that is about $1200...

Next question. This room and the garage below it is about 20 feet from my main circuit.

Is it better to place the circulator closer to the loops/manifolds? Or is it better to have them on my pump rack near where the pumps will draw from the circuit?
 
Here's the link to the Uponor manual:
http://www.uponorpro.com/~/media/Ex...2_Update.aspx?sc_lang=en&version=100120121144

Page 224 and 225 have the double groove aluminum plate and Joist Trak curves.
Thermofin and Thinfin should be similar to Joist Trak performance.

I believe Viega also offers a Thermofin manufactured product, but I dont know if it is Thermofin or Thinfin.
http://www.viega.net/cps/rde/xbcr/en-us/IM-PRCT-0208_(Climate_Trak_Install_Manual).pdf

Pexsupply.com carries Joist Trak. Your local plumbing supply house might be able to get you a quote as well.
Thermofin was $2 / linear foot, plus shipping. Call them for a quote, or look at the Northeast Radiant Store. Or get a quote on the Viega brand plate too.




If you have forced air, can you run radiant down to say, 15F outdoor air temperature and make up the difference when it gets colder than that with a simple water to air hx? I'm assuming you don't want to do all your heating through the water to air hx. Lots of things to consider, don't get a case of paralysis by analysis.
 
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Tom Sullivan at UP solar solutions makes some really good quality transferplates for any size pex pipe you need. They fit way better (tighter on pipe) than the other non extruded types I have seen and they are reasonably priced.
He has various lengths. They are 6" wide and cheaper than storebought too. The 70% wrap is correct if you take a little time installing them. I have used the extruded type too and they also work well, but the holes had to be drilled out, they were way too small for a drywall screw.
http://www.aluminum-solar-absorbers.com/solar-absorbers-tips-tricks.html

We are now stocking absorber in 24" and 30" lengths, for 1/2" standard (70%) and 5/8" (90%) wrap, pre-stamped and ready to ship. Since nearly 80% of our orders are for these 4 sizes, we decided to stock these sizes so many orders may now be processed and shipped the same day. Large orders, in excess of 200 to 300', and custom lengths will still need to be processed as ordered, which is usually within a couple days.
• Standard Absorber for 1/2" copper or PEX ;
Under 100 lineal feet; $.75 per foot
100 lineal feet or more; $.70 per foot

• Standard Absorber for 5/8" for PEX;
Under 100 lineal feet; $.78 per foot
100 lineal feet or more; $.73 per foot

• Standard Absorber for 3/4" copper or PEX;
Under 100 lineal feet; $.82 per foot
100 lineal feet or more; $.77 per foot
* Any orders under 50' will be assessed a $10 "press set-up charge" unless left in the order bank until we're processing another larger order.

I have used the 120 V thermostat on radiant wall project I did. It works good to control circulator pumps and eliminates the need for a controller/transformer.
 
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For half inch those seem like very good prices compared to other offerings from what I remember.
As far as installing heavy extruded plates self piercing #8 x 3/4 hex head screws and a cordless drill go in great, with or without a predrilled hole.
 
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Design Temperature: -4
Temperature Differential @ 65: 69 degrees
Walls 576-130= 446 @69deg/R18= 1709 BTUH
Windows 130 @69deg/R4= 2242 BTUH (based on a converted U-value... so not 100% sure)
Cielings 594 @69deg/R38=1078 BTUH
Total: 5659
Air exchange heat loss:
69x(.5x4500)x.0183=2841 BTUH
Total heat loss: 8500 BTUH
8500/(23x23=529)=16.06 BTU per SQ ft.
EFF (Guess 90% useable, kitchen island/peninsula) 16.06/.9=17.84

WELL....

Uphonor says temp with double groove plates @ 22.24 is about 140-145 degrees and @ 17 BTUH its significantly below 140!

Uphonor says that with their premium Joist Trak plate system, temp is around 100 degrees @ 17 BTUH!!!

Nice. I can hang chickens from the cieling and cook them.

So I contacted UP Solar to order plates via email. 800ft of plate coverage is $560 (plus shipping whatever that will be). If I do their 90% coverage option where you use a size bigger (5/8") and utilize special clamps to wrap the plate further around the 1/2" pex... It will be around $600 and change.

Thanks mudd!

Lowes sells plates (Apollo brand) came out to $900 for 800 ft.

The plates at Menards are JUNK... Wow.
 
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Got my boxes from Greg and Tom at UP Solar. 800 ft for around 700 shipped. Plates are a lil boogered from shipping but a couple taps with a hammer should fix. They busted ass to get these shipped out! Visually I'm satisfied with the product and i tthink the clamping toolwill work great to overcome the contact issues thin pplates have. A hand stapler doesn't sink em quite all the way through. Wonder if an air stapler and pointed sstaples will do the trick...
 
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