shaedog
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| 12/22/2008 8:46 AM |
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I have 16" centers with both 2 by 8 and 2 by 10 boards. The pex is ran and secured to the underside of the floor.
1) the air gap seems to be optimal at 2" between the floor and the radiant barrier. is this the best? i would think more would be inefficient. and less might cause the pipe to contact the barrier causing a radiant heat loss.
2) radiant barrier. Seems there is a lot of discusion regarding the type of product that is best. from my research a tinfoil radiant barrier then bat insulation is best. the bubble style is in effective? if so can someone recomend a supplier or product?
3) thermostats. i have three completely different zones. one in concrete. one under tile and one under hardwood i have mixing valves etc. to control the water temperature.
I plan to base load the house and then use my pelet stove to comensate for the cold nights. I would like to have one central thermostat with three remote floor sensors and three setpoints in one display. I cannot seem to find one? The zone controls are 24 v ac. relay controled so I don't need to switch 120/240 volt.
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BadgerBoilerMN
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| 12/22/2008 9:21 AM |
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Suspended tube or sub-floor radiant systems without the benefit of aluminum emission panels have very limited output potential and will require high water temperatures. As you have a radiant slab requiring low design water temperature e.g. 110°F and a suspended tube perhaps needing as much as 180°F you now also have a more challenging close piping design making outdoor reset (the best path to efficient comfort) nearly impossible to achieve.
Radiant barriers of any kind are not as important as R-value and air-tightness.
Floor sensors are rarely needed nor optimal in residential applications. It is best to "set and forget" most radiant floors as response time can be a factor.
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MA
www.badgerboilerservice.com |
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shaedog
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| 12/22/2008 9:31 AM |
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thanks for the feedback.
I agree with the "set and forget" . that is likely how it will start. I have seperate zone pumps and flow control so I will be able to do that. I was just tring to investigate my options for control.
I do understand the requirement for the different temperatures.
I did run double 1/2 pex in the joists. but, maybe I am wrong here but I was under the impresion that the plates only create efficiency gains in temperature change when the system demand is changed.
If I base load the system eventually the plates are a mute point? meaning the final water temperture set point will not be different with plates installed.
i think you are correct that the R value of the under joist insulation is critical. More the better.... was looking for options
thanks
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BadgerBoilerMN
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| 12/22/2008 9:49 AM |
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The overall efficiency (necessity) of emission plates is often ignored for the extra cost. It does not make it right. They certainly change the design temperature and no "loading" can change that fact.
Insulation is based on design temperature; the higher (less efficient) your design temperature, the insulation you will need. Suspended tube designs are cheaper and perform accordingly. |
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MA
www.badgerboilerservice.com |
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NRT.Rob
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| 12/22/2008 12:04 PM |
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I agree with everything morgan has said here, except for the floor sensor bit.
there are several thermostats out there that can take a floor sensor in addition to using their air sensors: this allows a user to have direct control over another aspect of their comfort (the minimum temperature of a large, direct contact radiant plane under their feet).
I think they are great additions to any system; however, one per zone is quite adequate. |
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-=Northeast Radiant Technology=-
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shaedog
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| 12/22/2008 2:00 PM |
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thanks for the feedback
but,
I am still not understanding why with out the plates I would need hotter temperature water or increased water flow?
if I never change the flow rate or temperature would the floor not reach an equilibrium temperature? I realize if I left a door open and then without the plates my recovery time would go up. I am not trying go go cheap. I am just trying to understand. If i see a need or someone can explain the need then I will install them
I agree the better the insulation under the reflective radiant insulation the better and sealing the ends would be very important.
sorry for being stuborn here.
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NRT.Rob
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| 12/22/2008 2:11 PM |
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the water temperature you need to drive X heat through a subfloor is determined by the average conductivity of the assembly.
Another way to say this is, if heat can flow more freely, "equilibrium temperature" is higher for a given water temperature.
This is because you get a lot more conduction from pipe to subfloor if you have aluminum contacting more of the pipe, and spreading that heat out effectively to more subfloor, quickly.
without plates, you have very little conduction. transfer is thus weaker and heat flow is reduced. and more goes back to your heat source. |
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-=Northeast Radiant Technology=-
NRTradiant.com |
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shaedog
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| 12/22/2008 2:25 PM |
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now that makes sense. thanks
so if my heat transfer is slow without the plates due to poor radiant transfer I would need hotter water to obtain the same floor temperature which is reducing efficiency.
increasing the flow would have a margional gain as it is all about heat transfer.
now, if i am going to install the plates...ugh i have about 1200 feet of pex under the floor....that is a lot of plates....
i heard that if you don't plate all the pex you get hot / cold spots on the floor.
by the way i am runnning a climatemaster GEo thermal 036 (3 ton) unit with a pond loop and have 120 gallons of water storage.
the unit will be connected through a smart meter that will hopfully be able to run during off peak electrical rate.
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BadgerBoilerMN
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| 12/22/2008 6:30 PM |
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It is more a matter of performance. I will take longer to react to heat loss and may not reach sufficient floor temperature at design conditions.
Most ground source heat pumps will only generate 120°F (marginal design temperature for any sub-floor radiant system) so back-up boiler should be fuel-efficient. Many of these systems require a second stage driven by Euro-panel or a fan coil.
I first start a design with a heat-load-analysis, this give you the load that determines the design water temperature required, which is dependent on the type of radiant floor you choose.
Hot and cold spots - or striping - occurs more in the old-fashioned staple-up systems.
I don't care whom you employ, but these steps are best performed by an experienced designer before the DIYer or inexperienced professional orders the first part.
Not being critical, just saving others the headaches.
Best of luck.
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MA
www.badgerboilerservice.com |
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NRT.Rob
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| 12/23/2008 8:18 AM |
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| if you're doing Geo, unless you have second stage heat plates are pretty much a forgone conclusion. You don't want to run a geo system any hotter than you have to (and while they may be rated for 120, you never want to run them that hot). |
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-=Northeast Radiant Technology=-
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shaedog
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| 12/23/2008 8:26 AM |
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I realize from the feedback that the plates are worth the effort. i thank you for helping me understand the need. since there is already a double pex run per joist i will source double grove plates. i would imagion the plates could be skipped under walls etc.
even one small storage room i could not install the plates and the result would be a cooler room!
thanks guys |
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NRT.Rob
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| 12/23/2008 10:28 AM |
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double groove plates are lightweights.
you do not want lightweight plates. You want heavy gauge plates. These are plates that are installed, then PEX is pounded up into their exposed groove. |
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-=Northeast Radiant Technology=-
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Blueridge company
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| 12/23/2008 9:16 PM |
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Double pipe plates will be hard to apply at this point as your staples and pipe pattern will vary. look at RHT single plates 5 x 24 inches or other type, you will have more options working with an existing pipe system. Heat transfer plates will help, floor thickness and cover will also be a consideration on design temp.
Dan |
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Dan
BlueRidgeCompany.com |
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shaedog
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| 12/24/2008 8:23 AM |
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I have not yet terminated any of the pex runs as i didnt have the answers i needed with respect to how i was going to do the floor. One zone of three 250 foot loop runs of 1/2 PEX (two runs per joist) is under 3/4 hardwood, 1/2 plywood and 3/4 tongue and groove boarding. The other zone is 250 feet under ceramic and 5/8 tongue and grove plywood. I also have a cement floor with two 200 foot loops.
with the GEO system temperature maximum of 120 degrees and the varying application i think the plate as per the discusions above will make life better. just a bit more work.
Stuborn as I am and i is an Electrical EngineerI still wonder about once reaching equilibriun temperature and flow to make the wife happy the plates are.....not needed...not trying to say someone is wrong just having difficiulty getting it into my head..i will though, install them as i am capable of listening...
thanks for the help
MERRY CHRISTMAS FOR THE FROZEN NORTH OF CANADA |
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NRT.Rob
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| 12/24/2008 9:52 AM |
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you do not want to run geo at 120. geo gets significantly more efficient the cooler you run it, to the point where it is almost a "get the temp down at any cost" proposition. I have seen several systems die running at 120 as well, whether they are rated to handle that temp or not, it's apparently not easy on the system. I am not a geo expert, I am just reporting what I've seen and what I've seen from geo experts, but there is a geothermal forum on this site you can hit for more info on that.
You want heavy gauge plates unless you have significant backup heat available in an air system. Not lightweights of any kind, single groove or other.
Equilibrium (room) temperature is determined by two things: Heat flow out of the room (heat loss) and heat flow into the room. We are not talking about heat loss here, only the heat gain side, so assume heat loss is constant, the question is how do you equal that with heat gain. Note the time component here: you lose X BTUS per hour, you need to gain X BTUs per hour as well. It doesn't do any good to gain X BTUs in two hours, as the room will get cold in the meantime.
Think of it another way: do you think that putting carpet down has no effect on your water temperature because "at equilibrium" all else is equal? I hope not. If not... why not? Because insulation reduces the average conductivity through the subfloor, slowing down heat transfer, reducing output at the same temperature gradient across the subfloor.
Not installing plates is very similar to installing carpet or insulation above your radiant for this purpose; it too reduces the average conductivity from water to top of subfloor surface. Significantly. Very significantly. It's adequate for some purposes, but unless your particular heat load is tiny, tiny, tiny, or you have supplemental heat in another form, it's not adequate in your situation.
Where did you get this impression that plates only help with startup speed anyway?
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shaedog
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| 12/24/2008 10:05 AM |
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i am getting smarter by the minute. thanks for that explanation.
i have the operational curves for the GEO unit. the EER or COP numbers are very dependent on load and as you mention temperature. more so on load rather than temperature but both are critical. these units are better efficient the harder you work them. But, having said that it takes tuning of the lake loop and heat loop flows along with the set points for temperature to get into the efficient range. if you do not do the proper set up your efficiency sucks big time. aoso, yes the top end temperature setting does have an effect on efficiency.
we have only a 1000 square foot home. very well insulated and have a pellet stove currently heating the place but the plan is to have it for the very cold nights.
somewhere i read or was convinced regarding the plate efficiency error. the carpet analogy helped.
slowly i will have this system complete.
thanks
Merry Christmas |
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NRT.Rob
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| 12/24/2008 10:13 AM |
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Use at least a small tank with reset. I think you'll like it ;)
well then.. do you know what your heat load per square foot is here? heck maybe it's tiny tiny and I'm just lying to you ;) I should have asked that much earlier. |
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shaedog
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| 12/24/2008 10:25 AM |
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long story..the unit supplier did the heat load calculations. i origionally was planning to have my garage (bigger than the house - 1200 sq ft) included.
The load calculation required a machine that draws way to much power for the remote location and service i have. (i didnt want to spend 6 grand to upgrade service) they recomended 5 tons
So, we cut out the garage and went down one unit size to a 3 ton and the response from them was that i was close to accurate design size. they would not supply me with the numbers....i dont think they are to smart on these systems yet...but we are learning
i plan to play with adding the garage and posibly a hot tub. iboth would be through a heat exchanger and likely only be able to run one at a time.
I recognize theati will hit limitaions on the unit but the curves are there to help as i go to determine the COP and remain efficient.
your correct regarding the smaller water storage tank helping. along with that it has the Domestic hot water pre heat so running longer is also a benifit there.
fun learning all this....
but, we have the pellet stove and that is all we have had for several years and we coninue to improve the houses R value |
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shaedog
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| 12/29/2008 9:26 AM |
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| thanks, i am looking for plates. i cant seem to find the ones refered to "heavy guage" and the pex pushes into it? |
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NRT.Rob
Registered Users
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Posts:733
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| 12/29/2008 10:21 AM |
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| Pretty much everyone has some variant. they are typically 4 feet long, 4 to 5 inches wide. Thermofin, Thinfin, Joist Trak, Climate Trak, etc. |
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-=Northeast Radiant Technology=-
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