radiant heat loss because of pex placement?

panman

I have a 2800 sq.ft home. plus a 576' heated garage. 2 living levels.The lower level is a finished basement. There is radiant placed in aluminum fins on first floor and radiant in the cement of the finished basement. I have a trinity ti-200 propane boiler with 5 zones, 2 taco mixing valves and 1 grundfos pump. My problem is that the pex tubing in the finished basement was placed in 2'' of insulation, 3'' of sand, then 5'' of cement poured on top. It doen't seem to keep up during cold Maine winters. 10 degrees and under, the system runs constantly and temp downstairs drops to 64. Uptairs stays warm. Any suggestions??? Thanks- Peter

Robert_25

Heating the ground

If I understood your post correctly, are you are saying that the pex is entirely beneath the slab in sand? Is there is insulation and vapor barrier under the pex? Having the tubing not in the slab itself is a big problem, and if it is heating damp soil...all you are doing is wasting fuel.

panman

radiant heat loss because of pex placement?

Yes there is a proper 2'' insulating pex tubing barrier with 3'' of sand on top. Then 4''to5'' of cement. The previous owner was trying to do the mass heating thought process that was whirling around in 2006. He had built 350 high class homes and this one was for him and his wife. Beautiful home but some times we get caught in the over thinking things trying to improve commen sense. As i said, the zone runs all the time during the winter and cannot keep up in real cold conditions. It does not help that i have berber carpet that has an r-value of 3, but even the tiled bathroom floor is only luke warm at times. I have thought of many ways to fix the problem but not at a cost effective way. Peter

Jean-David Beyer

the tiled bathroom floor is only luke warm at times.

I live in New Jersey that I imagine does not get as cold as it does in Maine. Design temperature where I live is 14F. I find my floor seldom gets to what I would say is "warm." When it is 50F outside, I put 75F water into the slab, and that is enough to maintain 69F in the house. When it is 14F outside, I need 112F in the slab. I can feel that if I am barefoot or wear thin socks. It got down to about 9F for a few hours last year, so I was putting 118F into the slab for a while. On days like that, my IR thermometer reveals floor temperatures in the high 80s; I consider that definately warm.



So "warmness" of the floor alone does not seem a good way to tell if you are supplying enough heat. It might be that the heat loss of the house is too great and more insulation, better windows, and air leaks may be needed. When my old non-modulating boiler was in use, the floors could get too hot for comfort when walking around barefoot. Try to avoid going over 120F water in the slab. If that won't do it, consider adding radiant panels on the walls or ceiling.

Gordy

Heat sink

Heat sink is what was trying to be accomplished. The Berber carpet is killing any heat that it is producing. Bottom line the tubing is being insulated from below by the xps, and from above by the concrete floor, and Berber carpet. The area with the least r value barrier between them wins. So you are getting the heat just very slowly.



 A heat sink is what ends up being under an uninsulated slab such as in older radiant slabs, and newer incorrectly installed radiant slabs.

 It all works its just how much energy you want to use to do it as you are finding out. Trade the Berber for some low r carpet, and you will see some improvement.



Gordy

panman

radiant heat loss because of pex placement?

Thanks Gordy, for a couple of years my wife and i have talked about tearing up the carpet and laying tile down to take away the carpet r-value. It is a $500,000 home and this is about the only weak aspect of the home. Too bad because 90% of the time the furnace keeps up, but cold stretches are when the heat is REALLY needed down stairs. Would you recomend tiling the floor and running 160 degree water temp? What about a circulator with a constant 160 degree water temp? at times other zones don't come on because of the demand of water temp? Thanks

Gordan

Something's not adding up

You have two mixing valves but only one circulator? Every mixed circuit would require its own circulator.



If your Ti200 has the Sentry 2100T controller (and I'm not sure whether there are any that don't), it's capable of outdoor reset. This can automatically vary the temperature that the boiler will heat the water to, based on measured outdoor temperature (an outdoor temp sensor is required.) If you're not currently using this, you should. If you are, it is possible that it's not configured correctly. Can your mixing valve(s) also be set incorrectly or malfunctioning? Do you have a schematic you could post, or some photos of the works that you could mark up to indicate what's what?

kcopp

Cut the radiant out....

and go to either properly sized cast iron radiators or enough baseboard that will work at the same temp. OR break open the floor and do it right.

SWEI

outdoor reset

If the slab is fed by a thermostatic mixing valve, it will fight the boiler ORC (unless the mixing valve is motorized and controlled on its own curve.)

Gordy

Peter

 I really did not have time for a lengthy post, but Gordan brings some things to light that should be investigated further before beating the system up to bad.



Gordy

panman

radiant heat loss because of pex placement?

gorden. My outside reset temp is on and seems to be working fine. We had a temp of 36 and the outside reset read 37. The taco mixing valve that runs the 2 zones in the finished basement have a Mix and supply of 125. MAX temp is set at 130 and min set at 120 degrees. They were set at 80 and 90 degrees when i moved in, but could not come close to heating in colder weather. I have noticed that when 2 or more zones are running the other 2 take a while to kick on because the boiler cannot keep the temp up on all the zones at once. The top floor has 2 zones and has aluminum fins with  water temps that are set at 140 max supply.From what i have read, radiant in cement with a carpet and pad over a 2 r-value can cause the boiler temperature to be set  40 degree higher to make up for the carpet!! Thoughts!! Thanks PS I have talked to a few heating techs that say that pex under the slab should still heat the area fine because of how well the house is built. Thanks for any info- Peter

kcopp

the sand acts as...

an insulator too... I don't get why the old wives tale w/ sand still exists. All that sand w/ the concrete the system can't respond well. You need supplemental heat at best. Maybe a control w/ a slab sensor might help but I would abandon it.

Gordan

Yes, clearly.

In an outdoor reset environment the thermostatic mixer can at best be a limiting device. That's why I think that their effect in this system has to be examined. Proportional mixing is possible (non-thermostatic, fixed mix ratio) or something motorized that has its own reset curve, either controlled by the boiler's ODR (not gonna happen here) or with its own ODR controller.



I thought that I'd ask for more facts before trying to state a diagnosis. :-)

Gordan

MAX temp is for your whole system

So, the two mixing valves are one each for the two slab zones? And they're set to 125? And the boiler max is set to 130?

There should be circulators on the "slab" side of the mixing valves. The mixing valve partially (or totally) hydraulically isolates the slab tubing from your system loop. It does this by partially (or totally) blocking the flow from the system into the slab, and at the same time diverting flow from the slab return, to the degree needed to produce the desired slab supply temperature. Only, without a circulator in the slab zone that would make it a "slab circuit", there's nothing to make the water flow back around (through the mixing valve) from slab return to slab supply. So there's no mixing. So, the moment that the boiler starts making water that's hotter than the mixer's setting, the mixer will throttle more and more flow from system supply to the zone, in vain effort to reach its setpoint, until the flow is virtually shut off. Voila! No flow means no heat.



Mind you, I'm going by what you said - a single circulator. If that's not correct, then this diagnosis will likely not be, either.

panman

radiant heat loss because of pex placement?

Gorden, yes there is only 1 circulator. And yes i believe it is on the slab side. I will check tonight and try to get a picture. Yes, there are 2 taco mixing valves. Everything you have said makes perfect sense and the picture is becoming clearer that maybe an adjustment to the system (another ciculator ect) might help alot. I did have one tech that came to the home to clean the furnace tell me something about the set up looked odd, but then he went back to cleaning. Thanks for your replies, much appreciated!!!!! Peter

Gordan

Yes, please post those pics

Also, please post all of the setup parameters for your boiler. We may be able to suggest simple alterations that do away with one or both of those thermostatic valves. Also, if we can be reasonably certain that your boiler won't make water that's too hot, you could temporarily set your mixing valves to full hot, which should confirm whether what I suspect is going on, is actually going on. You may not even need another circulator, if the mixing valves serve no good purpose. It all depends on the details, however. Loop lengths for all your zones (even the upstairs ones) would also be good info. The fins that you're talking about - is the tubing suspended in the joist bay with little clip-on UltraFins, or are there transfer plates that are attached directly to the subfloor? If the latter, are they thin (flashing-type) plates or the thick, extruded aluminum type?

panman

radiant heat loss because of pex placement?

Gorden, the main floor has stapled aluminum transfer plates. They are the thinner flashing type. As far as the boiler temp output, the specs say 230 degrees at max temp. I will try to get the best pics of the boiler set up on tonight when i get home.Thanks-Peter

panman

radiant heat loss

Gorden, the zones down stairs have 6 loops going into each zone manifold. Doing the math leaves me with roughly 6

300' loops for the den zone and 6 200' loops for the bedroom zone down stairs which is going through the taco mixing valve on the left in pics. Main floor has roughly 6 300' loops in livingroom and 4 200' loops for master bed and bath. the taco mixing valve on the right supplies heat for those. It is 1/2'' pex. The temp outside currently 12 degrees and the thermastate is set at 72 down stairs and it is 66 degrees with the mixing valve running both zones all day and loosing ground. By morning it will be 64 down stairs. The main floor seems to keep temp fine but when all zones are running there is a greater temperature swing before latter zones kick on. Gorden, i did notice last night that when my 80 gallon water heater kicked on, the mixing valve for down stairs stopped circulating and water temp was 89. 5 below this morning, upstairs 72, down stairs 66 and mixing valve struggling to circulate 105 degree water. Thanks for looking

papadennis

Tubing in sand

I won't try to diagnose your problem, but I will tell you that tubing in sand can work. Our church basement (built in the 80's) which is about 60' x 120' has 3/4" black poly tubing buried in sand  (no insulation underneath) under the concrete slab. The slab heat is currently controlled by a Taco I-Valve & it's own circulator. The tubing placement would not be a correct installation these days, but who knew back then. Some of the 3/4" poly tubing developed leaks & because of the way it was installed (60' runs side to side w/ access under benches on each side) we were able to run 1/2" Wirsbo through the poly (w/ some effort)  & make new connections on the ends. Even w/ that lack of contact to the actual concrete, the floor (covered w/ vinyl tile) heats w/ no problem & this is in Alaska.   

Your basement I believe, can be made to work just as well.

 Good luck, Dennis

Gordy

efficiency

Pappa Dennis,



Its not that it will not "work". Its all about efficiency, and control. Getting the heat where it needs to be quickly, and providing the most comfort. This all equals lower energy costs.  There is plenty of evidence out there that the old way worked, but fuel was cheap back then.



Gordy

Gordan

To paraphrase Daffy Duck...

"Aha! Terminology problem!"



See, those are not mixing valves. They're injection mixing stations that have circulators built into them. So... my diagnosis would not be accurate here, as there ARE circulators on each of the slab circuits.



Here's what I see. There are two mixed circuits, one for upstairs and one for downstairs. On the upstairs mixer there are two zones, and on the downstairs mixer there are THREE zones - what's the third one?



Mixing is done via injection mixing stations. These come with their own outdoor sensors and can run their own reset curves. We'll want to come back to that. Mixed circuits are piped off of the primary loop via closely spaced tees. This is all in order, but it does have some interesting consequences. One of those consequences is that the "downstream" mixed circuits will see a lower primary loop temperature than the "upstream" mixed circuits. This is because the return from the mixed circuit is mixed back into the primary loop. In your case, the downstream mixed circuit is the downstairs one. It is critical that the boiler provide hot enough supply temperature, and enough flow, to ensure that all of the circuits receive adequate supply temperatures. So, we'll need more information about your boiler parameters, as well as the parameters for each of the RMB-1 mixing stations.



I see two black strap-on temperature sensors for the upstairs RMB-1, but I don't see any for the downstairs RMB-1. Without those, I struggle to understand how the mixing station would be able to do its job. Can you look around and see whether anything is wired to the downstairs RMB-1?



Oh, and - when your indirect comes on, your space heating SHOULD cut out. That's called DHW priority, and it's to make sure that all of the boiler capacity is available to domestic water heating. The theory is that DHW calls are relatively short in duration, and DHW priority should not result in the space cooling very much, if at all.

Gordan

What kind of supply water temperatures...

...are you running through this?

panman

radiant heat loss because of pex placement?

Gorden, the third zone is our heated garage which is set at 50 and never comes on due to being well insulated and on south side. What type of perameter info do you need. pressure gauges ect???? I will look for those temp sensors for the downstairs RMB-1. I am puzzled because even though the pex is under slab, the home is extremely well insulated and 2 of the 4 walls are in the ground. Should not take much radiant heat to keep warm. Thanks for your time!!!!!

Gordy

RMB-! xblock

 Don't know how the RMB is set up. May have to go with delta t, or set point if its set up for ODR. I think there is to much lag, and lack of response for the tubing in the sand for ODR.



Gordy



Gordy

panman

radiant heat loss because of pex placement?

Gordy, my first initial thought was X the mixing valves and pump a steady desired temp in the zones, especially the basement slab.Maybe that is an option? I am not an expert on heating as you can tell from my posts, but am not in the dark either. My carpet pad and carpet covering the downstairs 1400 sq.ft  area probably does not help any. I did the math and both are near an R-Value of 3 !!!!!. Not helping!! Thanks for your thoughts. Peter

Gordan

Upon closer inspection...

I think I do see those sensors. They're little and not wrapped in insulation like the other ones, so I missed them the first time around.



At this point, it's nothing obvious. Things are properly piped and appear to be properly wired, but there's no way to know for sure without checking everything out in detail. There are also a lot of parameters to consider here. (For instance, the RMB-1 could erroneously be configured for boiler protection, which is not necessary with your boiler and would likely result in too little heat being supplied to the slabs.) My hunch is that this isn't working, or is barely working, in any weather - it's just that you notice it more when it's cold. Whatever heat there is in the slab zones is likely leaking from the upstairs zones.



For giggles, wrap some pipe insulation over those two sensors (they're shiny little things with wires sticking out of them, cable-tied to the pipes - one just below the closely-spaced tees of the downstairs RMB-1, and the other on the pipe connected to its lower right port.) The RMB-1 does display all sorts of useful info about what it thinks is going on, what temperature it's trying to provide, what temperature it's actually providing etc., but you'd still need to know how to get it. Here's a link to a page with the manual, Instruction Sheet in the Documents section.



http://www.pexuniverse.com/store/product/taco-rmb-1-radiant-mixing-block



For starters, you could tell us what all the info on pages 11/12 is.

Gordan

With the correct temperature, should be OK.

Delta T would be an even less direct way to compensate for heat loss with all that mass in the way. If you look at the manual, that's really just a way to limit temperature rise in order to avoid thermal shock, so it could only result in even slower response. Setpoint wouldn't compensate at all. Outdoor reset, with an appropriate curve, should at least allow the mass to average out some sort of floating setpoint between the daily highs and lows. Should be able to get it to heat correctly if the emitter is capable.

panman

radiant heat loss

Gorden, I have written down all the info that my Taco mixing valve is doing.

i copied the pages and wrote beside each display what the my display was showing. Please note that it was 5 degrees outside at the time and the main floor zones were not running. Both the basement floor zones were running. The den was 69 and bedrooms were 67. Hope the copies are visable. Thanks for your time- Peter 

Gordan

Let's try something

Adjust the boiler minimum temperature setting to as low as it will go and report what happens.



You'll want to do this on the other RMB-1 eventually, as well. Can you post the same info for both, when both are calling for heat?

panman

re-lets try something

Gordan, (Got your name right finally) my apologies. I dropped both boiler min temp to 80. I will do the info when all zones are running. I checked my trinity manual to see if the boiler has a set boiler min temp preferance, but could not find one.Will this effect my DHW? Thanks for all your time. Peter

Gordan

There's no low return temperature for your boiler

That parameter on the RMB-1 is supposed to keep plain old non-condensing boilers from getting damaged by too low system return temperatures. It is completely unnecessary for a condensing boiler. It will in no way affect your DHW.

Zman

Raise the temp

Unfortunately your tubes are very low in the mass. This you cannot change, It does look like you have significant emitters (lots of tubing). You want to make sure your pumps are working correctly. I assume you cannot hear air in the system? What kind of Delta T are you seeing between supply and return? If this is less than 20 degrees. I would assume you have adequate flow. I think your only solution at this point is to increase the mixed temperature. You may need upwards of 160 degrees on the coldest design day to overcome the slab thickness and downward heat loss.I would manually run this temp up and observe the change in slab temp. I simple inferred gun would help greatly. 

panman

re-raise the temp

Zman, thanks for your thoughts. My TACO mixing block has an outside temp control that is ON. I don't think i can use the DELTA-T when that is on. If nothing major shows up as far an adjustment to the system, my wife and i will pull the carpetand pad up this summer and lay stain the concrete or lay some tile. Thanks for you thoughts- Peter

panman

radiant heat loss because of pex placement?

Gordan, The only difference i noticed so far since we turned the min boiler temp down to 80 is that the boiler runs alot less!!!! It was 13 degrees here in Maine this morning and all zones were off except the down stairs den which was 68 and running. I will write down the info on pages 11 and 12 when all zones are running tonight and then if all checks out, i will know the system is fine and look into pulling the carpet this summer. Thanks for taking the time to help- Peter

Gordy

Gordan

  Been thinking about your post. I just can not shake the notion that ODR can bring the questionable rooms to life.  It would seem that the slab would lag the response to that strategy unless it where an extended period of same weather conditions.



 But then I guess if you beat the slab with heat it will be hot when outdoor temps warm up. Still a fly wheel game.



Gordy

Gordan

That sounds like an improvement...

If I'm understanding this correctly, you now have a basement zone that's getting satisfied - that would certainly be good news!



There are other parameters we can play with, but none of them would have made a difference without fixing this boiler protection snafu. It was limiting how much hot water the slab would get. Let's let things gel for a bit to see what happens once they stabilize, and then we can try to optimize some - play with reset curves, as Zman points out, or figure out why your outdoor sensor is saying it's 20 degrees when it's 5 degrees outside - that kind of stuff. Tearing up the carpet is probably a very good idea, but there's a good bit of THIS heating season left to get you through, so let's worry about that first. :-)

Gordan

Setting vs. observing

Zman didn't mean that you should use the "delta-T limiting" feature of your RMB-1, just that you should measure the return water temperature coming back to the mixing station from your slab (upper right port on the RMB-1) and calculate the difference from the supply temperature. That, and checking the floor temperature with a point-and-shoot IR thermometer, are good diagnostic steps to see what's happening with your slab and the tubing in it.

Zman

Raise the temp

Thank you Gordy for the clarification. You should be able to raise your mix design and mix max while keeping the outdoor reset active. Don't be afraid to go to the setpoint mode for troubleshooting.John Seigenthaler writes some great articles on the effect of tubing on surface temp.

Zman

Raise the temp

Thank you Gordy for the clarification. You should be able to raise your mix design and mix max while keeping the outdoor reset active. Don't be afraid to go to the setpoint mode for troubleshooting.John Seigenthaler writes some great articles on the effect of tubing on surface temp.

Gordan

Yep, all good suggestions...

But let's allow the system to stabilize a bit before making further changes. Given the mass, it will probably take a few days to figure out whether ODR setting changes are necessary. There were two things that jumped out at me when I saw that Peter had the RMB-1s, one was the possibility (as it turns out, the actuality) that he had boiler protection turned on and the other, after seeing what his RMB-1 was reporting, is what's causing it to report an outdoor temperature that's 15 degrees warmer than the actual conditions.



Once those are resolved, then I'd be inclined to tune the RMB's reset curves, and thereafter the boiler's reset curve.

panman

radiant heat loss because of pex placement?

Gordan, we are suppose to have a cold 0-5 above zero night. I can get all the zones running and provide you with page 11and 12 info if you want. i do not know why the outdoor temp reads 15 degrees warmer than the acual temp. They are on the northside 8 ft up. underneath my main floor deck. Thanks- Peter