New radiant Under Blue stone room not heatng

k1jos

We have a 250 sf entry room 20 x 15 new concrete slab (6-10 inches trap/gravel and 6 inches concrete. Our plumber laid down 250 linear feet if 1/2" pex on top of a reflective insulation board and we covered the pex just enough with portland cement to set in natural bluestone. He has the pex on 2 manifold and running about 120 F. Ambient outside has been mild in lower NY state about 30 evenings and 50 in day. The system has been running for 48 hours and the return lines are still cool as is the stone. he said the slab and stone are such a huge heat sink it will take many days to reach equilibirum. does this all sound right?

tia
jerry

Gordy

Depends where the pex ended up in the 6" concrete pour (middle), and how thick the insulation was he used. That is a lot of mass. So yes it will take a while. How is the slab controlled, and what is heating the water?

jonny88

2 days and return lines are cold.Did he get all the all the air out of system.

k1jos

Boiler is a few year old Burnham. The 6" slab was first poured and cured for several weeks then the reflective insulation sheets (about 1") laid down. The Pex went on top of this secured to a wire mesh and then an additional 1" of concrete was poured to just cover the pex. Finally another 1" or so of mortar was applied to secure the Bluestone. We do have a sensor in the concete but to get it started I removed the thermostat and just twisted the wires together to keep the zone valve on all the time until the floor warms up. He said he bled the manifold but I can ask him to do that again, I can feel the two feedlines in the bsaement and they are nice and hot while the return lines are cool - so I figures the water must be circulating OK. SHould we increase the temperature -- not of the boiler but of the manifold - seems stupid at this point to be adding cold water to the mix to bring down the boiler water temp? Can pex take the same temperature as baseboard hot water? My boiler is supplying the entire house - there is an old existing radiant hydronic floor to my family room.. this was built in the 1950's over a slab with a small subfloor and then ceramic tiles - that room is huge - about 35' x 25' with 30' ceilings and lots of glass and the system keeps the floor anbd room toasty warm with little effort so I figure the boiler has to be OK and not the problem. The new system just was taken off an old baseboard control valve zone.

Any advice appreciated.

Rich_49

Could you post a couple pictures of the manifold , boiler piping and circs/s ?

How was this new radiant bled ? Sure sounds as if downward heatloss is minimal and it should have responded by now .

How did he determine what temp water to use and what spacing also ? Many times people don't feel that the floor is warm enough when in fact it is warm enough to perform the task . In other words warm floors do not always happen but the space is maintaining room temp . Ignore the floor temp for a moment and tell us if the room feels cold .

k1jos

Attached are 3 pictures of the manifold, mixing valve and original zone valve from boiler that feeds the manifold. I dont know how he determined the proper water temp - i think no calculations just "experience". Hard to tell if room is right temp as it is adjacent and widely open to the big family room radiant. The family room has warm ceramic tiles while the bluestone entry is always cool... i will get an IR temp monitor to check actual temp and to see i can find the pex pattern coming thru.

Zman

Well the goods news is your problem can be solved without tearing anything up.
The bad news is, you need to install a circulator within the mixing loop. The way you are set up now, as soon as the the mixer sees the high temp water coming from the boiler it starts closing. With no circulator in the loop, flow stops within the loop and the water never gets to the floor.

Zman

It would typically look something like this...

k1jos

Hi Zman, thanks but no picture was attached or it weas corrupted. My boiler has 5 zones and I thought there was a single circulator for all and only the solenoids zone valves opened or closed. So when the radiant is calling on the zone check valve doesnt that turn on the main circulator that the other zones are using as well?

Rich_49

Mixing valves require the circ to be inside the mixed loop so as to enable it to bring water in from return and supply to blend them . You will require another circulator for the radiant zone .

Zman

Try this...

Zman

k1jos said:

Hi Zman, thanks but no picture was attached or it weas corrupted. My boiler has 5 zones and I thought there was a single circulator for all and only the solenoids zone valves opened or closed. So when the radiant is calling on the zone check valve doesnt that turn on the main circulator that the other zones are using as well?

That is how your regular zones are working. With 3 way mixing , you lose the flow to the radiant side as the valve starts mixing in less hot water and more cold water. Your "plumber" really should know this as it is in any installation manual.
Yes you do want to mix the water temp as the floor and room will get way too hot with the high temp boiler water.

hvacplumber7

Rich and Zman have it nailed. I've got my in floor running on 3 manifolds just like they said. And their also right about this being a very basic install that any compatant heating guy should know. As a side note, the whole knowing by "experience" is the easiest way to find the guy that just doesn't want to take the time to do the job right. Maybe you should question if this is the type of contractor you want to give your hard earned money to.

k1jos

I follow what is being said but i can feel the two outflow pex lines coming from the manifold going to the room and they are both hot... so the mixing seems right - i can also feel the two return lines back to the manifold and they are cool. So it seems the heat is getting to radiant floor but getting sucked up. Thats why I asked if increasing the temperature would be advisable??
Is there anything I can measure or test to help diagnose the problem?

4Johnpipe

I'm afraid all you are feeling is heat stacking...

Rich_49

You have received your diagnosis . It is correct , the heat you are feeling is thermal migration and nothing else . I am sorry to say but until you do what is necessary and has been told to you , you will not have heat in that slab under the Bluestone . We do this for a living , it is not a hobby . Increasing the temperature will just make those small sections of pipe near the manifold hotter . Look up the install manual for any heating type mixing valve and tell us what you find .

Zman

Rich said:

You have received your diagnosis . It is correct , the heat you are feeling is thermal migration and nothing else . I am sorry to say but until you do what is necessary and has been told to you , you will not have heat in that slab under the Bluestone . We do this for a living , it is not a hobby . Increasing the temperature will just make those small sections of pipe near the manifold hotter . Look up the install manual for any heating type mixing valve and tell us what you find .

As Rich said, I small gulp of hot water makes it through the valve before it starts closing. Once it closes no water flows until the valve cools off.
This is not one of those, "more than one right ways" topics.
Your mixing setup is wrong and will never work correctly.

k1jos

OK i didnt understand the mixing valve was thermally active, i thought it was a passive valve set up to set the temperature of the final mix and then it was fixed in flows. If it has active thermal opening/closing mechanism then i understand why my system wont work. many thanks...

JohnNY

Wow. There are still plumbers out there signing up to install radiant floor heating that have no idea of the basic mechanics of the system. How can this be?
Very fortunate, @k1jos, that you posted here for the right answers.

Gordy

How is the radiant under the tiles in adjacent room set up ?

k1jos

I didn't want to open THAT can of worms :-) The larger room radiant was installed in 1950 !!! it is all copper piping I assume with four runs in and out but i dont recall anything that looked like a modern manifold - just copper piping with 4 tee offs for in and another set for out. It has a large mixing valve coming off the baseboard system with an old style temperature gauge. I dint recall if that had any wiring to suggest it weas a pump but I will go down and look more carefully now. let me take some pictures and share with you.

unclejohn

Dose he still need the zone valve with the pump? I would remove the zone valve as well. Those honeywells typicaly have a cv of 3.5 which is pretty low.

k1jos

i guess if no zine valve then yiu need a check valve?

hot_rod

Viega , and many others offer a manifold module that has the pump, mixing valve, and manifold all in one piece,just connect into the boiler loop, connect Pex and wires and they work perfectly

I'd use a small delta P circ with the multiple zones.

Hopefully a load calc was performed to assure those two loops are adequate?

k1jos

I installed mini-splits last summer and called the top 12 installers within 25 miles. I kept calling because i wanted someone who would do a heat load/loss calculation but only one did a load calc and he came within 1/2 ton of the others. The others said their knowledge of the area climate, topgraphy- shading, exposure directions, home construction, etc got them as close as any software package. In the end I went with recommendations on Angie's list as I had no other point of reference and the Fujitsu systems worked quite well in all rooms.

Ironman

k1jos said:

I installed mini-splits last summer and called the top 12 installers within 25 miles. I kept calling because i wanted someone who would do a heat load/loss calculation but only one did a load calc and he came within 1/2 ton of the others. The others said their knowledge of the area climate, topgraphy- shading, exposure directions, home construction, etc got them as close as any software package. In the end I went with recommendations on Angie's list as I had no other point of reference and the Fujitsu systems worked quite well in all rooms.

That's because the Fuji's are inverter driven and modulate their capacity from 40 to 110% of their rating. That leaves a lot of wiggle room for improper sizing, though a load calc should have been done.

It's not that way with hydronics: everything is designed and SIZED based on the load calc. Your floor is your emitter. How are you gonna vary its size? It's only gonna give so many buts per square foot based upon all the factors involved. How many buts will that be? Will they be enough? You don't know and we don't know without an accurate load calc.

Raising the water temp will give more output, but the floor will become uncomfortable if the surface temp exceeds 84*. And, it will overheat the room on milder days if you raise the water temp that high for colder days. A smart mixing valve that uses outdoor reset and varies the water temp should have been employed.

Proper design is essential in radiant and hydronics or else the results will always be undesirable to say the least. A lot of times, the floor won't function at all. Kinda like what you're experiencing.

k1jos

is the same true for baseboard hydronics? i already see a lot of swings depending on outside temp. can anyone recommend anyone in the area just north of NYC?

SWEI

I would suggest repiping both floors using outdoor reset controlled mixing. The load calc will tell you if you need two temp curves or one.

Ironman

Try the contractor locator on site. There are several good men on here from NYC.

Zman

unclejohn said:

Dose he still need the zone valve with the pump? I would remove the zone valve as well. Those honeywells typicaly have a cv of 3.5 which is pretty low.

unclejohn said:

Dose he still need the zone valve with the pump? I would remove the zone valve as well. Those honeywells typicaly have a cv of 3.5 which is pretty low.

If the zone valve has a cv of 3.5, that mixing valve likely has a cv of 2 or 3. Most medium sized circulators will overcome that much resistance, it is just a waste of energy.
This really comes down to what the owner is trying to accomplish. If you want to heat the room, just put in the circulator.
If you want to maximize comfort and efficiency, do the math and put in smart mixing valves...

Rich_49

Where exactly North of NYC ?

k1jos

I am in Katonh, NY about 50 miles North