New Radiant System Not Getting Warm

Cold_Paul

Clueless homeowner here,



Before I call up my contractor I wanted to get some additional info since our relationship is not the best, I was wondering if someone could give me some advice or opinions?



We recently moved into our new home. Here is my issue, the system barely heats up! There are 2 zones, front half and back half of the house. If I turn on the system at 8:00am in the morning and leave it on till 10:00 at night. The best the front of the house would get was around 68 and back would get to 72. The outside temp range is 50-65.



The water heater is set at 125 but the temp gauge on the manifold stays around 85 with a pressure of 20 psi with both zones on.



When I only turn on the back half of the house the temp goes to around 95 and the floor after a couple of hours gets nice and warm to the touch.



When I turn only the front half the temp drop backs down to around 85 and the floor barely get warm to the touch.



The Noritz stays on constantly.



The circulation pump is set to low.



There are 2 additional access panels in the walls, one in the garage and one in the back bedroom. The incoming water tube and copper manifold is warm but the return tube and manifold are barely warm at all.



Any ideas what is wrong?



Am I suppose to run the system all night to heat the slab? I have had the system on for about 4 days, from 8:00am - 10:00pm.



I turned on the system at 7:00 am, right now it is almost 8:00 pm. The front is 66 and the back is 72. The Noritz is at 125 and the gauge says  85 with 20 psi



Thanks

Ironman

Issues

 The first major issue is they should have used a boiler, not a tankless. Be prepared to hear that from probably every pro on here.

 The second issue is a result of the first: the tankless has too much head (resistance to flow) for the 15-58 pump to be able to move enough gpm through the heat exchanger.



From your pic it's difficult to discern all the details of your system. Could you post another of the piping to the right of the heater?



A third issue is that a slab does much better if the t'stat is left alone. Set back does not work well with a slab.

Cold_Paul

More picts

Thanks, I have seen all the comments about tankless systems on the boards...



When the architect first told us about the radiant system, we were told that there would be a conventional water heater, the contractor changed it to the Noritz, I believe.



Is there a way to make it work with the Noritz?



When you say "Set back does not work well with a slab" what do you mean?

If I leave the Thermostat for the front at heat = 70 on "auto", the boiler would probably run 24/7 since the front has yet to go above 69.



Looks like I could have another mess with my contractor ahead....



Here are some more picts.

Jean-David Beyer

Setback with slab.

"A third issue is that a slab does much better if the t'stat is left alone. Set back does not work well with a slab."



I am a homeowner, not a heating professional. But I know Ironman is completely correct about this.  The downstairs of my house is an on-grade slab with radiant heat in it. It is the part of the house with the largest heat load.



Before I thought much about what goes on in heating a house, I bought a fancy Honeywell CT3600 thermostat that can set 4 different temperatures for each of 7 days; 28 different temperatures each week if I want them. It even has "Smart Response" that can turn on  the heat earlier than the times set, so that the desired temperature will be achieved at the desired times.



I thought I could save money with it. I have no doubt this thermostat would work well with a forced hot air system. It might work OK with finned-tube baseboard operating at the usual design temperatures (around 180F). But for a radiant slab, it is useless except if I go on vacation for a week or more. The thermal mass is so great that setbacks basically do not work at all. If I change the temperature, it takes about 4 hours for there to be any noticable temperature change. In a 24 hour day, I typically cannot get the setback to lower the temperature by 5 degrees. Similarly for recovery. I would need to start the recovery around 9 or 10 PM to get the house back up to daytime temperature by morning. The smart response is not smart enough to learn to turn on the heat that much in advance. It may get to an hour or an hour and a half, but I doubt it would ever get to 12 hours in advance. If then. Basically, the house lags behind the thermostat by 12 to 24 hours. This causes other problems that I won't bore you with here.



So what I do is let the thermostat call for 69F all the time. When the house drops to around 68, the heat comes on; when it gets to around 70F, it goes off. The boiler does have outdoor reset, so the temperature of the circulating water adjusts to barely keep up with the varying heat load as the outdoor temperature changes. Ideally, I would set the reset so that the water circulates continually. I do not quite dare to do that, because I want a little margin to take care of extremely windy days, etc. But it sometimes runs the circulators 18 hours a day, so it is pretty close now. Right now, it is 42F outside and the water is circulating at 86F. My bedroom is 70F and the room with the termostat is 69F.

Ironman

Pump Speed

For right now, try setting the pump to high speed. I'll take a closer look at your pics a little later and get back to you.

EJ hoffman

clean the filter

clean the filter on the cold water/return line at the bottom of the heater.  You need one more pump the way it is plumbed to overcome the head loss of the heater.  Put it on the hot side at the Noritz heater.  If it runs 24/7 not a big deal, it is running on low fire because your pump is probably only pulling 2 gpm through the noritz, check the flow rate at the controller. 

Cold_Paul

Filter

Thanks, I'll let the contractor touch it since I am still under warranty. I turned the current pump to high but it did not seem to do anything. I left the system on all night, the front this morning at 7:00 was at 55 and the back was at 62. The temp on the gauge on the manifold was 85 at 30 psi.

Gordy

Pitiful piping

 Paul if the Architect spec called for a conventional water heater they are only about 75% efficient in a radiant application. The noritz is a bout mid 80's. A mod Con boiler is in the mid 90's, and higher.  Shame on both parties.



 All though Tankless can work they are not made for radiant heating apps.....I don't care what anyone said. Actually most tankless Manufactures void their warranty now, when used in a radiant app. Its hard on them.



You say you have 2 zones. How many loops are in each zone? 



If you try, and push 2 gpm through the tankless that leaves 1 gpm for each zone. Now if you take that 1 gpm divide between the loops for that zone. IF you only have 2 loops per zone you may be okay with .5 gpm in each loop.



Another detail would be how long is each loop? if its 1/2" pex should be 300' max.  If longer you start to run into pump head issues which requires larger pumps. Also creates Higher delta T's in the loops which makes for less comfort. 



This of course all depends on the heatloss calculated for each zone. I'm sure the heating contractor did heatloss calculation .......Right? This will dictate your water temps, and flow requirements for each zone.



Also remember if you have a super insulated tight home. Do not expect your radiant floors to always feel warm they may only feel neutral to the feet if everything is setup properly.



Gordy

Cold_Paul

Heat Exchanger

Sorry, Like I said I know nothing how this system works technically.

What does the heat exchanger do? Right now the hot water pipe from the Noritz to the heat exchanger is very hot with the Noritz at 125. There is mixing valve on its way to the exchanger. If I follow the pipes to the temperature gauge and where it goes out to room the temp is around 85-90. Why is there such a loss in temperature? Could I adjust the mixing valve? It seems to be locked down with a screw and says Honeywell am-1 with a sticker showing 70 in one direction and 180 in the other.

Gordy

Components

The heat exchanger is where all the heat transfer from the burner to the water happens.  With a tankless the passage ways for the water to flow through are very narrow. This is because in a domestic water heater application you are running higher pressures, and flow rates than in a radiant application. So to get good heat transfer you need narrow passage ways.



  Because of this you have to use a larger pump to get the proper flow through the heat exchanger. Much larger than a boiler.



125* out of the Noritz seems low to me if you have a mixing valve.  The mixing valve mixes return water from the loops with the supply water from the boiler er tankless in your application. This is why you have such a temp drop after the mixing valve the return water right now is cold. What is the mixing valve set at?



One other thing are you heating your domestic hot water with this unit also?

Cold_Paul

Zones

I don't know yet if the the architect spec. a boiler, but we where under the original impression that a "tank type" boiler would be in our service room. I think the contractor also sub-contracted the radiant system. With the holiday, I don't expect to hear any response till next week.



In any case, my zones

The Front of the house (zone 1) has 5 loops.

1  - entry

2,3,4 are for the living/kitchen (one open room)

5 - guest bedroom and bathrrom



The Back (zone 2) has 3 loops.

1 Master Bedroom

2 Office

3 Hallways



I do not believe any loops are 300'

The house is 2200 sqft the walls are concrete panels with 6" metal studs - with I think r-13 insulation. Double pane glass.

Gordy

Should also add

Noritz does make a "Hydronic Boiler" it would be the NH series though. It has the ASME stamp. Can't tell from the pic if that is an NH series.

Cold_Paul

Noritz and Mixing valve

The domestic water is from a separate Noritz units and works just fine.





I can turn up the Noritz I think to about 140.



The mixing valve is turned all the way to the clockwise position which the sticker says is 70*, should I tunrn this the other direction to the 180* position?



The Noritz says N-0751M-DVC which when I looked online in under the NR98 series, not the NH!!!

Gordy

Pex Size to manifolds

What is the size of the pex to the distribution manifolds for the loops?



IF the mixing valve IS set to 70* you could try bumping it up a little bit.

Let it run don't turn it on, and shut it off. It will take a while to charge the slab.....Please tell me the slab is insulated!



I still think there is piping/pumping issues that need be resolved.

CMadatMe

Gotta Love

That nice clean white tank? Why is there a thermal expansion tank on this?

While this is the piping diagram for the NH the piping still applies for the NR98.

http://noritz.com/u/plumbing_diagrams/nh_boiler/1b_nh_series_zoned_radiant_only.pdf

Gordy

Typical P/S

 La typical Primary Secondary Set up.

CMadatMe

Yup

Plain Jane. Gordy, I've noticed alot of these applications lately. Seems like the tankless is being shoved into consumers faces more for heating. It's taking the same footprint as radiant did. You don't need those expensive darn plates and you don't need an expensive efficienct boiler when this efficient water heater will do the trick.

Gordy

NH owners manual

Shows examples of baseboard, and fan coil setups using 180* water. Do not see a radiant app setup in the owners manual.



Funny how the link you pasted shows flow rates of no less than 4gpm, with 17 gpm max.



Plus return temps no less than 80*

CMadatMe

Probably

The 4gpm min is probably because of the low end btu ratings on the NH 55,000 input at 82% efficiency leaves you with about 45K or so. Ala 4gpm flowrate. Water temp is most likely to protect that copper hx.

Cold_Paul

Pex size

The Pex is 3/4 from the pump and 1/2 at the manifolds loops.

I have left the system on auto / heat at 70* since yesterday.

We had sun all day so the outside temp was around mid 60*

In the back zone got up to 72 and the front up to 70.

Around 7:00 pm the front zone started slowly fall, by 10:00pm it was at 62*

The back stayed around 70*

This morning at 6:00 am the front was down to 55* and the back was at 62* . The outside temp went down to the high 40's.

I do not know if the slab was insulated.  I am preparing notes and questions to send to my architect and contractor today.

Gordy

heatloss

Hmm.  Seems that your room temps drop rather quickly for the given outside air temps.

What are your floor coverings in the radiant floor areas?

If it were me I would demand that the tankless be removed, and a boiler be installed. At the very least re plumb the present tankless correctly. Per P/S piping diagram.

I see a bronze pump, and a cast iron pump, or CI pump could be stainless steel. You said your domestic hot water was heated by a separate unit. Was some or all  of the pex not O2 barrier



Find out if slab was insulated. Its not that it will not work. It will just take a lot more energy to work. And be slower in response time because the heat is going into the ground, and out the perimeter.



You paid an Architect, and a Plumber or heating contractor for a functional system. They have failed. I can't believe they are not on the spot to rectify your issue



Radiant heat is a science not a guess. There are reasons why a heatload calculation is done. There are reasons why certain heat sources are used, there are reasons why tubing install procedures are used, and there are reasons insulation details are used.



To many people think you throw a bunch of tubing in, heat it with what ever you want, and wa la you got radiant heat.  This is what kills the industry.  People always remember thier bad experiences before they remember the good ones when it comes to money spent.



Gordy

CMadatMe

I'm with Gordy

The first question and first request you should be making to all is...Where is the heat loss and radiant design? I want to see it. There should be no reason as to why they won't produce it other than they didn't do it. You paid them for the job and that's part of what you paid them for.



I would then tell them to get rid of the tankless and put in an appliance that is "RATED" as a boiler.

Cold_Paul

Thanks for all the info

Thank you all for all the info!

I am emailing my contractor and architect today. I feel now I have a better understanding of what the possible issues are. I will ask about the heat and radiant design.



As to Gordy's  questions:

The domestic heater is another Noritz unit that has copper pipe going out to all the fixtures. The radiant unit is the only one that uses PEX. I do not know if any of the pex is O2. The 3/4" says Aquapex 1006 on the side and I can't read what is on the 1/2" loops.



The floor is polished concrete surface.



I will let you guys know what response I get.

Gordy

Non Barrier tubing

Paul,

 Just so you know AquaPex 1006 is not oxygen barrier tubing so all components in the system need to be non ferrous metal.  Or these components can be ferrous metal if isolated from the tubing through a heat exchanger. This is because this type of tubing allows oxygen to diffuse through the tubing into the system. Its not that it can not be used its just the fact that bronze or stainless pumps, and other components cost more money. Most Professionals do not use it for radiant heating applications.



The supply tubing to the manifolds of 3/4" should carry about 54000 btus at 5.4 gpm with a 20* delta t.  Or about 27000 btus at 5.4 gpm with a 10* delta t.

Cold_Paul

Temperatures?

Thanks for the info on the pex.

I have send an email off to the contractor and architect, both I assume are on vacation so we shall see.

I do have a couple of last questions, what should the ideal temperature out of the boiler be? and what should the ideal temperature of the water as it goes to the manifolds be?



Thanks,

Gordy

Depends

On your heatloss calculation Paul.



This dictates the water temps, and flow rates for the zones.



Typically with in floor radiant you do not want to exceed 85* surface temps for comfort reasons. This does not mean that 85* is what your floor temps will be all the time, its a maximum.



Gordy

Cold_Paul

The system is now working!

Here is what went down, the guys from the heating sub contractor came twice.



The first visit, I found out that they were never called back to do the final start-up of the system. When they came out to turn the system on, the contractor had lost power to the site (another story). The result was there was air in the lines because the contractor had just turn the system on himself.

They drained the system and filled it properly. the PSI went from 20 to around 70.



This did not fix the problem as the temperature going out was still only 85º when the boiler was at 140º.



The second visit, they checked the filter on the Noritz as EJ Hoffman mentioned and it was packed!! Packed with  "construction debris".  When they turn the system on the temp instantly went up to 110º.



Side note: I am in  Los Angeles and I guess not many people have radiant system out here. The slab was not insulated because I was told no one does that out here. The heating sub uses a company back east and in Seattle to provided the pre-built manifolds, parts and tech support.



The house is nice and warm now!