Radiant Floor Heating 2800sqft House

evanlifetv

Hey all, I need some help... I'm a super handy person, but Radiant Floor Heating has a lot of information online, and its hard to decipher whats true and whats not. So here is the story:

We bought a house about 6 months ago, and I did a major remodel on it, about the only thing left to fix/clean up at this point is the radiant floor heating. I cannot find anyone local to Oklahoma thats even willing to come out and take a look at it to see what my next steps are and assess it's current state. Pretty much nothing is mounted, and there are some things that I see as being odd. Dual tankless units & dual pumps mainly, and the fact that pretty much nothing is mounted!

It is a closed 3x Valve/Manifold System, Installed in 2003. The Heating Source is 2x Navien NR-240 plumbed in parallel (that are supposed to be a couple years old). A couple of the rooms are colder than what I think they should be, but the house seems to be heating. I'm just trying to get this cleaned up and "right" before it gets cold for any extended period of time.

So, how bad is it? I plan on tearing most of the stuff off the wall, and re plumbing it so that its mounted at least, but now is the time to make it right also, so lay it on me, and hopefully I can get that stuff done too. So, Thoughts and explanations???

markp1

I'll take a shot at this...

First, you only need one of the Navien boilers. The 240 is good for up to 199K BTUH, which should be far more than you need (a manual J calculation would help confirm though).

Second, the gas pipe should be black iron, not flex-line.

Third, the piping around the boiler should be in copper, not pex.

Fourth, the grundfos pump shown is pumping toward the expansion tank / air seperator, and it should pump away from it.

This brings up the entire layout though. I'd start with looking at the documentation from Navien on suggested layouts.

Another source are the Caleffi idronics issues (http://www.caleffi.com/usa/en-us/technical-magazine - start with number 12 (hydronic fundamentals), proceed with zoning (number 5), and balancing (number 8)).


If it was me, I would not try to salvage the current layout... I'd take it all down / apart, and reinstall with an appropriate layout.

Good luck!

Ironman

Wow, what a mess. Sorry, but you said you wanted it straight up.

1. Those are tankless water heaters, not boilers. They are not designed, controlled or approved for space heating no matter what an internet peddler says. They probably won't last 3 years if things go the norm. I, as well as others, have addressed this endlessly on here. You can do a site search and find threads about it.
2. Does the system have O2 barrier pex? If not, it needs to be isolated by a heat exchanger as you attempt to make everything right.
3. The heat loss calc is essential to sizing EVERYTHING.
4. I concur that sawzall surgery and a complete re-do of the near boiler piping is very much warranted.

Rich_49

Some array of whatever I had on the truck . I concur with what has been said so far but think I have observed something worse than the anti plumbing . How much work have you done on this house and what was it ? If you insulated and air sealed in your upgrades you need to find someone immediately to pipe the combustion air inlets to the outdoors . Does this arrangement also make your domestic hot water ?

Zman

You already know you have a mess.
If you only had one of those hot water heaters, you would be oversized by at least 400% .
Determining what type of tubing you have will be an important step. If it does not have an oxygen barrier, that changes things a bit.
A room by room heat loss is absolutely needed as well. Many manufactures provide apps that do this for free. Slantfin boilers has a pretty good one.
Carl

SWEI

What part of OK? I would probably call IGSHPA and saee if they can point you at a local member who does RFH work.

evanlifetv

Well it looks like @markp1 gave me some good light reading, I'll dive into that this afternoon. I plan on tearing it all down and starting "fresh". I have some work and research to do for sure now!

@ironman Most of it is O2 barrier, I will convert it all in the redo. Sawzall is most deff in order it sounds.

@Rich, no air sealing has been done in the garage/shop area, only inside the residence. The Garage/shop is about 1500 sqft of space that those units intake from. Domestic hot water comes from a third tankless unit.

@Zman, I'm looking at that app from Slantfin now. Thanks for that tip.

From a high level standpoint would you all agree:
* I have a mess!
* I have tankless units, not a boiler so Oxygen Barrier Pex should be fine for that, max temp is 120? (I really don't want to go buy a boiler this week.)
* Shouldn't have a pump before and after expansion tank. (should they both be after, in series?)
* I likely only need 1x of those tankless units, heat loss calc will confirm.

** Most of the questions I can probably answer myself once I finish the reading material above, but just wanted to ask anyways.

Thanks for all the help everyone, its nice to find a place where pretty much everyone says the same thing.

Zman

Be sure to get yourself in the mindset that what you have is the work of an absolute imbecile. The only thing you system seems to have going for it is you have approximately the right number of loops in the slabs, hopefully that part of the system is OK.
Don't be lured into the thought process of "what is wrong with my piping?". Everything is! Pipe sizing,materials,boiler circulators, layout, you name it...

Star from scratch and you will be glad you did.

The Navien's are the worst possible choice for a heat source. The are not boilers and are comically oversized.

For a few thousand more, you could have a really nice condensing boiler, properly sized with outdoor reset.

Could you use one of the Naviens to heat your domestic water (they are designed for that) and one for spare parts? Craigslist?

Carl

evanlifetv

Ha! I love it @Zman, I'll be doing a lot of research.

We didn't talk about loops, I have 13 separated into 3x zones/manifolds. That sound about right for 2800sqft?

My domestic water is heated by a Paloma Tankless.

Its hard for me to understand the necessity to spend the money for a true boiler when I will only need heating for 1/12 of the year.. maybe a couple months total. We like our house about 66-68 degrees in the winter, just seems that a boiler would be overkill in the warmer climate of Oklahoma... am i wrong in that thinking? I haven't researched the differences in the tankless heaters vs boilers, so I'll be doing that soon.

markp1

Under no circumstance should you keep either Navien as the source of heating your home. If the other indirect water heater you mentioned is plumbed right, and supplying enough hot water for you, I'd suggest selling both of the Navien's, taking that money, and buying a correctly sized mod-con boiler.

If you setup your new system using a tankless water heater as a boiler, you are designing for failure.

markp1

Boilers are designed to operate a closed loop system, with heated water circulating back through the boiler.

Tankless water heaters are not designed to operate a closed loop, nor have the water loop back to themselves at all.

hot_rod

Tankless heaters are designed for large temperature increase, 60- 120F low flow conditions, @ 3 gpm or so, exactly the opposite of how a radiant heating system operates.

A low cost option is a regular water heater. I have done many small radiant jobs with electric or LP fired WHs here in SW Missouri. Check with your code officials, there are some brands that are approved by the manufacturer for hydronic applications, State and Bradford White, for example.

Operating cost may be the same or less once you see how tankless heaters respond to radiant conditions

evanlifetv

Dang you all are awesome... so much brain power.. Ok, I'll Look at some boilers. Of course the follow up question to that would be what brand do you recommend?

Ironman

evanlifetv said:

Dang you all are awesome... so much brain power.. Ok, I'll Look at some boilers. Of course the follow up question to that would be what brand do you recommend?

You'll get some difference of opinion on boilers brands, but the consensus seems to be that the models that use the fire tube heat exchanger are preferred. Lochinvar WHN, Triangle Tube, HTP fire tube, Weil McLean has two models. And there are some others. The Dunkirk/Utica laser tube is also a good design. Viessmann is first rate.

One thing to definitely understand is that the design and installation has to be done by a COMPETENT hydronics pro; he's 98% of the equation.

There are several men on here that offer design services.

Ironman

Are any of your loops "staple up" or are they all in slab? If so, do they have heat transfer plates? How long are the loops?

evanlifetv

@Ironman, no idea on loop length, they are all in slab.

evanlifetv

So @ironman, who can I hire to design this system? I think that is really the next step for me. I understand enough to know, that its not right, by a long shot, and I need to get it that way. So, if you are interested in doing a system design for me, I'm all ears and willing to pay of course.

hot_rod

where abouts in OK? There are some reps and dealers down there that know and design radiant, maybe I can connect you with some one close by.

evanlifetv

@hotrod I'm in Edmond, OK. I have called the 12-15 biggest in the OKC/Edmond Metro and the answer I have got from them all is basically "We don't know or do enough of it to take it on right now". I even called a couple geo thermal places, and they told me the didn't do "Remodels", only new construction... I have been striking out.

Ironman

evanlifetv said:

So @ironman, who can I hire to design this system? I think that is really the next step for me. I understand enough to know, that its not right, by a long shot, and I need to get it that way. So, if you are interested in doing a system design for me, I'm all ears and willing to pay of course.

P/m me with your contact info.

SWEI

You can use a tank style water heater (even a tankless if you add a buffer) but in order to perform properly with high mass radiant, you will need outboard valves, piping, and controls that will make the price of a mod/con boiler look much more attractive.

Bob will set you straight.