Tankless Water Heater For Floor Heat

[mjwalsh]

Warranty & future insurance thoughts

Do you know if the warranty applies if you self install it? Some manufacturers won't warranty it if you install it yourself.

Rudy & others,

A lot of times the tankless does not have a local distributor or certified installer for their specific unit ... it seems like that can be a factor. From experience ... if the company wants to get out of obvious warranty compliance that will try to do that anyway. Back in 1985, I had a warranty problem that was caused by the contractor of our super hi efficiency modular 150K boilers at the time. Long story short, the contractor passed the buck to the wholesaler, the wholesaler passed the buck to the distributor. The factory would not talk to me directly. I had to hire a mechanical engineer who i had known & grew up with from my high school days. We got it resolved ... but not without effort & needed persistence. Organized precise documentation comes into play.

That does not leave 2Biz, myself & others who take on the installation off the hook both with warranty & future insurance coverage completely ... if enough evidence is shown that it was done according to factory specs & code ... hopefully ... the justice system would still come down on our side.

If the company cares about their sale they should be willing to go over your concern up front so there is a meeting of the minds ... & also so they do not leave themselves wide open for some key error or omission done during installation.

Sometimes the warranty is some kind of fine print legalese prorated gobblygook anyway.

mike walsh http://www.kingkoin.com/USA_Deficit_Reduction.html

 

[2Biz]

Do you know if the warranty applies if you self install it? Some manufacturers won't warranty it if you install it yourself.

That I don't know....I would think the same would apply to a boiler though. So if its a board or something simple that fails, I'll replace it myself. If the heat exchanger goes, I'll replace the whole unit. It would probably be cheaper that way. I still think I would be money ahead... I could replace the whole unit in about an hour or less since I installed the service valves and used plenty of unions! How much would it cost to get someone out to work on it? Where would you even find somebody that knows anything about it that could work on it...

Ok, so the downside to living in a small town!

 

[2Biz]

I remember having a hard time sizing pumps in the planning stage. So I called both Pex Supply (they have engineers who specialize in Hydronic Heating) and an Engineer at Takagi. They both told me a Taco 009 was big enough to supply the demand heater with enough pressure and flow. Well, they were wrong. I had to purchase (2) additional Taco 013's along with changing out the Taco 011 loop circulator with an 013....The additional cost was $750....After that fiasco, I took the time to learn the charts/graphs on pressure and flow of different pumps. The (2) 013's supplying the heater and (1) 013 loop circulator was perfect.

The point I'm trying to make is you can do all the right things and try to talk to the right people and still get burned. And if (2) different engineers led me astray, I wondered who in the world could service this thing? So given the cost of the unit compared to a $10k boiler, I decided to take the risk. A $10K unit could fail just as easily at the worst possible time and you'd have to rely on someone to get there and fix it. My way of thinking, if its that bad, I just order another heater (Probably at a price cheaper than a service call and parts) and install it myself in about the same time it would take somebody else to get there, order parts, and attempt to fix it....And at the cost of these heaters, an operator could have one on hand as a spare???? We do the same for pumps and other spare parts! You'd still be way ahead....

 

[JMMUSTANG]

2Biz is the model you have T-H3-DV-N Indoor Tankless High Efficiency Condensing Water Heater (NG)?
If so this one says "Indoor".
Just to clarify for me you have both your hot water to your chemicals and the underground connected to one tank?
Thanks

 

[2Biz]

The T-H3-DV-N is the one I have. It says "Indoor" because it has to be mounted indoors. They make ones that can be mounted outside. I have two separate systems in my ER....The 199K BTU Takagi is for floor heat and I just installed a Phoenix 199K BTU 55 gallon water heater for my hot water float tank. My pump stand is gravity fed both hot and cold water...And yes the "N" stands for natural gas...

 

[Rudy]

This recent discussion has got me seriously thinking about replacing a 40 gal. 40K BTU hot water heater that is used solely to heat my automatic bay arch. It's just a home water heater that uses a Taco 007 to circulate glycol when it drops below 33 degrees outside. This setup is old...and obviously very inefficient. It's either on, or off. It's plumbed as one giant loop.

A primary/secondary loop coupled with a tankless could be the way to go.

I'm having a hard time finding an aquastat (that could be used to sense return line temperature) that senses between 40-120F AND has an adjustable differential. I never checked what my present return temperatures were.....but I'm guessing it's pretty cold. I'm worried that if there's not enough differential....the setup could short cycle.

What are you using for an aquastat? Is the differential adjustable?

 

[mjwalsh]

A primary/secondary loop coupled with a tankless could be the way to go.

I'm having a hard time finding an aquastat (that could be used to sense return line temperature) that senses between 40-120F AND has an adjustable differential. I never checked what my present return temperatures were.....but I'm guessing it's pretty cold. I'm worried that if there's not enough differential....the setup could short cycle.

What are you using for an aquastat? Is the differential adjustable?

Rudy,

We improvised with Independent Energy Goldline controls from Rhode Island. They have reliable adjustable differentials They use a simple low cost thermister that can be taped on the return pipe with a heat sink compound & then covered with insulation. They have been 100% reliable for us for over 25 years now & have 2 stages & we are using he alarm output on one of them as a 3rd stage.

For our condensing multipulse by hydrotherm high efficiency modular 150K boilers ... we have been told that the colder the return temperature the more efficient they are. I think it has something to do with more condensation happening. In their brochure they used an example of cast iron radiators used in a huge church building showing in their tests giving significantly more efficiency.

How cold the water at what part of the piping will be a main criteria when we eventually put in our planned tankless to supplement our existing. I also like the idea if one 150K boiler goes down ...there won't be quite as much of panic in getting it up & going again ... especially during the worst part of some of our North Dakota winters.

mike walsh www.kingkoin.com

 

[cantbreak80]

Rudy,
How about the Johnson Controls A419?

They also offer a brass submersion well for the sensor that could be teed into the return piping.

 

[Rudy]

Thanks! That's exactly what I'm looking for.....

BTW.....I'm looking hard at a Navien units. Any opinions Navien vs. Takagi?

 

[2Biz]

The A419 is electronic. The one I used was mechanical...

http://www.supplyhouse.com/Honeywel...5-200F-range-5-30F-Adj-Differential-1738000-p

I used a submersion well "tee'd" into the return line instead of using the strap on kind. I would think either would work just fine...

Do you know if the Navien heaters have flow restriction through the unit. My Takagi is rated for 10gpm flow. It takes at least 80 psi to get 10gpm. At 40 psi input pressure you get roughly 7 gpm....The (2) Taco 013's in series give me 40 PSI...I could have went to a different style pump but it would't have been so efficient as the two 013's...Comparing the 40-50° temperature rise I needed using the Takagi graphs, the heater would restrict flow to 7 gpm anyway to get the 40-50° rise, so the pump setup I went with was perfect...

 

[Rudy]

My present setup (for a 3 and 2) has a 319K BTU Raypak for the floor heat and a 266K BTU Raypak (using an 80 gallon storage tank) for Domestic Hot Water. Both boilers are plumbed with 2" copper pipe.

While this discussion would work for either boiler.....why couldn't I make my present 2" pipes the "primary" loop using my current circulators? I'd feed the primary with a "secondary" loop from the tankless unit(s) using closely spaced tees. Essentially, I'd remove a Raypak, connect the two open ends.....and then insert two 3/4" closely spaced tees into a straight run of 2" pipe to make the secondary loop connection for the tankless?

My present circulator for the floor heat runs 5 amps at 120V. That's not to crazy. Certainly there's enough capacity....because it's been working fine for over twenty years. I'd just have to have a big enough pump to insure adequate flow and pressure in the secondary loop. In your case, you used two Taco 0013's.

Make sense?

Stated another way....

Why couldn't a Raypak be removed, and replaced with a straight run of 2" copper pipe which had two closely spaced tees (2"x3/4"x2") properly spaced and then connected to a 3/4" tankless loop?

 

[2Biz]

I don't see why it wouldn't work. You'd basically be making it like my setup with primary and secondary plumbing. 2" is pretty big! 1" copper can flow about 35-40 gpm....From what I remember, you only want 2-3 gpm flowing through each loop....

I used 1" up to my Heater. Then reduced it down to 3/4" into the service valves. Made it much easier to plumb that way.

Do you know the flow rate of your circulator for the floor heat loops? The reason I ask, I calculated the total head pressure in the system/loops and from tee's, elbows, and the size tubing in the floors. What I came up with was about 20-25 feet of head. At this amount of head, the 013 chart/graph said the loop circulator would flow roughly 14-16 gpm. So given the fact my Takagi flows about 7 gpm, it is sized perfectly with the primary flow rate. The Tagkagi outputs 1/2 that of the loop circulator. When my return temps are 70°-75° and I heat 1/2 of the return glycol to 105°, my output glycol to the bays is 90°. The pumps are sized as close as I could get them.

What you don't want, is a loop circulator that pumps too fast or too slow. It has to pump roughly twice that of the through-put of the demand heater. Too slow and you could create a situation where the closely spaced tee's would allow heated glycol to recirculate back through the heater and would disrupt the flow between the closely spaced tees. Too fast and you won't be able to heat the glycol up enough. Make sense?

 

[mjwalsh]

What you don't want, is a loop circulator that pumps too fast or too slow. It has to pump roughly twice that of the through-put of the demand heater. Too slow and you could create a situation where the closely spaced tee's would allow heated glycol to recirculate back through the heater and would disrupt the flow between the closely spaced tees. Too fast and you won't be able to heat the glycol up enough. Make sense?

2Biz & Rudy,

I don't wan't make too much extra expense for anyone & my system covers a lot more piping & more boilers & inline heat exchangers so maybe it is not a fair comparison. Our overall system (all tied together) involves balancing valves called Gerand out of Minneapolis ... that can actually test the actual flows through the ports of each valve ... something we never regretted putting in. If you have friend who both owns & is skilled enough with one of the Autodesk MEP softwares ... & it was not too overwhelming time-wise for he or she to run flow calculations that way. It is possible in the Revit version the manufacturer info might automatically come in once the Revit Family is loaded & placed properly.

If a contractor with the Gerand tester had it & you were organized ... it would probably be a very minimal charge.

mike walsh www.kingkoin.com

 

[2Biz]

I think your right, your system is much more complex than ours and maybe needs more automated controls. Ours is pretty simple...Really all that's needed is a temperature gage on the return line from the bays and one on the line going back out to the bays. If you don't have your pumps sized right, a simple (manual) flow control valve allows you to adjust the speed/volume of flow so you can get the temperature you want back out to the bays. Again, ours is much less complex than yours...

I did my homework and tried to size the pumps so I didn't need any valves to control flow. That's why I posted links to literature on how to do the calculations. You don't want to guess at any of it....

 

[mjwalsh]

Fail Safe Low Water Cut Offs on the variety of tankless units???

I think your right, your system is much more complex than ours and maybe needs more automated controls. Ours is pretty simple...Really all that's needed is a temperature gage on the return line from the bays and one on the line going back out to the bays. If you don't have your pumps sized right, a simple (manual) flow control valve allows you to adjust the speed/volume of flow so you can get the temperature you want back out to the bays. Again, ours is much less complex than yours...

I did my homework and tried to size the pumps so I didn't need any valves to control flow. That's why I posted links to literature on how to do the calculations. You don't want to guess at any of it....

2Biz,

True story ... I will never forget "before a major update" when I set up a meeting between the contractor, an experienced mechanical engineer, & myself. The "master plumber" contractor kept dozing off during the meeting ... to the point he needed to be awakened with a nudge .

Your process makes good sense ... I was just sharing some potential options ... just in case the boiler system gets more intricate for some of us. Of course we all know that a "working order" flow switch is critical to prevent too low of water flow that will possibly shorten the life of many of the more modern condensing boilers. Do most of the tankless units including the Naviens have a fail safe low flow shut off switch already built in? A heads up ... we also had put in engineer specified Honeywell low water cut offs & engineer specified Bell & Gosset glass encased visual flow gauges ... both were not durable enough for long term use ... so they were discontinued.

Like you say ... sometimes the more old fashioned ... just doing the time proven math & graphs ... is the best !

mike walsh http://kingkoin.com/USA_Deficit_Reduction.html

 

[2Biz]

Any demand heater is "Flow" activated, so basically they all have a low coolant shutoff, just a different way of achieving the same thing. If they are not getting fluid, they don't start. The worst possible thing I see is you could burn up a pump... And I feel that is unlikely since they are not a rotary vane type like a procon. I have a system pressure gage that I glance at every time I'm in the ER in the winter. Even when the system isn't activated or above 32°, if it deviates from 10psi, then I will know something is wrong. If something breaks loose when I'm not there and depleats all pressure and coolant, then the demand heater won't get fluid and it won't ignite. It needs .5 gpm flow to turn on. Again, trying to keep it as simple as possible.

Thanks for the heads up though, makes for great discussion....

 

[washboy222]

Hey 2Biz thanks for all this info it has been a big help. Last winter my 20 year boiler went down mid winter and replaced it with three takagi tm-32 units and found your post after completing it, needless to say I am up grading to your design with hydraulic separation and the correct pumps. My question is where did you get the info on putting two taco 0013 pumps in series? I have looked at the curves on the taco web site but didn't find info on pumps in series. I will need 6 pumps, would you still use the taco pumps in series or go with one larger pump?

 

[2Biz]

I don't remember where I read the information about putting pumps in series. In a 2 pump series configuration, the pressure output of each pump is added together. GPM is the same as one pump. If you put two pumps in parallel, GPM is doubled, pressure stays the same as one pump. With the (2) 013's in series, I get 40psi which puts me up to about 7-8 gpm, the flow I needed for the Delta rise through the boiler. I also like the Taco design. IF the motor ever fails, you leave the pump installed inline and just replace the motor insert.

Yes, I would do it the same way and not use a bigger single pump. The Taco 013's run on 2amps each. My whole sytem, 3 Taco 013s
run on 6a of 120v. You go to bigger pumps/motors, and you'll use more electric. I designed this system to be the most efficient I could possibly get by with. Last winter got to -16° here. My floors stayed ice free.

It sounds like you have a lot more SQ FT to heat than I do, since you have (3) TM-32's. I'm assuming your talking about just how to pressurize the heaters and not the loop circulator pump. That is a different animal. What are you using there? My 4 bay works very good on one 013. With the head pressure calculated in, I get about 16 gpm flow. 3-4 gpm per bay which is what you should shoot for.
I should say I have 5 zones, one is in the trough...But you barely count it. Its more like a bypass. There's very little heat loss in the insulated trough.

I looked at the TM-32's...They have about a 15% less efficiency rating than the one I bought. Since the price was similar, I decided on going with the higher efficiency. An added benifit, was being able to exhaust with PVC. So far I have absolutely no complaints...

 

[2Biz]

OK...Here is a link that might explain it a little better than what I attempted. I don't think I read it here, but it says the same thing...

http://www.engineeringtoolbox.com/pumps-parallel-serial-d_636.html

 

[2Biz]

I guess if there was one thing I would change it would be the acid neutralizer I made for the floor heat. I’m not as happy with it as I am with the one I made to go on the Ultra High Efficiency HTP hot water heater I installed. I made it with clear see-through pvc so I could see the condition of the limestone without opening it up. It’s a lot easier to service too. I’m going to change the one out on the floor heater this winter, in my spare time!