Tankless Water Heater For Floor Heat

[2Biz]

Anybody care to share information about using the new style tankless water heaters for floor heat? I need to replace my old Jarco 350K btu money pit with something new and more energy efficient.

I’ve been doing some extensive research and comparing different demand heaters, Takagi, Paloma, Rinnai to name a few. Some are condensing units and some non-condensing. The non-condensing are usually about 84-85% efficient and the condensing units are 94-98% efficient. The condensing units can be vented using PVC while the less efficient units need to be vented using stainless steel vent pipe with a condensation drain added to the vent stack which is more costly.

Some of the heat exchangers are copper and some are Stainless steel and copper. The condensing units usually use stainless and copper.

The problem I’m having is trying to determine what will work and how well it will hold up running Polyethylene Glycol in the system. Most of these demand heaters are manufactured for heating “Water” and don’t offer details or suggestions when using them in hydronics or snow melt systems which is basically what we have.

I have my eye on this model after doing some research…It’s the Paloma PHH-32RDV. It’s a condensing boiler with a 94% efficiency rating. It has a copper/Stainless steel heat exchanger, 199,999 btu rating, can be vented using PVC, has a direct vent cold air intake, and can heat water +35° at 9.5 GPM and 77° at 4.9 GPM Temperature rise.

What are the pro’s and con’s of using a heater/boiler like this? This one is realitively inexpensive compared to “Boilers” on the market. The one I mention can be bought for less than $1300 which is considerably cheaper than the Takagi TM32 commercial that only uses a copper heat exchanger and has to be vented using Stainless Steel Pipe. I know some of you are using these demand heaters for floor heat. So tell us what model your using, why, and how well its working for you. Thanks!

 

[Buzzie8]

This website should be a great help. It shows plumbing of radiant floor heat using a on demand heater:

http://www.radiantcompany.com/heatsources/Takagischematics.shtml

 

[Whale of a Wash]

Those are nice diagrams. I just bought a Lochinvar 199K 96%
eff. boiler from carwashboilers.com Not sure if this makes a difference,
but every 2 years we have the boiler inspector stop by. $35 to the state,
and the inspector is sent by my insurance co. They test the low water
cutoff, and the overpressure valve. I know the palomas shut off when
out of water, but not sure if it would meet our states specs, like the
other boilers. I bought the boiler for $4200, and found a hvac guy to
do the complete install in a couple weeks- plumbing, gas, and electrical
changes plus drill a 4in hole thru concrete for the single intake and
exhaust. Just 4 to 5 hours at their rate plus materials they figured.
Am I missing the obviously cheaper way to go. Why should i spend
more for about the same?

http://www.carwashboilers.com/knight-high-efficiency-boilers.html

 

[mjwalsh]

Something to consider

Most people are not aware that more glycol causes a loss of heat transfer with the same input BTU expenditure. I myself was surprised when I first saw a mechanical engineering trade journal article showing the proof etc. a few years ago.

Something to consider ... especially the potentially more harsh winter areas & the more dense the glycol needs to be.

At our place we have just boiler water in the main boiler setup. That way at the point of combustion it is more efficient. From there we use Spirec heat exchangers to circulate the boiler water on one "in & out" of the Stainless Exchanger & the glycol on the other "in & out". I did get help from a mechanical engineer back in about 1991 or so for the original setup on the design. We don't regret having gone with that approach. Here is a link to the Spirec website.

http://www.spirec.com

mike

 

[2Biz]

The more I research this the more issues I'm finding that needs to be overcome. The glycol being one of them. It consumes about 10% of the total BTU output. Another issue I see with the Demand Style Wall heaters is the amount of Head Pressure you need to overcome in the unit itself to produce the rated flow. Let alone the head pressure in the zones. The Takagi T-H2-DV-NG 199K BTU Condensing boiler adds 110 feet of head pressure in the unit itself at the rated 9 gpm flow rate. It would take more than a Taco Stye pump to produce the PSI to obtain the rated flow.

This is not going to be as easy as I had thought. Theres a lot more to it than putting a Taco pump between the boiler and manifolds. There are diagrams out there that shows it can be done. I'm not giving up yet...

Thanks for the Input so far.

 

[2Biz]

This website should be a great help. It shows plumbing of radiant floor heat using a on demand heater:

http://www.radiantcompany.com/heatsources/Takagischematics.shtml

Thanks for the link! Although I already found it and studied it hard! In the list of Schematics/Photos, the one labeled "A 2-zone CLOSED system" comes closest to what I need to put together. I believe this is called a Primary and Secondary loop system. This way one pump takes care of the boiler and one pump (or however many you want) takes care of the zones. I need to call Takagi and see what size pump is required just for the boiler.

I found (2) pulications online for snow melt systems that might be of use. I uploaded them to my server for download. There is some good information about how to size a system for snow melt. Basically what we're trying to accomplish.

http://bcoweb.com/photos/Viega_Snow_Melting_System.pdf

http://bcoweb.com/photos/CPS_Snowmelt.ppt

Addining another useful link...

http://www.radiantcompany.com/manual/index.shtml

 

[pitzerwm]

You will need a multistage pump

 

[2Biz]

I called Tech support at Takagi and he said a Taco 009 SS pump is what they recommend to supply water/glycol to the boiler. 10 gpm and 35 feet of head pressure. This is just for the boiler. You need another pump for the loops.

This diagram (Attached) is about as simple as you can get. It is all you need for Snow Melt and when using a Condensing-Modulating Boiler.

http://bcoweb.com/photos/piping schematic.pdf

 

[mjwalsh]

I called Tech support at Takagi and he said a Taco 009 SS pump is what they recommend to supply water/glycol to the boiler. 10 gpm and 35 feet of head pressure. This is just for the boiler. You need another pump for the loops.

This diagram (Attached) is about as simple as you can get. It is all you need for Snow Melt and when using a Condensing-Modulating Boiler.

http://bcoweb.com/photos/piping schematic.pdf

2Biz,

I wonder if the following unit's own built in circulator would mean the unit's circulation would be taken care of ... eliminationg the need to buy a Taco 009 pump?

http://www.globalindustrial.com/p/p...l-gas-water-heater-circ-pump-mini-buffer-tank

mike

 

[2Biz]

Looks like a nice unit and comaparable to the Takagi T-H2-DV-ng or the new style T-H3-DV...The Takagi has slightly higher ratings...6.1 GPM @ 60° temp rise and 5 GPM @ 75° temp rise compared to the Navien's 5.8 GPM @ 50° temp rise. It does have a nice feature, dual SS heat exchangers. The Takagi only has a Primary SS heat exchanger and copper secondary.

I downloaded the Navien's manual and it didn't have anything listed on the pump specs. So I can't help you with that. But you might want to take a look at the diagram in this brochure on the plumbing hookups. It has a hot outlet and hot return along with a cold water inlet. Different than the Takagi which only has a cold intake and hot outlet. Here is the link to the brochure:

http://www.navienamerica.com/PDS/ft...NP/Brochure/Navien_condensing_NRNP_120823.pdf


I don't know how you would plumb this model with the internal pump and having the "Hot" circulation loop with the single cold inlet....I would call Tech Support to see how that works.

 

[2Biz]

I purchased the Takagi 199K BTU condensing boiler and would like you’re opinion. These newer units have multiple pump control modes built in as long as you control your pumps (through an external relay) and the boiler control board. They are listed below.

There is a nice feature (“A” Below) where the pump will run for a minute every 30 minutes so the control board can monitor the line temps and fire accordingly. This could be set in series with the outside T-Stat to the pump relay which would cycle the pumps every 30 minutes once the system has reached set point or the outside temps are low enough to active the circuit.

OR, I could simply run the pumps off the outside t-stat directly which activates the boiler…(Boiler activates when it see’s flow) using option “D”. Then as long as the outside temp is below 32° or set point, the pumps are on and the boiler modulates (13K btu-199k btu) to keep line temp at set point (100°-120°).

In your opinion, what would be the best way to go with this?

Had to break up the post and modes...See below...

 

[2Biz]

A) Recirculation Control: No. 5 ON
Feature: Maintaining temperature in a standard recirculation loop, providing hot water in a quicker
amount of time.
Function: The pump is only set to run when the temperature of the water in the recirculation loop is
more than 9°F below the set temperature of the T‐H2‐DV/T‐H2‐OS.
The pump will run for about 1 minute every 30 minutes to determine whether the water
temperature in the entire recirculation loop is more than 9°F below the set temperature.
If the water temperature is more than 9°F below the set temperature, the pump will remain running
until the water in the loop reaches the set temperature. Otherwise, the pump will stop for another
30 minutes.
If the inlet thermistor of water heaters detects that the water temperature is more than 9°F below
the set temperature before those 30 minutes have elapsed, the pump will activate immediately and
remain running until the water in the loop reaches the set temperature.

B) Storage Tank Circulation Control: No.6 ON
Feature: This is to ensure a higher rate of recovery for storage tank applications.
Function: The T‐H2‐DV/T‐H2‐OS heats the water 5.4°F higher than its set temperature. The
circulation pump between the storage tank and the water heater will continually remain running.
After set temperature has been reached in the storage tank, the T‐H2‐DV/T‐H2‐OS will fire off and
limit the water flow rate to less than 2.6 GPM, to continually monitor the temperature throughout
the system.
Note: In this mode, the pump will continually remain running.

 

[2Biz]

C) Energy Conserving Recirculation: No.5 and No.6 ON
Feature: Operates similarly to the standard Recirculation Control mode, but saves more energy by
limiting the temperature within the recirculation loop.
Function: The temperature of the recirculation loop is never kept above 120°F (49 °C), regardless of
the set temperature of the T‐H2‐DV/T‐H2‐OS.
Right bank of dipswitches

D) Normal Control (Default setting): No.5 and No.6 OFF
Feature: This mode provides no special pump control. Pump activation can only be turned ON or OFF
by the TM‐RE30 remote controller.
Function: The pump will run continually all the time as long as there is a power supply to the T‐H2‐
DV/T‐H2‐OS. The pump will only stop when the TM‐RE30 remote is turned off. Water in the loop will
be maintained at the set temperature of the water heater.

 

[2Biz]

Scratch the question, not that I was getting input anyway. The Takagi T-H3-DV that I ordered, didn't have these options. There was no manual online at time of purchase and was told it was like the T-H2 but better. Anyway, I'm installing an Aquastat in the return line to control the Boiler pump. Probably a more robust method of controling the boiler than using the control board.

 

[Bubbles Galore]

So at this point, what is your setup looking like? Are you using a multi stage pump like Bill suggested or are you going with the Taco pump? I am still researching, but for the money the TH2-DV still appears to have the most bang for the buck. I look forward to hearing how your install progresses. Thanks for the updates.

 

[2Biz]

The tech I talked to said they were having board issues with the T-H2-DV but didn't go into any details. He said definately worth the extra $300 to get the H3. The only differences in the two is the H2 is 9 gpm where the H3 is 10 gpm and the H3 doesn't have control board support for the circ pump. Thats why I'm controlling the Boiler pump with an Aquastat off the return line. The primary loop pump will run constantly below 32°. Switching to the Taco style pumps is huge as far as electric cost savings. 1.7 amps of 110v v/s 9.0a of 220v comparing to the pump I currently have that came with the Jarco.

I went with the Taco 009 for the boiler secondary loop and a 011 for the Primary loop. I'm only heating 1600 sq ft so the 011 will supply each of my 4 zones with about 4 gpm accounting for head loss. There are a lot of calculations you must make before settling on the right pump. The 011 can flow 31 gpm and has a head range of 31 ft. It developes about 15 psi of pressure. My geograghical location recommended 125 btu per sq ft so the 200k btu boiler is sized perfectly.

The Taco 009 for the boiler was what the Tech recommended. It flows 10 gpm and has a head range of 35 ft. The two pumps working together in a primary/secondary loop system should work great. You want the primary pump to have more flow than the secondary...See Diagram...It will make sense...

http://bcoweb.com/photos/piping schematic.pdf

I'm hoping to start on the install this week. We're getting hammered by Sandy right now. High winds and Snow covered ground this morning. Rare for Southern Ohio in October! Will post pics after I'm finished...

 

[2Biz]

BTW...When I was draining the antifreeze from the system, I purged with 5 psi of air pressure and purged each zone seperately. I hooked a 3/8 id hose to the drain valve and put the end in a 5 gallon bucket. The AF came out with such force it shot out of the bucket and shot clear across the ER and all over me!! So if the primary pump developes 15 psi, it will have plenty of power.

I won't make that mistake twice!

 

[Bubbles Galore]

He said definately worth the extra $300 to get the H3. The only differences in the two is the H2 is 9 gpm where the H3 is 10 gpm and the H3 doesn't have control board support for the circ pump. Thats why I'm controlling the Boiler pump with an Aquastat off the return line. The primary loop pump will run constantly below 32°. Switching to the Taco style pumps is huge as far as electric cost savings. 1.7 amps of 110v v/s 9.0a of 220v comparing to the pump I currently have that came with the Jarco.

I went with the Taco 009 for the boiler secondary loop and a 011 for the Primary loop. I'm only heating 1600 sq ft so the 011 will supply each of my 4 zones with about 4 gpm accounting for head loss. There are a lot of calculations you must make before settling on the right pump. The 011 can flow 31 gpm and has a head range of 31 ft. It developes about 15 psi of pressure. My geograghical location recommended 125 btu per sq ft so the 200k btu boiler is sized perfectly.

The Taco 009 for the boiler was what the Tech recommended. It flows 10 gpm and has a head range of 35 ft. The two pumps working together in a primary/secondary loop system should work great. You want the primary pump to have more flow than the secondary...See Diagram...It will make sense.

If I am understanding correctly, you are still using a pressurized system and are using a Taco pump for circulation in the bays and an additional Taco pump for circulation through the condensing boiler, correct? How are you going to isolate the condensing boiler so that the Taco pump that circulates the glycol through the bays won't push through into the boiler? Are you going to use NO/NC solenoids based on return line temps?

Did you go with just (1) 200k btu boiler? Did it end up being the H3? What is your total amount of concrete that needs to be heated?

Sorry for all the questions, I am just trying to understand how you are going about setting up your system.

 

[2Biz]

This will be a closed system pressurized to 12-15 psi and No solenoids are needed to keep flow from going through the boiler when the boiler pump is not activated. It has to do with hydraulic seperation between the primary/secondary piping and the closely spaced tee's to the boiler. See these publications for clarification:

http://www.comfort-calc.net/primary-secondary_piping_tutorial.html

http://bcoweb.com/photos/HydSep.pdf

It is very critical where and how to "Tee" in the secondary (to boiler) piping.
It is explained in detail in the links above.

I mentioned I am heating 1600 Sq Ft of concrete. I sized my system based on 125 BTU per sq ft for my geograghical location. (200,000/1600=125 btu psf) Yours may be different.
And since you have 3200 sq ft, you may need to link (2) of these units together to get the necessary output.

I am controlling the primary circ pump with an outside t-stat and the boiler pump will be controlled by an Aquastat off the return line from the return zone manifold. Even though the boiler is modulating, I will have more control over it using the Aquastat...The lowest temp setting on the boiler is 100°. I see no need to keep the zones heated to 100°. The aquastat will just give me control of the zone temps.

 

[2Biz]

Maybe these links will explain Hydraulic Seperation better:

https://www.hydronicworkshop.com/shoppingcart/pages/Understand-Hydraulic-Separation.html

http://www.radiantcompany.com/heatsources/primarysecondary.shtml