Tankless Water Heater For Floor Heat

Thank you for the links. I will check them out a bit later. You weren't kidding, there are a ton of variables to take into account. Please continue to update us on the progress.

2Biz said:

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

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2Biz,

Thanks for the links. Our intricate hydronic system uses a few Spirec heat exchangers & we have to be careful that our boilers are never starved for water. In our case, we are heating 3 zones for our laundromat & back rooms etc. ... besides the zone for our overhead unit heaters in our bays, dog wash floor heat & our deicer system plus the heating of our domestic water all on a sequenced modular system that is connected via its piping. We have a place for a Navien tankless with its built in circulator but will have to make sure the piping will pick up the additional hat water at the proper rate. I am hoping that the Navien's built in circulator will pick up off of the city water pressure main piping & then return the now heated water to the same 60 psi city water pressure piping that tied in with our three domestic 45 gallon storage tanks. I assume that the built in circulator will maintain the proper flow to the Navien tankless for maximum output!

Sometimes I think it is a miracle our existing system works as good as it does. On one of your links it shows use of a pressure regulator to balance the flow to what needs to happen. A mechanical engineer way back in 1985 assisted us making sure the balancing valve was done right. Judging by the info on the links it looks like there are even more ways to get the flows just right besides just choosing the pumps. One of our Grundfos pumps has the option of 3 different speeds though.

mike

continued from last post ...

Summertime, our dog wash & our laundromat is cooled with our icy inlet water being preheated on the way to our heat exhanged domestic storage tanks. There again .... primary & secondary flows are definitely a factor.

The key is keeping the initial & ongoing expense from getting out of proportion!

mike

mjwalsh said:

The key is keeping the initial & ongoing expense from getting out of proportion!

mike

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You wouldn't loan out that "Key" would ya?

Sounds like you've got quite an elaborate setup while mine is very simple and basic. I am installing several ball valves in the primary and secondary loops to help get the flow dialed in if needed and also to help service the system. There is no way to get it absolutely perfect by sizing the pumps alone.

The new Condensing Boilers have features that the old boilers didn't have. The modulating gas supply valve and automatic water flow valve make the system a little more forgiving compared to the old systems. And since I am only heating the floor loops with this boiler, there is no need to iscolate the glycol with heat exchangers...Tying floor heat with potable water can add a lot of cost.

Thanks for adding to the thread. Floor heat is a big part of our car washes and there really isn't a lot of information here on the subject. It can be quite complex, even with a basic installation like mine.

If you're replacing that old boiler, don't throw it out. I got $320.00 for the copper that was in it. Applying the $$$ to the new system saved 10% off the install...

I'm glad to see the recycling centers are cracking down on copper theft. They recorded my license plate number and scanned my drivers license. They also issued me a check instead of giving cash. Hopefully somewhat of a deterant to people stealing it and cashing in....

I'm glad to see the recycling centers are cracking down on copper theft. They recorded my license plate number and scanned my drivers license. They also issued me a check instead of giving cash. Hopefully somewhat of a deterant to people stealing it and cashing in....

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I've heard it's helped a lot. Now if the police come looking at a recycling yard for something reported stolen, if they find it they know right where to look for the thief. They issue checks so homeless people can't get cash for copper wire stolen from an abandoned house.

Its time to give an update on the Takagi T-H3-DV install. It wasn't without issue. Long story as short as I can tell it...Got some bad advice from a Takagi Technician. He suggested a Taco 009 pump to supply the boiler. Doing so only yielded 2.5-3.0 gallons a minute through the boiler at any temp setting. Way too low..

So I went back to the drawing board and did my own calculations...What I came up with required (2) Taco 013 circulators in series to get the necessary head pressure or PSI that the boiler needed for maximum flow (About 40 psi). Lots cheaper and safer than a rotary pump or multi stage pump. I'm thinking they could require a regulator and additional bypassing to make them work in this application.

After installing the new pumps, I am getting double the flow and close to the advertised flows. 70° temp rise is yielding 6 gpm...70° inlet temp-140° outlet temp...But after running the boiler for about an hour, the flow starts to decrease. The culprit is in the tiny screen filter at the inlet to the boiler. It is extremely fine mesh and very small. Its possible when I ran the cleaning solution through the system, It wasn't completely dissolved (It was granular and needed dissolved in hot water). SO cleaning the filter gets it back to the correct flow. I've got a 5 micron filter coming to run between the service ports to help clean the glycol. Hopefully this will resolve the remaining issue...Here are some pics of the install....

Before with (1) pump....





After with (2) pumps supplying pressure to the boiler...





40 PSI Supply pressure after installing (2) pumps.

Forgot to mention...The three Taco pumps you see pictured run on about 6 amps total @ 120v. 2 Amps each.....This is a significant savings compared to the pump that was on the old boiler. 10 amps @ 220v...Another feature I liked about the Taco pumps, is if they ever go bad, you take it apart and replace a cartridge that contains the bearings and has the impeller attached. Takes less than 5 minutes to take apart and put back together. Plus the housing stays inline, one less thing to worry about...Two Thumbs up on the Taco pumps...

Well, I am very interested in seeing how this works out for you this winter. Please keep the updates coming. Depending on how it works out, maybe we can convince the moderator to put this up as a "sticky".

Thanks for all the information.

I'll definetly keep you posted. Testing it @ 40° temps outside yielded:

Boiler set point 140°;
Temps out to bays 110°;
Return Temps 70°-80°

Didn't take too long to get the return temps to 70°. So given this data, looks like it shouldn't be too hard to keep slab temps above freezing even down to 0°...We'll see....

2Biz said:

I'll definetly keep you posted. Testing it @ 40° temps outside yielded:

Boiler set point 140°;
Temps out to bays 110°;
Return Temps 70°-80°

Didn't take too long to get the return temps to 70°. So given this data, looks like it shouldn't be too hard to keep slab temps above freezing even down to 0°...We'll see....

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What are you using to control the pumps and on-demand heater? What are you using the sense the return lines? Are you actually measuring fluid temp or are you attaching a sensor to the outside of the return line?

The Takagi is basically on and in standby as long as there is no flow to the heater. I have a relay set up to control the pumps off the secondary output of the weepmizer. At the weepmizer set point, the relay latches in and starts all three pumps, which in turn starts the boiler. The boiler is pressure activated. I installed an Aquastat that monitors the return line temp..No strap on, its the bulb/well type. To test, I have the Aquastat set at 80° with a 20° temperature differential. When the return temps reaches 80°, it kicks off the two supply pumps to the boiler...The zone pump keeps running. Once the return temps reach 60°, the boiler pumps kick back on to complete the cycle...

Be sure to use the outdoor reset feature on the tankless if it has one. I used my HTP Boiler for the first few weeks without the reset hooked up and wasted a bit of fuel. Basically what the outdoor reset does is change the boiler set temp based on the outside temp, IE: as it gets colder the boiler temp rises to meet demand only. When it is 30* my boiler set temp is pretty low at 85* but goes up to 115* as it gets down to 0*.
BTW: I have my boiler setup so that it basically runs 24/7 if it is below freezing so that it is not cycling on/off. The boiler runs less efficiently when it is turning on/off several times an hour. My 399,999 BTU boiler typically runs at about 38% capacity (151,999 BTU).

Mine doesn't have the outdoor reset feature. What it does have is a computer board that modulates the flow and burner (BTU Output) based on incoming water temperature and the user adjustable output temperature. Once I get a handle on what preset temperature it takes to keep the bays from freezing over, I'll be able to leave it at that temperature and the control board will modulate the burner and flow to to run as economical as it can...The colder it gets the bigger spread there will be between the temperatures of the incoming and outgoing glycol. The boiler will then step up BTU output to keep up with the colder temps coming in. Once the outside temps rise, the Takagi will automatically back off on the BTU output based on the rising incoming temps. Basically it does the same thing as yours only in a different way.

How many bays are you heating on 152K BTU? I have 4 bays and about 1600 sq ft....

BTW, at what outside air temp do you have your boiler set to come on. Right now I have both the boiler and heat tape in the trough set to come on at 35° from output 2 on the weepmizer. I'm thinking this is a little high and could come down a few degrees...

2Biz Thank you for coming back and giving an update on your project, most posters don't come back and give an update.You did nice clean install, everything looks good. Keep up the good work and thanks again for the update.

Thanks for the compliment! Without the help, knowledge, and willingness of the members here on the forum helping others, I definitely wouldn't be where I'm at today in this business. Just trying to payback and pay it forward.

Looks great! How much $$$ do you think you have tied up in this? I need to do something about my older wash. Last winter was mild and I kept my old system limping along. Not sure I will be so lucky this year. Bill P. has posted multiple times about an open system he used but I never quite understood it enough to attempt it.

2Biz said:

Mine doesn't have the outdoor reset feature. What it does have is a computer board that modulates the flow and burner (BTU Output) based on incoming water temperature and the user adjustable output temperature. Once I get a handle on what preset temperature it takes to keep the bays from freezing over, I'll be able to leave it at that temperature and the control board will modulate the burner and flow to to run as economical as it can...The colder it gets the bigger spread there will be between the temperatures of the incoming and outgoing glycol. The boiler will then step up BTU output to keep up with the colder temps coming in. Once the outside temps rise, the Takagi will automatically back off on the BTU output based on the rising incoming temps. Basically it does the same thing as yours only in a different way.

How many bays are you heating on 152K BTU? I have 4 bays and about 1600 sq ft....

BTW, at what outside air temp do you have your boiler set to come on. Right now I have both the boiler and heat tape in the trough set to come on at 35° from output 2 on the weepmizer. I'm thinking this is a little high and could come down a few degrees...

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It is a 4 bay (nearly 2000 sqft with aprons) but the boiler is sized for 2 more bays for when I can add 2 inbays.
I have the boiler set to come on at 33*. I figure that the temp drops slowly enough that there is no way that ice will be able to form in the +/- 15 minutes it takes for the floor to come up to temp.

Buzzie8 said:

Looks great! How much $$$ do you think you have tied up in this? I need to do something about my older wash. Last winter was mild and I kept my old system limping along. Not sure I will be so lucky this year. Bill P. has posted multiple times about an open system he used but I never quite understood it enough to attempt it.

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If it wasn't for the fact I bought undersized pumps to start with, I would have had about $3500.00 in it. When you do your calculations, study the flow chart graghs of the boiler/demand heater and also of the pumps and make sure you order the right size. There is also an allowance that needs figured depending on the percentage of glycol your using in the system. It in itself adds head pressure. I used Noburst mixed @ 35% which will get me freeze protection down to 0°, flow protection down to -10°, and burst protection down to -60°....The glycol alone was $350.00....Expensive stuff....

If you factor in that I got $310.00 for the copper that was in the old boiler, the complete system cost about $3200.00...

Eric H said:

It is a 4 bay (nearly 2000 sqft with aprons) but the boiler is sized for 2 more bays for when I can add 2 inbays.
I have the boiler set to come on at 33*. I figure that the temp drops slowly enough that there is no way that ice will be able to form in the +/- 15 minutes it takes for the floor to come up to temp.

Click to expand...

I was thinking the same thing. Even the heat tape in the trough doesn't need to come on at anything higher than 32-33°. I've ran my weep alone down to 20° with no heat in the trough and didn't get freezeups. This was before having the heat tape installed. The trough was previously heated with a loop from the boiler.