Will a Tankless Water Heater Work for Radiant Floor Heat? Pros & Cons
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- Опубликовано: 15 фев 2020
- Will a Tankless water heater work for Radiant Floor system? Are they reliable and will they last? This video explains my experience with a Tankless Water Heater heating a 3200 sq ft building with 12 ft sidewalls , 4700 ft of 1/2" pex in the COLD Minnesota weather. Find out if it will work!!
My heater is a Takagi T-H3M 120,000 BTU Condensing Modulating Tankless Water Heater. I overpaid for a rebranded one by 40% so hopefully this will let you not make the same mistake I did! I am no way compensated by Takagi for this, it is my experience so far with this heater.
Pole Barn Garage/Shop is 3200 Sq Ft with 12' interior height. I have it set at 57 degrees inside for both zones. Zone 1 has about 3500 ft of 1/2" Pex. Zone 2 has about 1200 ft of 1/2 Pex. Running 1/2 GPM in most loops ( Loops by wall run .75 GPM as more heat loss) 
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Its funny, I have two tankless WH's - a Takagi for domestic water, a Rinnai for hydronic (7 cast iron radiators, 1200 sq. ft home). The cost of both tankless heaters was still less than half of the Navien combi our HVAC guy recommended.
Been running the Rinnai for almost 3 years with no issues. I think people run into reliability issues because of lack of proper maintenance.
As you said, you run into periodically to make sure things dont get gummed up. I do the same, I also have a Magnaclean filter for the main loop and individual WYE strainers for each loop. Knock on wood, no problems so far. In fact, my system has been more reliable than a neighbors high-dollar Navien boiler.
Jason, Good video. I couldn't tell how many pumps you are using for the 3,200 sf floor with 12 loops. I am planning 12 loops for a floor of 3,000 sf with one zone, so I wonder how many pumps I will need. Just one? Thanks in advance.
Hi Jason, Very interesting video and timely for me as I'm looking to put in a radiant floor system unit in our off-grid pole barn/house. A couple questions. Do you have a system diagram and a component list of the items you used for your hydronic heating system? like check valves, pumps, seperators, expansion tank (everything on the wall). Also did you say you have a pump per zone for your system? Are you combining loops into a zone that's dedicated to a circulation pump? Very interesting subject and video and thanks for your help!
This setup is using zone by pumps as my one loop/zone has around 3200 sq ft of tubing . My other one has 1200 ft of tubing. For smaller applications , you could use 1 manifold and zone valves and have it zoned by valves. So I have 2 zones for 2 different areas , one for big garage part and 1 for my shop part. So I have 2 zone pumps and 1 main boiler pump. I think I will do a video breakdown of the parts required to make main boiler panel and then to make the zone panels. Might take me a week to do but future video
Just got that video up of my component list
Using a TK3 is pretty impressive for heating a slab. I'm gong to use one for Baseboards in a 600 sq/ft addition. I already have a TK Jr for 2 baths and it works great.
I was surprised that it heats all that glycol in the 4700 ft of tubing , and can heat the building in -20 degree weather easily. Been 3 years and still working great
Great video , thank you . Curious how much heating your 3200 sf space with the tankless Heater costs on average during the cold months? We are going to be setting up a similar system with approx. same square feet.
I have some videos showing the heating costs, but roughly around $550 a season in Minnesota. This year is more due to the extra charge for the "Feb 2021 Weather Event" . That is the charge that they list for the Texas mess.
Will check out the other videos , thank you.
Jason, I am running a tankless for my radiant floors in Detroit MI. What I am finding is is running full time. Will this be very hard on the tankless? I am worried because it is constantly firing. There is still more work to do to button up the house and I know it will work better if I finish the insulation and such. Do you have thoughts on the constant running? Thank you!
You either don't have enough tubing for your sq footage or your building has too many leaks or not enough r value. You should take an IR thermometer and check your slab temperature or floor temp. That will show you if its your tubing or your above insulation not doing its job. Slab temp should be a few degrees higher then your air temp inside . I am working on a video on how to troubleshoot problems like yours and some solutions.
Thanks for the post. I have about 1,800 sq ft. , single zone, pex is in, all runs are of equal length, but haven’t decided on heating source but have seriously considered a tankless heater.
Hope did you handle your balancing? I understand that if runs are of equal length and single zone that valving/balancing isn’t necessary. Any thoughts?
Your manifolds have balancing valves built in. But if your runs are close in length, then only the first couple balancing valves usually need to be adjusted. Pretty simple to do
Hi Jason,
THANKS for the video! Do you heat with propane, natural gas or electric, with your tankless?
Natural gas, electricity to expensive. Once ng hits $1.35 per therm then electricity is cheaper
The tankless companies will reduce the heat exchanger warranty to 3 years if it is being used as a boiler due to more wear and tear running continuously in heating season. The water moves slower thru the tankless water heater than the boiler and the tankless is designed for large temperature swings not small differences like 20 degrees. Turn down ratio is 15:1 on the boiler....tankless can not do that = less control
I just talked with Takagi Technical Support about a warranty and they say to use Gycol voids warranty. Only potable water. Not sure if you have knew this. I have found many older owners' manuals saying its fine with closed-loop systems
I think they got some heat from lawyers or the boiler association and so omitted the closed loop radiant heating in the new ones. Since I purchased this when the manual stated it was ok, they can't refuse any warranty work on older units. I personally would purchase another one and just give up warranty as mine has been running fine. You could buy 3-4 of these for the price of a boiler, so it's up to each person as long as they know the facts. Thanks for the information to let others know.
What fluid are you running through the boiler and pex? Just water? Or water with antifreeze?
I am running cryo tek 100 antifreeze mixture . Has corrosion inhibitors since in a closed loop could get rust/ minerals even from purified demineralized water. Also if pure water freezes at 32 , your pipes in ground may not freeze or get hurt, but anything above ground may break. Tankless water heater, pumps. Pipes, etc. Thanks for watching
When did you switch from a boiler to a tankless? Also, what part of Mn? I'm between Brainerd and St Cloud.
I always had a tankless and am located in Anoka County, so north suburbs
Condensing water heater? Hmm.. Will the Delta be too small on a small system? I have a 400sf kitchen with 300’ of pipe in the slab. Thoughts?
You should be able to run a lower output temp to heat that area and still get good results, just make sure its a modulating condensing unit. That's assuming correct insulation in your building. Thanks for watching
what kind of breaker system do you have for the electric is this for floor heating only or do you have a separate system for you water
The water heater is ng but I have a 50 amp breaker about 25ft from it in case gas becomes too expensive. This is only for in floor heating
I just bought a house that was vacant for 7 years and it had hydronic heating. While it was vacated people stole everything including the copper out of the attic. I have fixed the electrical but the hydronic heating system is intimidating to me. 14 pex runs in and out of the slab, as far as I can tell there is going to be 3 channels but with check valves, pressure sensors, solenoids, air eliminators, temp sensors and controllers, it is a bit overwhelming when you have never done this before. any suggestions as far as study materials or maybe a contractor that can lend a hand near Spokane WA?
Just search for 3 zone panels ( I believe that is the 3 channels your talking about) and see how they do it. You can have zones by pump or valves. So if your heating multiple rooms, you could have a thermostat opening the pex run ( or multiples) and still use 1 pump for the 14 runs. ( Zoned by valves) Basically you would be shutting off that flow to the pex runs in that room. Its not that difficult once you understand the basics , and then you would just reverse engineer the manufactures panel by looking at pictures and save $200-$400 per panel. Just google zone by pumps, or zone by valves and you wouldn't need a contractor if your handy at sweating copper as some of the shutoffs need to be sweated / soldered
The efficiency quoted is based on cold water inlet You cant get condensing heat unless the return water is quite cool Unlikely in a radiant heat application unless you install with a big buffer tank
This condensates at about a 5 gal bucket of water over 8 hours. So it is extracting it from the exhaust pvc pipe
My inlet temp to water heater usually starts at around 64 degrees and once its fully operational it is around 78 degrees . It never gets above 82 degrees for cold water inlet , as the building gets up to temp before it gets that hot. Maybe on higher temp systems will not get those effiency ratings but on a low temp radiant system it can come close
Jason,
This was really helpful.
Just purchased T-H3M-DV-P for my new 2000 SF Morton Building in SD.
Can you tell me the spec on your vent and where you purchased it?
Thanks!
It is called a concentric vent kit , comes in 3 or 4 inch depending on what your manual says. Just uses PVC as the Modulating / condensing water heaters extract all heat out of exhaust to be efficient . I was going to order it online or go to Home depot, but my local heating / ac store actually beat any price. Call up a local heating /ac store and they may actually sell you one cheaper even without an account.
Thanks Jason...and thanks again for the video!
I'm assuming you're using it for a radiant floor heating?
If it vents with stainless steel pipe, that can cost as much as the unit depending on how far you have to run it. I'd recommend a unit that vents with PVC if you have to run it a long way.
If you buy a condensing water heater , that will only use PVC pipe as it extracts most heat out of exhaust , so you can use PVC. Add in a modulating feature, and it will vary temperature to what is needed to save on fuel costs. Been happy with mine and happier with my gas bills! Thanks for watching
@@JasonRUclips which do you have a video talking about the gas, do you hear woth propane or natural gas and how many gallons do you use a season?
@@cmiller8006 I use natural gas and the meter reads 1915 cu ft and installed in 2018. I have videos on my gas usage during winter months , if you want to see the breakdown. I am located in MN and keep it heated to 58 degrees .
Is your system Natural gas or Propane? I would need a propane version of this boiler if they make one.
Mines natural gas but they do make propane version, just instead of an "N" at the end put a "P" and should pull it up
Nice video and a great install, however I don't know why you didn't go for the max 199,000 BTU tankless. For a building that size and in that climate I can't understand why you didn't!
I didn't have no reference so I had a company who designs thermal mass radiant heat systems provide the items for me , and they gave me that size. It works great and I have never had a problem with it not being able to keep up , even when it is -30 outside! Knowing what I know now , going bigger would probably be better as long as it has same gas consumption per hour . So like if mine runs 4 hrs now, the bigger one uses 2x more gas but runs for only 2 hrs , then they are the same. Don't want to spend more on gas for same output since if they both heat the same amount of water , the pumps can only pump x amount of water through tubes , so doesn't matter if its a bigger unit or not. If that makes sense? Mine will actually throttle down when the water temp is at the preset amount as it modulates , so its not overworked or undersized.
Hi, I have radiant heating system at my house and I need to replace the boiler. How much does the cost you think the labor for replacement the boiler. Thank you.
It all depends on your location , but probably around 4 hrs of labor. So labor rates vary, but between $75-$120 and hour is going rate. You need to call around and check the rate quotes in your area.
@@JasonRUclips I am located at St.Louis. Please, let me know if you have anybody around St.Louis.
@@baikseyoung1489You would have to contact a plumbing company or HVAC company in your area.
Thanks for showing us this Jason. One question. How are you regulating the output temperature to 88 degrees? Are you using a mixing valve or is the heater simply set to this temperature?
The system uses hydraulic separation so the panel has a boiler pump and each zone has its own pump. So basically I just use the heater temperature to regulate the temp. Once you find the correct temp for your building size, it will not overshoot . Now if I know its going to be warm and I don't turn the temp down, then it will overshoot by a few degrees but who cares. When my smallest zone is on ( 1200 ft tubing) the temp will run about 100 degrees if I have it at 120 on heater. Once the bigger zone ( 3500 ft tubing) kicks on then the temp goes down . Just need to find the right setting for your building
@@JasonRUclips excellent, thanks!
I was reading the warranty and it says that it wont be covered under warranty if its not installed by a licensed plumber or contractor. if I install it myself i guess im not covered?
You will be covered but you must have receipts and everything must be up to code and installed properly. Its like doing your own brakes and oil changes on a new vehicle , you need to document everything and have receipts to be covered. By law , they cannot exclude you from warranty if you do it yourself. BUT if you didn't do something correct, then they could exclude you for that. That means having it inspected by city and getting a permit if required
Jason,
I just poured the concrete on my shop. It's 13x20 with 9 foot ceiling. Slab is fully insulated and I've only got one 250' 1/2" Pex loop in it. What size propane tankless heater should I use? Seems like it only needs to be like 16,000 btus from the calculations I found online. Finding a tankless that small is hard. Smallest I've found is 42,000 btus.
You need a modulating heater that will go down to 16k btu . They will be listed like at 42-70K BTU but will step down to whatever btus is needed. Google Modulating Tankless heaters and you should be able to find one.
did you find a hot water heater to work. I have a similar sized shop that is ready for a boiler/heater too.
Still happy with your tankless water heater? Enjoyed watching all of your barn/shed build. Just built a 2000sq' polebarn and about to buy the tankless water heater over the boiler.
Ya it works great, just make sure its also rated for radiant heat. I am running over 4700 ft of tubing in my building and still heats it. Thanks for watching
Could this heat up 3000 sq ft worth of radiant floor in four zones?
My shop is a 40x 80 so 3200 sq ft using a thermal mass build. So I'm using about 4700 ft of tubing! It keeps my building warm even when it is -30 below zero. You would need a couple of zones with pumps per zone . Thanks for watching
Easy way to control the temps is thermostat on the pump. When temp drops the pump activate which starts the water heater.
The systems have that as it is controlled by the zone relay box. Each pump has their own thermostat and tied into the zone relay .
I have a 200sf shop with tubes in the floor. I was hoping to use one of the $200 on demand boilers. Do you think that would work? I would wire the tstat to the circ pump.
Could you get me all the parts list you use? I am going to set up the heating system in my shop soon thanks
I did a video listing everything. It's called " BUild your own radiant heat panel" search my videos. Thanks for watching
What size is your plumbing from the heater to the panel?
It is 1 Inch pipe, if you watch my video " Build your own Radiant panel" it will list all the parts and what pipe I use. Offhand , I don't know if its the K or L copper pipe I used but in the video should list it. Thanks
@@JasonRUclips Thank you!
I was thinking on using one to heat and supply dhw on a 2000 sqft house, your thoughts?
You need a combi boiler / water heater . They run about 2K -4K as they keep the water separate for domestic drinking water from the in floor heat.
Brian - late response but ... I use a single Takagi 199k btu TH-3 for both domestic hot water and for 980 sq ft of underfloor heating on our ground (concrete slab) floor. We're using an Amtrol 26 gal. HW tank (with a heat exchanger coil in it) as a buffer tank and the heat exchanger to keep the underfloor loops complete isolated from potable hot water. The Amtrol tank usually has the heat exchanger connected to a boiler and that heats the water. We're using it in reverse .... the Tankless heater heats the water in the tank (via a 3.5 gpm recirc pump, or when there's hot water demand in the house). The recirc pump is controlled by the thermostat and controller that is part of the Amtrol tank (for which we paid $650 when we installed in in 2006).
This setup is part of the Takagi Tankless heater "recommended configuration" documentation, where it is documented in detail. It reduces the cycling of the Tankless heater because the Amtrol buffer tank has 137 deg water, which creates 100-105 deg input to the radiant floors. The tank water temp slowly drops as the radiant floor pumps water through the zone loops cool it. When water in the tank reaches 123 deg. , the recirc pump kicks in and the tankless heater heats the tank back up to 137. (yes, the tankless output temp is set at 158 deg to accomplish this). Any call for domestic HW fires the tankless heater to replenish HW drawn from the Amtrol buffer tank.
Domestic HW temp is regulated by a mixing valve.
We've had this setup since mid 2006. Works great. First Takagi unit lasted 14.5 years. New unit cost $1100, simple replacement. Domestic HW and underfloor heat costs us under $30/mo in gas on average.
@@WakeUpAmerican000s What part of the US are you in? Curious, b/c of the low $30/mo (natural gas?). In NEK VT we spend a *lot* more in the winter with a Polaris 34G open system.
Jason,
Did you run Glycol through the system? or just water?
Eric
I ran Cyro tek 100 mixture and I went with a -40 burst , like around 65/35 . If someone has this system then they are using it for heat , then they should run glycol , since they are probably in a colder climate. Why take a chance with a water only mixture when adding glycol will prevent any problems. If the natural gas supply stops or electrical outage , then the system could freeze above ground. The ground pex will probably stay above freezing , but anything above ground will freeze. Just easy insurance and it doesn't affect the operation of the unit. Thanks for watching!
in a 50% solution ethylene glycol's specific heat capacity compared with pure water is decreased at least 20% at 36 degrees.
Jason, I'm just about to do this in our home with our Rinnai tankless that also runs our domestic water supply. I have two questions for you. Do you have any concerns about impact of frequently cycling a tankless? I actually expect this more on the domestic draw for us, for example turning a sink on and off several times while doing dishes. My second question is, when the hot water comes back to the tankless on it's return journey through the slab (or underfloor) is it cold enough to trigger the Tankless to continue heating? I could imagine some scenario where water leaves the tankless at 130F and returns at 110F and the Tankless may have trouble do such a small amount of heating. However, maybe this is never the case. Curious about your thoughts. Thanks! I'll look for your other videos :)
You would have to get a combi tankless water heater and there should be no problems. Can't use a regular tankless for domestic and heating
In slab heating , you want a small delta T. So a 20 degree difference in temp is ideal and a tankless will have no problem turning on. You want a modulating condensing water heater is it applies different amount of heat . If its hot coming back, it scales the flames down. If its colder, it gives it more heat. Saves gas
Just came across this video so I know it’s starting the conversation back up, but your unit supplies heat to the domestic first and then to your floor. Cycling doesn’t matter at all, it’s made to cycle regularly.
@@123gonow Thanks for the input. That makes sense. I'm glad to hear these tankless units are happy to be cycling all the time :). Coming from things like well-pumps I think of rapid cycling as a no-no, but not here!
How many gpm pump are you running?
They are Grundfos UPS15-58 pumps so 17 GPM . I run 1/2 GPM to loops and the boiler pump runs 4.5 GPM to water heater. I run mine on low to medium speed . I have a breakdown of system in my 1 video. Thanks for watching
Will they honor that warranty if they see it has been used outside of its use case? A boiler runs a lot more than a water heater.
In the instructions for this brand, they state that it can be used for radiant heat . Some brands may not state that , so they might not honor it. But they might as radiant heat is only for 6 months where water heating is everyday. Also with radiant , it usually will run steady and that means less wear/tear . Water heating is constant on/off multiple times so the gas solenoids/valves will wear quicker .
@@JasonRUclips Thank you for a great reply. We have a 200k BTU Navien that I'm thinking of running a radiant system with. Great info.
Eric - Takagi currently will warrant their tankless unit as long as the on/off cycles don't exceed 300 per month. My setup uses a 26 gal buffer tank with a heat exchanger, so the tankless heater does not cycle or run continuously when the radiant system calls for heat.
I've done all installation & maintenance work on the Tankless heater myself. Takagi tech support and tech documentation is good. Parts come from So. California. I installed our first Takagi unit in 2006. It lasted 14.5 years supplying both domestic HW for our family of four, and radiant heat for 980 sq ft ground floor. Yes, I had to replace some parts along the way, so yes, we were without hot water for a few days during that 14.5 year period while waiting for parts to arrive.
Does it heat your bath water also?
If you want to heat both, then you need a Combi Boiler.
You'll need a buffer tank with a heat-exchanger if you want both domestic HW and radiant heat from the same Tankless heater unit. We paid $650 for the Amtrol 26 gallon hot water tank back in 2006. It buffers hot water delivery to the house, the 26 gal provides heat to the coil embedded in the tank (part of the radiant system closed loop). Detailed diagrams of the setup was part of the Takagi recommended use-cases documentation. This setup uses the Amtrol HW tank "in reverse" of how it is usually used with a boiler feeding the embedded coils to heat the water in the tank.
What is that coming out of it?
Please tell me what your referencing, as the white lower pipe is for condensation/ water. The white upper pvc is for air intake and exhaust
It uses propane?
This one uses natural gas, you can get it for propane though
Wow, where did you buy it for that price? Its $2700 on amazon
The Hot water heater is a Takagi T-H3M-DV-P , which supplyhouse has for a lot less
Wait a minute. A tankless is cheaper than a condensing boiler?
Yes a Tankless condensing water heater is around $800 compared to $2300 plus. Make sure tankless says its suitable for space heating in manual
Why is it saying in the directions that this unit isn't suitable for radiant heat only applications?
They changed it because I think other manufacturers were complaining and also about maintenance problems , as my unit and even looking online at supply house still lists it as space heating applications. I believe also during the off season, people let it sit for 6 months without running so that can gunk it up and cause problems. I run my unit once every 3 weeks to keep everything working.
@@JasonRUclips what pump controller are you using?
I got a price today on a boiler for 3950.00 I’m not spending that! Lol , I have a cabin just North of Iron Mountain, MI in the U.P. Of Michigan. Looking for ways to save on my heating.
@@tomquick2594 If you watch my video on " Build your own radiant heat panel" I list all the parts , I would have to look but its a name brand one.
@@tomquick2594 Ya the water heaters run about $800-$1000
I'm heating 1200 sq feet. Building one for my house
Radiant heat is the only way to go , if I ever built a home I would build it with radiant. You won't be sorry doing yours. Good Luck and thanks for watching
Jason Hello. You’re video has inspired me as a creative solution for heating floors. I have a few questions. Context: I’m trying to turn a school bus into a mobile home for no more than $15K. It’s called the Schoolie movement and many 20 year olds like me are members. My bus plans include 2000 watts of solar panels on the roof with 2000 gallons of drinkable water storage in the bus undercarriage.
Your creative Idea to radiant floors got me thinking, could I use a tankless water heater to radiant heat my floors hydronically?
I don’t know if the electric wire version of radiant heating is feasible because it would eat up my electricity storage.
Do you think a solar water heater would be a good idea to help a radiant floor system too?
Since you’ve already done radiant heating. Figured I’d ask.
@@DylanBegazo A school bus wouldn't be ideal for energy storage. You could use it for like baseboard heaters with radiant, but your still burning NG/ Propane so you would be better off using like a Ice Fish House heating system. It wouldn't work that good and would cost more then just using a Vent free/ Vented furnace
Jason interesting. Is NG/propane the only way that you’ve found or can I use my solar charged batteries instead? I’m writing down what you said so far.
@@DylanBegazo Put it this way, a space heater is about 1500W and will heat about 150-200 sq ft of really good insulated area. (Avg about 130 sq ft) Now your inverter needs to be at least 3000w and depending on your battery storage and Amp hour it adds up to not being economical or practical. NG per 100,000 BTUs runs about 55 cents ( Per Therm) Electricity to put out 100,000 BTU would need 30 KW @ $.12 per kilowatt. (Now if your off peak, it could get down to $ .04) So you would be looking at $3.60 compared to $.55 cents per therm standard rates. Cost of gas is actually like .33 but they add delivery cost for pipeline. You may get cheaper as your not paying for gas lines only your storage tank. You could try working like a solar water heater and pumping that through baseboard heat exchangers but probably wouldn't be reliable and weight of water
That is a condensing water heater but I don't see a drain tube. Am I just not seeing it or??
If you look behind the copper pipe , you will see a 1/2" PVC that runs into the slab. It blends into the white wall pretty good
Can't hear a thing you are saying.