My radiant heat setup, running off a 40 gal water heater

[maxspeed96ct]

Its been up and running for about a week now and Im loving it.

I have the temp set at 60 right now , and honestly it feels warmer due to the nice even heat and the way it heats everything.

Details
-40 gal natural gas water heater (36,000 btu) , set at about 115deg
-25x24 attatched garage with 2 ~300ft loops of 1/2 pex.
-007 circulator
-manifold from pex supply
-Taco switching relay running off a wall mounted t-stat

The water heater is doing a great job, it barley runs and we've had temps in the teens the past couple of days.

I'll update with the running cost next month when my bill comes.

 

[Fastback]

That's cool, I love DIY systems!

 

[CNGsaves]

Nice setup.

What part of country? What are current outside temperatures?

What's your total invested in system, with details?

 

[vartz04]

Dad did the same thing at his house for the garage and basement. Still working great 5 years later.

 

[socapots]

Very nice.
That water heater is also for water to the house?

 

[rburke65]

Alaska....Hawaii.......it would help us to know?!

 

[maxspeed96ct]

I'm located in Connecticut , the water heater is additional to my normal house water heater . I wanted to keep the pressure down and keep the systems separate .

As far as costs , the most expensive part of the project was the 2" under slab insulation . It kind of shocked me actually I didn't realize how expensive it was.

Now the piping and valves and such can get expensive but you don't have to go as crazy as I did , I just got mine as alittle barter deal from a freind and some stuff I had since I work in the hvac trade .

The pex tubing price I don't remember but it wasn't much , water heater was about $350, 007 pump was about $75, manifold was $100 and zone valve relay was just over $100 , but you could save a few bucks and just use a 120v Tstat if you wanted .

 

[jlckmj]

Nice!

Looks like an addition or expansion onto the older garage?

You should do a write up on the whole thing, there are always people on the board that are looking to add onto their garage and don't know where to start.

Jim

 

[maxspeed96ct]

Nice!

Looks like an addition or expansion onto the older garage?

You should do a write up on the whole thing, there are always people on the board that are looking to add onto their garage and don't know where to start.

Jim

I have alittle thread in the gallery section , it started off as a single car port .

http://www.garagejournal.com/forum/showthread.php?p=2877746&posted=1#post2877746

 

[CNGsaves]

Finished reading your whole thread on garage build-out and this garage floor radiant heat is Excellent since the tubes go directly into basement where you've got additional NG hot water tank. Both the garage and radiant floor turned out GREAT!

For new construction of houses with attached garages, this would be great setup to ALWAYS be stubbed into the basement - - - most especially in cold weather states.

Curious how your floor has handled the runoff of snow melt when you bring vehicles into the garage? Is everything draining/running like you wanted?

 

[maxspeed96ct]

Finished reading your whole thread on garage build-out and this garage floor radiant heat is Excellent since the tubes go directly into basement where you've got additional NG hot water tank. Both the garage and radiant floor turned out GREAT!

For new construction of houses with attached garages, this would be great setup to ALWAYS be stubbed into the basement - - - most especially in cold weather states.

Curious how your floor has handled the runoff of snow melt when you bring vehicles into the garage? Is everything draining/running like you wanted?

My concrete guys did a good job pitching the floor , there's one spot where some water puddles next to the chimney but it dried qwk , only thing I didn't like was the moisture on the widows an garage doors . I may get a dehumidifier to run on days the cars have snow on them. But ill see how bad it gets .

 

[moonlight_ken]

Am i clear on the fact that you used a standard run of the mill water heater?

 

[maxspeed96ct]

Am i clear on the fact that you used a standard run of the mill water heater?

yup normal home depot 40 gal.

Also I forgot the mention its fed with your typical boiler auto feeder set at about 20 psi and a backflow preventer.

 

[maxspeed96ct]

Just figured I'd update the thread. My heating costs here in CT to keep the garage at 64 degrees F were about $25-30 a month using natural gas. Towards the end of the winter season I turned it down to 62 because 64 felt like 67 with the nice even radiant heat.

Only negative to heating a garage, is the humidity is terrible if the cars are wet or worse have snow on them . I think I will have to run a small Dehumidifier next winter if dropping the temp down doesn't help the issue.

 

[BadgerBoilerMN]

Humidity for lack of ventilation, look for your vehicle exhaust rusting out. Dehumidifier will help but will create heat and shut down the radiant floor a good part the season while burning expensive electricity.

A humidistat on a small bath fan may be the answer.

Most atmospheric water heaters will not last when direct piped and run at low temperature.

Need a flow check?

Need an potable water expansion tank?

 

[tylernt]

Most atmospheric water heaters will not last when direct piped and run at low temperature.

You've got me worried now... no radiant heat, but I have an natural draft water heater and a recirc pump on my house. What about it kills the water heater? Just that it runs so frequently when used for radiant?

 

[Highbeam]

There's a lot of steam in the exhaust of a gas water heater. Steam is a product of combustion like the steam from the exhaust of a car in the winter. That steamy exhaust can condense on the cold inside of a low temp water heater. That condensed steam will be highly corrosive and the inside of the water heater is steel which will rust and flake and drop chunks down into the burner area.

Plus, that natural draft gas water heater is only like 60% efficient.

 

[BadgerBoilerMN]

Highbeam has it. You must install a proper mixing valve. Single temp is fine, though most run them much hotter than necessary, but the water heat should be kept at 140°F plus, or sustained flue gas condensate will kill it.

I have atmospheric water heaters running for 20+ years on baseboard and fan coils and 15 plus on radiant floors but the water heater runs hot. Not cheap, but hot.

If you want cheap fuel bills, you buy condensing water heaters. Small jobs won't warrant the investment unless you are using a combi water heater for living space and DHW.

 

[tylernt]

Maybe this flue gas condensate thing depends on local climate? I'm in a semi-arid region and atmospheric water heaters here last for decades at 120°F and then die of mechanical malfunction, maybe because there's not much humidity in the air to begin with.

 

[CNGsaves]

That's great setup OP to have toasty garage in mid 60's, and super affordable since you're using natural gas.

Might just need a big fan on a timer for the humidity issues, or combination with a de-humidifier.

So is this closed system with normal water?? Pressure come from city water applying pressure through the back-flow valve?? Do you "bleed off" / use some of the water to keep it fresh??

Anything you would do differently now that you've gone through a winter??

 

[maxspeed96ct]

Humidity for lack of ventilation, look for your vehicle exhaust rusting out. Dehumidifier will help but will create heat and shut down the radiant floor a good part the season while burning expensive electricity.

A humidistat on a small bath fan may be the answer.

Most atmospheric water heaters will not last when direct piped and run at low temperature.

Need a flow check?

Need an potable water expansion tank?

I'm just going to turn the space temp down even lower to see of that helps first , I had it set in the low 60s . And when we pull our car in everyday it would realy spike ( 200 degree car engine does raidiant alot when already in a warm space)


I have a flow check in the system , aswell as a expansion tank .

The water heater will condensate as much everyone thinks . But i can also turn the temp up alittle without hurting anything, I don't think it has to be se as high a 140 . 90% of residential water heaters run without a mixing valve and last just fine .


The one thing I would do different after going through one winter , is I would not have installed vapor barrier in the space . Should have just insulate and been done with it .

 

[BadgerBoilerMN]

The lower the water temperature the more the condensate.

Nearly 100% of tank-type water heaters run without a mixing valve, 10 years on average. Of course they are not generally being used as boilers. We design many combi DHW/space heating systems, all have mixing valves, none with checks or potable water expansion tanks.

 

[milnerpt]

Why are you regretting putting the vapor barrier down before the insulation? Just because of the hassle?

I wouldnt think that it would be contributing to your humidity issues... in fact, the only thing it would do is assist by preventing additional moisture from coming up from beneath the slab?

coming from a new inquiring mind trying to figure out his own radiant floor project.....

 

[maxspeed96ct]

The lower the water temperature the more the condensate.

Nearly 100% of tank-type water heaters run without a mixing valve, 10 years on average. Of course they are not generally being used as boilers. We design many combi DHW/space heating systems, all have mixing valves, none with checks or potable water expansion tanks.

One thing you need to consider is this is a closed loop system , I'm not letting fresh oxygen into the system as you into a normal water heater .
Oxygen is the enemy and contributes significantly to anode rod rot and tank failure.


I'm confident I'll get at least 10 years out of this tank.

Why are you regretting putting the vapor barrier down before the insulation? Just because of the hassle?

I wouldnt think that it would be contributing to your humidity issues... in fact, the only thing it would do is assist by preventing additional moisture from coming up from beneath the slab?

coming from a new inquiring mind trying to figure out his own radiant floor project.....

It traps all the moisture , for example if I pull a car into the warm garage after its been driven through rain in the winter. It turns the garage into a green house / sauna .

 

[Fun pain]

yep the only drying effect you have right now, is the cars.... Vapor barrier in every garage I have done, has either took it out or installed an air handler/exhaust fan/ etc, to exchange the air with dryer outside air. Your bring moisture in and no way to get it out.... I vote for a couple 100cfm bath fans with humidistat, cause yours is pretty much a running garage.

 

[maxspeed96ct]

yep the only drying effect you have right now, is the cars.... Vapor barrier in every garage I have done, has either took it out or installed an air handler/exhaust fan/ etc, to exchange the air with dryer outside air. Your bring moisture in and no way to get it out.... I vote for a couple 100cfm bath fans with humidistat, cause yours is pretty much a running garage.

Thanks I'm going to look into it, I may try running a humidifier on the rainy / snowy days if I don't get anything permanent by the winter. I know it will run my bill up a little but will it actually even help ?

 

[milnerpt]

Makes sense with the cars. Im slowly researching finishing out a 9 ft crawl space with a radiant floating slab.... but am definitely going to get the barrier in there.... no wet cars to worry about, and lots of moisture surrounding I want to keep out....

regarding your water tank crapping out because of oxygen.... with your closed system you are running O2 barrier PEX?

If O2 is so problematic with water heaters, why do they run regular PEX with my plumbing and my DHWH? Isnt the O2 diffusing into the PEX running throughout the home?

 

[maxspeed96ct]

Makes sense with the cars. Im slowly researching finishing out a 9 ft crawl space with a radiant floating slab.... but am definitely going to get the barrier in there.... no wet cars to worry about, and lots of moisture surrounding I want to keep out....

regarding your water tank crapping out because of oxygen.... with your closed system you are running O2 barrier PEX?

If O2 is so problematic with water heaters, why do they run regular PEX with my plumbing and my DHWH? Isnt the O2 diffusing into the PEX running throughout the home?

I would highly recommend just skipping the barrier . And let the humidity work its way out . Otherwise you'll end up in my shoes add fans and etc .

o2 is problematic in heating systems , that's why they have special heat barrier pex . There's no reason to have it on your regular water heater since your letting fresh water and oxygen on a regular basis . Since my unit is used as space heater vs a normal potable water heater it should last a little longer .

This will work and last even at the lower temp setting , as long as your btu's are enough for the space . Guys that do radiant installs for profit won't tell you it will because they would rather sell you a $2500 boiler since they can mark it up a few hundred and make money before even stepping into your house .