Radiant Heat / Hot water

[Tyrol67]

Planning on installing a Takagi JR tankless water heater for in slab radiant heating. It sure would be great to get hot water for washing equipment out of the same system, but I plan to keep anti freeze in there for the heating system. So, I have two thoughts. 1. Disconnect the heating system for the summer and use the heater for hot water only or 2.) Is there some type of heat exchanger set up that would work where the ant-freeze solution would be heated by the heater and provide heat to the heat exchanger. I am thinking that solution 2 gets a bit complicated. Can the heat exchanger truly provide instant hot water, can it handle the thermal shock, etc. Since I won't necessarily be in the garage routinely, I don't want to risk running without anti freeze. I also realize that mixing propylene glycol with regular water is not advised, though I don't plan on drinking it
Has anyone had any success with any setups?

 

[Ezzie]

There are hydronic boilers for just this application. I selected a Triangle Tube model - the Prestige Excellence 110 (PE110). It's available for either propane or natural gas and has an internal 14 gal. tank for a domestic hot water circuit - more than enough for most shop uses. The floor circuit is totally isolated from it and even has a built in circulator to minimize the amount of external plumbing needed to connect to your floor. The AFUE is 95% so a very efficient boiler. More info here.

http://www.triangletube.com/PDF/Prestige Cond_Boiler/Excellence_Lit.pdf

 

[tdkkart]

Since I won't necessarily be in the garage routinely, I don't want to risk running without anti freeze.

One note here is that if you don't have intentions of heating the shop full time you may want to look into something other than in-floor radiant heat.

Think of your floor as a giant rock. If you bring it up to temp and hold it there maintaining that heat does not take alot of energy, however getting it up to temp takes ALOT of energy and considerable time.
Depending on the size of your heating system and the square footage of your building it could literally take days to raise the temperature after loosing the heat in the floor.

The heated portion of my shop is 16x30, well insulated and heated with a 40 gallon electric hot water heater. Last week I accidently shut the system off for approx. 24hrs. The outside temp was approx 30*, inside started at 60*.
In 24hrs the temp in the room dropped only 5*, however it took nearly 2 hrs to bring it back to temp after turning the system back on.
Conversely, in normal conditions when the thermostat calls for heat the system only runs 5-10 minutes to satisfy the thermostat.

 

[Tyrol67]

Thanks for replies.
Ezzie: The boiler would be great, but I'm looking to spend a bit less, therefore the Takagi. That boiler would be nice though!

Tdkkart: Understood on the radiant heat and thermal mass. I already have the tubes in the slab and couldn't resist having a warm floor. I'll need to find a reasonable standby temp and realize it won't get warmer fast. It should be a lot better than working out in the driveway though.

Looks like I'll may just need to switch the system over for summer.

 

[GerryL]

I'm doing a similiar project now. I have a 30x50 shop up; weathertight, tomorrow I start insulating. I already have the tubing in also. There's a lot of decisions on how to heat that water! I'm leaning towards trying the Tagaki JR also, although some companies tell me I'll need an extra pump or two over that required with a boiler, and the electrical costs add up. I'm not sure if they're just trying to sell boilers! The JR seems package appears to be available at a reasonable cost...
-Gerry

 

[Tyrol67]

Gerry, Not sure why they are calling for extra pumps. My shop is 26 x36. I have 3 zones ( 1 per bay), each with about 250 of 1/2" PEx. Based on the design I received and confirmed with pressure loss calcs. one pump should do it. I'm not running a separate tank and the system is a closed system. This is for system dedicated to heating only, not hot water. Hopefully I'll start install next week.