Hydronic source for small loads

Wayco Wayne_2

an existing water heater you could use a Taco X block to extract heat from it. It has a flat plate heat exchanger already on board. The only consideration for germs is to leave the primary/domestic water side free to a convective flow. In other words no check valves or Flo control devices. This way there will be no stagnant water build up in the off cycle

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JimL

Hydronic source for small loads

Given the contractor never mentioned radiant as an option, and the hot air is nearly complete, I have a homeowner looking to heat some floors with hydronic radiant down the road. The slab was poured last week...less any tubing.... and the homeowner is totally disapointed. It is getting near drywall time and the forced air is near completion. The homeowner wants to warm some living area floors (kitchen and LR) as well the bath floors up stairs. Given the homeowner objection to electrically heating the floors, we are looking at hydronic under floor for all. Total area to be heated I'm told is around 600 SF but that will be verified later this week. Since I have never been asked to look at hydronic installs this small, what would be the recommended solution for a small hydronic heat source and control given the small loads, existing hot-air system, and the homeowner objection to electric. Gas is available but the loads will be smaller than the low end of most modulating boilers. Lastly, would you recommend just monitoring floor temps for control to avoid fighting the hot air? It seems everyone has a different opinion on this and I welcome your suggestions. I do not yet know the size or type of DHW yet or if it is even installed at this point.

Rodney Summers

my neighbor used a water heater for his room adittion around the same sqft. you could also use a small boiler

Brad White_35

I agree that a DHW Heater

may be the way to go, but only if used as a closed system set up as a boiler would be. Not quite as efficient as a condensing boiler, but at least they are rated for 150 psig and for full raw water. At less than 15 psig I would assume, and with recirculated water, it should last a lot longer and for less cost. But no frills here, right?

I think your principal options are warm board or if too thick, Climate Panels or other thin-slab types. And yes, I would control the floor by floor temperature for the reasons you stated. If the radiant floor was more pervasive and not limited to a few areas, I might re-think that and use the floor radiant as a base-line of heat to take it as far as it could go before using air.

I feel the HO's pain! There was a story Dan H. wrote about a contractor who always built houses with the basement slab "radiant ready", all tubed and stubbed up ready to go and at no extra charge. He only charged them for the tubing if they elected to go ahead and fit up the system with manifold and controls. He took a risk doing this but his experience is that the homeowners ALWAYS took him up on it and never regretted it. Good marketing. Pass that on to your contractor for the next job. It is truly God's Work on earth.

JimL

I absolutely agree on the closed loop if coming off the DHW. Not a big fan of the open direct. At this point though, anything above the floor is out. They are ready for rock in two weeks...subfloors and door framing are long completed and so my plan was to install underfloor with plates in the 2nd floor areas to get them rockin' and then take some time to figure out the first floor and controls. It will all be underfloor with plates in the end. That free tubing thing is a nifty idea. We just came off a home show this past weekend and it's amazing how many people just won't consider putting it in slab. However...even more people who asked about installations over an existing slab. Really need to find a way to get these people together.

Brad White_9

Staple-Up with Extruded Plates

is indeed your best option at this point. I advised a friend to at least install radiant floor in bathrooms if not the kitchen family area or everywhere else. Brand new home and he is a builder. He only did his bath and kicks himself for not doing more.

If you can get the disparate folks together, there is a Nobel Prize in Hydronics waiting for you.

hr

Small electric HW

tanks are what I use. Even a 1500 watt 120 volt 6 gallon electric would give you 5100 BTU/ hr. That may be plenty for 600 feet of warming, which is generally 10 btu/ sq ft or less.

Higher wattage elements are available if you neeed more output.

Keep in mind these small "homebuilts" would not be an ASME listed appliance, if inspectors insisit on that.

And for some reason those small 6 gallons cost as much, or more than a 30 or 40 gallon. But i like the small capacity for standby loss and small space installations. i do add a 30 lb relief in addition to the factory installed T&P.

hot rod

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schiller

we do alot of these projects. the lowest cost options all ways involve a standard water heater. we often pipe the water heater like a boiler and use a flat plate heat exchanger to keep the "boiler water" seperate for the rest of the house. you will need a flat plat H.E, mixing valve,a couple of pumps (Bronze if on the potable side)expansion tank and air seperator and some type of pump control(we use tekmar)
good luck Troy

JimL

Thanks for the info on the source. I'm considering a Tekmar 510 with a aux slab sensor to drive the floor temps in each bath to a neutral to warm temp without overheating the space. Can the 510 be configured for this "or" control scheme using the aux slab sensor?

Timco

Hotrod...

1) I do not see a expansion tank on that setup...Any reason?

2) Do you use the water heater as it would typically be installed? I have seen people pull the dip-tube and use the CW tap & the drain for the supply & return, and the HW tap for the fill/ exp tank. Is one way better?

Tim

Rodney Summers

try this webpage http://www.aimradiantheating.com/ they have this boiler room in a box its quite interesting. j.h.