Aquastar for supplemental hydronic heat [RE-wrenches]

[Ray Walters]

Aquastar125BL: I have run my floor heating system for 4 years with one.

 Problems: It needs at least 1 gal./ min to even fire. It will work on less
flow new, but gradually sediment buildup reduces flow through the heat
exchanger which causes it not to fire reliably. Aquastar reccomends 1.8 gpm
min.
 Problem 2 is that without a storage tank or a whole lot of slab, the
return water reaches higher and higher temps. The Aquastar (even on its
lowest setting) is still going to raise the temp about 90 degrees at 2 gpm.
(this temp increase would be less at higher flow rates). My system has only
one TACO  009, No zone valves or transformers, one 24vdc thermostat and AC
relay. AC Pump draw is 140watts. DC is < 1watt. I have a tempering valve
which bypasses the Aquastar at high temps.

Reccomendations: 
I. Travis is right about the fuel effeciency being better at 4 to 5 gals/
min. Electrically that will translate to a larger pump though.According to
125BL Manual, you'll need 18 psi at 4 gpm. (2 psi at 0.5 gpm) Looking at
Total Effeciency (Fuel Eff. + Electrical Eff.) is trickier. I'd guess a
TACO 011 would get you around 2.5 gpm and would be a good compromise. For
higher flows,you may be looking at a Grundfos UP26-96 or even a 26-99. I
couldn't give  accurate power draws without actually measuring it. Probably
in the 200 watt range.

II. Your baseboard heating will come up to temp much faster than my mud
slab. The Aquastar will probably shut itself off due to overtemp in less
than 30 minutes without a tank to temper the temp. Even with a tempering
valve,you'll need some type of thermal storage. 

Conclusion: Switch to a small regular hot water tank with some DC El Sid
pumps to circulate to the baseboards. The Aquastar will be more trouble
than its worth in a baseboard only application.

Ray
Remotech
Ray at SolarRay.com



>I am installing an Aquastar instant DHW heater for total off grid moutain
>cabin (weekend use only) as part of a solar/gen/battery alternative energy


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