To be clear, I didn't mean to imply that 300 watts is enough heat.(Based on David's stated specs for his Versalab, 0.3 to 0.6 gal/min "should be satisfactory.") But it seems fairly easy to use a pair of them. Whereas if you only had 40 watt heaters, you'd need fifteen of them.
Is your air temperature appropriate (around 68F/20C)?
If so, can you put in a largish tank and then let the air warm it to what you need, with maybe a little help from a downstream aquarium heater?
It is called a heat exchanger and works both ways although industrial ones are made for more efficient use and unidirectional
May not be needed in North Tejas, but here is South Luisiana which BTW is a whole lot warmer than N. Tejas, I have a dedicated 12 gal water heater for the darkroom. Water heaters are frigging cheap. A whole lot cheaper than an "industrial heat exchanger." If mine is unused, I have an "on/off" switch and I just turn it off. If sporadic use is bad for them, get a new one in 10 years when it craps out. You'll also be able to wash your hands with "warm" water for those 10 years during the winter in the darkroom and then be able to get off the computer and actually spend the time printing. That's what I did today, water was coming in at 62 Deg, and the "dedicated water heater" warmed it up to 70 through the control valve.
Originally Posted by David Brown
I have a similar setup inside an RV garage that the previous owner used to store race cars. I ran off the well pump line and split to the water heater and then the chiller. I have the setup shown in the LLF Forum darkroom portraits around page 51-52, and here in the Darkroom Portraits II, and also under a thread for Intellifaucet Installation:
If I may, I suggest that you listen to your wife. I do mine and it's made for a better marriage. :p