Donald,

Here are some of the specks from the Precision Temp web site for the RV500. This is only a partial list.

Type: Gas instantaneous, direct vent water heater designed for recreational vehicle and mobile home use. Full gas modulation temperature control.  Dimensions: 13.5" Wide x 13.5" Deep x 14.5" High. Weight: 27.5 pounds. Rough-in dimensions: Add 1/4" to above dimensions. For retrofit, see special
directions.
Clearances: Zero clearance top, bottom and sides. 2" in back for hook-ups
Construction: Modular, three assemblies; gas, electronics and water.
Burner: High primary air, 12 element, atmospheric type. Aluminized steel body with stainless flame strips
Heat exchanger: Copper fin tube type with wrap for cooling.
Electronics: Plug in, works-in-a-drawer.
Case and flue assembly : Galvanized with painted aluminum access door (polar white or colonial white; surface or flush mount).
Mounting: One inch mounting flanges with corner pieces and door jamb included.
Must be mounted in accordance with local codes or in absence of local codes,
Manufactured Home Standard, Title 24 CFR, Part 3280 or Recreational Vehicle
Standard, ANSI A 119.2/NFPA501C
Hook-ups: Electric: 18-2 x 2' lead.
Gas: brass 3/8" flare inside case rear or side accessible.

Water: 1/2" OD copper tubing. Brass compression to 1/2" NPT elbow can be installed or as specified.

Fuel: Propane at 11 WCI
Capacity: 53,000 Btu input - 42,500 Btu output at maximum burn at 8.5 WCI manifold pressure.15,000 Btu input - 9,600 Btu output at low burn at 1.2 WCI manifold pressure.
(85°F temperature rise per gallon per minute continuous flow at high burn).

Fuel consumption: 2.55 lbs per hour at maximum input. ( At 2 GPM of water, 20 lbs of propane will produce over 940 gallons of hot water).
Power: 12 VDC at 1 amp. Operating range is 9 to 15 VDC.
Flue gas temperatures: Under 300°F.

Hope this helps. Their web site is www.precisiontemp.com/index.html
Tom and Catherine
87 Sovereign (Belle) 25'
96 Dodge TD (la Bete) 22'
WBCCI #4956