Aquahot Overflow Tank was low today. AH was hot, overflow tank just below the full COLD mark.
Radiator cap on the main AH unit had failed, seperated when I removed it (top, spring, and seal all in seperate peices. Aquired new cap at Autozone. Topped up tank to lip before putting new rad cap on.
Overflow tank had a crack on the back of the tank. Dark stains in compartment where leak had run onto basement floor. I "wonder" if the failed radiator cap over-pressurized the tank leading to the crack?
I used rubbing alcohol, then wire brush to clean plastic overflow tank crack and to rough it up, patched with slow heal JB weld (15 hours for complete cure). Back in service tomorrow morning when JB Weld is healed.
The used AH boiler fluid (pink version) had turned brown in color. A few minutes research on the internet, some people say boiler fluid shoud be drained and replaced once in a while, others say never needs drained and replaced.
Opinions on replacing boiler fluid, and total gallons needed if so?
Rudy?
I would think it needed to be treated like antifreeze in engine
Chris
Dan, The only two reasons I know of to replace the fluid are it has been contaminated or you want to.
If your heater has an electronic control board, the black 8.5 by 11 board with lights, or if your heater has been rebuilt and is a model RM100, you need GRAS (generally regonized as safe) boiler fluid. If your heater has the three clear relays and a row of fuses, you can use engine antifreeze.
Radiator cap and the overflow hose at the radiator cap need to be air tight.
To change out or to remove contaminated fluid, drain the AH coolant. Fill with 16 gallons of distilled water and run the pumps. Drain again and fill with 16 gallons of new proper fluid.
Rudy - that particular AquaHot has always had GRAS boiler fluid in it, and I believe there is a sticker on it (from the factory) not to use engine antifreeze.
Dan - as a datapoint, I think that rad cap was new somewhere between 2012 and 2014. Believe that's also when we replaced the overflow tubing, which had some cracking in it at the cap end and was sucking air as a result.
I have always topped up with pink GRAS when needed (minimal need). I had a radiator cap fail on the AH once before, losing fluid at the rad cap.
Parts man at autozone says he sees lots of the caps with the pressure relief (red lift arm) fail as plastic parts are used for that relief system. This time I bought one without the lift arm, all metal.
Dan your overflow tank is vented, cap didn't over pressurize it, just age and fatigue.
On page 8 of the Aquahot manual for the AHE 100 02S an ethylene glycol antifreeze is indicated. Although my overflow tank (2003 U320) also has a sticker that indicates to use a GRAS or propylene glycol based antifreeze. My solution also appears brown in the tank. I wonder if that sticker was added by a service person at some point. I may drain my tank at some point but I plan to fill it with an ethylene glycol antifreeze mix.
I would caution against this. GRAS boiler fluid is required in newer AquaHots (the design changed somewhere around 2002, I believe) and you are at risk of boiler fluid mixing with domestic hot water with the newer design (heating coils immersed in coolant). That is the reason for the GRAS antifreeze/fluid requirement.
Switching to a non-potable type of fluid could be hazardous to your health.
Aquahot Antifreeze Solution-Important Information (https://www.foreforums.com/index.php?topic=7191.msg31043#msg31043)
What heating system is best for winter use? (https://www.foreforums.com/index.php?topic=10323.msg48049#msg48049)
I remember having a sales customer come in saying his aquahot was not performing as it had in past winters. I told him to let me know what they found. He later told me the tech changed the fluid in the aquahot, and told the owner, "the fluid ph was off, changing the fluid would fix the issue". The owner later reported to me that after the service, the issue was fixed.
You might want to change the drain valve if you change fluid. Distrubiing it aftet 24 years. Mine leaks now.