What do you think about building a little wooden leg system on top of the heater for the pressure tank? Would that be ok in the book of water heater rules?I guess you are OK now, but for future reference, trickle a little water from a faucet while setting the PRV.
You think that less precharge will keep you from blowing up some bladder more? Modern tanks don't have bladders. And when they did, the bladder usually contained water, not air. The diaphragm stretches more with less precharge air.Set the ETs pressure to 1-2 pounds below the PRV setting...that will put it at the neutral point...the air pushing and the water pushing it equally. WHen it's higher, the stored water in the tank will be the cause of that spurt when you open a valve. ANd, you will be blowing up that bladder further than it was designed to be.
Instructions say same. "3. With tank empty of water, adjust air precharge to match cold water supply pressure" (http://www.amtrol.com/wp-content/uploads/2017/09/9015-942-03_17-Thermal-Expansion-Tank-IO.pdf), Water pressure varies. If the tank size is smaller, I think you will get maximum capacity and life by matching the air precharge to the highest normal pressure (maybe 4 AM).If it's sized properly, it will last the longest when you install it per the instructions...
Do you have a basis for your claim?The ETs are designed so that the bladder or diaphragm is at it's neutral (design) point when the pressure is equal on both sides.
15o psi of water would be excessive pressure. You probably are thinking about something else.Excessive pressure means it is always stretched.
The basis of my claim is the installation instructions for ALL ETs...set the precharge to the static water pressure in the system and it will work as designed.Do you have a basis for your claim?
15o psi of water would be excessive pressure. You probably are thinking about something else.
80 pounds of air would not stretch the diaphragm.
When the pressure rises 10 psi, the pressure is still equal on both sides. Not meaningful. The purpose of the expansion is to allow a place for the water to go so the pressure does not exceed 90 psi. If water pressure is at 60 at times and precharge is 63, no problem.The basis of my claim is the installation instructions for ALL ETs...set the precharge to the static water pressure in the system and it will work as designed.
It sits against the tank as it does when it is shipped from the factory. Put 50 psi of water above the precharge, and the diaphragm stretches.When the ET is pre-charged higher than the static pressure, what do you think happens to the diaphragm? It stretches beyond the point it is designed for.
Makers say set to the same pressure. You say set below that pressure. I suggest set at the pressure or a little above. Both will work if the tank has a little reserve capacity.You're free to believe what you want (even if it's wrong), but to preach against the manufacturer's instructions should not be part of it.
No...look at the ET sizing calculator on say the Watts website...it will tell you the actual volume available for expansion...it's many times more than the expansion of the water. Because of that, the small amount of expansion means that the pressure doesn't have to rise much at all to accommodate it. The only way that number works out is if the precharge is at the static water pressure. Too little air, it will take more volume change to raise it. Too much air, it's already higher, and the bladder won't start to move until the house pressure rises to match. IF there was no expansion available, and all of the system was perfectly rigid and not leaking, the pressure would almost instantly spike until something leaked. But, most houses have at least a few hoses on things like faucets, toilets, etc., and those aren't as rigid as copper, but still, they don't swell much (and it's a good idea to not make them try!), so there is a little delay before you might see the pressure start to rise. Plus, the burner in the WH isn't all that huge, and the water temperature rises somewhat slowly, and that affects the rate the water expands - it's linear one degree...a fixed amount per volume.For instance if we had accurate measurements and the pressure tank read 65psi but the house pressure was 70psi. Wouldn't the tank be full all the time?
This is awkward, but...
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