djdavenport
Member
I'm a little baffled. I have a Navien NCB 240 that feeds a 10 gal electric buffer tank. I noticed that the T&P valve on the tank was dripping a little, so I checked the pressure, and it was spiking at about 140 psi. It goes from normal to the high pressure whenever the element in the electric HW kicks in. The contractor had not put in an expansion tank, so I figured that would solve it.
But, today, in checking, the high pressure only occurs BETWEEN the Navien HW outlet and the buffer tank (and probably the whole DHW system, although I've only checked the pressure at the tank.) Not on the cold water inlet side, (so my plan of putting in the expansion tank on the main right after the PRV would have done nothing. That pressure is normal.) I am guessing that there is some kind of check valve in the Navien that is not allowing the high pressure that builds up in the buffering tank back through. Is that a logical conclusion?
As far as a remedy, should I put the expansion tank on the hot (and high pressure) side?
Thanks for your advice.
But, today, in checking, the high pressure only occurs BETWEEN the Navien HW outlet and the buffer tank (and probably the whole DHW system, although I've only checked the pressure at the tank.) Not on the cold water inlet side, (so my plan of putting in the expansion tank on the main right after the PRV would have done nothing. That pressure is normal.) I am guessing that there is some kind of check valve in the Navien that is not allowing the high pressure that builds up in the buffering tank back through. Is that a logical conclusion?
As far as a remedy, should I put the expansion tank on the hot (and high pressure) side?
Thanks for your advice.