Bull headed tees

Jack

I was visiting a job at a beauty spa with two Rinnai Continuums piped to a Aqua Booster tank with a 009 Bronze pump supplying the Rinnai's. The Rinnai's checked out fine. Gas pressure was excellent and dropped only .5" with both units working. All mechanical components were working as designed but the system would not run. Here is what I found. The two Rinnai's were about 75' away from the tank and stuffed up into a dropped ceiling, to which I must say that just because they fit...does not mean they go there. The riser pipe came up to a bull headed tee on the cold feed. The pipe went around to the rt to feed one unit and around to the left to feed the other unit. Hot water pipe returned by the same path, met on the run of a tee and fed down to the tank. If one unit was isolated, the other would fire up fine and operate as desired. This was true of both units.

When the A-stat called it made the pump, which created the flow which turned the turbine, inducer, spark, gas, flame (in a very short time)and then both units would go into error. I've seen this on two jobs in the past two weeks. The problem was that the Rinnai's were starting fine on the flow, but when the two hot pipes (flows) came togethr into the tee (about 12' of pipe on each side) the flows collided and stalled the flow turbine right at start-up. Perhaps a better way to say it is that it created a kind of recoil. This took place in a short time frame. It would stall the flow turbine just as the board was still proving flame current and properly lock out the unit.

I cannot understand why a system would be piped like that, but...it was. When I left the contractor was re-piping to feed from one side or the other and reverse return. I do not understand why folks would try to balance flow with bull headed tees. I'm also interested to see what the flow increase is from the pump. You can read the flow to a tenth of a gallon on the touch pads.

Jack

Bull Headed Tees

I was visiting a job at a beauty spa with two Rinnai Continuums piped to a Aqua Booster tank with a 009 Bronze pump supplying the Rinnai's. The Rinnai's checked out fine. Gas pressure was excellent and dropped only .5" with both units working. All mechanical components were working as designed but the system would not run. Here is what I found. The two Rinnai's were about 75' away from the tank and stuffed up into a dropped ceiling, to which I must say that just because they fit...does not mean they go there. The riser pipe came up to a bull headed tee on the cold feed. The pipe went around to the rt to feed one unit and around to the left to feed the other unit. Hot water pipe returned by the same path, met on the run of a tee and fed down to the tank. If one unit was isolated, the other would fire up fine and operate as desired. This was true of both units.

When the A-stat called it made the pump, which created the flow which turned the turbine, inducer, spark, gas, flame (in a very short time)and then both units would go into error. The problem was that the Rinnai's were starting fine on the flow, but when the two hot pipes (flows) came togethr into the tee (about 12' of pipe on each side) the flows collided and stalled the flow turbine right at start-up. Perhaps a better way to say it is that it created a kind of recoil. This took place in a short time frame. It would stall the flow turbine just as the board was still proving flame current and properly lock out the unit.

When I left the contractor was re-piping to feed from one side or the other and reverse return. I do not understand why folks would try to balance flow with bull headed tees. I'm also interested to see what the flow increase is from the pump. You can read the flow to a tenth of a gallon on the touch pads.

This was a new one to me.