Hot box GPM ratings

Has anyone used a hot box that is rated for lower gpm like 4 gallons and ran 5.5 through it? If so will the water just not get as hot because of the water exposure to coils being shorter? The flow switch is rated for up to 18 gallons I believe.

I literally was just wondering the same thing. I seen schedule 80 1/2in listed for 4gpm, ut i don’t see a problem for 5gpm.

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Why not just buy a hot box rated for your machine’s output?

I have a 4gpm pump with a 4gpm hotbox already. Was gonna but a new 4 gpm engine and pump to go with my hotbox. Started thinking that I dont need the temp up to 250 so maybe with a 5.5 gpm machine I may still be able to get to 160 or so for my desired temp since thats what I usually use.

If it were me, I’d just sell the 4gpm hot unit and use the funds to help purchase a 5.5 hot unit. That way you don’t sacrifice any flow, don’t have to worry about if it will get hot enough, don’t have to recalibrate fuel/air mix to achieve an efficient burn. The few dollars difference in cost would be worth it to me just for the simplicity. Your mileage may vary.

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Chances are the only difference is the nozzle size in the burner. But you’ll have to check your burner and look up it’s btu/ nozzle rating