Water heater replacement help

[shadow111]

Currently have an 11 yr old Rheem 50 gallon power direct vent and the inducer assembly is bad. ( motor seized)
Considering a power vent replacement however i believe combustion air supply may a limiting factor.
The burner is 40,000 btu and the cubic feet of available draw is 1200. Using a formula I have , it gives me a max of 24,000 btu.

The home is modern and air-tight and has a condensing furnace, HRV.

I think I’m in a situation where the new budget-friendly power vent heater will be inadequate and that I should just spend the money and put a new rheem direct vent power vent assembly on to repair the problem ( even though the tank is 11years old. )

So, looking for confirmation that a replacement heater with power vent only is the wrong option ( based on available combustion air)
And/or whether the Power unit replacement is the right way to go.

Thanks.

 

[Reach4]

the cubic feet of available draw is 1200.

Where does that number come from?

 

[Sponsor]

 

[Fitter30]

Where does that number come from?

Rule of thumb 50 cu ft for 1000 btu's
1200 cu ft 24,000btu's

 

[John Gayewski]

Do you have two pipes? One for intake and one for exhaust?

 

[Master Plumber Mark]

Getting a new 12 year old Rheem motor will set you back easily 500 bucks if you can even find one..
I have thrown out a good number of them over the years that were still working fine.....

You are worrying too much about air intake .... the old unit did well for 11 years and the new one
you pick out is more modern and up will probably last about the same amount of time too.... maybe more...

If you are really worried about the air intake , many homes in my area have added a 3 to 5
inch flu pipe in the tight mechanical room that is stubbed up into the open attic (if applicable)
and brought down to about 30 inches off the floor for more air intake for both the furnace and heater.
Some have done the same thing with a vent into the crawl space too (if applicable)..

just get a new unit and dont sweat over it