New home with 300 gallon tub and small radiant heating load

solradman

Looking at a job that will have a 300 gallon soaking tub and a heating load of 37,551 Btu's. Home will have radiant floors and plan is to using a mod-con boiler. Would a 199,000 Btu boiler and 80 gallon indirect be better than a couple tankless units just for the bathroom with tub. Thinking the tub will need 250 gallons as fast as possible. Any recommendations?

Robert O'Brien

Separate the DHW and heating loads

Larry Weingarten

Hello, Any chance they would go for a smaller capacity tub? If so, you could combine systems. Looking on-line, I see 60 gallons for deep soaking tubs. 300 is a lot! If they are inflexible, I'd look at tankless units jut to serve that tub. You're probably looking for at least 5 gpm at a 90 degree rise for half of the water. That's 25 minutes to fill!

300 gallons could be OK if the water were treated and the tub stayed full, like a hot tub.

Yours, Larry

EBEBRATT-Ed

@solradman

Where I come from that's not a soaking tub it's a swimming pool!

If they have the $$$$ for that they have to have the $$ for the water heater to feed it.

Zman

300 gallons is a big tub. I have never seen one that big without it's own heater.

bob eck

Two 199,000 tankless has water heaters will give you about 11 GPM
RINNAI makes a demand duo 199,000 tankless on a 119 gallon storage tank. They now have two 199,000 tankless on a 119 gallon tank.
Vaughn has 119 gallon indirect water heater that you can get two coils in it.
Check those options out.
How many times are they going to fill a 300 gallon tub?
Is this on a municipal water system or on a private well?
If on a private well system what how many GPM does the well pump produce. If the well pump only pumps 7 gallon per minute that is all you are going to get.
If on a well system do they have their own septic system that 300 gallons dumping into a older septic system can cause problems.

Solid_Fuel_Man

Tankless shines in this example. I agree with Bob eck, two will give better results. Will this place have a private sewer and well, or municipal?