Water Heaters - Supplemental tankless water heater

I am looking for a tankless water heater to use as a supplemental heater to a heat pump water heater. I have only found one so far and it is does not have all that I am looking for.

What I need is one that runs on propane, does not require more than a 1/2 inch gas line, and is direct vent. The one I found (Bosch 1600PS) is not direct vent and has water connections of 1/2 inch, which seem rather small.

Any guidance is greatly appreciated.

Check this one out

http://www.rinnai.us/Products/water_heaters/overview.aspx

There are others similar out there. This is one I hear a lot of good things about.

Check this one out

http://www.rinnai.us/Products/water_heaters/overview.aspx

There are others similar out there. This is one I hear a lot of good things about.

Thank you plumbingods. I wasn't sure if you were directing me to a specific item or the full line by Rinnai. I had been through their products, but I looked again and none seemed to meet the criteria with the first problem being they all require at least a 3/4" gas line where I need one that can use a 1/2".

3/4" seems awful large for propane. Let me look into it further.

Mark { plummingod }


IIRC someone told me about the 3/4 inch gas fuel pipeline size due they have low WC burner rating [ this info is not 100% verified ]

But other hand with most LP i know with 14" wc if the burner is under 180KBTU it will get by with 1/2 inch copper but if someone run a steel fuel line the bet is off they have to be bumpped up to 3/4 inch size reguardless if it is 14" or higher system in there.

I ran into that sisuation more than once due some of my customer do have LP or Natual gaz stand by generator and it can really ruin the customer day if not planned right.

For the LP system with stand by generator it very typically to see 3/4 inch with 14" WC system in the house.

{ I useally keep the generator fuel line seprated from the house fuel line for good reason :cool: }

and quick side note Mark check the Fuel gas piping size chart it will show up.

Merci,Marc

french277V,

Thanks for your response. My LP tank is about 75 feet away from the location of the water heater. I have looked at the charts and, IIRC, that is too far for 1/2" as the pressure drop is too great for the larger units. Plus, since the tankless is going to be supplemental to a heat pump water heater, I do not need the larger capacity of the ones that require 3/4" gas line. I think, in the worse case, I will only need to raise the temp of the water about 20* - 25*F. Having a unit that can modulate down fairly low seems to be of greater benefit.

Sorry for slight delay reply but if your LP tank have one regulator on the tank itself and also second regulator on the wall on the house just before the gas pipe do go in.,,

If so it should be ok due the line pressure between the tank and house regulator useally about 2 PSIG so that will take care of the issue with pressure/flowage.

But for the tankless waterheater to turn down to low setting [ low firing rate ] that can be little tricky myself i am not fully famuair with the control system on gas fired tankless unit but electric verison yeah i can able figure it out easy.

That part I will let Mark { plummingod } take that part if he have few tricks in his sleeve i think he may have a idea or two but let him chime in when he get in here.

Merci,Marc