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Takagi questions

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David Meiland
David Meiland Member Posts: 12
in THE MAIN WALL
2Br/1Ba house, 2 occupants, existing 40 gallon tank taking up floor space that we want for other uses. My thought is to install a Takagi on a piece of out-of-the-way interior wall space that's just right for it. I'm a GC and not a plumber although skilled enough with pipe (and wire and flue) to get the unit installed correctly.

Four questions:

1. Any experience with the T-K1S model (apparently quite new) vs. the T-K2? Or, would a TK-JR work? We do not have a giant spa tub with a 10 GPM filler. Kitchen sink, lav, washer, tub/shower... that's it. Everything within maybe 25 feet of pipe of the heater location. Well water, very cold in the winter, fairly mild climate (just a few freezing days in winter).

2. Fuel is propane, pipe is 3/4" black iron. Fuel passes thru a regulator on the exterior of the house, and goes into a 12" section of 3/4" pipe. Immediately after that 12" piece is a tee, and 3/4" pipe goes in two directions--one way to the kitchen stove and water heater, the other way to a propane fired heating stove. While I'm pretty sure that the two individual 3/4" branches are capable of carrying adequate gas to their respective destinations, I'm not sure about that initial 12" piece.... it seems like a possible bottleneck, but then again it's so short. Thoughts on that? Do I need a 1" regulator?

3. Washing dishes by hand (yes, I do that)... turning the hot water on and off to rinse. Seems like the flash heater would send a few seconds worth of cold water into the line every time the faucet is opened. I'm having a hard time seeing how a flash heater can deliver consistently hot water when the tap is opened and closed frequently such as when rinsing. Sorry... I'm dense about some of this. I do not want my wife to kick my butt after I install this thing.

4. Last Q: vent stack will be directly from the top of unit, 8' vertically thru ceiling, unconditioned attic space, and then roof. I'm assuming I need double-wall cat. III material due to the penetrations of ceiling and roof, and wall mount location on sheetrock. Correct?

Thanks for reading, and any comments greatly appreciated.

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  • Weezbo
    Weezbo Member Posts: 6,232
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    heres a few thoughts.....

    Propane acts stupid when its called upon to zipp out and do its thing some times...the reason is it is a liquid and what you want to be burning is Gas. here is how that comes about the demand is too heavy,it tries to meet the demand the pipes and tanks exteriors get colder and colder,this temperature is signifigantly colder than the surroundings,condensation forms Rapidly it turns to ice which is good as it acts like an insulator,buh thats bad as it allows it to flow faster as a liquid...buh not for long! soon your having a sputtering comming out of the heater or appliance or nothing at all. so...propane lines and regulators need to be sized on these considerations...........There is a sharp guy name Tim here whos really really into gas and lp you might get his opinion........flash heaters work for On Demand calls for domestic hot water almost like lightning:) its because thats what they are designed ta do..........pump out super hot water right NOW!:).....you would have your hands full figuring out controlling it and flow rates supply and return temps....I think that some storage buffer tank would have to be in the equasion.... now there is something elses that crosses my mind,...you are not considering using it for domestic hot water and heating...Are you?....if so let me say that isnt a very good idea..for you the happy camper taking a bit of a holiday ...you might not survive the time off much less enjoy yourself. ...the other idea was the venting... what about straight out the wall?...the other thing of interest would be domestic water while it could be delivered at 15psi via gravity and you could bump the recirculators Up to 15 psi how many psi is recommended by the manufacturer on the unit? if a domestic water pump surges or cavitates due to over use or outdistancing the draw down,or a vaccum leak,or bad foot valve or check,...ummm...then what? These are thoughts that cross the mind. then the other thing i thought about was well maybe i could get a Bigger propane heater...the same variables are still there...:(
  • lchmb
    lchmb Member Posts: 2,997
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    anther point of view

    question 1. No experience with Takagi, sorry


    question 2. Propane pipe sizing is based on total BTU load and longest length of run. If you can give me those then it would not be a problem with answering your question. Although I would want to guess you are probably alright. The 12" length that comes in is no problem. You are burning the vapor not the liquid so it will not bottleneck.
    As to a 1" regulator, that would be in the commercial range. Doubt you need that.

    question 3. even though you are turning it on and off you have probably filled the dish pan to start, so the water in the pipes is already hot. You are just taking this water prior to it going cold so I don't think that is an issue. Rinnia has a system where you can control the temperature at different point's in the house. And it is designed for this type of use so I would guess Takagi is similiar.

    question 4. Like I said previously, I am not familiar with this unit but I would guess (I know i shouldn't) that the unit is similiar in style to other instant unit's and is easier to vent sidewall. I would check with a Takagi rep and see what he thinks....
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