sizing a tankless water heater
#11
Hi, we have a Bosch exterior tankless gas water heater and I'm looking for a replacement. I know the current Gal/min flow rate. Is this really the primary number I want to compare when looking for a new unit?
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#12
GPM at a given temp rise. 5 @ 100 degrees is not the same as 5 @ 85 degrees
Blackhat

Bad experiences come from poor decisions. So do good stories. 


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#13
Got it - thanks.

Also, what's your opinion on a DIY option for swapping one heater with another, knowing the gas and plumbing lines are already run? I've called around for replacement costs and am floored by some of the prices. $2500 for a new heater. I also asked what if I supply the heater and I'm getting anywhere from $1000-$1200.

I think worst case I can shut off the gas, hook up the new heater and then perhaps call the gas company to come finish the gas hookup? Or is there way more to it than that?
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#14
There's no way I would play with Gas. If you mess up...BOOM!

I had a neighbor years ago who did his own gas work.
His wife didn't trust him & she called the gas company.
They ended up shutting off his gas until he had a certified gas fitter fix the mess he made.
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#15
If you are uncertain, the wise choice is to hire a pro...
Being cheap, and confident, I ran new steel gas piping to a dryer, a range and the new gas fired fireplace in the addition I built, including cutting and threading all the pipe by hand. Every joint was tested before igniting...20 years ago...I have a neighbor (master plumber) who lent me the tools, but declined his recommendation of how to test for leaks...He suggested a lit match/lighter... I used soapy water...the rest, as they say, is history. I did not chintz on valves...used the best quality available
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#16
thanks for the additional thoughts. With a shut off valve on the gas line, I think it would be easy to shut that, install the new heater, minus the gas line, and then have the gas company do their part. I guess that's what I was trying to inquire about.
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#17
I ran my own gas lines but had the gas company come out and inspect them.
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#18
You could make a phone call and find out if a flexible appliance connector is legal in your jurisdiction. That makes it dirt simple.
Blackhat

Bad experiences come from poor decisions. So do good stories. 


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#19
Ha, cube farmer. I had to look that up. Close, but I work from home.....

Yeah, part of the problem with the cost is that I'm trying to get the house ready for sale. The existing tankless is working, but throws an error code every week or so. I go reset it and it works again for another week. I was just trying to do the right thing for the new owners (and get out of the task of having to reset it), but at this price, I'm not sure.

I found a Rinnai for around $625 that matches what we have (143k BTU out and 6.3gpm). We've been fine with that for 8-9 years so I think the new people can, too. Just need find a reasonable way to get it installed. Next step is to call the gas company to see about them hooking up the gas if I do everything else. We already have a flexible attachment line with shutoff valve.

A tank isn't really an option as this is mounted to the side of the house outside.
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#20
thooks said:


Gee...a cube farmer shocked at the price of a replacement water heater? Who would have thought?



As far as 'sizing' a tankless water heater like you have- you have two choices. You can get the 180k BTU model or the one higher (250?). That's about it.


There is no sizing. You get about 6 GPM of water at about 100°F temperature rise out of the 180 MBH unit and I think about 8-9 GPM out of the 250 MBH unit.


I have never really heard anyone complain about the 180 MBH units.

I still feel that you really can't beat a good, standard 40-gallon gas-fired water heater. I bought a Rheem for $280 at a scratch-n-dent place (a Platinum Pro model.... $600 at HD). There was nothing wrong with it. $100 in a expansion tank, fittings, valve, etc., 4 hours later I have a new water heater. The old one was 19 years old (AO Smith) and wouldn't produce much hot water. It was not clogged, but I imagine there was some huge scale build up.

We had 8 people in the house over the holidays. I know at one time 2 showers were going continuously and the dishwasher seemed to be running constantly. The water was always screamin' hot coming out of the tap. I am thrilled for my $400.

$2500 will be the norm for a water heater replacement (tank-type) in 2-3 years. I predicted that $1200-1500 would happen... it just came a couple years quicker. The reason why? Nobody is pushing their kids to learn a trade. Nobody wants to be a plumber/electrician/mechanic/pipe fitter.




No shortage of the trades workers here however there is a shortage of pay for them. Trades start pay at $8 hr and many will top out at $16hr. I find it funny that the fast food workers make more than many in trades. Good reason not to work in them here.
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