this is New Construction, at least for the Granny. So its hard to take Temp
Measurements now. (-; We live off well water. Though when the Granny unit
is all said and done, it will be pumped out of a semi buried 2500 gallon
Tank.

For the Granny, its going to have at most the Dishwasher and the Shower
going at once, so that would top out the 4gpm, and if the water was 33f, a
70f rise at 4gpm would be enough even if it dropped a few between the
tankless and the shower. That is worst case. Most of the time it will be
just one application at a time in the Granny, so at 2gpm for the shower most
units are 120f+ temp rise. The LP under the house is 3/4" and the main feed
is not in yet. They know we are going tankless, so they did things
accordingly.

The one I really need to think about is the main house.

I'm kind of stuck between a rock and a hard place. I have 2 location where
I need hot water. The back end of the house, 70'+ away from the Existing
tank heater, and the Kitchen, 20' from the tank heater in the opposite
direction.

it Currently takes 2 minutes for the water to get to the back end of the
house for showers. So I'm thinking of cutting off the Hot at the Kitchen
split and just putting in a 4gpm @ 70f temp rise at the back end of the
house. So the 2 full baths get the Instant Hot.

Then some day when I redo the front end of the house, replace the Tank with
another tankless to take care of that end of the house.

I've thought of getting just one bigger unit for the entire place and doing
recirc. I don't mind the 2 minute wait, its the water in the Septic
Tank/Leach field I worry about.

Better to have one big unit or two medium sized units? Cost Aside... hey
I could put in a By Bad valve so if one unit failed I'd have failover in a
pinch?

Decisions, decisions...
"m Ransley" wrote in message
...
Are you sure 4 gpm at your main incomming, mine varies on time of day
and season.

70 f rise , did you test water temp at-near the heater and the loss it
experiances at its use point, you should measure shower head output
temp, I loose apx 5-10f.

What is your temp incomming lowest, in a cold year, test now but lower
it 10f easily.

Cross comparing can only be done possibly on a specification since
rebadging, recasing, or a single line for Bosch is likely.

It is better to upsize than make an expensive mistake. Although I do
fine with 117000 btu and 4 gpm and 33f incomming not even set to high,
my shower output might be 1-2 gpm. Be sure your gas can handle the extra
load, im sure your furnace is not near 180000+ btu. Load must be
measured with all apliances on.

Look for a unit that maintains output temp and has a remote thermostat,
my unit does not maintain output temp, it maintains temp rise, so in
winter I must turn it up manualy. But I am happy with the savings I get.