tankless water heater - Contractor Talk - Professional Construction and Remodeling Forum

p1grinder · 02-08-2009, 10:05 PM

i'm trying to decide on a tankless, i have 39 degree water in the winter, and want about 12-14 gpm at peak usage. so i need a 65 degree rise. the noritz n-0931 can only give a 30 degree rise at 11.1 gpm, so should i conect two noritz n-751 's wich gives a 30* rise at 9.8gpm/65*at 5.2gpm. will the water be moving to fast for the too small units?

mdshunk · 02-08-2009, 10:12 PM

Something's messed up here. Where did your 14 gpm number come from, specifically? Would you mind listing that out, fixture by fixture? It makes no sense. The max limit for a shower head is presently 2.5 gpm, so that's something like 6 showers at once?

p1grinder · 02-08-2009, 10:27 PM

5gpm: 2 shower heads
4gpm: bathtub
2.5gpm:kitchen sink?
2.5gpm: dishwasher?

or
cloths washer and laundry tub.
am i off on these gpm rates?

mdshunk · 02-08-2009, 10:32 PM

You're seriously going to have someone using two showers, somebody running a bath, someone else doing dishes in the dishwasher while the kitchen faucet is wide open? You have a big family, I guess.

p1grinder · 02-08-2009, 10:47 PM

two shower heads in master shower, kids in the hall bathtub, dishwasher, and sink or clothswasher. that would be about 10 minutes after dinner, if we had enough hot water but we dont, so we do the {whait for the 40gal water heater to reheat dance}

mdshunk · 02-08-2009, 10:49 PM

So put in a regular Rinnai or Noritz and don't do all that suff in the same 10-minute period. Easy solution.

p1grinder · 02-08-2009, 11:05 PM

well it's ten min after dinner for 30 to 40 minutes. the noritz n-931 will provide a 65* rise at 6.5gpm wich means if the kids take a bath you cant use both shower heads in the master shower without losing heat (right?) my plumber is thinking about a holding tank in the basement to raise the water temp a liltle, the basement is about 60*, so all i need is a 45* rise, which the n-931 can do at 9.3gpm and that aint too bad, but is that the right thing?

plumber1a · 02-09-2009, 09:08 AM

I have found that these heater are very restrictive to the flow of water, if your running multiply fixtures at once the volume of hot water will decrease, even to a trickle. Adding more heaters is the solution or a storage tank, but I feel a storage tank defeats the purpose of "tank less" Give yourself some extra and figure at peak demand or you might not be happy. Remember these heaters work on demand, so minimal demand= minimal cost to operate. They are expensive, so you need to get it right the 1st time.

A.D. Const · 02-11-2009, 09:24 PM

Quote:

Originally Posted by plumber1a

I have found that these heater are very restrictive to the flow of water, if your running multiply fixtures at once the volume of hot water will decrease, even to a trickle. Adding more heaters is the solution or a storage tank, but I feel a storage tank defeats the purpose of "tank less" Give yourself some extra and figure at peak demand or you might not be happy. Remember these heaters work on demand, so minimal demand= minimal cost to operate. They are expensive, so you need to get it right the 1st time.

As per manufacturer spec. you need 3/4 supply and distribution lines on a tankless Water Heater to get the GPM advertised.

p1grinder · 02-12-2009, 07:16 PM

what about inderect water heater, i got a boiler very close, how do you guys feel about those things. i don't know that much about those setups.??

nhmaster3015 · 02-12-2009, 09:07 PM

The indirect will outperform the tankless in every single catagory.

KillerToiletSpider · 02-12-2009, 09:30 PM

Quote:

Originally Posted by nhmaster3015

The indirect will outperform the tankless in every single catagory.

No it won't.

p1grinder · 02-14-2009, 09:52 PM

Quote:

Originally Posted by KillerToiletSpider

No it won't.

could you be more specific?

p1grinder · 02-18-2009, 02:52 PM

i'm looking at a weil-mclain, its looks like a good model but everything really depends on the boiler right

A.D. Const · 02-18-2009, 10:03 PM

Quote:

Originally Posted by p1grinder

i'm looking at a weil-mclain, its looks like a good model but everything really depends on the boiler right

Yes it depends on the boiler, if you have a modulating boiler supplying your indirect, then I see no better system, otherwise its a matter of opinions, some preffer tankless other indirect. If it was me I would still go with the indirect. For a few reasons, but that's another th

read. Hope this helps

p1grinder · 02-19-2009, 01:23 PM

i wish i had a nice boiler!! it used to be an old coal fired, it's been converted to gas, its huge!! if it breaks down i'll kinda be happy, but what part of it would break, whould yhe cast iron crack or what, the gas regulater is new and pump clucth ist too

Holmstedt · 02-20-2009, 01:42 PM

Have you considered running 2 or more units from different locations? Say one near the kitchen/laundry room then a second by the master/kids bath? (or master bath /laundry- kids bath/kitchen) How far away would the storage tank be? Per most manufacturer spec. you should not have more than a 40 ft run to any fixture.

p1grinder · 02-20-2009, 10:08 PM

Quote:

Originally Posted by Holmstedt

Have you considered running 2 or more units from different locations? Say one near the kitchen/laundry room then a second by the master/kids bath? (or master bath /laundry- kids bath/kitchen) How far away would the storage tank be? Per most manufacturer spec. you should not have more than a 40 ft run to any fixture.

two tankless or two indirect tanks?