On demand hot water heater and a holding tank question, also NAVIEN any good?

JoeG

Hi, I am looking at getting the NAVIEN Model # 240 with the circulator pump on Demand Hot water heater. I need one that can produce alot of hot water I have a big whirlpool tub to fill and I like long showers. There are at times Six peopl in the house.

1. I have a fairly new 50 Gal bradford white propane hot water heater that I d like to use as a storage tank any tips on plumbing it?

2. Is this a good way to go? The bradford white couldnt keep up with demand.

3. Aer the Navien units anygood?

Jack

Tankless

are all about flow and temp rise. how many gallons in the tub and how fast does it fill? Get a bucket and stop watch, time it. Or figure out the cu ft of the tub to the level you typically fill it. 7.48 gallons/cu ft. As I represent Rinnai I will limit my comments to Rinnai. For a large household the RC98HPi model will at 70F rise provide 5.4 gpm. The V75LSi model will make 4.3 at same. A good showerhead is 2.5 gallons at 112F. Low flow showerheads are 1.5. Clock you faucets. Energy conservation is all about water conservation too.

JoeG

Whats Temp Rise?

The tub I think is 100 Gal. I also have a shower tub combo standard and another shower. Plus 4 sinks washer and dishwasher.

Charlie from wmass

If water quality is good

you should stream line and just use the tankless unit and keep the system streamlined.

JoeG

Not sure how the water is

The company recommended a holding tank they were worried about teh tub, I am unsure why the tub would effect it. as long as teh gpm was the same.

Charlie from wmass

They may be worried

about how long it will take to fill if the water heater is sized to suit all your other needs. Note on rise, my well water is 43 degrees Fahrenheit all year long. the 70 degree rise would only give me 113 degrees F not quite what I need to do dishes or shower. As the rise needs to increase the units become quite large. In order to make a sale some contractors are selling underrated units and collecting their money and leaving jobs that simply do not work as was understood. What is your heat source for the rest of your home?

JoeG

Force hot air

As of now it is forced hot air. Down the road Ill prob change it.

Jack

43F year round!!!

Charlie, please check that. What I have typically;) seen with water supplies in New England is in line with the USGS surveys. 52-55F summers. Usually what I see is a period of about 3-4 months, Jan-March, where the water temps may be depressed into the 40's. Every system has a personality of course, but it takes time for the frost to get to the water supply piping. Once there it takes time for it to come out.

Charlie from wmass

Granite and marble deep well

I have checked the temp on many occasions it is 43 year round. Maybe as high as 45 in the dog days of summer.

CMadatMe

Temp Rise

Temperature rise is the difference between the cold water coming into the unit and the hot water leaving the unit. DO NOT EVER, EVER size an on demand heater off the charts the manufactures provide. Seen too many issues using them. The proper way to size an on demand heater is as follows:



gpm x temp rise x 500 = btu's required

Example:

If I want to make 7.5gpm in my market to 120 degree water temp.

7.5 x 70 x 500 = 262,500 btu's. I need an on demand heater that can produce 262,500 btu's. If I lived in a wamer climate that rise would change thus my btu requirement would change. The literature manufacturers produce is nation wide not for particular parts of the country.

JoeG

Temp Rise

So how do I find out the temp of the water in NY ? Any help on the btus I am looking for? I plane on Ordering a navien 240 A which is there biggest unit.