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Seems like an easy question but I can't get an answer... How long can a shower be?
We have a Rheem 42VR50FV / PRO50-40F natural gas water heater (50 gal) that's coming up on 7 years old. we have the extended warranty kit for total of 12 years.
We got our bathroom redone and have a 2.5g rain head showerhead in there.
With that flow rate, is there a rule of thumb how long we can take a shower / sequential showers before it gets cold? It seems after 10 - 15 minutes, we're turning the temp valve up / finishing up. Which I guess is right? that's 37Gallons so that's most of the tank / the make up water is nice and cold...
From this page,
It talks of 1st hour gallons of 83. Calling rheem, they can't explain what that means.... certainly doesn't seem that you can take a 83 gal/2.5GPM = 33 minute long shower expecting it to be warm.
it's just wife and me now, but when kids come home, we do have to plan who / when takes showers so they are all warm. That's the way it is? A good argument for an instant hot unit? They say 50 gal is a nice size unit for 4 people... as long as you aren't all getting ready near the same time?! : )
Oh, it's a Toto anti-scald valve. That just keeps you from getting scalded right? It doesn't keep the temp the same as hot line drops in temp? Do those exist? Set it for temp you want and then it does what's needed (as best it can) to keep it that temp as hot water drops in temp?)
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And the anti-scald valve is just that -- it limits the maximum, but won't maintain temperature. For that you need a thermostatic mixing valve -- and that won't do it either, once the water heater is run out.
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
You can extend usage by raising the storage temp. However a thermostatic mixing valve should be used.
Wilson Services, Inc
Northampton, MA
www.wilsonph.com
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Elevate the tank temperature as other have mentioned and more cold gets blended extending your drawdown.
Higher operating temperatures do reduce the tank life and cause more minerals to precipitate out. At some point a larger tank makes better sense if you have a high demand and dump load.
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
> It's late at night, so a flip answer... I knew a Chief Petty Officer once who insisted that one could get soaped, scrubbed, and rinsed clean in 1 minute and 30 seconds by the watch. He was right...
My father was in the Marines, add shaving and getting dressed to that list and change the time to 5 minutes. He’s 72 and has slowed down, but yeah the military gets it done. In boot camp they timed the head calls.
EcoSteam ES-20 Advanced Boiler Control
Boiler pictures updated 2/21/15
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EcoSteam ES-20 Advanced Boiler Control
Boiler pictures updated 2/21/15
https://www.facebook.com/media/set/?set=a.10202744301871904.1073741828.1330391881&type=1&l=c34ad6ee78
Yours, Larry
If your water is coming into the building at 45 degrees and you need your shower water to be 105 degrees, that would mean your temp rise delta would be 60 degrees.
24,800 / 60 / 500 (constant) gives you .83 GPM continuous.
It gets a little more complicated with the storage side of things. Depending on the tank temp you maintain, the storage in the tank gives you a bit of a buffer. With a 2.5 GPM flow and only .82 GPM production, you are always running at a 1.68 GPM deficit. If you could get the full 40 gallons of storage out of the tank, (you will only get about 1/2 to 2/3) you would get a 23 (40 / 1.68) minute shower before things get cold.
Your 10-15 minute showers sound about right.
Your solution would be:
Live with the shorter showers
Install low flow shower heads
Install heater with higher BTU output
Install heater with more storage
Albert Einstein
Heck, our 50 gallon electric does fairly well, 2 back to back showers, but 3rd one better be short. but I have a recirculation loop now so instant hot water and about 2 gallons extra storage essentially.
there are plumbing issues that appear to be water heater issues.
take the hot water pipe temp right at the outlet of the water heater and the temp elsewhere ant the same time. if the point of use is cooler the there is some cold water bypassing into the hot side diluting the hot water.
most water heater mfgs state a tank can provide 60-70% of the tank with no more than a 30 degree drop and be in specs.
a 50 gallon WH should give 30-35 gallons of water thats within 30 degrees of starting temp. i have never got them to state "at what inlet cold water temp" those ratings are based.
this time of year with the deep frost WH performance suffers
The tan ratings are based on a temp rise as well, say, 70F, so from 50F water you go to 120 and then you have x for the first hour.
In winter with city water you will have colder cold water, maybe even with a well. Take a 5 gallon bucket, measure the height and mark the half point, that's 2.5 gal. Run a shower into it for 1 minute and measure, that's your per minute gal, X 60 = per hour.
By the time your kids grow you'll be needing a new one anyway, if you have a boiler go with an indirect water heater which can put out in excess of 200GPH, nothing touches them for output and efficiency. But if you run the test you'll know what you need per hour.
https://www.amazon.com/Niagara-N2915CH-Chrome-Shower-Head/dp/B009HXAP9C/ref=sr_1_3?keywords=niagara+shower+head&qid=1550273675&s=gateway&sr=8-3
The first 50 gallon tank I ever installed was in a dairy farm house for the family. They needed a new WH and wanted a upgrade.
They had 5 boys and 2 girls, stairstep children including a set of twins. This means all the children were at home and covered just about every other grade in school. All sorts of activities in the evenings and for sure Sunday mornings. They had two 3/4 baths plus a full bath.
They milked cows twice a day (this implies showering twice a day for everyone.)
The 50 gallon tank was enough for all this activity. All the children are still alive today despite the short showers, thru strict training, they had to endure.
The parents of those 7 children are younger than me. (we had only 4 kids).
Wife and I survive now with a 120 gallon tank fed by a heat exchanger from an 80,000 mod con. Though her 50 gallon tub being constantly topped off can tax the system a little.
Our world has certainly changed.
My parents generation.....don't get me started!
City water here in southern NH comes in at 42 deg in February.
In Florida it's ~ 70 degs
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In a heat exchanger to heat water the energy you need to add is:
(GPM) x ( delta T) x (500.67) = BTU/hr
So using my tanklless coil in boiler : raising 42 deg F water to 101 and flowing it out thru my 3 GPM shower head from the 70's needs ~ 87.1k BTU/hr