Need solution for more hot water

[David Martel]

Bob,

Unfortunately Ransley's numbers were 200000+ Btu. This isn't helpful since a Btu is the amount of energy needed to raise 1 lb. of water 1 deg. F. If he had reported Btu/hr. his number might be helpful. Let's go on the assumption that he meant Btu/hr. Lets also assume that the water enters the water heater at 50 deg. and is heated to 125 deg.. I think a gal of water is around 8 lbs. so the system is capable of heating about 330 gals of water in an hour from cold to hot. Not bad but it can't keep up with the consumption of 30 gals of hot water/min. in his shower example since it is producing 5 gals of hot water/min. (I'm rounding a lot of numbers here). Ransley means to be helpful but frequently doesn't recognize when he is misguided. His example doesn't seem to work and his example has nothing to do with the OP's problem.

Dave M.

[HeyBub]

I'm assuming you have merged two families.

If not, what's different about your new house than your old one?

Get one of the kids to demonstrate how he takes a shower. I'll bet he turns the hot all the way up and adjusts the temperature with the cold tap. Show him another way.

[blueman]

Actually, burner is 40K BTU with 36.8 gallon/hour recovery rate. Is this considered a pretty "measly" rate?

[BobK207]

Dave- I agree, he was sloppy with his units but since he said it cost ~$1500 to 3000, was fed with a 2" water line & was meant for an apt. I figured it 200,000+ BTU per hour.

I based my calcs on that & factored in the efficiency.

IMO your assumption of 15 instanteous showers is a bit unrealistic.

Based on average shower length & the temporal distribution of shower start times you could develop a more reasonable estimate of the sustained short term hot water demand. I agree that a 5 bedroom / 6 person household needs either; a hot water warden or more hot water generation / capacity.

I've got a 4 (sometimes 5) bedroom / 3 full bath house on a 75 gallon LP WH; when there's lots of showering going on I make sure I'm not last. :)

We all kind of got off topic...............what is the best solution(s) for the OP?

Does anyone have a comment of the tankless fed by a medium sized tank WH; use the tankless as a "peaking unit"

or does it make sense to feed the tank with the tankless but change the control method so the tankless only helps when "needed"??

I have not thought this out completely but my gut tells that just get a bigger (or more) tank style WH's is not the best approach. Also the tankless units are big $'s and they only support 2 instantanous uses; as soon as three showers are running you're in trouble.

I guess demand reduction (shorter showers, low flow heads & shower spacing) is needed unless capital equipment & energy usage $'s are no concern.

cheers Bob

[m Ransley]

I guess you guys havnt been in many apt buildings of 12-14 units

200000 - 235000 Btu 100 gallon tanks are the norm and do the job fine, even heating cold midwest water in winter. I dont know the recovery rate , and these are 2" incomming high recovery heaters costing 3-4 times as much as a HD 100 gallon. I truely dought full loads from all aptartments are ever reached. I was just pointing out that 100 gallon tanks can be overkill for a house and higher output smaller tanks should be looked at first , just as one person said that he should put in a 100 gallon, there are options to look at. There are tankless by Rinnai that will handle his needs. There are tankless that are being refitted into apt buildings, sometimes 2-4 are ganged together. I beleive Rinnai has units up to near 280000 btu. With some restriction the 180000 btu Rinnai will handle 3 showers. There again it depends on incomming water temp. I go from a low of 35f to 72f incomming. At 70 f my small 117000 bosch could easily handle 2 showers that are restricted, I know ive tried it. All I need for a shower is 102f with no cold added. I know this may not help the OP , I first tried to point out conservation and the possibility his unit simply may be under fed gas or not operating right. I have also seen bad thermostats that dont cut in till temp has dropped very low 15-20f , hurting immediate recovery for constant use. He could possibly use a secondary tankless but for a bit more Rinnai has a model that will work for all his needs .

[TURTLE]

This is Turtle.

Well it seems to be one of the slowest rates that I have seen but there could be somewhere something slower. The Norm is [ 40 Gal. recovers in 40 minutes. ] [

50 Gal. -- 50 minutes. ] [ 30 Gal. -- 30 minutes. ] .

TURTLE

[oreo123]

I am doing a 4 plex with 2 beds in each unit. I use a single Super Store indirect 40 gallon tank. The boiler running the building has domestic priority and has an output of around 230 k btus. It works. If someone starts running out they shorten their shower time. If I were doing it again I would probably go to a 50 gallon tank. This is in Northeast and I have heard no complaints this winter.

Oreo

[Chuck]

Glad to see ya' back Turtle Chuck

[TURTLE]

This is Turtle.

Name Rinnal tanklessheater.

It is gas and can run 3 showers at one time and all hot water from 90ºF to 140ºF water temp. 24 hours a day / 7 days a week and never run out. Flow rate will be a little over 9 gal. per minute which the average shower will take 3 gal. per minute or less. On average they burn 30% less natural gas than a tank type. The burner heat rate can be from 15K btu to 200k btu , which also comes in Propane also , which all is controlled by a digital thermostat that you can set the water temp. as you like it from 70ºF to 160ºF . Also comes with 10 year warranty.

Bad part , it will cost you over $1K for heater and materials -- No labor. I have seen one work and they work fine and all the hot water you want.

TURTLE