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Old 02-19-2019, 02:05 AM
 
Location: The Driftless Area, WI
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How do you get 40*F inlet water? Supply pipes should be below frostline where it's always ~55*F.


Electric heaters are inherently less efficient than combustion heaters. Use electric only if power is "free."
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Old 02-19-2019, 04:43 AM
 
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Also, if it's installed outside be sure it has a way to keep the pipes from freezing during cold weather.
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Old 02-19-2019, 05:39 AM
 
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Quote:
Originally Posted by kwong7 View Post

I'm wondering if insulating your pipes might help since those inlet temps and perhaps the supply pipes might be cold-soaked.

Insulating hot water pipes always make sense especially for a long run. Whatever hot water is left in the pipe will stay warm for quite some time and the pipe will not be sucking as much heat out of newly heated water. This will also help prevent heat from going into the house during warmer weather.


I have on demand hot water from my coal boiler using a coil, the water gets hotter the more you use it.
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Old 02-19-2019, 05:45 AM
 
39,290 posts, read 40,634,876 times
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Quote:
Originally Posted by guidoLaMoto View Post
How do you get 40*F inlet water? Supply pipes should be below frostline where it's always ~55*F.

I'd imagine if the water reservoir is outside the temperature of the water is going to be pretty low.


Quote:
Electric heaters are inherently less efficient than combustion heaters. Use electric only if power is "free."

Efficiency and cost per BTU are two different things, electric heat should be 100% efficient as all the heat is used. Combustion heat will always have lower efficiency since some heat is loss to flue gases. The cost per BTU is what makes the gas cheaper.
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Old 02-19-2019, 07:34 AM
 
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My showers have a turn on/off handle valve. When I removed the valve handle, I saw I could decide what ratio of hot to cold water would come out before I could adjust the temp. Yours might be sent too high.

We had a tankless water heater which we replaced for a tank.
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Old 02-19-2019, 07:46 AM
 
Location: Land of the Great Bears
3,447 posts, read 1,889,293 times
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Quote:
Originally Posted by guidoLaMoto View Post
How do you get 40*F inlet water? Supply pipes should be below frostline where it's always ~55*F.
Source water can be a great deal colder than that. Electric water heater company brochures suggest that northern climes estimate their source to be 45F. Considering average annual air temperature around here is in the low 40's, ground temperature definitely isn't 55F.

Our city water source is from both rain and snow melt, stored underground in huge excavations from the early 20th century mining days. Ever been in an Alaskan mine shaft? Brrrr!

My wife says it's the coldest tap water she's experienced, by far. My number of 40F was an estimate though, so I should get the actual figure.
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Old 02-19-2019, 11:09 AM
 
Location: Grosse Ile Michigan
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Gas tankless are great. Electric not so much.

The problem with electric is you need intense heat instantly for the Tanklless to work the way you want it to. Electric heat heats up gradually. You simply cannot go from 0 to 180,000 BTU in one second. At least not without frying your electrical system. Electric tankless also tend to have more problems and not last as long.

Tankless conceptually saves money because you only heat the water you need when you need it. Reality is: the difference is tiny and you will use more hot water because you can.

They are a luxury item, not a green or cost saving item. At least not enough to make any difference whatsoever.

However with a gas tankless we have no problem getting instant hot water from ours even when it is 20 below zero outside. I think ours has a 180,000 BTU burner (although I may be mixing it up with our pool heater and it could be 210,000).

Where you can have a problem is if you run multiple demands for hot water at the same time. I was going to instal two tankless water heaters and the plumber talked me out of it. I wish I had not listened. Although now, with only three people living in our house most of the time, it does not matter. When we had 7+ one was often insufficient.

Last edited by Coldjensens; 02-19-2019 at 12:10 PM..
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Old 02-19-2019, 01:13 PM
 
Location: Land of the Great Bears
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Quote:
Originally Posted by Blind Cleric View Post
... My number of 40F was an estimate though, so I should get the actual figure.
Called our water works department. According to them, the warmest it gets in summer is 41. For month of January it never got above 35F.
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Old 02-19-2019, 02:00 PM
 
Location: NYC
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What I saw more common in Asia was tankless water heaters with propane tanks than electric ones. In Tokyo motel that I stayed in, there's a tankless outside in the balcony. The water never seem to get cold. The difference is that they don't don't have a lot of complex plumbing system. The bathroom was close to balcony and the tankless was right outside of it. Easy plumbing.

When you have a large home, a tankless system can be challenging to push hot water throughout the house. If you have bathrooms and kitchen all near each other I think it can work very well. When you have a lot of plumbing, the savings can be negligible as the systems often costs 3-5x the money and not nearly as effective as a big tank. The cost savings is usually negated by the cost and maintenance of the tankless system.
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Old 02-19-2019, 02:27 PM
 
Location: Grosse Ile Michigan
26,480 posts, read 62,739,275 times
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Quote:
Originally Posted by vision33r View Post
What
When you have a large home, a tankless system can be challenging to push hot water throughout the house. If you have bathrooms and kitchen all near each other I think it can work very well. When you have a lot of plumbing, the savings can be negligible as the systems often costs 3-5x the money and not nearly as effective as a big tank. The cost savings is usually negated by the cost and maintenance of the tankless system.
What?

there is no difference in "pushing" the water with tank or tankless. The waster is pushed by water pressure. the type of water heater only relates to the manner of production of hot water and has nothing to do with pressure or "pushing" the water. We have a fairly large house (3600 s.f. not counting the 1300 feet of finished basement which has another full bathroom plus washing machine.) The bathrooms are scattered two on the second floor, one on the first floor one in the basement. Then there is the kitchen and we have an outside hot water tap for a shower by the swimming pool. There is not problem with our tankless water heater due to the size of the house. It makes no difference whatsoever compared to a tank system. The system costs exactly the same as a tank system for ht plumbing work, because the pluming is the same.

You may be thinking of a recirculating hot water system which has nothing to do with tank or tankless (although recirculating systems generally require at least a small tank). That is the only way the size of the house has anything to do with substantial plumbing costs.
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