hot water heater

[winterhawke]

Just got a used hot water heater and put it in. When checking the electrical connections, I find that there is no juice going to the bottom element. There is juice present at the top element. Does this mean the heater is faulty or does that element turn on later? The top element is getting warm.

Thanks so much

[Phelps]

Did you internally transfer any wires off any of the stats? If not, I would say that your bottom stat/element will energize once the upper stat has heated up.

On water heaters, only one element comes on at a time. Each element can draw up to 4500 watts. One runs...then shuts off...and then the other one runs. The bottom one kicks on and off more often because the cold water enters down there.

For testing purposes, let the heater run as it is, with the top element being energized. Then, if you are in a hurry, and or want to make sure that you don't miss the energizing heating process of the bottom element... turn down the upper stat setting all the way, and turn UP the bottom stat setting. Then you should hear a click and the juice should now flow to the bottom stat and then onto the bottom element.

If it don't, then you have a faulty element or stat. Elements are easy to test with a volt/ohm meter. Turn the water heater off at the circuit breaker, making sure you have the right one turned off. To be sure, put your meter to 250 volts and put one probe on the top most black wire and the other probe on the topmost red wire ontop the upper stat. It should be 0. But to be absolutely certian, it's better to test in 110 volts and that would be to put one voltmeter probe on the black wire, and the other probe grounded to the tank. Then do the same test with the red wire. If both of these come up with 0 and you know your meter is good, then the water heater is indeed shut off. Then set your volt ohm meter to ohms and then put one probe on the one element terminal and the other probe on the same element's other terminal. The needle should move all the way to the right, to indicate a good element. But I always like to do one other test with the element and to make sure the element is not grounding out. With the power still off, put one probe on one of the terminals and put the other terminal on the tank. You should not get a reading. If you do, the element has a short.

If you fiddle with the stats, be sure to set them both back to a setting of your choice...perhaps about 130-140 degrees.(lesser if you have a small child/baby that could play wirth faucets and get scalded.)

[LazyPup]

By code the water heaters may not be set any higher than 125DegF unless all showers are equipped with an anti-scld mixing valve or their is a whole house anti-scald mixer on the hot water distribution piping.

[Phelps]

By code the water heaters may not be set any higher than 125DegF unless all showers are equipped with an anti-scld mixing valve or their is a whole house anti-scald mixer on the hot water distribution piping.

That's why I made the 'disclaimer' I did in my post about if there are babies and young children.

We all know that thermostats have settings on them that go higher. So one has to ask, why they make thermostats that go higher than 125, for residential water heaters?

It is only in more recent years that there have been all these warnings put on water heaters, new out of the box, about them being factory set at 120 degrees; and they have entire sides posted with all these warning labels.

We have become a fearing and letigious society. I think they know that people are going to most likely set the water heater higher. But that gets the manufacturer and the installer off the hook, legally.

I do a lot of work on college rentals that have lots of girls. I have had to revisit said houses that have one 52 gallon electric water heater that does not allow the second girl to finish her shower. Raising the temp up to 135 definitely helps. And I can hold my hand under 135 degree water quite a number of seconds without feelign like I am being scalded.

But the general advice would be for people to set the thermosat to the lowest possible setting as to where they aren't running out of hot water in some ridiculously soon fashion. That way they save energy, also.

[LazyPup]

Years ago it was a common practice to install a 40gal water heater in a 3BR house and we seemed to have an endless supply of hot water. We must also keep in mind that in those days showers typically had 4gal/min shower heads yet we very rarely ever heard a complaint about running out of hot water, why?

Prior to the late 1970's many water heaters had absolutely no insulation and of those that did have an insulation it was typically a thin 1/2" or 3/4" layer of fiberglass which seldom afforded more than an R2 to R5 value. During the fuel crisis of the early 80's there was a strong movement to reduce water heater standby heat losses by installing additional insulation blankets and turning the operating temperature down to 130 to 140degF. During this same period of time the Plumbing Codes and ASTM standards were revised requiring all water heaters to have a minimum of R-12 insulation. In order to achieve the new insulation standards, rather than redesign the outer skins of the heaters the manufacturers switched from fiberglass blankets to cast in foam insulation materials. In doing so, most water heaters presently have insulation values well above the mandatory R-12 with some having insulation that is approaching R-50 or more.

During this same period of time there were numerous incidents that gained mass media attention of children being scalded as they were put into bathtubs full of hot water. As a result the Plumbing Codes were changed which mandated that the hot water supply may not exceed 140degF to a house and the temperature at the shower or tub may not exceed 125DegF. In order to meet the new code mandated temperature standards the quick and cheap solution was to set the water heaters down to 125degF.

The problem here is that while it does insure that we can not have a scalding incident, in order to achieve a "Hot" shower, which is typically in a range of 110 to 115degF we must use almost pure "hot" water in our mix at the shower. This means that 80% to 100% of the water in our shower must now be heated in the water heater, as opposed to only 50% to 60% of the water when the water heater was run at 180degF. With the older 4gal/min shower heads a 10 minute shower consumed 40gal of water, 80% of which was coming from the water heater, which means we used nearly 1/2 the available hot water in the first shower, and for each gallon of water we draw off the tank, it is being replaced by a gallon of cold supply water, which has the effect of diluting the hot water remaining in the tank. The end result is that within 5 or 6 minutes the temperature in the shower is already falling well below the desired temp for a hot shower.

One solution was to change the shower heads from 4gal/min to the present mandated 2.5gal/min shower heads. While this did have the effect of reducing consumption, and in turn reducing the rate of cold water dilution in the water heater, none the less, we are still left wanting for hot water at the end of the first shower.

This in turn prompted the present reasoning that if a 40gal water heater cannot meet the need, we should install a bigger water heater, which explains why many new homes now have 60gal, 80gal and in some instances even 100gal water heaters, yet they still are not getting the desired endless shower.

Along comes the High Tech solution, the Tankless water heater, which promises an endless supply of hot water. This idea looks good on paper but it leaves a lot to be desired in the real world. A tankless water heater cannot heat water to a true set point, but rather they can heat the incoming water to a higher differential temperature, which is typically 70degF hotter than the incoming water temperature. This is fine in southern climates or in northern climates during mid summer where the incoming water temperature is approximately 55degF which would then produce an output of 55degF + 70degF = 125degF but what about mid winter in the northern climates where we have ground frost and the incoming water temperatures typically drop to 35DegF to 40DegF? This means that even at full fire the tankless is only capable of producing water in the 35+70 = 105degF range, which is well below the desired 110 to 115degF temperature of a hot shower.

So what is the solution? Believe it or not, the solution is so cheap and easy that it is almost a crime that it is not done.

For a mere $40 dollars and a half a dozen solder joints we can install a whole house "Tempering Valve" on the output of the water heater. The tempering valve takes hot water from the heater and mixes it with cold water to provide a constant 125degF output to the hot water distribution system, which is then fully code compliant. In turn, we can then turn the water heaters up to 160 to 180degF and the end result is that we are now only using about 50% hot water to our showers which dramatically reduces the demand from the water heater, and in turn reduces the rate of dilution in the water heaters. When configured in this manner a 50gal water heater is capable of supplying an almost endless supply of hot water to a family of 5 people.

[rattler]

For a mere $40 dollars and a half a dozen solder joints we can install a whole house "Tempering Valve" on the output of the water heater. The tempering valve takes hot water from the heater and mixes it with cold water to provide a constant 125degF output to the hot water distribution system, which is then fully code compliant. In turn, we can then turn the water heaters up to 160 to 180degF and the end result is that we are now only using about 50% hot water to our showers which dramatically reduces the demand from the water heater, and in turn reduces the rate of dilution in the water heaters. When configured in this manner a 50gal water heater is capable of supplying an almost endless supply of hot water to a family of 5 people.

Can you give a diagram of what this would look like?

r.

[LazyPup]

I have prepared the attached illustration of a typical "Tempering Valve" layout for an electric water heater. The tempering valve can be placed at any convenient location near the water heater and should be kept away from a gas water heater flue pipe which could cause false temp readings in the tempering valve.

As you can see, the layout is very straightforward. The valve is attached to the hot water line coming out of the water heater and a cold water bypass line is attached from the cold water input of the valve to the cold water supply line downstream of the cold water shutoff valve.

The output line from the tempering valve is connected to the Hot water distribution main line.

As you can see, installing the tempering valve typically only requires 7 additional solder joints and a short length of copper pipe to make the bypass.

Tempering valves are available at all hardware, home supply and plumbing supply stores. (Typically about $24 for 1/2" and $39 for 3/4" valves.)

[rattler]

Thanks

r.

[SpiceLand]

If this is the 'after' diagram, then what does the 'before' look like in terms of the percentage of hot vs cold and the flow of the cold which is diluting the hot? This may be part of a problem I am having too. If possible, can you show the 'before' diagram or standard flow as well? Rattler probably got the visual and fully understands, but I am a "basics-only handy ma'am". Thanks!

[LazyPup]

In the basic configuration as Hot water is drawn off the top of the water heater an equal amount of cold water enters the cold supply tap on the top of the water heater vessel, then travels down through the "Dip tube" inside the water heater where it is discharged at the bottom of the tank. In theory water reaches maximum density at 39degF and begins to expand as it is heated, therefore the incoming cold water is slightly heavier than the heated water and should stay near the bottom of the tank until it is heated and expands causing it to rise. This would be well and good if the burner we able to heat the water at the same rate as the demand, but this is not the case. Typically a 60gal. water heater has a 1st hour recovery rate of about 48ga. (A 60gal. electric has a 1st hour recovery rate of about 32gal).

If the burner is capable of heating 48gal/hour we can then divide 48gal by 60minutes per hour to determine the gal/min rate of heating the water.

48/60= 0.8gal/min.

By code the showers are now limited to a flow rate of 2.5gal/min.

By Code the maximum permitted temperature of the water supplied to a shower is 125degF unless all tubs & showers are equipped with anti-scald mixer valves, in which case the maximum allowable temperture of the hot water distribution system is 140degF.

The cheapest and easiest method of insuring the water at the shower will remain within the code specification is to set the water heater for a maximum operating temp of 125degF. The problem with this method is that a "hot" shower will range in the 100 to 110degF range therefore in order to get a hot shower we are using about 90% hot water in our shower mix. Again considering that the shower consumes 2.5gal/min this means we are demanding 2.5gal/min x 90% = 2.25gal/min of hot water while our water heater is only capable of making up 0.8gal/min for a net loss of 1.45gal/min. from the water heater storage vessel. This means that at the end of a 10min shower the water heater is left with 14gal of water to be heated before the next shower or hot water demand occurs. This 14gal represents 23% of the water heater volume thus all the remaining water in the water heater has now been diluted with 23% cold water. The end result is the water remaining in the water heater is now in the 90 to 100degF range, which is below the desired temp for the next shower. This would be fine if we could insure a 20 to 30 min. recovery time between showers, but often more than one family member desires their showers at almost the same time.

By installing the whole house tempering valve at the water heater we can then turn the thermostat up on the water heater to 160 or 180degF. With the whole house mixer set at the code maximum of 125deg the demand from the water heater is now about 70% hot water and 30% cold water which extends the reserve of hot water in the water heater. This 125degF water is then again mixed at the shower mixer so the actual demand from the water heater is roughly 60% of the total volume of the shower.

2.5gal/min x 60% = 1.5gpm.

We have a make up rate of 0.8gpm for a net loss of .7gal min.

The real difference here is that when the water heater was set at 125degF we only had a 10 or 15DegF differential between the stored hot water and the desired hot water temp so even a slight rate of loss had an immediate impact on the output temp, whereas with the mixer installed the stored water in the tank is at 180degF which means we have a 70degF differential between the stored water and the demand water temps. This means even if the water heater burner did not come on would could consume nearly 1/2 the stored water in the tank before we even begin to notice a drop in the output temperture, and once the burner kicks on the make up rate is nearly sufficient to provide a continuous demand. Allowing even ten minutes between showers is often long enough to make up the loss.

[Phelps]

LazyPup,

Read your post 5. Excellent idea. I have never heard of nor thought of that one before. Neat.