Tankless water heater wiring very weird!

[Dennis Alwon]

Nope that 24kw is a single phase. If you heat your water with electric and take showers just as long as before you will save on electric. You are not heating your water all day long.

Technical Specificationsimensions: 17? x 16? x 3?Weight: 23 lbs.kW / Elements: 24 kW / 3 elementsMax. Amps: 100 A @ 240 VCustomer Double-PoleCircuit Breaker / FusedDisconnect Required:1 x 110A or2 x 60A or​

3 x 40A

Yeah I see in the picture but the model says 24Kw has the model # then 3 -I assumed that meant 3 phase 3 phase

 

[mivey]

I don't see how that unit could be wired up with anything but a single branch circuit.

I would have thunk the same but the installation instructions actually show connecting up to 3 breakers parallel onto the power distribution block in the device. There is a statement that says in Canada you must use a single double-pole breaker but you can use up to three breakers in the US.

Check out page 13 and 14 of
http://www.buytankless.com/pdf/Hubbell-Tankless-O&M.pdf

A picture of the power distribution block is on page 19.

 

[weressl]

Ask them how they like their power bill after using it for a while. Better yet, check out the reviews and show them that. If I were going to need one that big I would go with gas.

Strange as it may seem but the instantaneous heaters do use less power than the storage types. Remember the time factor in the kWhr billing. The heater is only ON while the water flows while the storage type is on for hours to heat up the whole stored volume to the desired temperature, then switches on/off to maintain that temperature while the heat is being lost to the outside through the large, albeit insulated, surface area of the tank. In addition if you have used up all the stored hot water, you have to wait until the 3/5kW heater heats up the whole volume again. Instantaneous gas is certainly a better option, but not as efficient as the electric as you loose some of the heat through the flue.

 

[hillbilly1]

Strange as it may seem but the instantaneous heaters do use less power than the storage types. Remember the time factor in the kWhr billing. The heater is only ON while the water flows while the storage type is on for hours to heat up the whole stored volume to the desired temperature, then switches on/off to maintain that temperature while the heat is being lost to the outside through the large, albeit insulated, surface area of the tank. In addition if you have used up all the stored hot water, you have to wait until the 3/5kW heater heats up the whole volume again. Instantaneous gas is certainly a better option, but not as efficient as the electric as you loose some of the heat through the flue.

Your water bill will also drop too because of the limited water flow!

 

[Little Bill]

Strange as it may seem but the instantaneous heaters do use less power than the storage types. Remember the time factor in the kWhr billing. The heater is only ON while the water flows while the storage type is on for hours to heat up the whole stored volume to the desired temperature, then switches on/off to maintain that temperature while the heat is being lost to the outside through the large, albeit insulated, surface area of the tank. In addition if you have used up all the stored hot water, you have to wait until the 3/5kW heater heats up the whole volume again. Instantaneous gas is certainly a better option, but not as efficient as the electric as you loose some of the heat through the flue.

I thought they would be cheaper too until my customer told me what her bill was running and from the Many negative reviews on them. I hear plumbers all the time telling customers to go with gas if they insist on a tankless. What you failed to include in your assessment was the normal tanked model is only 4500kw and the tankless that is big enough to handle a good size house is around 24-27kw. If you are doing a lot of dishes, clothes, showers, etc. and run them for any length of time you have 27kw running all at once and the 4500 kw doesn't stay on that long if it has 2 element/quick recovery.

 

[infinity]

I would have thunk the same but the installation instructions actually show connecting up to 3 breakers parallel onto the power distribution block in the device. There is a statement that says in Canada you must use a single double-pole breaker but you can use up to three breakers in the US.

Check out page 13 and 14 of
http://www.buytankless.com/pdf/Hubbell-Tankless-O&M.pdf

A picture of the power distribution block is on page 19.

I still don't see how you can connect two or three circuits to a common power block. Shut one off and you'll have a back-feeding situation at the panel where as the off CB is back-fed energized at it's terminals.

 

[Dennis Alwon]

I agree with Rob. This unit is meant for one circuit. I was wondering how this unit got by 422.11 (F)(1) then I turned the page and saw 422.11(F)(3). :roll:

 

[weressl]

I thought they would be cheaper too until my customer told me what her bill was running and from the Many negative reviews on them. I hear plumbers all the time telling customers to go with gas if they insist on a tankless. What you failed to include in your assessment was the normal tanked model is only 4500kw and the tankless that is big enough to handle a good size house is around 24-27kw. If you are doing a lot of dishes, clothes, showers, etc. and run them for any length of time you have 27kw running all at once and the 4500 kw doesn't stay on that long if it has 2 element/quick recovery.

Actually I did not fail to include the size of the storage type kW size, I indicated 3/5kW, dependent on the tank size.

It is plan physics. The amount of water needed to be the same in both cases, thus the required energy is the same. Energy=power*time. To heat up a given volume of anything, you need energy or power input for a given duration of time. The shorter the (required)time is, the more power is required. Where the inefficiency comes in is in the heat loss, where the stored water needs to be re-heated as it loosses heat while sitting there, waiting for the next use. When, in your scenario, doing a lot of tasks that uses hot water, the storage tank will eventually run out of hot water.

 

[petersonra]

Do you have a make and model number for this unit? 24,000 watts to heat water, sounds awfully expense to operate.

The same amount of hot water is going to require the same amount of BTUs to heat it up regardless of whetehr it is a tankless or tank style. The tank style just run longer. The tankless only use electricty while hot water is being used.

The amount of energy saved over tank style heaters is often grossly overstated, and they cost a ton more. In most cases you would save far more money by insulating the hot water lines and the hot water tank.

 

[Little Bill]

The same amount of hot water is going to require the same amount of BTUs to heat it up regardless of whetehr it is a tankless or tank style. The tank style just run longer. The tankless only use electricty while hot water is being used.

The amount of energy saved over tank style heaters is often grossly overstated, and they cost a ton more. In most cases you would save far more money by insulating the hot water lines and the hot water tank.

I guess I should have stated that power consumption was not the only complaint. In colder parts of the country, the water in the ground is colder and takes longer to heat or doesn't heat well in the tankless. Also, there were complaints about the water getting cold or having cold "spurts" even after getting hot and running for a while. Also, as has been mentioned, the water flow and pressure is not as good with the tankless. I guess the #1 thing was the high initial cost vs 20+ years to recover the cost via the supposed energy savings. And, they are not maintenance free, they get clogged up with scale after a while and have to be cleaned out. Of course tanked models get scale in them also, but you can drain them occasionally and minimize this. On the tankless, you have to disconnect them (plumbing & electrical) to clean them.

 

[Sierrasparky]

One other big value with these units is that space for the unit is very small, its about the size of 20/40 load center and just as deep. These units take up far less real estate. As to cold spots when using the heater in shower, the key is to keep the amount of pipe to a minimum.

 

[kwired]

Ask them how they like their power bill after using it for a while. Better yet, check out the reviews and show them that. If I were going to need one that big I would go with gas.

I thought they would be cheaper too until my customer told me what her bill was running and from the Many negative reviews on them. I hear plumbers all the time telling customers to go with gas if they insist on a tankless. What you failed to include in your assessment was the normal tanked model is only 4500kw and the tankless that is big enough to handle a good size house is around 24-27kw. If you are doing a lot of dishes, clothes, showers, etc. and run them for any length of time you have 27kw running all at once and the 4500 kw doesn't stay on that long if it has 2 element/quick recovery.

I guess I should have stated that power consumption was not the only complaint. In colder parts of the country, the water in the ground is colder and takes longer to heat or doesn't heat well in the tankless. Also, there were complaints about the water getting cold or having cold "spurts" even after getting hot and running for a while. Also, as has been mentioned, the water flow and pressure is not as good with the tankless. I guess the #1 thing was the high initial cost vs 20+ years to recover the cost via the supposed energy savings. And, they are not maintenance free, they get clogged up with scale after a while and have to be cleaned out. Of course tanked models get scale in them also, but you can drain them occasionally and minimize this. On the tankless, you have to disconnect them (plumbing & electrical) to clean them.

The issue is, as you are starting to point out - how long of a payback period?

The tankless unit should use less energy as it is only heating when there is demand. True the instantantaneous demand is higher but total amount of energy needed to raise X gallons of water Y degrees remains the same plus what is lost from the tank when not being used on a storage type heater.

If you have a customer that that is using more energy you might want to make sure they do not have a hot water line that is leaking or unknowingly supplying constant hot water someplace. This will raise the bill even with a tank style heater.

The increased amount of instantantaneous capacity means larger transformer, conductors, service equipment, etc to get the job done. This means more investment in getting the thing installed which will add to the payback period. Another consideration to add to payback period is service and maintenance. Typical storage tank heaters require little maintenance - especially if not running hard water through them. When they do need maintenance they are not too expensive to work on in general as the problems and parts are pretty simple.

 

[Dennis Alwon]

In colder parts of the country, the water in the ground is colder and takes longer to heat or doesn't heat well in the tankless.

I thought water in the ground below a certain depth 10 feet or so- I am sure that varies- reaches a constant 50-55 degrees.

 

[weressl]

I thought water in the ground below a certain depth 10 feet or so- I am sure that varies- reaches a constant 50-55 degrees.

I don't think that you'll find water lines buried 10' deep. I believe the frost-line in the North is about 3' or so.:lol:

 

[Dennis Alwon]

I don't think that you'll find water lines buried 10' deep. I believe the frost-line in the North is about 3' or so.:lol:

I was thinking well water but I believe the actual depth is closer to 4' unless you go into the arctic.

 

[Little Bill]

I thought water in the ground below a certain depth 10 feet or so- I am sure that varies- reaches a constant 50-55 degrees.

I got this info from one of the mfg, they state that in certain parts of the country that have a colder climate the units won't work as well. Also read that in some of the review sites. I'm just reporting what I found when researching them and from what my customer told me.

 

[mivey]

Actually I did not fail to include the size of the storage type kW size, I indicated 3/5kW, dependent on the tank size.It is plan physics. The amount of water needed to be the same in both cases, thus the required energy is the same. Energy=power*time. To heat up a given volume of anything, you need energy or power input for a given duration of time. The shorter the (required)time is, the more power is required. Where the inefficiency comes in is in the heat loss, where the stored water needs to be re-heated as it loosses heat while sitting there, waiting for the next use. When, in your scenario, doing a lot of tasks that uses hot water, the storage tank will eventually run out of hot water.

It is not as plain as you think. A heat pump tank water heater uses less purchased BTUs because it steals energy from mother nature to get the job done.

 

[weressl]

It is not as plain as you think. A heat pump tank water heater uses less purchased BTUs because it steals energy from mother nature to get the job done.

Yes, it is as plain as I stated when the compariosn is made between the electrical resistance ehated storage type and instantaneous water heaters. Of course we can also introduce solar assist heaters, which of course opens up a whole other discussion.:roll:

 

[kwired]

Incoming water temperature can be effected by some things. When I lived in town I'm not sure what temperature the city water supply was but it was warmer than the water I pump out in the country that is coming directly from the well. That city water warms up some while in the lines vs being used right after it is pumped. During periods of high use in town - like during hot and dry weather and lots of people are watering lawns I had noticed the water was colder - it was not in the lines for as long.

 

[mivey]

Yes, it is as plain as I stated when the compariosn is made between the electrical resistance ehated storage type and instantaneous water heaters. Of course we can also introduce solar assist heaters, which of course opens up a whole other discussion.:roll:

I would think solar assist would help either type unit, even a NG unit.:roll:

At any rate, you have to compare how efficiently you can store heat vs providing instant heat. Just because a heat-pump type unit is different doesn't mean you should just throw it out. You would not throw out a heat-pump central unit when considering the efficiencies of home heating would you? My point was the ratio of energy purchased to water heated is not a constant between tank vs tankless technologies.