tankless water heaters

[dumbcluck]

has anybody dealt with these tankless water heaters?
i've got a customer who just bought one to replace his electric wh which is fed on a 2pole 240v 30a. the new one requires 2- 2pole 240v 40a. max 71a. the guy currently has a maxed out panel with only a 70a main. he dosent really want to change out the main. any ideas?

 

[quogueelectric]

Cold showers for him.

 

[dumbcluck]

looks that way.


i should mention that he thinks 70a is more than 40a so it should be o.k.

 

[ivsenroute]

I assume you will do what is right and only agree to do a compliant, safe installation.

I will tell you that I found one like you desribed and they don't work well for showers. A DIY did the job himself, upgraded the breaker to a 60A but did not upgrade the existing 10awg.

The electric tankless water heaters will reduce flow in order to maintain temperature. So what happens is that the water drops to a drizzle once another hot water fixture is opened. The GPM ratings for electric ones suck and should be limited to handwashing.

This guy will be sorry once he buys it.

 

[dumbcluck]

not to worry, it will be done properly or not at all. i just need to impress upon him the need to upgrade his main and not just find someone who is hungry enough to do it as is.

 

[charlietuna]

The guy has two choices--upgrade the service or call the gas company. If he is a friend, tell him to call the gas company because gas is 60 percent more efficient at heating water than resistive heaters. A house almost needs to be designed for ELECTRIC tankless water heating. And too many installers attempt to get by on an undersized electric tankless unit by available service amperage and the customer is really in a mess--not enough hot water--every light in the house dimming--and a unit that will never produce sufficient hot water. I wired a buddies house who insisted on tankless electric--he had a 3,800 square foot house 3 1/2 baths and the specified unit required a 70 amp and a 40 amp 240 volt circuit. We ended up with a 300 amp service. The unit runs great..... And I never realized that 45 percent of the energy consumed by your water heater is wasted by storing it! And most electric utilities list the water heater using $45.00 in billing per month! Thats a sizable amount of waste!

 

[sub3marathonman]

The electric tankless water heaters will reduce flow in order to maintain temperature. So what happens is that the water drops to a drizzle once another hot water fixture is opened. The GPM ratings for electric ones suck and should be limited to handwashing.

This guy will be sorry once he buys it.

I have not found that to be true with mine, a Tempra 12. AFAIK it continues to heat at the maximum, the water continues to flow, but the temperature rise of the water is reduced and may not hit the set temperature. It is true that you must research the GPM ratings though.

In my setup it is strictly for the master bathroom, which is on the other side of the house. I also have the water heater on a switch so I can leave it turned off. (I understand that using the breaker isn't good practice, so I upgraded to the switch when I built my new house.)

It takes a 60A breaker, and has no effect on any other electrical equipment when it comes on. I have a UPS protecting a TV in the other room which would sound an alarm when the voltage drops too. My service is 200 amp. I can't imagine a homeowner with just a 70 amp main even thinking about tankless though.

You really do have to plan things out for the electric tankless heaters. I too would agree that a whole house would probably be much better served with a gas tankless one, but for me that wasn't a real option. If you must have electric you could either do things like I did or else put smaller ones in the bathrooms and by the kitchen sink.

 

[Micksbroke]

I say go with gas.
I installed one (Rannai) And it works great.
Uses very little gas and single 15 will take care of it. Its only for the fan and igniter.
You can put a 20 or 30 gallon tank beside it need be.
That will last a long time.

 

[charlietuna]

All these problems are due to not being sized and or piped correctly. Also understand that tankless heaters have a very fine filter inside the unit and thats why you will notice a strange valve arrangement under them. It's for backflushing which normally(depending on the cleanliness of your water) needs backflushing with viniger once a year. When the flow decreases, it is telling you the filter needs backflushing--takes 15 minutes! The better units also have a very small pump that will run to cause a slight increased pressure across the unit--and if there is a fine bypass at your system's end it will circulate hot water throughout your system. I installed a gas unit when i built my house two years ago--three baths-typ. kitchen and clothes washer, a gas fireplace(i never use) and an outside hot tub. I installed branch temp. controls to all the bathrooms which nobody uses--the master unit is set at 130 and that seems to satisfy everyone's needs. So when you take a shower you just turn the hot water on "wide open" and your ready to go! Now the hot tub, i reset the temp. to 140 and fill it up--i don't use the hot tub electric heater and i don't store the water--just dump it when we're thru with it--easy to maintain and stays very clean. The master stat will automatically reset to the preset temp. of 130 as soon as the hot tub is full and the water is turned "off"! I only refilled my propane tank once after living in the house after eight months--- now i have my gas bar-b-que,tankless heater,gas clothes dryer,gas stove and gas oven,fire place not used and i only burnt 55 gallons of propane fuel which relates to about $160.00 -- I was happy with that! I am on a spring fed well and have not had to backwash my tankless heater yet??? We have never had a hot water problem. the unit is about the size of a small suitcase and hangs on an outside wall vented directly to open air via a stainless steel vent. The unit carries a 30 year wanentee--made by NORITZ ! Local schoolboard has changed every school over to them and is saving serious money!!! The unit must be designed for the demand use just like a range or people will complain and have problems!

 

[Len]

electric water heater

electric water heater

electric tankless are horrible for resi use. they cannot keep up with demand. For an electric tankless to actually work properly you would need to install one with about 150amps. Tell him to put a regular electric back.

 

[chris500]

From what I have seen of them, the people who are unhappy with them are the ones who buy the lowest end one they can, which is typically undersized for their needs.

The people who purchase correctly, and of a proper size, are extremely satisfied with them. Economically I don't know, but theoretical they are great.

 

[TOOL_5150]

I say go with gas.
I installed one (Rannai) And it works great.
Uses very little gas and single 15 will take care of it. Its only for the fan and igniter.
You can put a 20 or 30 gallon tank beside it need be.
That will last a long time.

I did as well. I lucked out and was able to install it close to the gas meter. Brought a dedicated 15a to it, installed a disconnect and it was ready to go.

~Matt

 

[dereckbc]

Electric tankles are only good for point of use like a sink in the kitchen where flow rate is not important because it will be low. The only useful ones are LP or NG.

 

[augie47]

I've seen about 25 or 30 of the "whole house" tankless installs. Of that number, 2 or 3 folks were satisfied and they installed ones that were in range of 30+ kw or so.
I've seen an equal or greater number of gas units and the satisfaction rate was close to 100%.

 

[charlietuna]

Please do not confuse insta-hots with tankless water heaters--ain't even close to being the same!! If you provide proper power ---FOR A PROPERLY SIZED TANKLESS WATER HEATER (NOT AN INSTA-HOT)----- it will provide selected hot water until you run out of water or run out of power ! The customer will not know the difference because the water temp. will remain constant throughout his house! Undersize the unit to suite his service size and you are selling the homeowner nothing but problems which can be blamed on everybody!!

 

[Power Tech]

I tell all my customers to get gas.

 

[MGordon]

Reteric Response

Reteric Response

I think that the tankless is a good option but I would have it set up per bathroom not for whole house. Lot of money spent that way. It would be cheaper I believe for the bathrooms individually.

 

[charlietuna]

Individual units would not be cost efficient and would require at least twice the power additions to the service--instead of a 300 amp service it might take a 400 amp service. Remember, the cause of the high electrical power requirement is to instantly heat an unlimited number of gallons to a set temp! Now this number of gallons is determined by the rated size of the tankless unit.

 

[ohm]

I installed a 2.5 GPM tankless unit to an 80 year old lady living alone. I requred a 50A 240 feed. She had 1/2" copper lines and never ran any hot water at more than one location at a time.

I simply hooked the cw inlet of the tankless to the output of the 30 gal. unit but she left the 30 gal. unit turned off. Our plan was to leave it off unless the tankless unit failed. Now her 56 deg. rises to 70 deg. in her pantry (30 gal heater location) before it gets heated.

Her showerhead was rated 2 GPM and she always had plenty of hot water. Saving a bunch on power.

Only problem was our selection of tankless heater. It failed after about four months due to terrible design.

 

[Minuteman]

I once installed one for a customer with a 125 amp service. Darn thing required three 40 amp circuits for it's three stages. No matter what I did, the kitchen lights would flicker when the thing came on. I was able to adjust it so that the bathroom and bedroom lights would not flicker, unless there was demand from 2 places (like 2 sinks, or 1 sink and washing machine).

Folks decided to live with the flicker rather than upgrade the service.