tankless water heaters

[Greg Swartz]

I have done 2 tankless systems: 1 electric and 1 gas.

Both customers are happy with the throughput, but the electric one just asked me to install another one. I declined. The electric one took 3 - 40A - 2 pole breakers, and was rated for 40 gallons. He really likes it. Can't remember why he wants another one. Told him several thousand dollars for a panel upgrade...

The gas one I installed was for a 6000 sq ft house. It used a 15A breaker, supplied the radiant heat for the entire house (all 6000 sq ft... yes, even the garage), as well as all the bathrooms, AND the kitchen appliances! I was thoroughly impressed. I believe it was Rannai system.

 

[dreamsville]

I've never been fully convinced that timing water heating saves that much. When the timer energizes, you have to heat that water back up again.

Larry,
Granted I only have 25 years of experimentation, but I've convinced myself :smile:. The key is that you've got to buy a good insulated tank, not the cheapest one you can find as most people do.

Why use power to keep that water at its peak temperature constantly throughout the day when you end up diluting it anyway.

 

[charlietuna]

The storage of hot water results in a 45 percent energy loss in any tank type water heater. And gas is 60 percent more efficient at heating water than electric resistance elements. The proper sizing and location of any tankless heater (gas or electric) is very important--but any tankless setup is much more efficient than a tank type heater.

 

[ohm]

I've never been fully convinced that timing water heating saves that much. When the timer energizes, you have to heat that water back up again.

Larry,
Granted I only have 25 years of experimentation, but I've convinced myself :smile:. The key is that you've got to buy a good insulated tank, not the cheapest one you can find as most people do.

Why use power to keep that water at its peak temperature constantly throughout the day when you end up diluting it anyway.

I agree a well insulated tank is worth the extra bucks but insulation only prolongs the inevitable. No matter how well a pipe is insulated it will still freeze, if heat is not added.

Also true, why heat a tank up to 135 deg if you're going to dilute it to 120 deg. every time. The same can be said about buying 150 proof booze if you're going to add water or ice cubes!

 

[enosez]

Electric Tankless for Radiant Floor Heating???

Electric Tankless for Radiant Floor Heating???

I picked up a whole house tankless unit at big blue for $75 on clearance. Seems someone purchased it to use and found out that it needs 125 amps to run. Their loss my gain.....My Garage has an empty 200 amp panel!!
I was going to attempt to use it for my radiant floor heat in my garage. My design temp is 130 degrees and figured that the heater could handle tthis temp considereing right now with 130 on the supply side I get 90 on the return.
My only concern is will I have to slow the flow through the unit for the cold cold days.
Any body out there use one of these or install one for radiant floor heating?

 

[megloff11x]

If you want to warm it up fast, you have to supply a lot of power. It sounds like he needs a new service anyway. These days you need 150-200A in most homes, especially if you have lots of gadgets. I have 100A but I live pretty spartan - I have only one 20" TV and without a surround sound system.

I haven't heard much good about tankless heaters either. And after my Army days, I like to enjoy a shower that includes hot water and a decent flow rate. I figure I've earned it.

Matt

 

[SmithBuilt]

I agree a well insulated tank is worth the extra bucks but insulation only prolongs the inevitable. No matter how well a pipe is insulated it will still freeze, if heat is not added.

There is a marathon tank that only looses 1 degree per day, not being used, I'm sure thats what dreamsville is talking about. An engineer that is close to me that pushes the 100 gal marathon tank and insulated hot water loop and the timer. The poco in my area will do a cheaper rate in the middle of the night, they don't like to so you have to be persistent.

 

[ohm]

There is a marathon tank that only looses 1 degree per day, not being used, I'm sure thats what dreamsville is talking about. An engineer that is close to me that pushes the 100 gal marathon tank and insulated hot water loop and the timer. The poco in my area will do a cheaper rate in the middle of the night, they don't like to so you have to be persistent.

Sounds like with off-peak billing and a timer it's a winner.

 

[ohm]

I picked up a whole house tankless unit at big blue for $75 on clearance. Seems someone purchased it to use and found out that it needs 125 amps to run. Their loss my gain.....My Garage has an empty 200 amp panel!!
I was going to attempt to use it for my radiant floor heat in my garage. My design temp is 130 degrees and figured that the heater could handle tthis temp considereing right now with 130 on the supply side I get 90 on the return.
My only concern is will I have to slow the flow through the unit for the cold cold days.
Any body out there use one of these or install one for radiant floor heating?

Some units have a minimum flow cut-off switch and some don't allow over 70 deg water on the inlet. But I believe you've got a winner.

 

[RHJohnson]

I have done 2 tankless systems: 1 electric and 1 gas.
The gas one I installed was for a 6000 sq ft house. It used a 15A breaker, supplied the radiant heat for the entire house (all 6000 sq ft... yes, even the garage), as well as all the bathrooms, AND the kitchen appliances! I was thoroughly impressed. I believe it was Rannai system.

I see you are in CO......Are these systems set up to drain all the water if you lose power. If not....what happens in the middle of a severe cold spell to prevent pipe bursting.
I'm in Alaska. We need closed systems w/anti freeze.

 

[jrannis]

The label on my 30 gallon water says that it costs $414 per year to run the unit.
Considering that you would have to pay for electricity no mater if you had a tank or not I would have to wonder how much money could you really save by installing a tankless heater.
Gas would really be the only way to go for a retrofit.
New construction might be a good decision for tankless electric unit as mentioned earlier.
Until then, we will enjoy changing meter cans due to burned up lugs from all of the handyman installations in town.

 

[charlietuna]

jrannus,
The figures on your tank sound about right--power companies estimate about $45.00 a month to heat an average water tank. Studies show that 45 percent of that energy(gas or electric) in a tank type heater is lost thru the walls of the tank to it's ambient surroundings. In your case that is 45 percent of $414, which is $186.30 a year. Now in your case, if(?) the water heater is located inside a conditioned air space, your would require your air conditioner to remove that heat lost due to the storage of water in the tank type heater. This cost would depend on the efficiency of your A/C system, but it will more than double the $186.30 figure. People who live up North may only face this issue 6 months of the year....

 

[Greg Swartz]

I see you are in CO......Are these systems set up to drain all the water if you lose power. If not....what happens in the middle of a severe cold spell to prevent pipe bursting.
I'm in Alaska. We need closed systems w/anti freeze.

The electric one was not set up to drain. Good thing is that the piping was inside. The gas one, was set up to drain. It too was inside, but the house was all concrete: Walls, ceiling, floor... When we trimmed the house in January, we closed the door, and the 10 degree 30 MPH winds had no noticable affect on the house. In fact, you couldn't even hear the wind until you got close to the door.

Out here, Fire Suppression systems are required to be dry systems due to the weather. The old style ones though, are set up with antifreeze.

When I worked on the Denver Convention Center a few years ago, it dropped to -10, and the wind brought it lower. The upper level was WIDE open, with all the hi-rise buildings around, it created a wind tunnel. No one was allowed near the edges of the building, due to gusts. Anyway, there were mad rushs to shut off all the water, as well as drain the systems on the colder days.

 

[ohm]

I see you are in CO......Are these systems set up to drain all the water if you lose power. If not....what happens in the middle of a severe cold spell to prevent pipe bursting.
I'm in Alaska. We need closed systems w/anti freeze.

Since all the systems I've looked at have a 360 deg. heater coil and must be flooded at all times, a blow-down rather than a gravity drain would be required to prevent flooding. However, if the building is that cold you have more problems than a bulging heater.

 

[GrayHeadedMule]

How many of you guys installing these things have a master plumbing license? Just wondering! :roll:

 

[ohm]

How many of you guys installing these things have a master plumbing license? Just wondering! :roll:

I read a DIY plumbing book once:smile:

 

[charlietuna]

They have this plastic gas line and you can run it like "Smurf Pipe" -- even has compression fittings !!:grin:

 

[LarryFine]

How many of you guys installing these things have a master plumbing license? Just wondering! :roll:

No, I'm not a licensed plumber, but I did stay at a Holiday Express last night!

 

[dreamsville]

There is a marathon tank that only looses 1 degree per day, not being used, I'm sure thats what dreamsville is talking about. An engineer that is close to me that pushes the 100 gal marathon tank and insulated hot water loop and the timer. The poco in my area will do a cheaper rate in the middle of the night, they don't like to so you have to be persistent.

I'm doing another HW tank-timer install this week. A non-profit institution that originally wanted on-demand under sink units. They decided it was the better way to go. :smile: