Unlimited hot water

[PineRidge]

I wanted to share one of my latest projects with you all. Our water heater was going on 13+ years and was affording us less and less hot water. We have no chimney or B-vent for the furnace or water heater to vent to so the furnace and the original water heater both vented out the side of the home via PVC pipe. The original tank was a AO Smith Power Shot and was at best 80% efficient. Conventional gas or propane water heaters maintain a specific amount of water 40, 50, or more gallons of water at a specific water temperature 24 hours a day so there is wasted fuel.

After some consideration we decided to go with a American on demand tankless heater and since there are 3 adults in the home we opted for a 199,000 BTU at 95% efficient unit. A on demand heater has no storage tank like its conventional counterpart. It only heats water when there is an actual demand and does so immediatly so there is little waste.

Sice the original water heater was still functioning we decided to do the install over a period of a few days working on it for an hour or two when we had the time. Once the final connections were made and the tankless heater thoroughly tested we then took the original AO Smith tank off line.

With the on demand heater whenever a hot water faucet is turned on the heater senses the flow through the heater and immediately fires the burners. We have well water and as such the digital readout indicates the inlet water temperature at 59 degrees F. The outlet temperature is currently set to 140 degrees F but is easily changed via the keypad on the front of the heater. I have no prior experience with tankless heaters but I can tell you that it's a real pleasure having an unlimited supply of hot water and it's nice not to be wasting fuel heating water when you don't need it, or away from the house.


On demand tankless water heaters are by no means new technology, they have been used in Europe for some 20+ years. I was surprised that when in Home Depot picking up some copper fittings the gal checking me out asked what my project was and when I mentioned tankless heater went on to say that she had lived in overseas for years and enjoyed having all the hot water she ever wanted. She went on to say that she couldn't understand why they weren't in widespread use here in the US to which I replied big price difference!

 

[Bob77064]

That's a very neat installation. We have a tankless water heater and have been very happy with it and the gas bills.

 

[scott_vt]

Good Mornin Mike,
Very nice job on the installation, we can see youve done this before !

For years I have been thinking of doing the same and getting rid of that power user electric that I have ! We have propane on site so it would be an easy enough convert.

Any idea on propane usage ? Thanks for sharing your project !

 

[dave1949]

Looks, good. From the photos, I can't tell if the plywood is in direct contact with the block wall, but if it is, and depending on the humidity level in your basement, you'll want to watch for moisture and mold gathering on the backside of the plywood.

The only complaints I've heard from people with on-demand heaters is, because it takes a certain flow rate to turn them on, it's hard to get a dribble of hot water. The other is that a few have had condensation freeze-ups where the exhaust exits the pipe outdoors in really cold weather.

Do you think you can determine the change in your gas usage (eventually) compared to the old unit?

 

[PineRidge]

Good Mornin Mike,
Very nice job on the installation, we can see youve done this before !

For years I have been thinking of doing the same and getting rid of that power user electric that I have ! We have propane on site so it would be an easy enough convert.

Any idea on propane usage ? Thanks for sharing your project !

Thanks Bob and Scott.

There are some factors that would determine your usage Scott. The size of tankless heater you purchase American offer 3 that are dependent on how much hot water at any given moment you need. IE: 1 or two people taking showers at the same time with another appliance such as a clothes washer using hot water. And of course the cost for propane in your area. your results may vary....

 

[1fastbob]

Couple of comments....I would be a good idea to insulate your hot water lines to make it even more efficient. Also a water softener is recommended as well water will eventually coat the heat ex-changer with scale requiring de-scaling or replacement. I will soon be installing a similar system in my home. I am NOT looking forward to a water softener and the feeling it gives the water when applying soap in the shower (slimy).

 

[V1Rotate]

I also have a tankless hot water system, however, mine also makes the heat for the baseboard radiators. I absolutely love the system, it is very cheap to run.
On my unit (and I suspect others) there is a gas valve that acts like a throttle, if there is only a small demand for heat or hot water the gas valve only opens part way so as to only provide enough flame to heat the small amout of water flowing through it. As the demand for heat or hot water inreases, the gas valve opens more, that way almost no heat is wasted.

 

[jinman]

On demand tankless water heaters are by no means new technology, they have been used in Europe for some 20+ years. I was surprised that when in Home Depot picking up some copper fittings the gal checking me out asked what my project was and when I mentioned tankless heater went on to say that she had lived in overseas for years and enjoyed having all the hot water she ever wanted. She went on to say that she couldn't understand why they weren't in widespread use here in the US to which I replied big price difference!

Mike, I always know that your projects are gonna be top-notch. That is a very nice install.:thumbsup:

I'd say the on-demand hot water systems used in Europe are common because of the cost of energy. We forget how spoiled we are to have cheap electricity and cheap fossil fuels in this country. If you double or triple the cost of energy here, the price of efficient low-consumption products will start to look much cheaper.

 

[dmccarty]

On demand water heaters do not work real well if one only has electric, which is one reason they are not used.

Then there is the cost of the units themselves. For us, the payoff on the tankless vs tank water heater was around 13-15 years at a minimum.

I thought for sure we would put in a on demand water heater when we built the house, but we only have electric, and because of the extra cost of tank less, we just went with an 80 gallon water heater. A big advantage for the tank water heater is that it provides a water supply in power outages. We have tapped that tank a couple of times. 80 gallons of water will last us quite a long time.

Later,
Dan

 

[s219]

I think the latest craze are hybrid systems, which have both an inline heater and a small reserve tank. I forget the reasoning behind it, but its supposed to give even better usability.

 

[mjarrels]

When I lived in the Philippines, I had a electric tank less system for the shower... but then the rest of the world runs on 220 volt power.

mark

 

[Whitnel]

We are building a house and our builder recommended putting a small 10 gal water heater in line with our tankless to help with low flow issues. He said that if you have a trickle of water it is hard for the tankless to heat the small volume of water. Anyone ever heard of that issue?

Also he said the vent coming from the water heater had to be a stainless double or triple wall pipe. I was surprised to see the exhaust vents that are pvc. Any gas fired units I have seen usually have a metal exhaust pipe.

 

[aczlan]

I think the latest craze are hybrid systems, which have both an inline heater and a small reserve tank. I forget the reasoning behind it, but its supposed to give even better usability.

The issue is that when you turn off the water with a tankless setup, then turn it back on, you get a slug of cold water in the system. The mini tank is to eliminate that slug of hot water and even it out.

When I lived in the Philippines, I had a electric tank less system for the shower... but then the rest of the world runs on 220 volt power.

Had a on demand heater in the showerhead of one of the apartments I lived in in Argentina. Worked well, but had me worried that it would short out and shock me as it wasn't on a GFCI.

Aaron Z

 

[bullbreaker]

We have a well with hot water tank system. I have always wondered the about life expectactcy of these new tankless units in areas where water tends to be very hard espeicially if someones softner goes down even for short period of time. Just wondereing / asking ? Anypro's/Con's ?


Boone

 

[EddieWalker]

I'm not familiar with that brand, but have been considering the Rinnai or Bosch brands. What did your unit cost and where did you get it?

Is PVC acceptable for a vent line? I've never heard of that before or even consdired it. For water heaters it has to be double wall metal pipe and I just assumed the same for anything that burns gas. Does it get warm to the touch?

Thanks for the post, your timing is much appreciated!!!

Eddie

 

[Dr Dave]

Nice looking install, my BIL installed a tankless electric unit, there were three 220V 20A circuits run to it. Its designed with three heating elemints, it senses demand and opperates, one, two or three at a time as needed.

Dave

 

[aczlan]

Is PVC acceptable for a vent line? I've never heard of that before or even consdired it. For water heaters it has to be double wall metal pipe and I just assumed the same for anything that burns gas. Does it get warm to the touch?

In a high efficiency gas furnace or HW heater you should use PVC for the air in and vent out. They actually don't recommend metal due to condensation issues.

Nice looking install, my BIL installed a tankless electric unit, there were three 220V 20A circuits run to it. Its designed with three heating elemints, it senses demand and opperates, one, two or three at a time as needed.

We have a Stiebel-Eltron Tempra 24 that runs on 2 60 amp circuits (actual draw is only ~22 amps/circuit). It works well for us in the summer. In the winter, we use a indirect 40 gallon one that is heated by the oil boiler.

Aaron Z

 

[dave1949]

We had an electric on-demand heater dedicated to a shower/bath tub in Germany. It would oscillate between cold and scald until I adjusted the cut-in/cut-out solenoids. After that, it was great and never needed any more adjusting.

 

[MossRoad]

Nice install PineRidge. :thumbsup:

I've got a question if you don't mind.
What's the cost difference between the instant unit VS a conventional unit?
We had similar questions when we were considering replacind our existing old gas furnace with a new high-efficiency unit and the payback in savings would have been something like 8-9 years... now even longer since gas prices have dropped.

I do like the idea of unlimmited hot water, however. There have been a few times when the kids have used all the hot water with back-to-back long showers and I have to wait a half an hour for just a warm one, let alone a hot one. That aspect alone may justify the cost difference for me.

 

[podagrower]

When I first read the title, I was scared, but then I saw GAS, and all was right with the world.

I have worked on the electric ones more than I want to admit, I replaced one unit completely three times, and enough parts on it to replace it another 4 times. I was never happier than the day the HO told me they were putting a tank unit back in.

Electric on demand heaters are fine for point of use, but will never work for whole house purposes. The new electric trend is heat pump, a compressor runs to heat the water, and exhausts cool air-free AC for the garage.