Unlimited hot water

[charlz]

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.

I dunno, I think 'unlimited hot water' would just mean 'unlimited shower time' for my daughter... I have turned off the hot water more than once to roust her out of there

 

[MossRoad]

I dunno, I think 'unlimited hot water' would just mean 'unlimited shower time' for my daughter... I have turned off the hot water more than once to roust her out of there

I've been tempted to do that, too! :thumbsup:

 

[dmccarty]

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

Hard water was another reason we did not install the on demand heater. A couple of years ago we were talking to the plumber who did the plumbing when we were building our house and we mentioned on demand hot water heaters for some reason. He said he refuses to install them anymore because he has seen too many problems with them. Hard water was one of the problems.

Later,
Dan

 

[sdkubota]

How warm is the exhaust coming off of these tankless heaters. I have a hard time believing there is an efficient transfer of heat when it occurs that fast. I also question how much more efficient they are then tank models. Yes, tank models do sit with heated water but if they are insulated well the heat transfer would be much more efficient. Like driving a 3 hp car down the road verses a 100 hp car. Yes, one goes faster but at much higher fuel consumption.

 

[PineRidge]

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?

Wow I didn't expect so many replies and I'll try to get to everyone who has asked a question. Short on time right now because of doctor appoint.

I am on well water and the pump switch was 20/40. I was instructed to go to a 30/50. The tech said the more pressure the better the install will be. I opted for a 40/60 instead of messing with trying to make an adjustment to an existing switch. I also installed a whole house filter to catch any sand before the cold water meets the heater. A small expansion tank was added to eliminate relief pop-offs.

Because our home is 84' long I originally installed a wild loop using ma small Grundfos pump that was controlled by a timer so it wasn't running when we were sleeping. We always had instant hot water there was never any wait involved. I was told the new heater needed a pump that could handle 35' of head at roughly 10psi. The cheapest I could find at the local supply house was a Taco 009.

So I went shopping on ebay and found a sub with the same ratings for $150 new. I'm still waiting for it to arrive. It will install where you see the 1/2" copper capped on my install.

Pricing: I can purchase a standard 40 gallon gas water tank for $150. The 199k American tankless heater was $1100. with a $200. rebate. The additional materials copper, fittings, PVC, pump, exp. tank, filter, ect. all added another grand.

These tanks are made to be vented with PVC (not foam core). They have secondary heat exchangers that wring all the usable heat out the gas/propane that they can making them condense slightly acidic water, hence you see the condensate pump on the lower right of the plywood panel. The flue gas temperatures are cooler than our gas clothes drier. They are rated to 2" or 3" PVC depending on the length of pipe that you need to run.

The instruction I received was to install the heater on an outside wall with double layer of 3/4" ply. I added a thick sheet of plastic between block/plywood to keep the plywood from drawing moisture from the block wall.

On a correction I set the tank initially at 160 degrees F not 140 degrees F. We like HOT water.

Other American facts

BTW: AO Smith acquired American and Takagni (hope I spelled that right.)

 

[ChristianHF]

This one is on my short list, the efficency is as good as tankless

GDHE-50-LP - AO Smith GDHE-50-LP - 50 Gallon - 100,000 BTU Vertex 100 Power Direct Vent Residential Gas Water Heater (LP Gas)

 

[PineRidge]

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).

Yes softened water is a must. We use a water softer that uses two separate tanks to soften the water. While one is regenerating you are always using the opposite tank. So unless you run out of salt you never run out of soft water.

The on demand heaters need to be de-limed once a year. You pour a gallon of white vinegar into a 5 gallon bucket. A pump is placed in the bucket and two water hoses are connected to the special isolation valves on the bottom of the heater. The vinegar is circulated through the heater for a short period of time with the tank turned off. Then the heater can be put back into service. It's a pretty simple process if the isolation valves are installed from the start.

 

[RobertN]

I'd be curious how that is handled in Europe etc? We can't be the only ones with hard water. As prolific as these are in other area's, they must have a way of dealing with it.

Hard water was another reason we did not install the on demand heater. A couple of years ago we were talking to the plumber who did the plumbing when we were building our house and we mentioned on demand hot water heaters for some reason. He said he refuses to install them anymore because he has seen too many problems with them. Hard water was one of the problems.

Later,
Dan

 

[vwnotrunning]

We made some strict rules on length of showers when we put in our boiler to have unlimited hot water. A few long showers can offset the efficiency very quickly. I did have to set a time and turn off the hot water during a few longer than necessary showers. After one of two times you only have to mention they have been in there too long - teenagers do learn quickly rinsing off soap without hot water is not fun.

Be sure to check on the circulation pump with your tankless unit. Several models cannot react quick enough to prevent overheating when hot water is returned via a circulation pump. You may need to add a thermostat on the return line to shut it down when the hot water reaches the pump.

 

[kenmac]

I have turned off the hot water more than once to roust her out of there

I use to have to do this to my oldest son ( who no longer lives at home) He thought I was the biggest *** for doing this. He wouldn't leave any hot water for anyone else to take showers......The biggest problem with tankless is ,, Most people will not perform the maintance that's required and end up with a stopped up water coil . Once stopped up. It has to be replaced. They had to stop at around 199 k btu for these. 200k and over is considered a boiler & have to be tested & rated as such

 

[dave1949]

<snip>

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

I've wondered about this too.

My propane 90K btu boiler would run about 30 minutes to recover our 80 gal indirect-fired hot water tank. It was well insulated, so the number of times it would run just to keep the 80 gal of water hot with light use, hand-washing, etc. seemed to be about twice a day. So, for the two of us, is was about five 30 min. burns per day, or 2.5 hours X 90K btu = 225K btu.

That is ~ 1.13 hours at a burn rate of 199K btu (225/199=1.13), assuming it is constant. I know some now have modulating/variable flames. Two showers per day, wash dishes, load of laundry, etc. can't add up to more than about 1.5 hours of use. It sounds like it ought to be cheaper on propane, but higher initial cost and maintenance.

Bosch used to make a unit that used the water flow to power the gas igniter. It didn't require electricity and had no standing pilot, that was aimed at off-grid solar users.

 

[valley]

Greetings, We have a tankless. This will be the third year, we too have a well. I haven't done any maintance to speak of. I do need to install a strainer, some chips and whatever do come from the well now and again. I'ed like to install one in our other place but the well there is very alkaline, I was wondering how much of a problem that would be. The cost of the unit also slows the rush to install them.

 

[ptgdigger]

Up north here they work ok when the water inlet temp is 45° or higher but on municipal water we get water temps in the range of 36° from early in December on through the winter. The last time I looked at these when I replaced my water heater 7 or 8 years ago there was no readily available model that could handle a 2.5 gpm shower head at a 100° rise.
Looking at the American data sheet in the OP it seems the biggest model (540) can give about 3.6 gpm at 100° rise, although you are still not guaranteed an acceptable result because of inefficiencies that can creep in with pressure drop, scale buildup and an insufficient propane supply which cannot make vapor fast enough in the coldest temps to support a 199,000 btu burner. So if you're in the northern tier or northeast do your homework, know the coldest water inlet temp to expect, know the vapor capacity of your propane storage at the coldest temps your area experiences and know the scale tendencies or hardness of your water.


Ray

 

[PineRidge]

Greetings, We have a tankless. This will be the third year, we too have a well. I haven't done any maintance to speak of. I do need to install a strainer, some chips and whatever do come from the well now and again. I'ed like to install one in our other place but the well there is very alkaline, I was wondering how much of a problem that would be. The cost of the unit also slows the rush to install them.

I would be concerned if you aren't doing the de-liming at least once a year. As lime builds your efficiency drops off and you stand the chance of plugging the exchanger. As an example of how fast lime can build we use a Keurig coffee maker daily. About every 6 months it starts to sound like a jet plane when it heats a new inrush of water. At that point I fill the water reservoir with white vinegar and run a couple of batches through leaving the vinegar in the machine for 15 minutes. The results are dramatic, the coffee pot reverts back to sounding like it did when it came out of the box new.

 

[sdkubota]

Greetings, We have a tankless. This will be the third year, we too have a well. I haven't done any maintance to speak of. I do need to install a strainer, some chips and whatever do come from the well now and again. I'ed like to install one in our other place but the well there is very alkaline, I was wondering how much of a problem that would be. The cost of the unit also slows the rush to install them.

An alkaline water source will deposit minerals if present in the water which is almost guaranteed.

 

[Dr Dave]

Vinegar also works great to clean the dishwasher, washing machine and showerhead.

Dave

 

[dmccarty]

I'd be curious how that is handled in Europe etc? We can't be the only ones with hard water. As prolific as these are in other area's, they must have a way of dealing with it.

Maybe they use water softeners? Different on demand heaters? We need a softener, but I don't want one, and at present, we don't have space for a softener. The plumber really did not like on demand water heaters because of the problems he had experienced.

Later,
Dan

 

[charlz]

Up north here they work ok when the water inlet temp is 45° or higher but on municipal water we get water temps in the range of 36° from early in December on through the winter. The last time I looked at these when I replaced my water heater 7 or 8 years ago there was no readily available model that could handle a 2.5 gpm shower head at a 100° rise.
Looking at the American data sheet in the OP it seems the biggest model (540) can give about 3.6 gpm at 100° rise, although you are still not guaranteed an acceptable result because of inefficiencies that can creep in with pressure drop, scale buildup and an insufficient propane supply which cannot make vapor fast enough in the coldest temps to support a 199,000 btu burner. So if you're in the northern tier or northeast do your homework, know the coldest water inlet temp to expect, know the vapor capacity of your propane storage at the coldest temps your area experiences and know the scale tendencies or hardness of your water.


Ray

That was the major discouragement for me when I first looked at these units my winter time inlet temp is about 40F. That and I would have to use electric, same as my HWH today. If we ever get natural gas here I may look at it again. My HWH is located in a central 'closet' under the stairs so it would require re-plumbing so it really has to be worth it.

I wonder if there is any efficiency in the colder climates to using a small tankless in front of a pretty small tank, say 12 gals. The hot water in the tank would act as a 'booster' to make sure you have hot enough water but you are only keeping a small amount at that temperature versus 40-80 gallons.

 

[sdkubota]

I have an 85 gallon electric "Marathon" ater heater. The circuit breaker tripped once and it took two or three days before I started to notice a decrease in water temperature. I really don't think they lose that much heat when sitting idle.

 

[PineRidge]

That was the major discouragement for me when I first looked at these units my winter time inlet temp is about 40F. That and I would have to use electric, same as my HWH today. If we ever get natural gas here I may look at it again. My HWH is located in a central 'closet' under the stairs so it would require re-plumbing so it really has to be worth it.

I wonder if there is any efficiency in the colder climates to using a small tankless in front of a pretty small tank, say 12 gals. The hot water in the tank would act as a 'booster' to make sure you have hot enough water but you are only keeping a small amount at that temperature versus 40-80 gallons.

If you want to pre-heat the water why not install a wild loop with a small circulater as I did. Then you always have hot water as soon as you turn on the faucet and the tank gets the advantage of the warmer water returning to it instead of 40 degree water.