Unlimited hot water

[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.