LC Brewing
Bronze Member
- Joined
- Jul 6, 2006
- Messages
- 68
- Tractor
- I wish (someday)
All the newer units I've seen have a 0.4 or 0.6 GPM "set point" for flow - low enough for the low-volume washers and such. As I said in my responses to the code post, I've been extremely happy with the Rinnai. I've had no issues with lack of flow through multiple uses, and no problems with outlandish energy costs.
The issues I've seen with using recirculation of any kind that actually circulates through the tankless heater are shortened life of the tankless unit (Rinnai cuts the heat exchanger warranty in half when used in such an arrangement) and decreased efficiencies. There is a minimum amount of BTUs expended for the thing to operate regardless of how much it really needs to heat the water, so you might liken heating the recirculation loop to using a blow torch to light a candle.
I had the Bosch unit running for the first four months in the house and had no recirc loop setup. When I switched to the Rinnai, I added the recirc loop with a 6-gallon GE 120V tank unit, a small Taco recirc pump (Model 006-B4 1/40 HP pump) and an aquastat to control the pump. We keep the tankless water heater set constant at 125 degrees, as well as the tank unit (so there is not a noticeable difference in water temperature when the 6 gallons in the tank has been used up). With the aquastat (senses temperature of the pipe immediately upstream of the pump) range of 95 to 120 degrees F, I notice the pump comes on about 3 times per day (I have not insulated the water heater or the piping yet - it is in my unfinished basement). We have seen no noticeable change in our electricity bills due to the addition of the water heater or pump. I see the tank as more of a thermal buffer than anything - considering that the combined volume of my 6 gallon tank and my 3/4" main hot water lines is about 9 gallons total (not a lot to have to reheat from around 95 to 125 about 3 times per day). And, as with all things in life - sometimes there is a small price we are willing to pay for the "luxury" of not waiting for hot water. Even better is paying that small price for the spouse to not have to wait for hot water.
Now, as far as CurlyDave's original question - it really has a lot to do with your local energy prices. If propane is reasonable cheap, it may be the best bet. If electricity is cheap (and you are willing to bit off the initial wiring costs and added service requirements - i.e. 400-amp main to the house), it may be a better way to go. When we built our house, I put in 400-amp service because I planned on adding exterior buildings and a shop down the road, and the PUD charged me an extra $1300 for "upgraded" service - claiming it was because the 400-amp service required a non-standard meter and extra terminations. Add to that the fact I had to run larger wire up my 700 foot driveway to the transformer (in two separate 3" conduits, no less), and larger wire into the house (in two more separate 3" conduits), and you can see how upgrading your electrical service can get costly. LP tank heaters have astounding efficiency ratings any more. They are also much easier to "plug-and-play" when/if they die. The design hasn't changed much in a long time, and probably won't any time soon. Tankless units may or may not be as easy to replace when they go out.
There certainly is an "up front" cost to tankless. With electric units, you are paying that cost through larger wire sizes, increased electrical service to the house, and high loads when the unit is running. With gas units, you are paying that cost through a high price for the unit (when compared to electric tankless), high cost for exhaust venting, and larger gas piping requirements. Add to that the "muddy" (at best) comparisons of efficiency between tank units (NG/LP/Electric) and tankless units (NG/LP/Electric) and it is really hard to tell what is truly "cheaper". There are simply too many variables to get a good answer - cost of each energy source, cost of installation, water usage habits (how much hot water do you really use, how often you use it, etc) - it really is different for each individual. If you are using a lot of hot water all at once and then don't use it again all day, you may be better off with a tank unit that has a slow recovery time - you simply drain down what water is in the tank when you use it, and give it all day to "recharge". If you use hot water all day in smaller doses, you may even be able to get by with one or several "strategically located" smaller tank units or a handful of "Point-of-Use" units and limit the amount of hot water piping installed in the house altogether.
One last thing to mention - I don't necessarily think that "endless hot water" will change your usage patterns. It's more of a comforting thought than a life-changing situation. In my last house, I had a 40-gallon gas tank unit. With my wife and I and two toddlers, we never ran out of hot water in normal use. I was up and showered and out the door at least an hour before anyone else in the house was up. My wife showered when she got a chance (stay-at-home mom). She used the water throughout the day for dishes, clothes, etc. At night, we would give the kids a bath, and maybe use some more hot water making dinner, doing the dishes, and some more laundry. Now, we have a bigger house, tankless (endless) hot water, and the kids are a few years older. But we still follow the same patterns, and the same usages more or less. About the only thing that has changed is now, I can start a load of wash, turn on the dishwasher, start washing the pots and pans, and my wife can run upstairs and run the bath for the kids without us worrying about running out of hot water somewhere in the middle of it all. I don't notice that we take longer showers, or spend more time using hot water than we did before. If anything, I think we use less water - especially since we have added the recirculation loop (don't have to run the water waiting for it to get hot) and all of our appliances are water efficient (dishwasher, front-load clothes washer). We don't pre-rinse our dishes much either before throwing them in the dishwasher, and our garbage disposal (yes, we have one, even though we are on a septic system) is ONLY for the stuff that inevitably ends up in the sink through food prep/cleanup.
That's my $0.02. As always, YMMV...
The issues I've seen with using recirculation of any kind that actually circulates through the tankless heater are shortened life of the tankless unit (Rinnai cuts the heat exchanger warranty in half when used in such an arrangement) and decreased efficiencies. There is a minimum amount of BTUs expended for the thing to operate regardless of how much it really needs to heat the water, so you might liken heating the recirculation loop to using a blow torch to light a candle.
I had the Bosch unit running for the first four months in the house and had no recirc loop setup. When I switched to the Rinnai, I added the recirc loop with a 6-gallon GE 120V tank unit, a small Taco recirc pump (Model 006-B4 1/40 HP pump) and an aquastat to control the pump. We keep the tankless water heater set constant at 125 degrees, as well as the tank unit (so there is not a noticeable difference in water temperature when the 6 gallons in the tank has been used up). With the aquastat (senses temperature of the pipe immediately upstream of the pump) range of 95 to 120 degrees F, I notice the pump comes on about 3 times per day (I have not insulated the water heater or the piping yet - it is in my unfinished basement). We have seen no noticeable change in our electricity bills due to the addition of the water heater or pump. I see the tank as more of a thermal buffer than anything - considering that the combined volume of my 6 gallon tank and my 3/4" main hot water lines is about 9 gallons total (not a lot to have to reheat from around 95 to 125 about 3 times per day). And, as with all things in life - sometimes there is a small price we are willing to pay for the "luxury" of not waiting for hot water. Even better is paying that small price for the spouse to not have to wait for hot water.
Now, as far as CurlyDave's original question - it really has a lot to do with your local energy prices. If propane is reasonable cheap, it may be the best bet. If electricity is cheap (and you are willing to bit off the initial wiring costs and added service requirements - i.e. 400-amp main to the house), it may be a better way to go. When we built our house, I put in 400-amp service because I planned on adding exterior buildings and a shop down the road, and the PUD charged me an extra $1300 for "upgraded" service - claiming it was because the 400-amp service required a non-standard meter and extra terminations. Add to that the fact I had to run larger wire up my 700 foot driveway to the transformer (in two separate 3" conduits, no less), and larger wire into the house (in two more separate 3" conduits), and you can see how upgrading your electrical service can get costly. LP tank heaters have astounding efficiency ratings any more. They are also much easier to "plug-and-play" when/if they die. The design hasn't changed much in a long time, and probably won't any time soon. Tankless units may or may not be as easy to replace when they go out.
There certainly is an "up front" cost to tankless. With electric units, you are paying that cost through larger wire sizes, increased electrical service to the house, and high loads when the unit is running. With gas units, you are paying that cost through a high price for the unit (when compared to electric tankless), high cost for exhaust venting, and larger gas piping requirements. Add to that the "muddy" (at best) comparisons of efficiency between tank units (NG/LP/Electric) and tankless units (NG/LP/Electric) and it is really hard to tell what is truly "cheaper". There are simply too many variables to get a good answer - cost of each energy source, cost of installation, water usage habits (how much hot water do you really use, how often you use it, etc) - it really is different for each individual. If you are using a lot of hot water all at once and then don't use it again all day, you may be better off with a tank unit that has a slow recovery time - you simply drain down what water is in the tank when you use it, and give it all day to "recharge". If you use hot water all day in smaller doses, you may even be able to get by with one or several "strategically located" smaller tank units or a handful of "Point-of-Use" units and limit the amount of hot water piping installed in the house altogether.
One last thing to mention - I don't necessarily think that "endless hot water" will change your usage patterns. It's more of a comforting thought than a life-changing situation. In my last house, I had a 40-gallon gas tank unit. With my wife and I and two toddlers, we never ran out of hot water in normal use. I was up and showered and out the door at least an hour before anyone else in the house was up. My wife showered when she got a chance (stay-at-home mom). She used the water throughout the day for dishes, clothes, etc. At night, we would give the kids a bath, and maybe use some more hot water making dinner, doing the dishes, and some more laundry. Now, we have a bigger house, tankless (endless) hot water, and the kids are a few years older. But we still follow the same patterns, and the same usages more or less. About the only thing that has changed is now, I can start a load of wash, turn on the dishwasher, start washing the pots and pans, and my wife can run upstairs and run the bath for the kids without us worrying about running out of hot water somewhere in the middle of it all. I don't notice that we take longer showers, or spend more time using hot water than we did before. If anything, I think we use less water - especially since we have added the recirculation loop (don't have to run the water waiting for it to get hot) and all of our appliances are water efficient (dishwasher, front-load clothes washer). We don't pre-rinse our dishes much either before throwing them in the dishwasher, and our garbage disposal (yes, we have one, even though we are on a septic system) is ONLY for the stuff that inevitably ends up in the sink through food prep/cleanup.
That's my $0.02. As always, YMMV...
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