Tankless Hot Water Heater

BradH70 said:

I'm considering replacing my Amtrol Boilermate hot water tank with a tankless LP fired hot water system. I use roughly 350 gallons of oil per year or about $1000 to keep water heated until needed. I would like to cut that cost in half or better if possible. Does anyone have any recommendations on good system? We are a family of 3 in a 2 1/2 bath house.

Thanks!

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Can't wait to see some answers. I am in the same boat (4 family, 2 1/2 bath) with a tankless water heater inside my Burnham Oil fired furnace. As of now, the burner is just cycled on to keep the tankless water heater to around 120-140 degrees. I use about 300 gallons a year as well and when the time is right, I want to say goodbye this method of heating domestic hot water.

I in the same both with both of you: Burnham oil boiler with an Amtrol indirect tank. Never measured the oil, but it's not inconsequential. We'll have to get a tank though.

Don't know if this will help but, when we added on to the house we installed a Rinnai tankless propane water heater. It replaced a 40 gallon LP tank. The house has 2 full and 2 half baths. One of the showers is a 2 person "spa" shower. Also, kitchen, bar, washer and utility sink use this. When we have guests often both showers and the kitchen sink are going at the same time with no problems. I don't have hard numbers but it reduced LP usage considerably.

There is a bit of lag as the system fires and pushes the cold water out of the line. Foam tube insulation on the hot water lines will minimize the inconvenience. The good news is you NEVER run out of hot water. The bad news is you NEVER run out of hot water. If you have someone in the house who loves a nice long hot shower they can stay in there until they are pruney and NEVER run out of hot water.

We did this 10 years ago and would never go back to a tank. The unit we purchased was the smallest "industrial" model, chosen because we have a big house. At that time the cost was about $1400 installed. We were installing in a new addition so we installed in the crawl space of the addition and routed the vent stack up and through the roof. 4 inch double wall SS for the vent / chimney.

We installed a Tarm dual fuel and now that we are getting used to the operation and capabilities the plan is to add a dhw coil and send the output to the Rinnai. If the incoming water is at or above the set temperature of the tankless it does not fire.

Hope this helps. And when I say "we" above I mean me, R32 insulated by nature,and the wife, R3, who really loves long hot showers to warm up in the winter.

I installed an Aquastar unit way back in the mid 90's. It was 175,000 BTU natural gas. Back then many of them didn't have the capacity required so I had to add a reserve tank. It was also a bit maintenance intensive. You had to keep the modulating valve clean and in good working order. Any kind of valve that has moving parts exposed to water can be troublesome as rust and calcium take their toll.

I would consider doing it again in our new home since the newer models seem to be so much better. Currently I have an 80 gallon electric that goes cold if you fill the whirlpool tub.

The only problem with the tankless water heaters is that they don't work well if you have a high efficiency front loading washing machine. Those washing machines typically inject hot water in short bursts and the tankless heater isn't able to supply hot water that way. The washing machine just gets short bursts of cold water. If you run hot water so the line is filled with hot water, that will only supply hot water briefly unless you have a long, well insulated hot water supply line to to the washing machine - the volume has to be large enough for the entire hot water portion of the wash cycle and insulated enough to keep the water hot for the entire length of the cycle. If it isn't, the bursts of hot water are too short to fire the tankless heater and the hot water is replaced with cold water.

It would be slick if a company sold a washing machine and dryer that includes a point of use hot water system with a small insulated tank and a heat exchanger on the dryer exhaust.

One thing no one Selling tankless heaters will tell you is you need to factor in your washing machine and diswasher into the equation.

If you have a modern diswasher and washing machine, you will never get hot water to these devices Unlike older washnig machines and dishwashers, newer ones tend to fill the hot water in "pulses" on-off on-off until they are filled with the required aount of warm to hot water. this on-off cyling tricks the tankless system into thinkning there is no demand for hot water! as a result you'll never again be able to run a load of clothes in hot water unless you also install a recurulating system and pump to trick the tankless system into thinking there is more hot water demand than there actually is.

my inlaws installed a tanless system and have all high effieiceny appliances and non of them work well now! they can take hot showers for days but the dishwasher heating element has burned out 3 times in the last 2 years since they had the system installed. the dishwasher was running the lement too long trying to boost the water temps. they now have to run the tap in the kitchen on hot only while the dishwasher starts its cycle!!

We installed a Rinnai tankless propane water heater in our house 3 years ago. It works great, and is the backup for our radiant heat system also. Regrading the hot lines for appliances: this is no different than a regular hot water heater unless you have a recirculating system. You could possible add an "on demand" recirculating system if you really needed hot water at certain taps/appliances. I would assume it would work on a push button timer system. Since the return water from recirculating would be warm, not much would be needed to keep the loop going. See http://www.rinnai.us/customer-support/faqs/tankless-water-heater/#question-10

Devo said:

The only problem with the tankless water heaters is that they don't work well if you have a high efficiency front loading washing machine. Those washing machines typically inject hot water in short bursts and the tankless heater isn't able to supply hot water that way. The washing machine just gets short bursts of cold water...

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was98strat said:

If you have a modern diswasher and washing machine, you will never get hot water to these devices Unlike older washnig machines and dishwashers, newer ones tend to fill the hot water in "pulses" on-off on-off until they are filled with the required aount of warm to hot water.

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Don't mix tankless water heaters and high efficiency front loading washing machines.

I have the rannai tankless using nat gas. We love its efficiency. We have a family of 5 total. In the spring,summer and fall when the radiant heat is not on, our actual MONTHLY nat gas usage is between $6-8! With service fees, etc it hovers just under $20 total per month. Please note that we cook on nat gas too with a 6 burner Viking rangetop (not exactly a small user of the btu's).

It does have some of the limitations mentioned above. The rannai is in the basement and the master bath is on the oppsite of the second floor, so we have a programmable recirc pump that comes on in the am so that the lines get warmed up b/f our morning showers. Only problem is you have to take a shower at roughly the same time every day to catch the warmed up lines. We found also, that the instantaneous boiler does not function well with rapid or frequent on/off demand such as when you are washing dishes and need to rinse. After we realized how efficient the unit was, we just run the water continuously for rinsing the dishes. Sounds wasteful, but really $6-8/month is not all that wasteful. (note; we are on well water so don't pay for anything other than the pumping of the water). Finally, we do not have a high eff washer so it's not been an issue but our bosch dish wash is supposed to be high eff and have not had any problems with cont. use for 5.5 years.

I've been helping my plumbing/heating contractor bud install Baxi Luna's. We've done three so far and they seem to work great no probs for any of the clients yet. Lots of brands to choose from, but get one that has local tech support. Fine Homebuilding had an article on using a conventional electric tank type DWH as an additional component in a tankless set up. Sounds counter intuitive, but I remember it making sense when I read the article. Search their archives a couple of years back.

Ehouse

Hard city water, hard well water, no water softner and short cycles all bad for these units.

Ehouse said:

I've been helping my plumbing/heating contractor bud install Baxi Luna's. We've done three so far and they seem to work great no probs for any of the clients yet. Lots of brands to choose from, but get one that has local tech support. Fine Homebuilding had an article on using a conventional electric tank type DWH as an additional component in a tankless set up. Sounds counter intuitive, but I remember it making sense when I read the article. Search their archives a couple of years back.

Ehouse

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Below is a link to the article (PDF file) that you mentioned. The link is black listed so I broke it into two parts:

http://www.finehomebuilding.com

/PDF/Free/021192082.pdf

I wonder why he uses electric instead of natural gas for the small tank. That's the only part that doesn't make sense.

Devo said:

Devo said:

The only problem with the tankless water heaters is that they don't work well if you have a high efficiency front loading washing machine. Those washing machines typically inject hot water in short bursts and the tankless heater isn't able to supply hot water that way. The washing machine just gets short bursts of cold water...

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was98strat said:

If you have a modern diswasher and washing machine, you will never get hot water to these devices Unlike older washnig machines and dishwashers, newer ones tend to fill the hot water in "pulses" on-off on-off until they are filled with the required aount of warm to hot water.

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Don't mix tankless water heaters and high efficiency front loading washing machines.

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Sounds like the appliance manufactures need to step up to the plate, how efficiency is the appliance if it requires 40 gallons of hot water to be efficient?

We installed a Bosch aquastar about 12 years ago, our well water is very hard and even with a softener a tank heater would only last 5 - 6 years the Bosch cost about 1.6 times more at the time but has paid for it self.

We installed a Bosch Aquastar about 8 years ago.

It cost a lot to put in, because it required a bigger supply line and a bigger, double wall vent.

I doubt it really saves much gas vs. the tank heater it replaced.

With the tank heater, the pilot light keeps the water hot. when I shower, about the time I finish, the 30,000 BTU burner starts up, and runs 10 or 15 minutes. With the tankless, there's no continuously burning pilot, but the 175,000 BTU burner runs the whole time.

Also, I found that when doing dishes I needed to let the hot water run continuously in order to have hot water at the sink. Every time you turn the water off, the burner goes out. When you turn the water on, then cold water enters the hot water pipe until there is enough flow for the pilot to light and the main burner to kick in. The hot water mixes with the cold in the pipe, and I ended up with tepid water at the faucet.

pyper said:

We installed a Bosch Aquastar about 8 years ago.

It cost a lot to put in, because it required a bigger supply line and a bigger, double wall vent.

I doubt it really saves much gas vs. the tank heater it replaced.

With the tank heater, the pilot light keeps the water hot. when I shower, about the time I finish, the 30,000 BTU burner starts up, and runs 10 or 15 minutes. With the tankless, there's no continuously burning pilot, but the 175,000 BTU burner runs the whole time.

Also, I found that when doing dishes I needed to let the hot water run continuously in order to have hot water at the sink. Every time you turn the water off, the burner goes out. When you turn the water on, then cold water enters the hot water pipe until there is enough flow for the pilot to light and the main burner to kick in. The hot water mixes with the cold in the pipe, and I ended up with tepid water at the faucet.

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I read the tankless heaters have a saving between 25% - 35% comparing same type of fuel, the the life expectancy of the tankless is ~2.5X longer. Also stated that a home designed around a Tank style heater could make the install more costly.

How close is your heater to the sink where you do dishes? I have not noticed the issue you are seeing, it takes time to flush out the cold water at start up just like it would with a tank heater but once the pipe is full with hot water I don't notice much of a difference in temperature during a normal washing time period. Maybe your heater is not sensing the water flow quick enough, when I turn on a faucet in the laundry room where the heater is located it seems to fire up almost instantly.

jjlrrw said:

How close is your heater to the sink where you do dishes? I have not noticed the issue you are seeing, it takes time to flush out the cold water at start up just like it would with a tank heater but once the pipe is full with hot water I don't notice much of a difference in temperature during a normal washing time period. Maybe your heater is not sensing the water flow quick enough, when I turn on a faucet in the laundry room where the heater is located it seems to fire up almost instantly.

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It was in the house we have moved out of, and the sink was in the old kitchen, which we replaced some years back. It was probably 15 to 20 feet from the heater to the kitchen sink. There are different models of tankless heaters, of course, and maybe ours was slower to light. It is the one with the generator that makes a spark from the water when you turn it on. Going from memory I think it took probably 4 or 5 seconds before it would light. The little spark would go two or three times before the main burner would kick on. If I left the water running it would be fine, but turning it on and off in short increments -- wash a dish, rinse the dish wash the next thing, rinse it -- didn't work so well. I probably ended up changing to wash a bunch of things and then rinse them all.

When we build the new kitchen we added a small electric tank heater (30 gallons maybe) right under the sink.

For me, I like how the tank heaters work better. I don't think I'd ever get another tankless, unless the price of gas was a lot higher. But if I had a tankless heater, it wouldn't be annoying enough to remove it either. So I'm not saying they're terrible, just my experience wasn't entirely happy.

Then again, we put it in nearly 10 years ago, and it shows no signs of wear. A tank heater that old would probably be near the end of it's life.

We have a Rinnai (sp?) in the cottage we just bought. I *LOVE* it. It doesn't take any longer to get hot water at a faucet than with the tank heater we've got at our old house. And we used it for 2 months and the needle on the propane tank didn't move much at all (stayed at about 70% the whole time). We used to for a shower or bath each day and dishes, plus misc-just got the washer this past weekend so no laundry. Just two of us. I would never go back to a tank system again.

Years ago we installed a tankless water heater and thought it was a great deal. However, the problem we had was that after someone drew water, say, taking a shower, and then turned off the water. Then perhaps 5 minutes later someone started drawing water, you needed to be sure to keep your hands out of the running water. The reason was that the remaining water in the lines of the heater super heated the water so that you always got a short but super hot spurt of water. After a couple of us getting burned a few times, the old water heater went back in.

A bakery in town also decided to install one of these heaters and kept it for just about a week before he also removed it for the same reason.

Backwoods Savage said:

Years ago we installed a tankless water heater and thought it was a great deal. However, the problem we had was that after someone drew water, say, taking a shower, and then turned off the water. Then perhaps 5 minutes later someone started drawing water, you needed to be sure to keep your hands out of the running water. The reason was that the remaining water in the lines of the heater super heated the water so that you always got a short but super hot spurt of water. After a couple of us getting burned a few times, the old water heater went back in.

A bakery in town also decided to install one of these heaters and kept it for just about a week before he also removed it for the same reason.

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Weird, ours doesn't do that. I shut off the water and turn it back on while doing dishes and have never had that happen.

How long have you waited before turning it back on? Makes me very curious because when I first saw these things I thought it was great. I have a suspicion that today's models are smaller and not so much water is left in the heater which would account for not having that hot blast. What model do you have. I know ours is no longer made and it was a propane heater.

Hm...a few minutes usually. I fill the sink, wash, then rinse-there's just two of us so I don't usually have too many dishes. It's a Rinnia 2520, also propane. We're set at 108F right now.

We had a Navien demand unit installed at the end of September and we're delighted with it. We use propane because our area (of SW CT) doesn't have natural gas, the big monopoly never bothered running lines. The Navien is a neat unit made in several models, including one that can feed both hot water and hot water heating.

It replaced an electric 80 Gallon tank that we've replaced three times in 20 years. Well water can be tough on any water appliance, although our second home is rarely a problem. In the last instance, the tank failed and flooded the basement two weeks before we planned to install the demand unit. Used a temporary tank provide by our plumber who did the install as fast as we could get the LP tank and lines installed and inspected.

At a total Electric cost bordering on 20 cents per KWH, the new unit, even with the higher price of propane over NG, should produce a substantial savings. We're told the Navien is somewhat better able to cope with well water variations. We'll see.

We do not have a recirculating feed line and don't really see any difference in that sense. We have lines that are a long distance from the burner, just as with the tank, and there is no distinction but one. The demand system doesn't run out of hot water. We don't have superheated water flow, i.e. it's output is regulated at 120 F. Unlike units of only a few years back, we don't have any variation in temp, e.g. when taking a shower.

We have high efficiency washer and dishwasher and don't see any difference in performance. Both of those are on short runs from the heater.

I would consider one of the newer "condensing" heaters. They can be vented with plain PVC pipe, instead of the super expensive pipe.
We have installed several of these at work.
All of these things do require maintenance, more so than their tank type predeccesors. We have a kit that we use to de-lime these heaters, basically a 5-gal bucket and a pump, filled with white vinagar that circulates through the heater.
There are "codes" you can enter to increase the max output temperature above and beyond 120*

loved my Paloma (Rheeme), the best feature is the remote thermostat, you set the temp to what you want and that is exactly what it puts out, never needed to use the cold water faucet to take a shower. I put it in myself and the one time a circuit board failed it was replace for free. Make sure your gas or propane company knows how to work on whatever model you buy, a coworker had her unit fail and no one in central NH would touch it, the one company that did show up gave up and left after a few hours and left it unplugged in the middle of the winter, the cold air came in the vent and froze it solid. (the Paloma has an electric blanket in it that will keep it from freezing as long as it has power) She ended up getting a different brand that her gas company recomended as they knew how to work on it.