Any Recommendations on a Tankless Water Heater?

[3thumbs]

We replaced a tank type water heater in our crawlspace because the "stubby" gas fired heaters are no longer produced. We got a Rinnai 75, and the only draw back to it is that it takes around ten seconds to get the water to the desired temperature. It takes about 3-5 seconds to ignite the burner, then 3-5 more to produce 120 (or whatever temp you set) degree water. That means that at the second floor bathroom, we will waste more time and water than before. We save enough on the gas bill to make it worth doing.
The tankless heater is twice as expensive as the tank type. However, in our case, it was the only choice.
Dave

[Tom Slick]

3thumbs, Do you have the remote thermostat setup?

Anyone have maintenance issues with their tankless? Maybe the "experts" I've consulted are [not] as knowledgeable as the actual users?!

[3thumbs]

I didn't opt for the remote thermostat. It was more expense, and I didn't see what I would gain by having it. If you want to change the temp, it is easy as the Rinnai has a simple up/down touch plate on the unit.
Dave

[Mr__Bill]

I have use tank-less heaters only as a guest and never really noticed a difference. In one house they had several in-line in the basement, when water demand exceeded one then the next kicked in to provide additional heat rise. I was told that two showers could run at the same time but all the heaters kicked in and the electric meeter started making a whirling noise They had the typical time leg as the hot water got to the spigot. The heaters were mounted with unions and could be quickly taken out, they had a short copper pipe to replace the missing heater. I was told that they had send several back for service in the first year.

In the other house they had little ones in each bathroom and kitchen and an oil fired boiler that also produced hot water. When the water from the boiler got to the electric heater the electric shut off. The idea was instant hot water and then oil fired hot water that was less expensive, and in the summer the boiler ran less often.

I knew people that used the tank less heaters with radiant floor heating and had no problems with them. It gave them room by room control of heat.

I would think that one deciding factor would be local availability of replacements and parts. Local plumbing supply houses may tell you which units have a high return rate.

All the units that I have seen were rated at temperature rise per gal of water at a unit of time, as in 40 deg with up to 5 gal per min.

The down side to the units is where the electric utility does demand time pricing, you can't heat the water at night and use it in the morning. Our local COOP tells us that it's coming here in the not too distant future.

Bill

[woodturner]

Ours are gas and they provide hot water for as long as you want. No limits. I was surprised to see Croketts and Rags note on the 40 to 45 degree rise.

Two different specifications - a tankless hot water heater can heat the water some amount over inlet temperature (typically 40F to 45F). In addition, you can control the outlet temperature.

So, if you have a tankless HWH that can provide 2.5 gpm at a 40F temperature rise, and you want 120F water, you can't heat water that is less than 80F at the inlet and achieve that flow rate and outlet temperature.

Typically tankless hwh's are rated at temperature rise per flow rate (e.g. 40F @2.5 gpm). One way to achieve a greater temperature rise for the same unit is to draw water at a slower rate.

One advantage of Paloma/Rheem is that they are stocked at Home Depot - so you MAY be able to get parts more easily. If you are replacing an existing tank type hwh that is not leaking, one option is to turn it off but leave it in place, so that the inlet of the tankless hwh comes from the outlet of the tank hwh. This options lets you use the tank hwh if the tankless fails and also provides a storage tank for inlet water so that some of the waste heat in the house is used to warm the inlet water.

[thestinker]

We put in a Bosch tankless about 8 years ago. Its large enough to supply 1 major outlet at a time. We adopted some kids and addded on. I love the tankless so much, we got a second one, which was cheaper than buying a larger one that would supply 2 outlets at the same time. The 1st one supplies the kitchen and old bathroom. The new one supplies the mud room and new bathroom. So I can still take 2 showers, or wash dishes and clothes at the same time. No complaints on the heaters, would never own a tank again.

Stay away from the electric ones, they cause nothing but problems. Mine are natural gas. They also make an LP version, which I would guess would work much like the natural gas ones I have.

Riley

[leehljp]

Just to clarify somethings that I see here -

ELECTRIC: I don't have any experience with electric ones. I haven't seen any, but I haven't looked for any either.

FLOW RATE: Ours does slow the flow rate for about 3 to 4 seconds and then it kicks back up to full flow. Of course the outlet full flow at the user set temp is about 85% of cold full flow. I don't know what our flow rate is but it is equivalent to our home in the US and most places that I have traveled.

Woodturner:

So, if you have a tankless HWH that can provide 2.5 gpm at a 40F temperature rise, and you want 120F water, you can't heat water that is less than 80F at the inlet and achieve that flow rate and outlet temperature.

Typically tankless hwh's are rated at temperature rise per flow rate (e.g. 40F @2.5 gpm). One way to achieve a greater temperature rise for the same unit is to draw water at a slower rate.

I can see how this is viewed from some mfg's perspective but that is not the case with us or with gas as we use it. I just talked with LOML about this and she was quick to point out that our water flow rate here is higher than in our US home. Most US shower nozzles come with flow-rate controlers built into the shower head. Over here, they don't and it is obvious. With that in mind and taking temp into factor, the Tankless units here deliver far more water at the output temp than the technicalities described.

I would think that this is more of a Gas/Electric difference, and if the temp rise is an electric versus gas differentiation, I would stay away from electric. However, it could be a company's design. IF it is a company's design, I would stay away from that company. To limit the temp rise to 40-45° at normal flow rate is to intentionally cripple it for some reason. Today's technology is way beyond that. My experience is with 15+ year old technology and it supersedes that info on the 40° - 45° temp rise at full flow rate.

I don't have the technical figures, but I do know that I can fill our ofuro (deep tub) with about 50 gallons in approximately 10 minutes (but no more than that) with water too hot to enter - in the middle of winter with the temp outside being - 5°C. I am sure that the water inlet temp is around 40 - 45°F. That would give it a 60°F rise at 5+ gallons a minute. This Ofuro thing is a cultural icon/way of life over here, so I am not stating this from an American perspective but a fact of Japanese life and expectation. (There are ofuru's here with a built in heaters also.)


TEMP CONTROL at the user location: Again, I don't know the price of the individual/remote thermostats, but they come in handy when kids are over and like to play in the sink. LOML likes to let kids help wash the dishes or even play with pots in the sink. Being able to set the control will be a benefit if kids and grand kids are prone to play with the water.

On this last issue, I am surprised how much we use the temp control, especially in the kitchen. LOML likes to keep it at 60°C, but I prefer it at 55°. Since LOML uses it the most, I leave it at her level most of the time.

SIZE: our two units are 20" x 14" x 7". I don't have the size of the ones at our former home in the Osaka area but they were somewhat smaller as we had three units there. Going from memory, I would say that they were about 18 x 12 by 7.


NOTE: I am quoting from the Japanese side and they have considerable more experience in this than the US side. Energy availability has been much more serious here in Japan for a much longer time and as such, they started working on energy efficiencies years ago. The fluorescent light bulbs, tankless heaters and other gas/electric units are where they excel.

OTHER TECHNOLOGY:
One other area that Japan excels - in which it is a new emerging technology(?) in the US are the electric commodes. Bu*t washing and drying, heated seats and more. Walk into the bathroom and the top lid opens, stand there 2 seconds while you undo your fly, and the seat lid lifts up; do your business, and the lids lower . . . and it auto flushes. Some even clean the lid. Others even test the liquid in the bowl for diabetic levels and more. Seriously! Prices for these range from $500 to $3000 for the lid/seat units and more for the chemical analyzers and dual level flushes.

[ragswl4]

Ours are gas and they provide hot water for as long as you want. No limits. I was surprised to see Croketts and Rags note on the 40 to 45 degree rise. I can understand that if that means a 40 to 45 degree choice in low versus high settings on the thermostat. But it does not make sense for a 40 to 45 degree rise from the entrance side temp.

I know that our tankless systems allow you to set the temp and they certainly have more than that. In fact they don't mention the "rise" over here. They mention just the outlet temps available. Our thermostats start at 37°C (98.6) as the lowest option, and tops out at 75°C (167°F). LOML keeps the kitchen set on 60°C (140F) and mixes cold with it to regulate the temp. I promise you that water is HOT. In winter, there is barely a noticeable drop in the temp for that setting. The one thing I do notice is that until the temp is achieved, the flow is slightly impeded.

By the way, the tankless units at this house are about 15 years old and are not as efficient as the new ones available today. Still, our gas bill for two people and guests about once months - for the two tankless units plus gas stove/oven are the equivalent of $60 - $80 a month over here in Japan, where energy is much higher than the US.

I was quoting the stats from the manufacturers. It appears that the GPM flow is directly related to the input water temp and the ability of the heater to raise that temperature to the temperature setting on the heater. As an example if imput temp is 55 degrees and the setting on the water heater is 100 degrees then that is a 45 degree rise and the heater will deliver 7 GPM. However if the input temp is 35 degrees then a 65 degree rise is required by the heater and then the flow will only be 5 GPM. Please understand this is not my science just what the specs on various tankless water heater are.

[Kristofor]

The amount of energy required to raise the water temperature a given amount will be the same in the US and Japan (though probably listed in different units ). A BTU = 1lb of water raised 1 degree F. The heaters have a finite capacity to dump heat into the water flowing through them in any specific amount of time. You can raise twice as much water 45 degrees as you can 90 degrees.

From what I've read many (most?) of the tankless units can/will cut the output flow to ensure the the unit is outputting the correct temperature water if at a lower rate, but some do not and if the temp rise isn't sufficient the out-flowing water will be below the desired temperature.

In the US converting from a conventional (or direct vent/power vent) to a tankless often requires changes to the natural gas system feeding it (upgraded regulator/meter, larger piping, etc).

My summer gas bill since moving into this house has averaged <$20 (call it half taxes and fees) with a conventional, but high efficiency tank style heater and gas stove. I don't know how much of the winter increase is due to the colder incoming water vs. home heating.

I don't think I'll ever make up the difference in price on gas savings going tankless, but the smaller footprint of a wall mount would make it easier to move around in the furnace/water heater/water softener/wiring closet... I read both positive and negative reviews but I've been hearing more positive anecdotes in general conversations with folks who have tankless units.

[woodturner]

Woodturner:
I can see how this is viewed from some mfg's perspective but that is not the case with us or with gas as we use it. I just talked with LOML about this and she was quick to point out that our water flow rate here is higher than in our US home. Most US shower nozzles come with flow-rate controlers built into the shower head. Over here, they don't and it is obvious. With that in mind and taking temp into factor, the Tankless units here deliver far more water at the output temp than the technicalities described.

Here is a link to the Rheem model sold at Home Depot under the Paloma brand name:
http://globalimageserver.com/fetchDo...9-d4328121e783

This unit can produce 5.3 gpm at a 45F temperature rise. So, if you live in the northeast US and winter water temperatures are 45F, you can get 90F outlet temperature. If you want higher temperatures than that, you can drop the flow rate - for example, you can get a 90F temperature rise at 2.6 gpm.

This information is for gas units - electric units can work as well, but the current requirements often make them impractical.

Your 50 gallons in 10 minutes example is 5 gpm. This Rheem unit could raise the temperature 50F at that rate. So, assuming winter US temperatures of -5C or 23F, which would likely give inlet water temperatures in the range of 45F or 7C, this unit would produce water at 95F or 35C.

You can certainly buy units that will produce more temperature difference at a higher flow rate, but it's often more economical to cascade two units
http://palomatankless.com/products/53/duonex.html

[woodturner]

In the US converting from a conventional (or direct vent/power vent) to a tankless often requires changes to the natural gas system feeding it (upgraded regulator/meter, larger piping, etc).

It depends on the unit - the smaller Paloma that HD sells does not require a larger gas line. They will all require a direct vent.

IF you can DIY, it may be less cost than a tank hwh. When I did mine, it was $600 for the tankless at HD (they will bargain on their prices), $175 for the vent kit, and a $300 tax credit, so call it $445 net - less than a high efficiency tank hwh.

HOWEVER, if you have to have it installed, you may pay $1000 to $1500 in installation fees.

I don't think I'll ever make up the difference in price on gas savings going tankless

It depends on how you use hot water. If you have a large family or are frequently drawing hot water throughout the day, the tankless may well cost you MORE to operate - a tankless draws huge amounts of gas when it is operating. On the other hand, if you only use hot water once or twice a day, the tankless will likely save you a lot.

The point is that if you are expending energy to maintain the water temperature in a tank hwh without using that hot water, the tankless will reduce your energy costs. In other words, if the tank hwh "cycles" a lot - it heats the water up, the water cools down, it reheats it, it cools down, it reheats it, etc. - the tankless will save energy. But if the tank hwh is only heating water that you are using, so that there is no "waste heating", the tankless will likely not save energy.

Primary advantages of a tankless are:
1. Literally endless supply of hot water
2. Faster hot water at distant faucets

[pelligrini]

Primary advantages of a tankless are:
1. Literally endless supply of hot water
2. Faster hot water at distant faucets

I don't think #2 assumption is correct. If the tankless unit and the other are providing the water at the same temperature the arrival of the hot water at the distant faucet would be the same. It takes the same amount of time to flow through and warm the pipes.

Quite a few of the houses we design will get a recirculating system using a pump. The hot water capacity is increased and it's always hot at the faucet. I doubt that it is very energy efficient though.

[woodturner]

I don't think #2 assumption is correct. If the tankless unit and the other are providing the water at the same temperature the arrival of the hot water at the distant faucet would be the same. It takes the same amount of time to flow through and warm the pipes.

The tankless will take in the range of 5 to 10 seconds to produce fully heated water at the output. The tank heater will draw for about the same period of time before fully heated water is drawn out.

As a practical matter, in my experience I actually get hot water at the faucet within 5 seconds with the tankless, tank hot water heater was more like 20 seconds.

While recirculating systems will overcome this issue, they are not energy efficient.

[billwmeyer]

My wife and I also noticed a delay in getting hot water from our tankless unit. I do not think it is as long as 20 seconds, but it is longer than we had with our tank unit. I have an older house, and when I bought it the hot water heater was in the open in the kitchen about 20 past where the water lines were needed. I moved it into a bathroom, where it was more hidden and was in the direct area of water usage. When it went out, I put in the tankless unit, which hangs on a wall and gives a lot more usable space.

As I said before, we love it and will not go back to a tank system.

Bill

[mschrank]

The tankless will take in the range of 5 to 10 seconds to produce fully heated water at the output. The tank heater will draw for about the same period of time before fully heated water is drawn out.

As a practical matter, in my experience I actually get hot water at the faucet within 5 seconds with the tankless, tank hot water heater was more like 20 seconds.

While recirculating systems will overcome this issue, they are not energy efficient.

I have to agree with Erik on this one...it takes a good bit longer for the hot water to arrive at distant faucets with our tankless vs the old tank. Reason being is that the fire doesn't start until a specified flow is sensed in the heater.