Instant Hot or tankless water heater

[sao123]

I have the bosch FX-125 Natural Gas Water heater.

It heats enough water to use in both the shower + 1 sink. It is sorta loud, but i dont notice, as i have the unit in my basement. If you dont have a basement, then it might be too loud for you.

I live in pennsylvania and i have a cold basementm, but have no problem getting 140degree water out of mine...

the one danger is that if your ventilation isnt done right and cold air gets into your heater it could freeze the insides and bust.


**The thing about the pipes is irrelevent, as you have to push hot water in the pipes whether you have a tank or a tankless...

 

[vailr]

If you're located in a cold climate, geothermal might be an option for raising the incoming water temperature.
An elongated loop of plastic pipe buried 3 feet underground would raise the incoming water temperature to 50 or 55 degrees F.
http://www.waterfurnace.com/earth_loops.aspx
http://www.waterfurnace.com/pr...s.aspx?prd=EW_Hydronic

 

[JC86]

I have a tankless Rinnai instant water heater and I love it. My monthly has bill is about $15. It used to be closer to 40-50 when I had a traditional heater. It takes about 10-15 seconds after you turn on the hot water before hot water starts flowing but that's a trade off i'm more than willing to make.
Keep in mind for faucets far away from the water heater, it takes a bit longer for hot water to get there.

 

[spikespiegal]

I keep hearing that instant water heaters save money when it comes to hot water demands that are sporadic in nature. However, I don't get why this would be in cases where you live in a colder climate

Here in Michigan I have to keep my normal house heater (new hot water boiler) on most of the year. If it's 25F outside, and I turn my thermostat on the boiler off, the middle of my house gets about 48-50F, but no colder. Why? Because the hot water heater in the basement radiates enough heat to keep it that way.

So, I can either use natural gas to heat my hot water bolier or hot water tank because the heat energy is going to be radiated into the house anyways. Nothing gained. Or, I would have to compensate with a instant water heater by using more natural gas to keep my house as warm. So, in the case of a cold climate, it would seem to be a debate between heating water with electric -vs- natural gas and the costs benefits of either, correct?

Obviously if you run AC a significant part of the year an instant water heater would be beneficial given all the BTUs that radiate from a conventional water heater.

 

[alkemyst]

Originally posted by: GagHalfrunt
2) Limited water volume. Only small volumes can be handled because it's got to be heated so quickly. Don't expect to run a shower and fill the washing machine at the same time.

For a small system perhaps.

I wanted to buy one of these but the damn gas line doesn't run by my house so I have about $3000 (after rebate) just to run the gas line to where it needs to be, then another $1500 to plumb the house (heater, dryer, oven/stove)...the water heater ends up being the cheap part.

At the same time I will move my overhead power service to underground (about $2000 with a new meter/box).

 

[TastesLikeChicken]

Originally posted by: GagHalfrunt

Originally posted by: Pabster
I only have experience with the electric models. Bosch, in particular. They're awesome.

Limited water volume is a common misconception. You can get a unit to fit any usage pattern.

If you're living in the middle of Libya that might be true. For everyone else there are usage patterns and areas where tankless sucks. There are two keys to determine whether tankless is the right option

1) Water volume daily. Tankless uses a LOT more energy when operating than a conventional tank. Most people don't use that much water and so won't run into a problem. Anyone that uses a lot will see their bills rise. The break-even point is usually 200-250 gallons daily. If you use that much or more you might pay more for a tankless

2) Most important is "temperature rise". Any decent unit can produce adequate flow if the water coming in is 75*, so if you're living in the middle of the Sahara there's no problem. For those in the real world, especially in northern climes, there's a BIG problem. The water coming into a home might be 35* or so. Typical hot water is 125*. That means the water must rise 90* before it leaves the heater. Even complete morons like a few people in this thread will see that there's a HUGE difference between making water rise 50* and making it rise 90*. A powerful unit that could supply 5 gallons a minute 50* rise might only supply 1 gallon a minute at 90* rise. And don't whine about the math, that's really the way it works, efficiency isn't linear. 5 gallons a minute is enough to run a single shower and maybe a faucet or two. It's not enough to run two showers or a shower and washing machine simultaneously. If you want more water delivery you need additional units with one supplying each bathroom or several hooked up in series so that the water rise load is split up.

Despite claims of "it works for me!!" be idiots who don't understand the entire equation that does not mean that it will work for you. If you live in Michigan the cost benefit analysis is very different than it would be if you lived in Florida. If you're considering one you have to CAREFULLY consider your water needs and the incoming water temps at your house. Otherwise you're going to be unpleasantly surprised when the output is barely a trickle.

Any tankless systems that I've seen have charts that define how quickly they can compensate for the various temperture gradients between source and output. It's one of the things one must take into consideration when purchasing a tankless system. Fortunately for idiots, engineers design these systems and take those factors into consideration so, as is generally the case, the idiots that get it wrong are those that try to do it themselves cluelessly and don't do the proper research. That's why most people should consult a plumber for recommendations instead of trying to do it themselves.

 

[IGBT]

..check the noise level. some of em sound like a jet flying by.

 

[Rubycon]

Originally posted by: spikespiegal
I keep hearing that instant water heaters save money when it comes to hot water demands that are sporadic in nature. However, I don't get why this would be in cases where you live in a colder climate

Here in Michigan I have to keep my normal house heater (new hot water boiler) on most of the year. If it's 25F outside, and I turn my thermostat on the boiler off, the middle of my house gets about 48-50F, but no colder. Why? Because the hot water heater in the basement radiates enough heat to keep it that way.

So, I can either use natural gas to heat my hot water bolier or hot water tank because the heat energy is going to be radiated into the house anyways. Nothing gained. Or, I would have to compensate with a instant water heater by using more natural gas to keep my house as warm. So, in the case of a cold climate, it would seem to be a debate between heating water with electric -vs- natural gas and the costs benefits of either, correct?

Obviously if you run AC a significant part of the year an instant water heater would be beneficial given all the BTUs that radiate from a conventional water heater.

Keep your existing tank heater and set it very low - perhaps 100F. It will use very little energy to maintain that temp and the rating of the demand heater will increase as its requested rise will be much lower. This would be of particular interest to those with well systems that have relatively cold water. Tempering 55-60F water to 100F for the "instant" system will make it work much better and a smaller unit can be installed. Some of the larger electric ones require 80+ AMPS at 240VAC. With electric/electric both tank and demand units could share the same 30A circuit and a contactor can be used to prevent both from running simultaneously.

 

[secretanchitman]

my parents have a takagi tankless water heater...its actually really nice and the hot water usually comes within 5 minutes.

 

[WarhammerUC]

Thanks for all the advices.. going to the dealer tomorrow to find out more and about other options... still got 3-5 month before actually doing install.. want to get more info..

 

[Howard]

Originally posted by: Rubycon

Originally posted by: spikespiegal
I keep hearing that instant water heaters save money when it comes to hot water demands that are sporadic in nature. However, I don't get why this would be in cases where you live in a colder climate

Here in Michigan I have to keep my normal house heater (new hot water boiler) on most of the year. If it's 25F outside, and I turn my thermostat on the boiler off, the middle of my house gets about 48-50F, but no colder. Why? Because the hot water heater in the basement radiates enough heat to keep it that way.

So, I can either use natural gas to heat my hot water bolier or hot water tank because the heat energy is going to be radiated into the house anyways. Nothing gained. Or, I would have to compensate with a instant water heater by using more natural gas to keep my house as warm. So, in the case of a cold climate, it would seem to be a debate between heating water with electric -vs- natural gas and the costs benefits of either, correct?

Obviously if you run AC a significant part of the year an instant water heater would be beneficial given all the BTUs that radiate from a conventional water heater.

Keep your existing tank heater and set it very low - perhaps 100F. It will use very little energy to maintain that temp and the rating of the demand heater will increase as its requested rise will be much lower. This would be of particular interest to those with well systems that have relatively cold water. Tempering 55-60F water to 100F for the "instant" system will make it work much better and a smaller unit can be installed. Some of the larger electric ones require 80+ AMPS at 240VAC. With electric/electric both tank and demand units could share the same 30A circuit and a contactor can be used to prevent both from running simultaneously.

Isn't micro growth a problem in "warm" tank heaters?

 

[Rubycon]

Originally posted by: Howard

Isn't micro growth a problem in "warm" tank heaters?

I suppose it could be a problem with intake water from questionable sources such as ponds and cisterns. In any case where there may be concern of minor microbiological activity several solutions such as irradiation by UV-C radiation from a mercury arc lamp (dwell time to ensure 65,000 microwatts/per square cm at 10mm depth from surface) will kill anything in the water. It can be on the input side or run with a recirculator on the bunker. Pt ORP monitoring with a 650mV cutoff ensures adequate oxidation-reduction potential of bunkered water. Larger systems need monitoring and stronger oxidizing agents such as O3 or chloramine/bromine injection.

 

[alkemyst]

you talking googlese or personal experience?