Hot water on demand water heater

[M7ZR6]

My wife and I are thinking about building a new house this year and were thinking of having a on demand water heater installed. With the price of natural gas we hope to spend a little more now to save later. So I thought I would see if anyone on here has one and what they like or dislike about it. I like the idea of an endless supply of hot water, and not heating water in a tank that I may not use till hours later. So does it work as advertised and worth the money over the traditional hot water heater?

Thanks for any comments that you can share that can help us make an informed desion(sp?).

Marc

 

[ruffryder]

My wife and I are thinking about building a new house this year and were thinking of having a on demand water heater installed. With the price of natural gas we hope to spend a little more now to save later. So I thought I would see if anyone on here has one and what they like or dislike about it. I like the idea of an endless supply of hot water, and not heating water in a tank that I may not use till hours later. So does it work as advertised and worth the money over the traditional hot water heater?

Thanks for any comments that you can share that can help us make an informed desion(sp?).

Marc

Most developed countries except for North America use them with no ill effects. I have used them before and like the ability of people to use multiple showers at the same time with no drop in water temperature. Though they take up a little space, and require gas lines to be plumbed into the kitchen and all bathrooms (I would think), they do give you back the space you would have used for the tank in the basement or where ever it would have been.

 

[Goldenwest]

I have a small one in my shop and I wish I would have bought a bigger one as I have to turn the water supply to it way down to get the temp at the faucet I want. It only runs the sink so not a big deal for me. Also know the cold water temp going into it as this will make your "size" decision easier. Most all are 220 not 110 so make sure your service is big enough............

 

[redlineguy]

Buddy had one in his old house and Liked it, no trouble at all, and Like ruffryder said Most developed countries except for North America use them.













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[ruffryder]

I have a small one in my shop and I wish I would have bought a bigger one as I have to turn the water supply to it way down to get the temp at the faucet I want. It only runs the sink so not a big deal for me. Also know the cold water temp going into it as this will make your "size" decision easier. Most all are 220 not 110 so make sure your service is big enough............

I thought he was talking about natural gas on demand hot water heaters?

 

[dragon12]

They are really good units. They use up far less space than a normal water heater and it only runs when there is demand for hot water. If you are not home, you are not heating a tank of water. Extremely efficient. Estimated annual energy savings over a 50 gallon tank is about $61.00. The burner will modulate to burn only the amount of fuel needed to heat the water you are calling for. If you are washing your hands in the sink, it will use like 30k btu. If you have 6 showers on, the heater will burn at maximum capacity (180k btu). These heaters have flow controls in them, so they will produce hot water at the set temp for as long as you want, but you will only get that amount of water out of them. They will not compensate for pressure by mixing in cold water like a tanked heater will, so if you have more demand for hot water than supply, you will see a pressure drop.

Some things to look out for. The gas demand for these heaters is huge. Each heater will require a supply line capable of handling 180k btu's. Be sure you have enough supply or you will get an error code and no hot water. Next, try to place the heater on or near an exterior wall to minimize the amount of vent pipe needed. Vent piping is extremely expensive and adds up quickly. And last, make sure you have the proper number of water heaters for your usage. They market these water heaters produce 8.5 gallons of hot water per minute. That number is tricky, because it is usually at a 40 degree temp rise. You probably have an incoming water temp of around 40 degrees in the middle of winter. You want 110 degree hot water, therefore, you have a 70 degree temp rise. At a 70 degree temp rise, the output is ore in the range of 4.5 - 5 gallons per minute. Figure each shower head will use approx 2.5 gallons per minute and you can run 2 showers at once without seeing a drop in pressure. Anything more than that and you hot water pressure will decrease significantly.

Sorry this is so long. Hope it helps.

 

[Sapling-Thrasher]

I have found that they do not work well in large homes that would normally be serviced by a recirc pump that gives you hot water instantly. You would have to wait for the water to get to the faucet that might be far away and then your are heating all of the water that is in the line to the sink etc and then it cools off when you are done washing your hands. I could go on and on about this but unless you are building a small home and the instant hot hotwater unit is central and close to all of the fixtures you are going to serve I wouldn't use them.

If you do buy one for a small home get a gas unit!! They do work well in small cabins/homes/shops.

I could go on about this but I would be writing a novel!!

 

[redlineguy]

I thought he was talking about natural gas on demand hot water heaters?

Me 2







.

 

[2broke4new]

I purchased one 2 years ago for my old farmhouse I "rebuilt". It is a 200,000 btu Richmond LP. I love it. Endless supply of hot water. It appears to be extremely effiecent. I went with that type for space and cost of use. I'm not home alot. The price wasn't alot more then a power-vent gas.
The downside, it has frozen up before. I live in SW IA, not extreme colds by anymeans, but the chimney has a very short run up (16") then straight out the wall (20"). I called the company and they want me to move it for less downdraft. I think if I could block the NW wind it would help. It has a heat blanket built in, so if power goes out, you may be in trouble.

 

[ruffryder]

I have found that they do not work well in large homes that would normally be serviced by a recirc pump that gives you hot water instantly. You would have to wait for the water to get to the faucet that might be far away and then your are heating all of the water that is in the line to the sink etc and then it cools off when you are done washing your hands. I could go on and on about this but unless you are building a small home and the instant hot hotwater unit is central and close to all of the fixtures you are going to serve I wouldn't use them.

If you do buy one for a small home get a gas unit!! They do work well in small cabins/homes/shops.

I could go on about this but I would be writing a novel!!

How large of homes you talking about?

I think the best method is to have multiple small units at each location, kitchen, each bathroom and laundry room. I thought this was how the did it in Europe? Or at least in the crappy hotel rooms.

 

[Sapling-Thrasher]

That depends. Gas units have a much better GPM rating because of the high BTU. If you start to install multiple units (especially gas units vents, piping etc) it will get cost prohibitive. I have not been to impressed with the electric units. Very high draw with very small GPM ratings.

If you have a home that is 3000 sqft or above these days its almost manditory to install a recirc pump. You would wait for hot water minutes on end if you didn't.

Ruffy, Your A frame isn't 3000 sqft?? You sure you live in Sammamish??

 

[ruffryder]

That depends. Gas units have a much better GPM rating because of the high BTU. If you start to install multiple units (especially gas units vents, piping etc) it will get cost prohibitive. I have not been to impressed with the electric units. Very high draw with very small GPM ratings.

If you have a home that is 3000 sqft or above these days its almost manditory to install a recirc pump. You would wait for hot water minutes on end if you didn't.

Ruffy, Your A frame isn't 3000 sqft?? You sure you live in Sammamish??

The real estate agent calls it 2300... but I would call him a lier, as that is only if you happen to live 1" above the floor. It is more like 1900 if you are 6 ft tall and actually like to use wall space...

 

[EastcapeAngler]

I have a small one in my shop and I wish I would have bought a bigger one as I have to turn the water supply to it way down to get the temp at the faucet I want. It only runs the sink so not a big deal for me. Also know the cold water temp going into it as this will make your "size" decision easier. Most all are 220 not 110 so make sure your service is big enough............

..Damn Kurt!!!! You must be bored...You NEVER post over here in the idiot section...them greenies are lookin' pretty good on yer posts though

 

[Jaynelson]

We just put one in about a year ago, it replaced twin 40 gallon tanks. Works awesome, no regrets at all. Shower for 2 days and never run out of water haha.

The brand we have is a Rinnai, I forget the exact model....maybe a 53i or something like that? Natural gas powered of course, I don't think the electric could keep up with the demands of a daily house.

Things that we ran into that are specfic to these units:

- They are picky who installs them....must be factory certified/trained apparently
- Choosing a model is specific to area and the temperature of your incoming water....how much does it need to be "stepped up"
- They are picky where you mount them....the combination intake/exhaust pipe, can't go under windows, under stairs, etc, etc
- Initially a little pricey, but savings should pay for the unit down the road, plus no risk of leaking 80 gallons of water into your house.

 

[Killerk]

We put one in our cabin more than 20 years ago.
I have been very impressed at how well it works.
Sure nice to have unlimited hot water while roughing it
It does take a while to get hot water to the kitchen which is the furthest from the heater.
It also takes a while for temp changes, but once you get used to it its not bad.
I would think that with todays technology a natural gas or propane unit would work great if used within its limits.

 

[M7ZR6]

Thanks for the replies everyone. It is nice to get feedback from peeps that have used this system. Yes I did mean a natural gas unit as I didn't think that an electric unit would work as well. Now all I have to do is see how much the builder will charge to upgrade from the tank heater.

From what I understand there is only one unit that will supply the whole house so it shouldn't be any more complicated plumbing wise. I am not really worried of a delay of hot water at the tap as where we live now there is a 30 sec to 1 min delay to all the fawcets So hopefully it will live up to the hype and also save us money on our gas bill.

 

[ArcticBoy]

Several of my contractors use them on towne homes for hot water and heat. One unit on the side of the garage.

 

[SNOW JW]

I have another question for ya. Are you heating your house with a boiler or heat tube floor heat??? If so then you will just have to plumb in a water maker to your boiler unit.

 

[M7ZR6]

I have another question for ya. Are you heating your house with a boiler or heat tube floor heat??? If so then you will just have to plumb in a water maker to your boiler unit.

I will have the lines for infloor heat put in the basement slab for future use. But you may have brought up another option that may prove to be a better use of money. I plan on eventually hooking up a boiler so this maybe a good way to kill two birds with one stone. I will have to price out that option and see.Thanks SNOW JW

 

[bigbone]

I have a rinnai and it works great. The only bad thing is every time you turn the water off when you brush your teeth or shave, you get a shot of cold water for 5-10 seconds.