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Unique On Demand Hot Water?


GolfVenture
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My question is “Not” to determine which way to go either On Demand or Traditional Propane Hot Water Tank.

My question is; Can I safely install an On Demand to feed my Propane Hot Water Tank

I replaced my Propane Hot Water Tank 3 years ago with a new Propane Hot Water tank.

Currently I have a basement apartment with 2 showers and my upstairs with 2 showers.

During weekends and holidays, the last person taking a shower can have a cold shower.

Sometime the 2 dishwasher and or 2 washing machine can be going also.

So we stagger the shower usage.

Soon my Daughter, Husband and 3 children will be moving in with me for a while.

I’m looking for an inexpensive and quick solution to provide Hot Water to my entire household.

I think that installing an On Demand to feed my Gas Hot Water Tank would be the most feasible solution.

I was thinking of installing an Electric on Demand to feed my Propane Hot Water Tank, so the Propane Hot Water Tank water input is always hot. Or until the hot water demand exhaust the 50 gallons and in addition to all the On Demand puts outs. But that should be an extremely rare if any situation.

Anyone know any caution or advise on doing this?

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My question is “Not” to determine which way to go either On Demand or Traditional Propane Hot Water Tank.

My question is; Can I safely install an On Demand to feed my Propane Hot Water Tank

I replaced my Propane Hot Water Tank 3 years ago with a new Propane Hot Water tank.

Currently I have a basement apartment with 2 showers and my upstairs with 2 showers.

During weekends and holidays, the last person taking a shower can have a cold shower.

Sometime the 2 dishwasher and or 2 washing machine can be going also.

So we stagger the shower usage.

Soon my Daughter, Husband and 3 children will be moving in with me for a while.

I’m looking for an inexpensive and quick solution to provide Hot Water to my entire household.

I think that installing an On Demand to feed my Gas Hot Water Tank would be the most feasible solution.

I was thinking of installing an Electric on Demand to feed my Propane Hot Water Tank, so the Propane Hot Water Tank water input is always hot. Or until the hot water demand exhaust the 50 gallons and in addition to all the On Demand puts outs. But that should be an extremely rare if any situation.

Anyone know any caution or advise on doing this?

I am not an expert in this area but Personally I do not see why not since I assume the demand only produces hot water when there is flow going through it. all your doing is supplying pre-heated water to the hot water tank which should eliminate hot water time lag. On the other hand Demand heaters come in all sorts of demand sizes to support multiple showers and washing machines etc at the same time. The cost to go bigger should not be that much more and by eliminating the hot water tank I am sure you would use less propane in the long run, specially since tanks use propane to heat and maintain hot water even when its not being used.

 

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I don't know if that would work. My only experience with an "On Demand" gas hot water heater at an apt I rented for a contract job was not a good one. I had to turn on the hot water at the sink in order to create enough demand for the heater to stay on and keep my shower from going cold. It probably would work because you only need it when there is a large demand and that is when it will stay on. Interesting question?

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I am not an expert in this area but Personally I do not see why not since I assume the demand only produces hot water when there is flow going through it. all your doing is supplying pre-heated water to the hot water tank which should eliminate hot water time lag. On the other hand Demand heaters come in all sorts of demand sizes to support multiple showers and washing machines etc at the same time. The cost to go bigger should not be that much more and by eliminating the hot water tank I am sure you would use less propane in the long run, specially since tanks use propane to heat and maintain hot water even when its not being used.

 

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Well my propane tank was initially installed in the basement garage 30 years ago. My thought is that the heat lost by the tank is only heating that area of the garage, heat rises which in turn heats the ceiling which is the floor of the main house. So the heat lost is not really lost. Well thats just my thought.

 

tks for your input.

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We've got a propane demand heater on our mobile home. It can keep up with unlimited usage so I don't see why you'd keep the conventional heater. It would just end up being a storage tank which you won't need.

 

I will agree with BlueSky, it needs pretty good flow to kick on. It might be an issue with a low flow shower head, which would also be true if you were using it to preheat the water to the tank. Somehow all my shower heads "open up" so it's not an issue for me.:hurts:

 

BTW, demand heaters use A LOT of gas when running. You'll need to make sure you have sufficient supply.

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Without knowing more about your home situation...I "venture" some out-of-the-box thoughts:

 

How about using your heater for the home to provide supplement heat to the hot water system.

If you have a hot air furnace, can you buy an "A frame type unit that you can pump your hot water plumbing through that will install in your heater? (kind of like how AC works inside a forced air heater) Same fan...etc..capture some of the house heat to heat the water.

 

Or..

 

My dad had hot water heat and he just tapped into the heater water circuit. It was complex at first glance, but really simple. A small pump provided the constant circulation based on a water temp thermostat...and whenever the heater ran, it also heated the hot water going into the tank.

 

Another idea:

 

If you can find the longest hot water run from the water heaters....or main water heater....you can run a return line (just a simple T-tap) from that farthest point back to the low side of the water heater drain on the tank.....this alone will circulate water for you without any need for power. (convection???don't remember). Allows almost instant hot water from any tap rather that running water for a few minutes before it gets hot.

 

Just some random thoughts here....

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Back once upon a time I had a solar hot water heater system. The solar system had an 80 gallon tank that during the summer would heat that 80 gallons up to 180°F. The hot water coming out of the solar tank went to the cold water input of my gas hot water heater. During the summer with 180° water coming in the gas heater never lit up. This did not cause any issues whatsoever with the gas water heater. During the winter the solar system was only able to take the incoming water from high 30°s to low 40°s up to mid 50°s, not a lot but it was still that much less gas needed to bring the water up to 120°. The gas hat water heater did have a mixing valve on it so that it would mix cold and hot to get an output to the house of 120°. You would not want to send 180° water to your faucets.

 

So with that said I do not see why your plan would not be safe. As to if your plan is practical will all depend on the cost of heating the water with gas vs electric. This cost differences will determine if you want the combined system or just a properly sized on demand heater or a properly sized tank system.

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Can't say I'm crazy about the idea. I think I'd opt for a second traditional tank, propane or electric, piped in parallel, or, better yet, a single larger tank, and you can opt for a high output tank as well.

The on demand heaters can be problematic, and the electric ones take a good bit of juice to run.....serious amp spike when they start. You'll need to be sure your power supply to the house / breaker box and wiring can handle it. :2cents:

Best of luck with your project; whichever way you go.:guitarist 2:

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So, as usual, I didn't read/comprehend everything:

 

Electric must be about the most expensive way to heat water. In the set up you're talking about your water will always be heated by the electric. All that tank will do is use some gas to keep it heated (which you don't need).

 

A better option might be to put the on demand on the hot side of the tank heater. That way it won't heat at all unless the tank gets cold. Save you a fortune on electricity. Of course that presumes the hot water in to the demand system won't cause a problem.

 

I've got to agree with uncledg: A second heater or one larger heater would be a better solution. Depending on how you're plumbed you might be able to have a separate heater on each unit without a lot of work.

 

Our home has two 50 gallon natural gas heaters. One serves the master bath and laundry. The other serves the kitchen and other bathrooms. We've never had a hot water problem. Another benefit is we don't have any long runs to delay getting hot water.

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:lightbulb: Just had an idea.

 

You could keep what you have, just turn the temp up to 180 or so and install a tempering valve to keep the output at 120.

Some smart person could do the math and come up with an exact answer, but that seems to me like it'd give you 50% more available hot water at the tap.

https://www.ebay.com/itm/Watts-3-4-LF-MMV-US-Tempering-valve/264148061138?hash=item3d80738bd2:g:MkgAAOSwwZxcJob7:rk:1:pf:1&frcectupt=true

Edited by uncledj
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:lightbulb: Just had an idea.

 

You could keep what you have, just turn the temp up to 180 or so and install a tempering valve to keep the output at 120.

Some smart person could do the math and come up with an exact answer, but that seems to me like it'd give you 50% more available hot water at the tap.

 

Great idea:backinmyday:

 

 

I changed to evening showers. Morning time saver :cool10:

 

 

 

AND, here in Indianapolis, Electric is by far the cheapest way to heat water, and I've even gotten used to electric heat pump heating. Lots of coal at our fingertips.

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We have had a demand water heater (we don't heat our hot water, just the cold water), natural gas and handles over 8 gpm. We have only one shower. We could not be happier. It saves room, we're never, never short of hot water, I can wash my car, my bike, my truck, my RV and my boat (if I had one) all lined up one after the other and then have a hot shower, and it's far cheaper on NG.

Some things to consider:

How many gpm do you need

 

How many gpm will your plumbing handle

 

There is no recovery time

 

Demand water heater specs are based on raising the water temp so many degrees at the rated gpm

 

It does take time to get the first of the hot water, and if you shut the water off, the heater is off as well, so keep your shower running while in there.

 

Your tank water heater heats your space as well due to heat loss, not so bad in the winter maybe, but it also happens in the summer the same way. Do you use AC? then that heat will have to be removed.

 

It's the only way to go, we were worried when we first installed it, but wouldn't go back.

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We have had a demand water heater (we don't heat our hot water, just the cold water), natural gas and handles over 8 gpm. We have only one shower. We could not be happier. It saves room, we're never, never short of hot water, I can wash my car, my bike, my truck, my RV and my boat (if I had one) all lined up one after the other and then have a hot shower, and it's far cheaper on NG.

Some things to consider:

How many gpm do you need

 

How many gpm will your plumbing handle

 

There is no recovery time

 

Demand water heater specs are based on raising the water temp so many degrees at the rated gpm

 

It does take time to get the first of the hot water, and if you shut the water off, the heater is off as well, so keep your shower running while in there.

 

Your tank water heater heats your space as well due to heat loss, not so bad in the winter maybe, but it also happens in the summer the same way. Do you use AC? then that heat will have to be removed.

 

It's the only way to go, we were worried when we first installed it, but wouldn't go back.

 

So you're saying it doesn't cut off due to low demand when you are taking a shower causing your shower water to run cold?

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So you're saying it doesn't cut off due to low demand when you are taking a shower causing your shower water to run cold?

 

We don't use a restricted head on our shower. Yes, it does take a certain amount of flow to activate the heater, not sure how much, but a trickle won't make it turn on. There are different specs for different heaters and then there are also a variation of setups that can tailor to your likes and dislikes. We are presently looking for one for my daughters house and look to be settling on a Navien.

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Most of this stuff is beyond our 'expertise' but...

 

IF there'll still be a Tank involved, we've never been happier than after we installed an 80 gallon Uber-Tank.

 

Yeah, initial higher cost, but Lordy the Peace of Mind is priceless.

 

Rgds, WRIDR

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Wow someone mention electric hot water tank? I thought those left with the dinosaur. My brother in law has three showers in three bathrooms and I have been there during family events when all three showers are being used at the same time. All he has is a demand water heater and it has no issues keeping up with three showers and sometimes the washing machine at the same time. The trick is to get the right size unit for the demand you wish to place on it. Secondly unlike a water tank it doesn't constantly reheat water that nobody is using and is just sitting there. When my water tank goes (maybe even sooner) I will be going demand hands down

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Unclecj' suggestion is the way to go; a second tank in series or a bigger tank. Everything else is too complex.

 

My :2cents:

Lots of hot water sitting there just giving off heat, that needs to be re-heated.

 

Wow someone mention electric hot water tank? I thought those left with the dinosaur. My brother in law has three showers in three bathrooms and I have been there during family events when all three showers are being used at the same time. All he has is a demand water heater and it has no issues keeping up with three showers and sometimes the washing machine at the same time. The trick is to get the right size unit for the demand you wish to place on it. Secondly unlike a water tank it doesn't constantly reheat water that nobody is using and is just sitting there. When my water tank goes (maybe even sooner) I will be going demand hands down

Keep in mind that electric is much slower in response time than gas, I wouldn't go to electric just for that item. Now gas, once it senses water flow, fires immediately to high performance and the water is HOT, it then cuts back to where it is needed and will constantly adjust the burner to keep the temp at set point. If you usage point is far away from the heater, it will take about the same time for hot water to arrive,,, well a bit longer, but then it doesn't run out either. On the other hand, if you shut off the water flow and then restart, you will get a shot of cooler temp. A good heater will stay active for a couple of minutes after the water is turned off, just to compensate for this type of an event. There are setups available to overcome this and have instant hot water at all times at all locations, but then you will have hot water 'sitting' in a line somewhere giving off heat.

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I've been toying with the idea of going to small on demand water heaters rather one central heater. It'll be a while before I do anything as I just replaced my NG tank heater a couple years ago.

 

25 odd years ago, while living on the economy in Germany, I noticed most of the apartments and homes there used small tank heaters in multiple locations, say one for the kitchen and one in the bathroom rather than a larger central tank. I think most of them were electric but I could be wrong about that.

 

I have seen on demand shower heaters but have not really looked into them. The heater is part of the shower head and the supply is cold water only. The concept is sound. Set a temperature on the heater and turn the water on. It would come up to temperature quickly and maintain that temp regardless of flow rate. Whether they work in practice or not I could not say.

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