Help with on demand and storage tank hook up.

JoeG

Ok, i am picking up a navien 240 with a circulator. I have a 50 Gal

Bradford White propane 50 Gal hot water heater that I want to use just

as a storage tank.







How do I hook this up?







What will tell teh on demand heater that the water in the water heater is cool and needs to be heated up?







Thanks

CMadatMe

Makes No Sense

Why would you want to do this? You are just turning an on demand heater into a storage tank. Defeating the purpose of only heating the water you need when you need it.

icesailor

On Demand:

It is my understanding from speaking to others that many "on demand" heaters are not coming on with very low flows leaving the hot water, cold. The solution is to use a tempering tank.

I'm not familiar with the equipment used here but if it is a on-demand type domestic heater, there is a way to pipe it. You could then use the smallest size heater and not over design the heater.

I would not in any use the gas storage tank as a gas fired unit after that. Disconnect the gas and use the on-demand heater as the heat source. That may be controversial to some but it has worked for me.

CMadatMe

Without a Recirc Line

Even a storage tank will deliver slugs of cold water. Most on demands need very little flow to activate them. If you have a boiler and want storage you might as well just pipe in an indirect.



Why would one invest a significant amount of money on a demand heater just to turn it into a storage tank? You might as well just upgrade the gas heater to a high recovery gas heater and call it a day.

Ironman

Defeating the purpose

You said you're getting a Navien 240 with a circulator. Are you referring to the Navien "Combi" model CH240 that has a built-in circulator and heat exchanger for space heating, or the standard model **240 heater?

 In either case, you would be defeating the entire purpose of a tank-less, on-demand heater by connecting it to 50gal. tank. The tank has a high rate of standby loss (especially a gas one), the tank-less has virtually none. The storage tank is necessary because the burner is only about 40K - 50Kbtu capacity.The Navien modulates its firing rate between 19K - 199Kbtu as the water flow rate thru the heater demands. This  means that it will produce over 5gal. per minute of continuous hot water. That's enough to run 4 to 5 showers simultaneously! And it's doing this at 98% efficiency vs. 65% of a tank heater. If you need more hot water than this, the solution would be to twin 2 of the Naviens together, not the storage tank.

Also, a note on the occasional problem that tank-less heaters have of not firing at very low flow rates: One of my product reps. who is extremely knowledgeable tells me this is occurring when cheap faucets from the big box store are installed. The checks in the faucet don't hold and pass cold thru to the hot side - thus no flow thru the heater.

JoeG

New to This

I am used to indierct off a boiler and I loved it. My new place that I am remodeling and will be moving into shortly has forced hot air and had a 30 Gal Electric Hot water heater which I got rid of, I had a 50 Gal Bradford White propane heater given to me andI have been in the house it came out of and it runs out all the time.



I figured Id try the on demand heater it has a circulator to go to a buffer tank so the water is hot even at low flow. I figured I could use the 50 gal as a storage tank and always have plenty of hot water. Should I hook the 50 gal up and keep it off and use it only as a back up shoiuld the on demand stop working?

CMadatMe

Why Did You

You decide to purchase an on demand heater? Was it the efficiency? By using the storage tank all are doing is tuning an on demand heater and making it a storage tank and are just throwing any money you thought you would be saving out the door.  I do have one question. How many gpm do you require for your new home and where do you live?

icesailor

Why did you:

You guys are using a heating solution totry to solve a plumbing problem.

If you use a high volume, high gpm instant heater for a low flow, low volume application, the heater will not come on at very low flows. Like warm water on pull out kitchen sink faucets. If on the other hand, you use a low output instant heater, the heater will come on but not give you high H2O output. If you must use a high flow heater, pipe it as a heat source to a small hot water tank. NOT a 50 gal. water heater. It is a waste of stored water. But you WILL have full pressure through the system because there will be no pressure drop through the instant heater coils. Pipe the instant hot through the water tank with a circulator and when the tank cools, the circulator will circulate water through the instant heater and the circulator will make the gas valve open and it will heat the water.

Domestic hot water heating is a plumbing problem with heating solutions applicable. Not the other way around. Heating loads are constant and high, 24 hours a day. Domestic/potable hot water heating problems are different with different solutions. With heating, you deal with a 20' drop in tempreture for recovery. In domestic hot water heating, you deal with 50'+ temp. drop/rises. If you had to supply loads like this for 24 hours a day, you would need a huge boiler to be able to supply hot water 24/7/365.

Recirc's don't solve the problem except that they will help with wasted water. But they should run as an on demand set-up.

CMadatMe

If I need Storage

Then why would I even think about purchasing a on demand heater? For the efficiency? It is a waste of money at that point. What ever efficiency you thought you were getting you are now giving back through the loss through the tank and the need to make more hot water than is necessary. Not all on demand heaters need alot of flow to come on. Nortiz for instance needs a min flow rate of .5 gpm. Navien needs the small little buffer tank in them so they can operate that the .5gpm and to get their efficiency rating.



If there is no re-circ line on a storage type heater you have to waste water down the drain to get hot water as it is. What would be the difference. I know "On Demand".On demands will make their hot water flow rates forever. The slug of cold water in the line has nothing to do with the on demand not functioning properly.



A btu is a btu whether in heating a home or hot water. The math is the math. If an on demand is sized properly and I don't mean by reading a chart it will deliver what you sized for...



GPM x Temp Rise x 500 = Btu's required

Bob Bona_4

I agree

with Chris. A storage tank defeats the purpose and principle of the tankless. 

JoeG

Not sure

I have a

 kit sink

2 bathroom sinks

 slop sink

Dishwasher

Washer

one normal tub shower combo

and a shower whirl pool 90 gal combo.

I take long showers and I like them hot there are four kids and two adults in the house not always at the same time. there's a chance both showers will be running at the same time.

Bob Bona_4

Keep in mind

no matter what the hot water heating source or how big, someone may suffer during multiple same-time tap draws if the distribution piping is not sized to handle it.

Don't expect good results if the whole house has 1/2" water piping throughout, for instance.

JoeG

1/2

Most of the has 1/2 pex, I am going to run 3/4 for the longest run to one of the bathrooms then itll be 1/2 inch to the fixture the fixtures are 1/2 in also, What is the issue with this?

CMadatMe

Showers

Are not the problem. That's 5gpm which just about max's out the Navien on a 70 degree rise. The Whirpool is the problem. Most likley that valve is delivering 7gpm plus through it. The on demand will make its rated gpm no matter how many showers are going at a time. I would size my on deman to handle the whirlpool and 1 shower or roughly 10gpm.



10gpm x 70 x 500 = 350,000 btus

I need an on demand heater that can produce 350,000 btu's. Which I don't believe a Navien can do. Nortiz on the other hand does a NC380

Bob Bona_4

Sounds

like new construction? Something like Viega's Maniblock home run system would be a good way to go so you have proper distribution and no one is left starving..

TonyS

The Navien you purched

is an A model. It not only comes equipped with a circulator but also a 2 liter stainless storage tank. You can use the circulator as you would any circulator for keeping hot water lines at the ready or you can turn the internal bypass valve and the circulator just circulates within itself. Because the A model is a kind of hybrid it effectively1 stops two issues with tankless water heaters. 1. there is no minimum flow rate and there is no wait for your hot water. 2 there is no cold water sandwich. What is the downside? There is now heat loss from standby, although minimal. There is really no reason to connect a water heater to your Navien but if for some reason you want to....it is easily done by using the internal circulator. The Navien would know how hot the tank is because the circulator would be continuously circulating the water between your Navien and the water tank.

JoeG

Is it

Is the circulator strong enough? to hold up to this kind of demand? And the mortiz 380 units is out of my price range for that price I d put in a boiler with an indirect, which is what I had in my old house installed and it was perfect for me.

JoeG

Naviven

Well I got the NR 240 A I hope I like it. Any tips on maintaining it?

TonyS

Tips

On the install, make sure you have sized the gas line and meter correctly. Also if you live in a freezing area be sure to use both exhaust and air pipes in a balance flue configuration.

After a argument with Mark E. over a year ago I shut down my water softner and installed an electronic water conditioner figuring I would soon need to acid wash the coil. Since then I have removed the water softner completely and have yet to clean the Navien, also the salt stains on my black fixture group has disappeared and there are no calcium stains. This has also lowered the chlorides in my water by eliminating the softner. So if you have water hardness, I would recomend one of these electronic conditioners.

JoeG

Water

I had my water checked at Home Depot,

The Hardness was a 3 Grains Per Gallon,

PH was 7.2

TDS was 140

and Iron was 0.5



The well hasnt been used in a while I am at this point only using the hose as I am redoing the house and the plumbing, Do these numbers change after a well becomes actve again? the well was muddy when I first started to use it but it has cleared up and I have found this to be normal for wells that sit for long periods of time.

TonyS

Good water

But check it after you use a few thousand gallons. Water can change anytime.

lolo21

install 50G storage tank in series

One solution:

you intall the 50G before the tankless, if it is located in a room that is let say 65F in winter and you incoming cold water goes down to 45F you can remove the tank insulation and you will have an extra 50G of water that only needs to raise 20F degrees less giving the tankless the extra push it needs on those very cold days.

Another solutions is the same set up but keep the insulation on keep the settings to the lower posible, that way your standby loses would be minimal if you could get it to go a low as 80F.

other solution put that 50G striped-oof insulation in front of a south window if posible and painted black.... add an artist touch and make it look like an sculpture! so your wife won't complain.

there's some diagrams in the internet...but i don't remember where....

icesailor

Water:

That water isn't all that bad but what is supplying the house with water now? A well or municipal water?

Charlie from wmass

good way to breed bacteria

Storage temps above 40 F and below 140F are great for bacteria cultures. Some ways to save fuel can cost lives. Like the dryer bypass that was popular in the 70's. This was quite a dangerous idea to save fuel.

JoeG

Wel

Around here Well waters is what there is. I did Shock it yesterday since has sat for Quite a while I did stir up some sediment the water is brown now but it will clear up. In a few weeks I ll Take water to teh lab to have it tested for bactieria.  The Navien is hanging on the wall it looks nice. I am going though instrutions they are kind of confusing.



P.S What was the dryer Bypass?

icesailor

Well Water:

You shouldn't excessively "shock" your well without reason. If you have never tested bacteria in your well, just because you didn't use the well for a long time, doesn't mean you will have a high bacteria count. The bleach will oxidize the iron out  of your well and make the water dirty for a while.

You would be just as well off to run your water at the tank for a few hours before putting it back in service. "The solution to pollution is dilution". Now that you have "shocked" the well, run it for a very long time to get the bleach out.

Is it a open well with a pump down it or a cased well with a pump in it?

JoeG

Closed Case

My Well has a Pump in a metal caseing tube with a cap on it, I am unsure how deep.



Everything I have read states I should shock my well everyonce in a while, I used to do it yearly at my old place. I used three gallons of bleach since i was unsure of depth, I had heard 1 gal to every 10 ft.

lolo21

watter between 40F and 140F is store in your pipes everyday

When you turn down your water heater down to minimum or to vacation setting (factory set) your water tank is well below 140F.

The tank gets flush every time you open a faucet, it is not sitting there.

That would apply to a close system.

Ironman

Not So!

Legionella Was produced in the DHW re-circ. line at 120deg. This is why boiler manufacturers are adding a tank sanitizing feature to their controls.

JoeG

Hooking it up

The tank would only have water init when need I would drain it out when not in use. I plan on hooking it up as a a normal water heater and putting it on line incase other goes out.