Tankless heater/Well Water?

[Stevie Vermunt]

Hi there! I have a couple questions but Ill explain myself first.

We have well water and it has methane in it from being in the badlands as well as fracking in the area I've heard? The well water is soft, and has high bicarbonate in it. Will a tankless be okay with this type of water? I wonder about corrosion over time..? We dont really get calcium or lime scale(?) because of the water being soft but I'm still curious. I asked my plumber but I haven't heard back in a couple weeks. Any help would be appreciated.

This tankless will likely go before our hot water tank, so that the tank can bring up the temp to 160. We own a small business and require a ton of 160 degree water, however it takes our tank about an hour to get hot enough for What I need it for. I would like to cut down on waiting/buffer time for hot water hopefully significantly.

 

[Dana]

What is the peak flow rate do you need for that "... ton of 160 degree water..."?

Is high-temp water going down the drain simultaneously with the flow, or is it drawn in batches, then dumped?

 

[Sponsor]

 

[Stevie Vermunt]

What is the peak flow rate do you need for that "... ton of 160 degree water..."?

Is high-temp water going down the drain simultaneously with the flow, or is it drawn in batches, then dumped?

I want to ideally fill one top load washer all the way full with hot water, once thats done, Ill fill the second washer. Theyll sit for 40ish mins just sitting there full. (With wool soaking in it). Then I will spin one out and start filling it, and then Ill spin the second one out and start filling it once the first one is full. Sit for 40 mins, do it all over again. For 8 -10 hours a day. So not a TON all at once but it needs to be 160 and the tankless doesnt heat it that hot. The tank could just heat it the 20° extra.

But Im mostly wondering if my water type + the methane in the water will cause anything bad/damage to happen to the tankless heater?

 

[Dana]

I don't know with certainty, but I doubt that dissolved methane in the water is going to negatively affect the heat exchanger in the tankless. Methane doesn't easily react with most metals (iron and copper pipes have been used for natural gas plumbing, whichis mostly methane). The stainless or copper heat exchangers in a tankless should be largely unaffected.

With a tankless the flow rate of the washer fill matters more than the volume or frequency of the fill, since the burner & heat exchanger size of the tankless will determine a maximum flow rate. The temperature difference of 40F incoming water and 140F output is 100F. A 199,000 BTU/hr-input residential water heater at 95% efficiency delivers about 190,000 BTU/hr to the water (in theory, and maybe only in your dreams.) The max flow rate is then 190,000BTU/100F= 1900 lbs/hour, or (/60=) 31.7 lbs/minute. At 8.34 lbs/gallon that's 3.8 gpm.

How many gallons does the washing machine take to fill with a load of wool in it? 15 gallons? 20?

What is the volume & burner size of your tank water heater?

 

[Stevie Vermunt]

I don't know with certainty, but I doubt that dissolved methane in the water is going to negatively affect the heat exchanger in the tankless. Methane doesn't easily react with most metals (iron and copper pipes have been used for natural gas plumbing, whichis mostly methane). The stainless or copper heat exchangers in a tankless should be largely unaffected.

With a tankless the flow rate of the washer fill matters more than the volume or frequency of the fill, since the burner & heat exchanger size of the tankless will determine a maximum flow rate. The temperature difference of 40F incoming water and 140F output is 100F. A 199,000 BTU/hr-input residential water heater at 95% efficiency delivers about 190,000 BTU/hr to the water (in theory, and maybe only in your dreams.) The max flow rate is then 190,000BTU/100F= 1900 lbs/hour, or (/60=) 31.7 lbs/minute. At 8.34 lbs/gallon that's 3.8 gpm.

How many gallons does the washing machine take to fill with a load of wool in it? 15 gallons? 20?

What is the volume & burner size of your tank water heater?

Im not sure of the volume of water for the washers. Theyre extra large Maytag top loaders. Let's say 20 to be safe. So I need 40 gallons every 40 mins, my hot water tank is 80 gallons, and its a brand new rheem(?) gas one. I cant upgrade as this water tank was the upgrade. We were told by a company that this should supply us enough hot water but obviously they weren't taking us seriously at all. So my cheapest option is to get tankless added before the tank. Tankless boasts almost unlimited hot water, meaning the tank has to work less to hear whats coming into it.. Are there tankless ones with higher flow rates? Any you would suggest?

Im not too good with this stuff at all, Im having a little trouble understanding what the math part is lol. Thanks for your patience with me.

 

[Stevie Vermunt]

Im not sure of the volume of water for the washers. Theyre extra large Maytag top loaders. Let's say 20 to be safe. So I need 40 gallons every 40 mins, my hot water tank is 80 gallons, and its a brand new rheem(?) gas one. I cant upgrade as this water tank was the upgrade. We were told by a company that this should supply us enough hot water but obviously they weren't taking us seriously at all. So my cheapest option is to get tankless added before the tank. Tankless boasts almost unlimited hot water, meaning the tank has to work less to hear whats coming into it.. Are there tankless ones with higher flow rates? Any you would suggest?

Im not too good with this stuff at all, Im having a little trouble understanding what the math part is lol. Thanks for your patience with me.

Our current flow rate is around 3 gallons per minute and I wont be filling the machines at the same time, because i know theyd just fill super slowly. So ill do one after another

 

[Jadnashua]

There are tankless systems that are designed so that they can be ganged up, and connected together via their controllers to adjust to the volume of hot water needed. They work in parallel, not series, though, as I understand it, so the max temp is still limited, but you can achieve a higher volume provided by more than one burner being utilized. Most all designed for residential use have a limited maximum outlet temperature that isn't as hot as you want. There might be commercial versions that can go higher (like what may be needed for a restaurant's dishwasher).

One thing to consider in your costing is the size of the gas supply lines, regulator, and meter. The burners need a moderately significant supply structure, or they don't work.

Water heaters (tank-type) also come with various sized burners. Those designed for commercial use generally have a much larger burner than those destined for residential use. What size burner is in the unit you have? Is it rated commercial?

 

[Stevie Vermunt]

There are tankless systems that are designed so that they can be ganged up, and connected together via their controllers to adjust to the volume of hot water needed. They work in parallel, not series, though, as I understand it, so the max temp is still limited, but you can achieve a higher volume provided by more than one burner being utilized. Most all designed for residential use have a limited maximum outlet temperature that isn't as hot as you want. There might be commercial versions that can go higher (like what may be needed for a restaurant's dishwasher).

One thing to consider in your costing is the size of the gas supply lines, regulator, and meter. The burners need a moderately significant supply structure, or they don't work.

Water heaters (tank-type) also come with various sized burners. Those designed for commercial use generally have a much larger burner than those destined for residential use. What size burner is in the unit you have? Is it rated commercial?

Its not rated commercial but we are at the end of our budget now so we just need something to do what I want, at least to get ud by until we can upgrade further. I will have about 2500 or 3000 to spend upgrading. And honestly, ideally I would like 2 commercial tankless and maybe a buffer tank for cold water to sit in so its not drawing on the well so badly, and no tank at all. I know some people in my "industry" who've done this and were able to have 7 top loaders going.

I was reading though that the tankless can take the cold well water, heat it to 140 (or even less) have that hot water go into the tank, tank heats it to 160 (the tank isnt supposed to heat it to 160 but for some reason it does), and therefore supply me with almost unlimited hot water (besides the rate the tank refills at/the rate in which water comes thru the tankless heater).. even if its giving me 150 for the one washer, its useable but 160 is ideal. I know our tank alone can fill 2 washers all day like this, as we have done it and the water supply is fine, but the hot starts to deplete quicker than Id like.

I was reading that 2 tanks might not be as efficient as doing it with a tankless and a tank, and space in my basement is limited.

Another plus side to this, is that the tank will only slightly heat the water coming in from the tankless system, and maintain that temperature, rather than work to heat it from ground temp. The tankless is more efficient than a tank, so I can see the bill being lower than having 2 tanks.

 

[Dana]

Im not sure of the volume of water for the washers. Theyre extra large Maytag top loaders. Let's say 20 to be safe. So I need 40 gallons every 40 mins, my hot water tank is 80 gallons, and its a brand new rheem(?) gas one. I cant upgrade as this water tank was the upgrade. We were told by a company that this should supply us enough hot water but obviously they weren't taking us seriously at all. So my cheapest option is to get tankless added before the tank. Tankless boasts almost unlimited hot water, meaning the tank has to work less to hear whats coming into it.. Are there tankless ones with higher flow rates? Any you would suggest?

Im not too good with this stuff at all, Im having a little trouble understanding what the math part is lol. Thanks for your patience with me.

What's the burner size on the Rheem?

I assume it's not a condensing model?

 

[Stevie Vermunt]

What's the burner size on the Rheem?

I assume it's not a condensing model?

I dont know the burner size on it. Id have to go look and Im in the shop currently. I think its "rheem performance" 80 gallon residential tank if that helps? But I have a tap that has a temperature gauge on it and can combine cold and hot and it goes to 160.

 

[Stevie Vermunt]

Oh my bad. Its a 50 gallon. 40,000 BTU. I couldn't find anything about a burner size lol

 

[Dana]

Oh my bad. Its a 50 gallon. 40,000 BTU. I couldn't find anything about a burner size lol

The combustion efficiency of non-condensing water heaters is about 80%, so only 0.8 x 40K= 32,000 BTU/hr is going into the water, or (/60=) 533 BTU/minute.

There is 8.34lbs/gallon x 50 gallons = 417lbs of water in the tank, so while the burner is running the temperature is rising at a rate of 533 BTU/417lbs= 1.28F per minute. So during the 40 minute interval the tank's burner can raise the temp by as much as 1.28F/min. x 40 min= 51F.

That means you can set the tankless to anything north of 160F - 51F= 109F and still have enough hot water. To have any margin set it to 120F or 125F, even 130F if you have to. But that means you WOULD be able to use a condensing tankless water heater for higher efficiency, since you really don't need more than 140F water out of the tankless (a typical max-out for a condensing tankless).

With the lower output temp from the tankless you'll get a marginally higher flow rate too. With it set to 120F instead of 140F it's only an 80F rise, so a 199K condensing unit would be able to deliver something like 4.75 gpm rather than the 3.8 gpm I previously calculated at 140F-out/40F-in.