On Demand Water Heaters/ Do's And Don'ts

 
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Old 08-26-2017, 12:43 PM   #1
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On Demand Water Heaters/ Do's And Don'ts


So the days of the old 60% efficient, standing pilot, 40 gallon (or whatever) hot water storage are getting a little more scarce. More and more new homes are being plumbed in with on demand condensing units or boilers with a loop to an indirect tank. We are also seeing a lot of retrofits going in the direction of tankless technology as well.
For the most part, this is a good thing. However, we in the trade have to rethink how we plumb in these things in some cases and have to really do our best to make the install work properly. We also have to educate our customers and prepare them that this is no simple re & re task like the old days. So I thought we should all share some of the do's and don'ts of this technology to save us all some headaches down the road in nuisance service calls and angry homeowners.
A few do's-
1)A hot water recirc loop is almost always essential. The ideal loop would consist of a minimum 3/4 main loop around to all of the fixtures with "tails" coming off to each one no longer than 6 feet. Also the main loop insulated with good seals and taping to prevent heat loss. This also keeps the floors from getting excessive heat in the summer.
2) Both the water and the gas inlets to the unit should be the first branch coming off. Especially the water line. These units work on flow sensors and need the most consistent pressure and flow to operate properly.
3) Whenever possible, try to locate the thing to minimize length of piping as much as humanly possible. Or if this is not feasible, then at the very least, try to game plan for where the most usage will be. I.E. the most used shower and/or bath. Of course, venting and gas come into play here which limits us in some ways.
4) Good drainage for the condensate. In a new home, plan for it in the slab rough-in with floor drain(s) nearby and indirect tees over to the walls where these new appliances hang. In a retrofit, if drainage is not accessible, a neutralizer and condensate pump may be needed.
5) Softened water if you live in an area that has very hard water issues. These things have very small waterways in the primary exchangers and restrictions can cause problems.
6) Maintenance and the owners being aware that they can't just ignore the simple tasks of cleaning air intake screens, condensate traps and water inlet filters. Also arrange to get the exchangers flushed out with vinegar or a citric acid solution periodically to clear scale build-up can really help.

The don'ts-
1) Home run manifold systems. These things aren't very efficient at any time but with tankless technology, they are just a nightmare. Waiting for hot water to get through 50 + feet of 1/2 inch line to have a shower? Kinda dumb when you think about it. Meanwhile the unit is firing at high fire the whole time trying to produce heat and often ends up causing it to short cycle and eventually give the occupant fits of rage. Also, if you are having your shower and someone runs a hot tap closer to the header, it robs you of heat.
2) Trying to "cheap out" when it comes to piping it. This is true for pretty much anything but especially for the new technologies. Size your piping properly and install isolations and drain valves for ease of servicing. Maybe for 5 years, the owner doesn't have an issue but when things go south ( and they will), they will be paying a service guy like me 2 or 3 times as much to fix the thing because of being cheap or a guy being lazy.
3)If you are a DIY'er or a novice and unsure of anything, DON'T EVEN ATTEMPT IT. I can't stress this enough. Too many people out there reading stuff online without a clue of how the stuff works. If you think you are smarter than us, you likely aren't.
4) Don't ignore small issues until they become large ones. I'm dealing with one right now that has been troublesome for years yet the owner "lived with it". Now he is trying to rent the place out and the tenants are furious and he's likely looking at several hundred dollars in time and material for me to get the thing just to a point of functional. Or possibly tearing it out and starting over which is thousands.
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Last edited by Ernie in Dawson; 08-26-2017 at 12:46 PM. Reason: added photo
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Old 08-26-2017, 09:14 PM   #2
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Re: On Demand Water Heaters/ Do's And Don'ts


Why do people pop in here and post blogs. It's actually quite rude. Do you really think we don't already know this stuff? If we don't, our plumbers do. This is a site for professionals.

Maybe you really meant to go to the DIY site.

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Old 08-27-2017, 12:21 AM   #3
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Re: On Demand Water Heaters/ Do's And Don'ts


I beg to differ, think it's a good thing to get information, helps with the overall view.
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Old 08-27-2017, 12:24 AM   #4
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Re: On Demand Water Heaters/ Do's And Don'ts


The more I hear about them, the less I like them which is ironic because in California they are now the default water heating system per Title 24 regulations.
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Old 08-27-2017, 12:28 AM   #5
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Re: On Demand Water Heaters/ Do's And Don'ts


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Originally Posted by Rio View Post
The more I hear about them, the less I like them which is ironic because in California they are now the default water heating system per Title 24 regulations.
What is the "them" you are referring to?

The tankless heaters? The recirc?

Andy.
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Old 08-27-2017, 12:30 AM   #6
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Re: On Demand Water Heaters/ Do's And Don'ts


I had a tankless installed, to free up room in my garage for a bigger laundry area. I've got zero complaints.


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Old 08-27-2017, 03:16 AM   #7
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Re: On Demand Water Heaters/ Do's And Don'ts


Quote:
Originally Posted by Rio View Post
I beg to differ, think it's a good thing to get information, helps with the overall view.
In my defense, I was exhausted and in a pissy mood. I probably pulled the trigger a bit quick on this one.

Also, with tapatalk you cant see how long they have been a member. It is just a pet peave. So many people post hit and runs to drive traffic to a blog or website, it just gets tedious.
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Old 08-27-2017, 03:52 PM   #8
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Re: On Demand Water Heaters/ Do's And Don'ts


Quote:
Originally Posted by ScipioAfricanus View Post
What is the "them" you are referring to?

The tankless heaters? The recirc?

Andy.
The tankless, it is possible to use a tanked but there are other requirements if one does so depending on the size of the water heater.

I've never had one but a couple of friends who have complained about lag times for heating if I remember correctly.

Last edited by Rio; 08-27-2017 at 06:03 PM.
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Old 08-27-2017, 06:50 PM   #9
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Re: On Demand Water Heaters/ Do's And Don'ts


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Originally Posted by Rio View Post
The tankless, it is possible to use a tanked but there are other requirements if one does so depending on the size of the water heater.

I've never had one but a couple of friends who have complained about lag times for heating if I remember correctly.
It takes a few more seconds to get hot water. You have to wait for it to ignite then transfer enough heat through the exchanger before water starts to heat. You get used to it.
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Old 08-27-2017, 07:26 PM   #10
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Re: On Demand Water Heaters/ Do's And Don'ts


You can always get a recirculating pump if it really bothers you. The can be motion detected or on a timer.

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Old 08-29-2017, 10:09 AM   #11
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Re: On Demand Water Heaters/ Do's And Don'ts


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Originally Posted by Californiadecks View Post
You can always get a recirculating pump if it really bothers you. The can be motion detected or on a timer.

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We have a tank in our house, but during the CA drought, installed a return loop line, with a recirculating pump on it. Each faucet, shower, washing machine, has it's own switch, with an LED that is on when the pump runs, until hot water reaches the furthest point. Want to wash clothes with hot water, hit the button and 40 seconds later there is hot water. Due to our washing machine being an HE the water would never actually get hot before. Plus we get hot water with zero water wasted, which is good for the environment NorCal has water issues, and SoCal is, well, a desert

Our friends in Paris France have on demand hot water heaters in the kitchens of their apartments. They are loud, draw air from the apartment, and take up space where a cabinet should be. No other options though.
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Old 08-29-2017, 07:26 PM   #12
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Re: On Demand Water Heaters/ Do's And Don'ts


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Originally Posted by Peter_C View Post
We have a tank in our house, but during the CA drought, installed a return loop line, with a recirculating pump on it. Each faucet, shower, washing machine, has it's own switch, with an LED that is on when the pump runs, until hot water reaches the furthest point. Want to wash clothes with hot water, hit the button and 40 seconds later there is hot water. Due to our washing machine being an HE the water would never actually get hot before. Plus we get hot water with zero water wasted, which is good for the environment NorCal has water issues, and SoCal is, well, a desert

Our friends in Paris France have on demand hot water heaters in the kitchens of their apartments. They are loud, draw air from the apartment, and take up space where a cabinet should be. No other options though.
Our HE washer is 2' away from the tankless.

They only reason I got a tankless was to free up space in my garage.
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Old 09-02-2017, 04:17 PM   #13
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Re: On Demand Water Heaters/ Do's And Don'ts


I didn't mean to post this as a blog or to promote anything. This install was done by a so-called journeyman and I just think it bears re-iterating at all times the things that many of us in the trade see on a daily basis.
Fwiw, I have been in the trade nearly 25 years and this particular installation is one of my pet peaves. I still see new installations being done wrong by licenced and ticketed "plumbers" who refuse to do research or read manuals and just think they know best and continue to do things the same way they always have. Not only water heaters but condensing boilers as well.
As for this situation, tech support at Navien gave me an RGA to replace the unit with the upgraded model. That is a huge relief to the homeowner. I spent yesterday afternoon doing that and with a few simple modifications and set-up, the occupants are able to now run every fixture in the house and get hot water and that is being set at 120 F. I gave them 125 just to make them happy. However, even with the unit covered by warranty, it will still cost the owner about a grand for all the diagnosing and back and forth with tech support along with the re & re.

Last edited by Ernie in Dawson; 09-02-2017 at 04:26 PM.
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Old 09-02-2017, 05:07 PM   #14
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Re: On Demand Water Heaters/ Do's And Don'ts


Quote:
Originally Posted by VinylHanger View Post
In my defense, I was exhausted and in a pissy mood. I probably pulled the trigger a bit quick on this one.



Also, with tapatalk you cant see how long they have been a member. It is just a pet peave. So many people post hit and runs to drive traffic to a blog or website, it just gets tedious.


If you tap on their name you should be able to see how long they have been a member and how many post they have...this is what I get when I tap on your name




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Old 09-02-2017, 06:56 PM   #15
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Re: On Demand Water Heaters/ Do's And Don'ts


One thing I will add that has nothing to do with the point of the original thread topic was that how long a person has been a member of the site or what his/her post count is means absolutely nothing. It doesn't mean a guy is just some DIYer looking for free tips.
My point was to make all the trades realize that they need to watch for things like this in their own homes and even on job sites and maybe guys like the idiot who did this job can get run out of the biz or be forced to re-educate himself and do stuff the right way.
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Old 09-02-2017, 07:20 PM   #16
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Re: On Demand Water Heaters/ Do's And Don'ts


My cousin has been a Union journeyman plumber in both residential and commercial for a very long time and he swears by them. Probably the biggest reason why they get a bad rap is from improper installation which causes issues. He has one in his house, and he installed one in his dad's house and they've been there for at least 10 years now and they have never had a single issue with either one


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Old 09-03-2017, 12:29 PM   #17
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Re: On Demand Water Heaters/ Do's And Don'ts


Quote:
Originally Posted by Ernie in Dawson View Post
One thing I will add that has nothing to do with the point of the original thread topic was that how long a person has been a member of the site or what his/her post count is means absolutely nothing. It doesn't mean a guy is just some DIYer looking for free tips.
My point was to make all the trades realize that they need to watch for things like this in their own homes and even on job sites and maybe guys like the idiot who did this job can get run out of the biz or be forced to re-educate himself and do stuff the right way.
I thought I aologized for my quick and froggy jump.

My point was we get people pop on here, write out some blather like, "Using a hammer can be dangerous, don't hit your hand", or "Paint cones in all kinds of colors and you should match it with your mood, and not drip it on the floor, as it will stick to the carpet". Then they are never heard from again.

Your post struck me the same way, the seriousness of the subject notwithstanding.

I am happy to see you aren't one of those posters and I hope you stick around.

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Old 09-04-2017, 11:47 PM   #18
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Re: On Demand Water Heaters/ Do's And Don'ts


Earnie, you mentioned how the water inlet and gas line should get first-dibs. Odds are, the house wasn't plumbed accordingly. In that case, how critical is the first-dibs thing?
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Old 09-05-2017, 07:05 AM   #19
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Re: On Demand Water Heaters/ Do's And Don'ts


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My cousin has been a Union journeyman plumber in both residential and commercial for a very long time and he swears by them. Probably the biggest reason why they get a bad rap is from improper installation which causes issues. He has one in his house, and he installed one in his dad's house and they've been there for at least 10 years now and they have never had a single issue with either one


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This doesn't make sense no matter what the heater type is:

"The don'ts-
1) Home run manifold systems. These things aren't very efficient at any time but with tankless technology, they are just a nightmare. Waiting for hot water to get through 50 + feet of 1/2 inch line to have a shower? Kinda dumb when you think about it."


The shower draws 2.2 GPM. This guy is saying it's better to wait for hot water to get through 3/4" line than 1/2" line? Wtf? The shower head is only drawing 2.2 so it's going to take longer to flush the cold out of 3/4" than 1/2".
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Old 09-05-2017, 07:36 AM   #20
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Re: On Demand Water Heaters/ Do's And Don'ts


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The shower draws 2.2 GPM. This guy is saying it's better to wait for hot water to get through 3/4" line than 1/2" line? Wtf? The shower head is only drawing 2.2 so it's going to take longer to flush the cold out of 3/4" than 1/2".
No he's not. Refer to #1 of the "do's":

Quote:
A few do's-
1)A hot water recirc loop is almost always essential. The ideal loop would consist of a minimum 3/4 main loop around to all of the fixtures with "tails" coming off to each one no longer than 6 feet.

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