Secondary Tankless Water Heater Under Sink - Plumbing - DIY Home Improvement | DIYChatroom
Advertisement


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Plumbing

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread
Display Modes
Old 09-13-2015, 01:21 PM   #1
Newbie
 
Join Date: Nov 2014
Posts: 20
Rewards Points: 40
Default

Secondary tankless water heater under sink


I already have a whole-house electric tankless heater that's working great, but I'd like it even better if I didn't have to wait for hot water to reach the kitchen sink. This is more a function of distance rather than a problem with the unit.

There's a spare 120v outlet where the garbage disposal is connected. It's on its own 20-amp circuit.

I'm imagining a point-of-use heater that could simply be plugged in and fed by the hot water line for instant and continuous heat. Do I have any options without a major overhaul of the current electrical setup?
Hankshanker is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 09-13-2015, 01:32 PM   #2
Member
 
Join Date: Mar 2007
Location: Long Island, NY
Posts: 11,194
Rewards Points: 5,348
Default


You would need to calculate the amount of water needed and then compare the load required to operate the unit. If the DW has a heater built in, you should be able to run the small demand heater if the line isn't shared.
__________________
Ron
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety."
B. Franklin 1759
Ron6519 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 09-13-2015, 04:38 PM   #3
Newbie
 
Join Date: Nov 2014
Posts: 20
Rewards Points: 40
Default


The faucet delivers 1.5gpm. The dishwasher heats its own water so that's not an issue.

What is an issue though is that 120v 20-amp circuit. The point-of-use heaters I've found either can't handle 1.5gpm or need more amps.

Right now I've got 77-degree inlet water that takes 90 seconds to peak at 113, which is 2 degrees less than the setting on the tankless heater.

Down here in Florida, the water supply is relatively warm all year, so I was hoping to find a small, inexpensive unit that could provide instant hot water for that 90 seconds it takes heated water from the main unit to reach the kitchen. After reading a few other threads about this issue, I'm getting the impression that my current circuit is insufficient for that purpose.
Hankshanker is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 09-14-2015, 12:26 AM   #4
Newbie
 
Join Date: Nov 2014
Posts: 20
Rewards Points: 40
Default


Update: A little more searching led me to mini tank heaters, a product I did not know existed until today. Lo and behold, they're expressly intended for the issue I want to resolve.

Those mini tanks are designed to plug into 120v outlets. How much of a problem will I have if a 12-amp mini tank and a 9.5-amp disposal share a 20-amp circuit? Occasional tripping? Poor performance? House on fire? What?
Hankshanker is offline   Reply With Quote
Old 09-14-2015, 01:07 AM   #5
Member
 
Join Date: Sep 2015
Posts: 201
Rewards Points: 402
Default


Quote:
Originally Posted by Hankshanker View Post
Update: A little more searching led me to mini tank heaters, a product I did not know existed until today. Lo and behold, they're expressly intended for the issue I want to resolve.

Those mini tanks are designed to plug into 120v outlets. How much of a problem will I have if a 12-amp mini tank and a 9.5-amp disposal share a 20-amp circuit? Occasional tripping? Poor performance? House on fire? What?
So every time you click the disposal switch and the heater happens to be on, the breaker trips. And it so happens that if you are in the kitchen and using hot water, you probably also want to run the disposal, meaning this may actually happen several times a week.

Not good. Also, not sure if it's even code compliant, I think something like the heater needs it's own dedicated circuit. I think you should run a dedicated circuit for the heater. Since you have to run wire anyway, you might as well run 220V with the right wire gauge and install a point of use tankless, so that you don't run out of hot water or waste energy keeping the tank hot if you decide to order take-out for a week.
Habeed is offline   Reply With Quote
Old 09-14-2015, 11:06 AM   #6
Newbie
 
Join Date: Nov 2014
Posts: 20
Rewards Points: 40
Default


Thanks for your input, Habeed. I can feel my fun and cheap little DIY project slipping away. Fortunately, my wife didn't even know we had a problem, god bless her, so there will be no harm done either way.

I'm trying to picture what it would take and guessing what it would cost to supply our kitchen sink with a 220v line to correct an issue that I apparently created for the fun of it. There's a second floor crawl space, an 18-foot ceiling and a concrete firewall between the breaker panel way over thither and the kitchen peninsula way over hither. I just don't see it, and for some reason I keep hearing the sound of chainsaws.
Hankshanker is offline   Reply With Quote
Old 09-14-2015, 05:11 PM   #7
Member
 
Join Date: Mar 2013
Location: Ohio
Posts: 5,698
Rewards Points: 1,942
Default


Did you ever consider a circulation pump system?
Ghostmaker is offline   Reply With Quote
The Following User Says Thank You to Ghostmaker For This Useful Post:
bob22 (09-30-2015)
Old 09-16-2015, 10:34 AM   #8
Newbie
 
Join Date: Nov 2014
Posts: 20
Rewards Points: 40
Default


Quote:
Originally Posted by Ghostmaker View Post
Did you ever consider a circulation pump system?
Those recirculators are confusing and expensive, darn it.

See, I recently saw a point-of-use tankless on sale for less than $100 and thought "Eureka! The solution to a problem that I didn't know I had until just now!"

Of course, all my life I've been waiting for hot water to reach faucets, not such a big deal in Florida, but I couldn't resist a potential fix that looked to be about as complicated as plugging in a toaster.

So what started out as a cheap and easy DIY solution to a minor plumbing issue has ballooned into a technical conundrum that may require one or two contractors and many, many dollars to complete. Oh well.
Hankshanker is offline   Reply With Quote
Old 09-16-2015, 02:42 PM   #9
Member
 
Join Date: Mar 2013
Location: Ohio
Posts: 5,698
Rewards Points: 1,942
Default


I was sort of thinking about this for your problem.

http://www.homedepot.com/p/Autocirc-...Q&gclsrc=aw.ds

I little more expensive but the toaster aspect is the same.
Ghostmaker is offline   Reply With Quote
Old 09-16-2015, 05:18 PM   #10
Newbie
 
Join Date: Nov 2014
Posts: 20
Rewards Points: 40
Default


Quote:
Originally Posted by Ghostmaker View Post
I was sort of thinking about this for your problem.

http://www.homedepot.com/p/Autocirc-...Q&gclsrc=aw.ds

I little more expensive but the toaster aspect is the same.
Ah, this is where it gets confusing, Ghostmaker.

That model, the E1, I believe is inappropriate for tankless systems because of insufficient flow rate. Even with adequate flow, I'm not sure I want the heater frequently activated just to keep the pipes warm because we all know those tankless heaters are juice hogs when they're running. We typically use less than 2,000 gallons per month, so after going tankless, I'd hate to go back to constantly heating water again for such low demand.

The E10, on the other hand, is explicitly designed for tankless, but it costs almost $500, which is more than I paid for the whole-house heater. I have to draw the line somewhere, ya know? And we'd still be dealing with the constant heating of water, or if we narrow the timer, not getting instant hot water sometimes when we want it.

So far the best plan is to wait about a minute and a half.
Hankshanker is offline   Reply With Quote
Old 09-29-2015, 11:27 PM   #11
Member
 
Join Date: Sep 2015
Location: North Carolina
Posts: 114
Rewards Points: 234
Default


@Hankshanker , I will follow this thread with interest. Did you have any specific "mini tank heater" in mind? Did you decide to install an under sink unit? I am considering the same approach, but have not researched it in detail.

I have similar issue in that my tankless hot water heater does not fire up unless the flow rate is 0.6 gallons/minute or more (IIRC). It is supposedly sized "correctly" based on the number of bedrooms/people in the home, but it barely comes on when taking a shower with no other usage activity. As an aside, I can easily take a shower at ~0.5 gallons/minute flow rate (maybe I have been conditioned by previously being the last person in the family to take shower from a traditional hot water tank before this new tankless unit) except for bigger issue of having no hot water, requiring me to turn up the flow rate to the point where I feel I am wasting water just to keep the natural-gas unit fired up.....all this is in addition to the 30-60 seconds of wasted clean water flow going down the drain waiting for the hot water to appear.

This also means that the kitchen sink rarely gets any hot water except for the coldest days of the year, as it is too wasteful to turn the faucet open at a higher than necessary flow rate and then wait for many seconds for water. I have considered installing small electric units in the kitchen and all the bathrooms for nearly instant-on small quantities of hot water, but have been reluctant because of cost and need for wiring in. It also seems to defeat the purpose of having a whole house hot water heater, but my whole house tankless unit has been a big disappointment, so using it less could be considered a plus.
RustNeverSleeps is offline   Reply With Quote
Old 09-30-2015, 02:24 AM   #12
Member
 
Join Date: Jan 2012
Location: Pittsburgh, Pennsylvania
Posts: 210
Rewards Points: 222
Default


You could wire the heater and disposal with a three way switch which is actually a single pole double throw switch which only provides power to one of the units at a time. Power would be applied to the water heater all of the time except when you use the disposal at which time it would switch the power from the heater to the disposal.

Last edited by bcgfdc3; 09-30-2015 at 02:33 AM.
bcgfdc3 is offline   Reply With Quote
Old 09-30-2015, 04:04 AM   #13
Member
 
Join Date: Sep 2015
Posts: 201
Rewards Points: 402
Default


Quote:
Originally Posted by bcgfdc3 View Post
You could wire the heater and disposal with a three way switch which is actually a single pole double throw switch which only provides power to one of the units at a time. Power would be applied to the water heater all of the time except when you use the disposal at which time it would switch the power from the heater to the disposal.
Clever.
Habeed is offline   Reply With Quote
Old 10-01-2015, 10:45 PM   #14
Newbie
 
Join Date: Nov 2014
Posts: 20
Rewards Points: 40
Default


Quote:
Originally Posted by RustNeverSleeps View Post
@Hankshanker , I will follow this thread with interest. Did you have any specific "mini tank heater" in mind? Did you decide to install an under sink unit? I am considering the same approach, but have not researched it in detail.

I have similar issue in that my tankless hot water heater does not fire up unless the flow rate is 0.6 gallons/minute or more (IIRC). It is supposedly sized "correctly" based on the number of bedrooms/people in the home, but it barely comes on when taking a shower with no other usage activity. As an aside, I can easily take a shower at ~0.5 gallons/minute flow rate (maybe I have been conditioned by previously being the last person in the family to take shower from a traditional hot water tank before this new tankless unit) except for bigger issue of having no hot water, requiring me to turn up the flow rate to the point where I feel I am wasting water just to keep the natural-gas unit fired up.....all this is in addition to the 30-60 seconds of wasted clean water flow going down the drain waiting for the hot water to appear.

This also means that the kitchen sink rarely gets any hot water except for the coldest days of the year, as it is too wasteful to turn the faucet open at a higher than necessary flow rate and then wait for many seconds for water. I have considered installing small electric units in the kitchen and all the bathrooms for nearly instant-on small quantities of hot water, but have been reluctant because of cost and need for wiring in. It also seems to defeat the purpose of having a whole house hot water heater, but my whole house tankless unit has been a big disappointment, so using it less could be considered a plus.
I didn't delve too deep into mini tanks because of the amperage issue on the existing disposal circuit. I also didn't want the potential of a tank leaking in a cabinet, and I didn't like the idea of going back to heating a water tank after going tankless. It was easier for me just to put this whole project on the back burner, pardon the pun, because the problem wasn't serious enough to warrant a lot of trouble or expense.

Your lack of hot water, on the other hand, is a big freakin' deal, and I bet there's a few smart folks here who could offer better suggestions than my wild guesses about what is going on. Have you tried adjusting the temperature setting? If it's too low, the water may cool down too much before getting to your shower. If it's too high, causing you to turn the valve toward cold, the hot side flow rate may not be enough to keep the heater heating. If it's not something that simple, maybe you should get somebody to look at your installation because what you're describing sounds really fishy. Or perhaps a recirculator is the way to go for you.

And what's with the half-gallon-a-minute shower anyway? Maybe you just need to open that showerhead full-throttle and take a real shower because it sounds like you deserve it, man.

The suggestion of a three-way switch by bcgfdc3 to accommodate a point-of-use heater has me intrigued. Would that satisfy the requirement of a dedicated circuit? A small tankless unit that can plug into a 120v, 20A line and be appropriate for a 1.5gpm faucet would be the ideal. Does such a product exist?
Hankshanker is offline   Reply With Quote
Old 10-01-2015, 11:00 PM   #15
Member
 
Join Date: Sep 2015
Posts: 201
Rewards Points: 402
Default


All the ones I can find with quick searches want 30 amps at 110 volts. So the only way is a small tanked heater like this one.

Edit : Ok, here's one. 0.5 gpm is what the manufacturer thinks it can handle.

You would need a 20 amp 3 way switch like this one I think.

Last edited by Habeed; 10-01-2015 at 11:08 PM.
Habeed is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tankless water heater to pre-heat incoming water matthet Plumbing 35 01-06-2017 12:39 AM
Under sink tankless heater powrus Plumbing 21 12-28-2014 02:09 PM
Chasing Ghosts - Phantom Water Leak FrozenMeatballs Plumbing 7 10-29-2014 06:03 PM
Tankless water heater tgillis Plumbing 3 09-18-2011 03:10 PM
Bosch 1600H Tankless Water Heater natemclain HVAC 13 08-24-2009 10:33 AM




Top of Page | View New Posts