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 04-30-2012, 11:16 AM   #1
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Tankless Water Heater


When I built my house I decided to try a tankless water heater. I'm not having any problem with this other then when hot water is first requested. It is a gas unit and the burner lights as soon as water is flowing but it takes about 10 to 15 seconds for the water to get hot at the outlet of the water heater. For someone to get hot water requires running water until the outlet temperature rises and then for this to reach a faucet. Richmond's help desk said I should have hot water immediately but I know better than this and it will take some time for the heat exchanger and the cold water that is in the heater along with what will be passing through, to get up to temperature. I will be calling back to the desk again but I'd like to hear what others have experienced along this line.
There is a second problem too. If hot water is being used and the faucet is turned off, the burner will shut down, but if the faucet is turned back on, there will be hot water from what is in the pipes but cold water will be drawn to heater and it will take the 10 seconds or so to get hot so after the pipes are purged you get a blast of cold water.
I'm thinking about some type of recirculating pump that could be on a timer that would move water through the heater before water is drawn.
Any comments on tankless water heaters and a recirculation pump?

a7ecorsair is offline   Reply With Quote
Old 04-30-2012, 12:58 PM   #2
Member
 
Join Date: Jan 2009
Location: WV
Posts: 2,954
Rewards Points: 2,088
Default

Tankless Water Heater


I also have a tankless heater, and love it. But with any kind of hot water heater, unless you have some sort of recirculation system there will always be a delay before hot water reaches a fixture. How much depends on how far from the heater the fixture is. Your second issue is what's known as a "cold water sandwich."

I don't know that a recirc system would work with a tankless heater. Unless the heater runs all the time, there's no hot water to recirculate.

md2lgyk is offline   Reply With Quote
Old 04-30-2012, 01:23 PM   #3
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Tankless Water Heater


My idea would be to have a recirculating pump that would be connected from the outlet back to the inlet. I would have to find a timer that would be mounted in the bathroom which could be used to turn on the recirculating pump prior to drawing water. This would cause the water heater to start up and pre-heat the water.
a7ecorsair is offline   Reply With Quote
Old 04-30-2012, 01:27 PM   #4
Member
 
Join Date: Jan 2012
Posts: 210
Rewards Points: 150
Default

Tankless Water Heater


How far away from the fixture is the water heater? This makes a difference, especially if you have water-saver fixtures like 2.5gpm shower heads, and .8gpm sink aerators. There's going to be a slug of cold water in the pipe between the heater and the fixture that you will get until the hot water makes it to the fixture.

Also worth mentioning, if you are using these low-flow devices (especially the sink aerator) there may not be enough flow to keep the heater lit continually. It could be cycling on and off, especially if you are tempering the hot water with some cold (you will then be flowing half or less hot water, depending on where you have the valves set). The solution to this problem is to set the thermostat on the water heater to the most comfortable temperature you want WITHOUT needing to temper the water with cold. IE so you are using "pure" hot water. This, of course is the exact opposite that you would do with a tank style water heater (where you set it really hot, and then add cold water at the fixture to reduce the amount of hot you are using). For example, set your tankless water heater for about 105-110 degrees for a shower, and then just turn on the hot water valve and enjoy. THis may be too cold for a dishwasher, so turn on your DW's water heating function to make up the diff.

A recirculation pump may not work very good with a tankless. The water heater could stay on almost continually due to there being flow through the heater almost continually!
av-geek is offline   Reply With Quote
Old 04-30-2012, 02:24 PM   #5
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Tankless Water Heater


Thanks for the replies but I think the point was missed. I'm trying to overcome the delay in getting hot water out of the tankless unit. Maybe electric units are faster but in my case it takes about 10 to 15 seconds for the water exiting the unit, not a faucet, to be close to temperature. This means water has to be drawn for 10 to 15 second and then the additional time for it to travel the pipe to the requesting faucet.
When a recirculating pump is used with a conventional tanked water heater, does it run all the time or is it started when needed?
a7ecorsair is offline   Reply With Quote
Old 04-30-2012, 06:48 PM   #6
Member
 
Join Date: May 2008
Location: Near Philly
Posts: 2,041
Rewards Points: 1,002
Default

Tankless Water Heater


I think the recirc pumps can be configured different ways: on demand (you push a button); when the water gets cold on the line (sensor activated); timed (like a light timer; circulates on a schedule).
bob22 is offline   Reply With Quote
Old 05-01-2012, 09:27 AM   #7
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Tankless Water Heater


My two baths and utility room are all close together and the tankless unit is in the crawl space under the utility room. The water is all plumbed in Pex so I think I'm going to look at installing a Pex manifold and a pump so I can circulate the water back to heater inlet. This will light the burner and heat the water in the lines and manifold.
I think I'll have to put a 120 volt 6 gal Point of Use under the kitchen.
a7ecorsair is offline   Reply With Quote
Old 05-01-2012, 10:05 AM   #8
Member
 
Join Date: Dec 2011
Location: Livermore, California
Posts: 265
Rewards Points: 250
Default

Tankless Water Heater


For your recirculating pump, I suggest looking up the maximum inlet temperature your tankless water heater can handle. I've noticed that a number of tankless water heater manuals specify a maximum inlet temperature below their maximum output temperature. So you may need to wire your pump to turn off if the water reaches a certain temperature.
a_lost_shadow is offline   Reply With Quote
Old 05-01-2012, 10:10 AM   #9
Member
 
Join Date: Dec 2011
Location: Texas
Posts: 110
Rewards Points: 77
Default

Tankless Water Heater


I do not have any experience with tankless heaters, although I am looking at one to replace my tank, but I did see an episode of Ask This Old House on their website and they were installing a recirc pump on a system that had a tankless water heater. It was a relatively new episode. Might help you out.
Centex2011 is offline   Reply With Quote
Old 05-01-2012, 04:22 PM   #10
Member
 
Join Date: Jan 2012
Location: ohio
Posts: 1,106
Rewards Points: 520
Default

Tankless Water Heater


try this it is a recirculate pump with a remote on so just hit button it clears cold out in like 5 to 10 seconds
http://www.gothotwater.com/hot-water...ivating-system
__________________
"be careful at listening to just one persons advise" said me
"be careful at listening to just one persons advise" said myself
p.s. not all i say is a fact but not all i say is my opinion.
jaydevries is offline   Reply With Quote
Old 05-01-2012, 04:41 PM   #11
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Tankless Water Heater


Quote:
Originally Posted by jaydevries View Post
try this it is a recirculate pump with a remote on so just hit button it clears cold out in like 5 to 10 seconds
http://www.gothotwater.com/hot-water...ivating-system
This is along the line of what I was thinking, thanks for the link.
a7ecorsair is offline   Reply With Quote
Old 05-01-2012, 05:01 PM   #12
Member
 
Join Date: Jan 2012
Location: ohio
Posts: 1,106
Rewards Points: 520
Default

Tankless Water Heater


yea you need the remote switch for recirculating pump for a on demand you can also if walls are open hard wire timer switches next to gfci outlet looks better, costs more though, and every time a guest comes over you are explaining what that switch is for if they are observant type
__________________
"be careful at listening to just one persons advise" said me
"be careful at listening to just one persons advise" said myself
p.s. not all i say is a fact but not all i say is my opinion.
jaydevries is offline   Reply With Quote
Old 05-01-2012, 08:01 PM   #13
Doing it myself
 
Alan's Avatar
 
Join Date: Apr 2006
Location: Crescent City, CA
Posts: 3,762
Rewards Points: 2,024
Send a message via AIM to Alan Send a message via MSN to Alan
Default

Tankless Water Heater


You can't put a recirculating pump on a tankless water heater without having a storage tank.
__________________
Journeyman Plumber
Alan is offline   Reply With Quote
Old 05-01-2012, 08:21 PM   #14
Member
 
Join Date: Jan 2012
Location: ohio
Posts: 1,106
Rewards Points: 520
Default

Tankless Water Heater


allen that is false check link in post 10
__________________
"be careful at listening to just one persons advise" said me
"be careful at listening to just one persons advise" said myself
p.s. not all i say is a fact but not all i say is my opinion.
jaydevries is offline   Reply With Quote
Old 05-01-2012, 08:34 PM   #15
Doing it myself
 
Alan's Avatar
 
Join Date: Apr 2006
Location: Crescent City, CA
Posts: 3,762
Rewards Points: 2,024
Send a message via AIM to Alan Send a message via MSN to Alan
Default

Tankless Water Heater


I don't care about the button. Where is the water going?


__________________
Journeyman Plumber
Alan is offline   Reply With Quote
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
water heater drip kdange1 Plumbing 6 Yesterday 05:26 PM
Tankless Water heater, worth it?? zacker HVAC 23 01-04-2012 11:34 AM
relocating water heater location going tankless bstinson Plumbing 2 12-07-2011 10:00 AM
Need to run gas line to Tankless Water Heater. anonymouscuban Plumbing 2 04-16-2010 02:56 PM
Tankless water heater - NEED HELP! LakersFreak Plumbing 39 11-16-2008 08:49 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.