Tankless w recirculating pump not getting hot instantly as it’s supposed to

[Sonny goldstone]

Hello all!

Since we don’t have a dedicated recirculating line, we’re using a crossover kit in the farthest kitchen fixture to make use of our recirculating pump.

Our heater is a Noritz NRCR111

The idea is to get instant hot water at the tap w the crossover installed...mine gets instantly warm 90 degrees for about 90 seconds until it gets to 125 temp - isn’t this supposed to be instantly hot not just warm?

 

[WorthFlorida]

It still takes time for the recirculating pump to push out the cold water. Pipe sizing and distance will impact it. To get instant hot water the recirculating pump must run most or all of the time but then your cold water will be warm. You'll be running a lot of cold water to get cool water if any. If you had a dedicated return line it may give a better results as you expect it to have.

From the manual, notice it state "more" instantly.
Hot water recirculation system: The Water Heater circulates and warms up the hot water in the pipe. When recirculation is operating, you can get hot water more instantly with less waste of water.

This is from the users manual page 9.
NOTE • As an energy savings feature, if you leave the button on and hot
water is not used for more than 3 days, the stored recirculation operation will be reset. To avoid this, turn the button off the Remote Controller when hot water will not be used for prolonged times (i.e. vacation).
• Auto-Recirculation Mode doesn’t operate when using On-Demand Mode.
• You can manually stop the Recirculation operation. (See page 13)

 

[Sponsor]

 

[Sonny goldstone]

Thanks for the info I had a feeling this might be the case...honestly it seems like a waste of gas to run the pump only to get warm water.

Also I’ve noticed that the only fixture that benefits is the one w the crossover actually installed - am I supposed to be getting it on all the fixtures?

 

[Bannerman]

I assume you are using a Noritz crossover valve which has an internal thermostat control that will stop circulation flow once 95℉ is sensed at that valve. This will prevent the water in the cold supply lines from becoming too warm.

Depending on the distance between that crossover valve and the WH, I would anticipate the water within the run before the crossover will be hotter than 95℉, but if that run is uninsulated or routed through a cool zone, there maybe sufficient opportunity for the water to cool once flow has been stopped.

If other fixtures branch off the pipe that runs to the crossover valve, they should each receive hot water more quickly (not immediately) as the hot water will not need to travel the entire distance from the WH, but will instead flow the shorter distance from the line already containing hot water. If you want more immediate hot at other fixtures, a crossover valve would be needed at each,

Using the home's cold supply lines for recirculation return is mostly a kluge when installation of a dedicated return line is not practical or is too costly. For more immediate and hotter water at each fixture, a dedicated return line would be needed from each fixture which will eliminate the need for crossover valves.

 

[Bannerman]

Duplicate

 

[WorthFlorida]

Crossovers need to be at the furthest fixture, pipe length wise from the WH. As Bannerman stated if the hot water runs the off to a different side of the home or to a second floor, a crossover would be needed for each branch. Plenty of diagrams on line on pipe runs and crossovers.

 

[Sonny goldstone]

I assume you are using a Noritz crossover valve which has an internal thermostat control that will stop circulation flow once 95℉ is sensed at that valve. This will prevent the water in the cold supply lines from becoming too warm.

Depending on the distance between that crossover valve and the WH, I would anticipate the water within the run before the crossover will be hotter than 95℉, but if that run is uninsulated or routed through a cool zone, there maybe sufficient opportunity for the water to cool once flow has been stopped.

If other fixtures branch off the pipe that runs to the crossover valve, they should each receive hot water more quickly (not immediately) as the hot water will not need to travel the entire distance from the WH, but will instead flow the shorter distance from the line already containing hot water. If you want more immediate hot at other fixtures, a crossover valve would be needed at each,

Using the home's cold supply lines for recirculation return is mostly a kluge when installation of a dedicated return line is not practical or is too costly. For more immediate and hotter water at each fixture, a dedicated return line would be needed from each fixture which will eliminate the need for crossover valves.

My house isn’t plumbed as a straight shot going from heater to farthest fixture.

it’s 2 stories so I think somewhere it forks off to provide water to the second floor through different pipes..

I asked my plumber about using multiple crossovers and I thought he said you can only use one - would I be able to install a second crossover on a fixture on the second floor - why would he think I can’t use 2?

 

[WorthFlorida]

A miss understanding. You cannot use two crossovers with two sinks on the same pipe run. All branches need one at the end sink. If all of the sinks had a crossover most of the water would only recirculate at the closest sink to the WH. It's like electric, water will take the path of least resistance. With a basement it should be easy to trace the pipes.

I have a two story house on a slab, 2nd owner so I do not know how the pipes were run. The best I could figure out is how fast or long it takes to get hot water at the sinks. My WH is in the garage, the water runs to the washer, then the kitchen sink, master bath, 1/2 bath, upstairs bathroom. The way the house is laid out I first thought there would be a split at the 1/2 bath to feed the second floor. For my house a crossover would need to be in the second floor bathroom, may be 60'-80'. Of pipe from the water heater.

 

[Sonny goldstone]

A miss understanding. You cannot use two crossovers with two sinks on the same pipe run. All branches need one at the end sink. If all of the sinks had a crossover most of the water would only recirculate at the closest sink to the WH. It's like electric, water will take the path of least resistance. With a basement it should be easy to trace the pipes.

I have a two story house on a slab, 2nd owner so I do not know haw the pipes were run. The best I could figure out is how fast or long it takes to get hot water at the sinks. My WH is in the garage, the water runs to the washer, then the kitchen sink, master bath, 1/2 bath, upstairs bathroom. The way the house is laid out I first thought there would be a split at the 1/2 bath to feed the second floor. For my house a crossover would need to be in the second floor bathroom, may be 60'-80'. Of pipe from the water heater.

I’m also in a 2 story slab house w WH in garage

...since the second floor seems to have its own “branch” would it work to put one upstairs in addition to the one downstairs?

 

[Bannerman]

Most tankless manufacturers recommend one crossover valve per system, but that will assume each fixture's supply is branched off a single supply line running from the WH to the crossover valve at the farthest end. Not all homes are plumbed that way.

While I agree with the narrative Worth provided, the crossover valves utilize a thermostatically controlled valve to stop flow once 95F has been sensed, which will change things somewhat.

The Noritz website indicates their Comfort valve is manufactured by Grundfos but I have not found specifications on either brand's site to indicate the recirculation flow rate through the valve when below 95F. IF for instance each valve will only pass 1 GPM and the WH pump is circulating 3 GPM, then there should be sufficient flow to allow 2 crossover valves on the same run to function concurrently.

If each valve will pass higher flow than the pump is circulating, I then anticipate the valve located nearest to the WH will consume 100% of circulation flow as Worth stated, but once that valve senses 95F and halts flow, circulation flow should then proceed on to the next closest crossover valve. With 2 crossover valves each located on different levels, I expect there would be no circulation flow to the upper level until the valve on the lower level achieves 95F and circulation flow is halted through that valve.

 

[Sonny goldstone]

Most tankless manufacturers recommend one crossover valve per system, but that will assume each fixture's supply is branched off a single supply line running from the WH to the crossover valve at the farthest end. Not all homes are plumbed that way.



While I agree with the narrative Worth provided, the crossover valves utilize a thermostatically controlled valve to stop flow once 95F has been sensed, which will change things somewhat.

The Noritz website indicates their Comfort valve is manufactured by Grundfos but I have not found specifications on either brand's site to indicate the recirculation flow rate through the valve when below 95F. IF for instance each valve will only pass 1 GPM and the WH pump is circulating 3 GPM, then there should be sufficient flow to allow 2 crossover valves on the same run to function concurrently.

If each valve will pass higher flow than the pump is circulating, I then anticipate the valve located nearest to the WH will consume 100% of circulation flow as Worth stated, but once that valve senses 95F and halts flow, circulation flow should then proceed on to the next closest crossover valve. With 2 crossover valves each located on different levels, I expect there would be no circulation flow to the upper level until the valve on the lower level achieves 95F and circulation flow is halted through that valve.

Would you say it’s normal when using a crossover to get water that’s warm (not hot) instantly but it still takes up to 90 secs to reach the temperature set on the heater..

are my expectations too high that I was expecting instant 120 degree water from my furthest tap?

 

[WorthFlorida]

Would you say it’s normal when using a crossover to get water that’s warm (not hot) instantly but it still takes up to 90 secs to reach the temperature set on the heater..

Are my expectations too high that I was expecting instant 120 degree water from my furthest tap?

Without a dedicated return line instant hot is not possible unless you want to live with warm-hot water on the cold side.

As Bannerman explained, the Noritz limits the return to 95 degrees then shuts the pump off. To get the 125 degree or hot water as you expect the cold water return would be nearly as hot. It would wasted water waiting for cool water and someone can be burned. Ninety seconds, which is a long time, could be for a few reasons. One, is new faucets is limited to 1.5 gallons per minute max if pressure remains at 60 PSI. Most are 1.2 gallons to meet local codes. I have four new Delta bath sink faucets and they are rated at 1.2 gallons per minute at 60 PSI. 3/4" PEX holds about 1.837 gallons per 100 feet. Assume your bathroom is 50 ft from the water heater that is almost 1 gallon of water to past through a 1.2 gallon/minute rated faucet if the pressure stays at 60 PSI but it usually drops as water is used. It could be at least 45 seconds before getting warm water without a recirculator. I have no recirculator and my main bath takes at least a minute before getting warm water. I have CPVC pipe.

Another is the setting on your WH. I do not know the workings of this unit. The settings may need tweaking, the flow sensor/monior or cpmputer setting is a little slow to know when to heat the water, or the bypass is not at the end sink(s). With your two story home and all the fixtures feed of the same hot water line, then the crossover should be in the second floor sink assuming it is the last fixture.

I finally found a diagram for a split hot water system.The black lines are the crossovers.

 

[Bannerman]

Although the specs indicate the crossover valve will stop recirculation flow at 95F, it does not state the temperature at which the valve will reopen. If perhaps the valve reopens at 90F, although the pump may be running the entire time, no water will circulate until the water in the valve cools to 90F. Any 'warm' water remaining in the supply line before the crossover valve will need to be cleared out before additional 95F water will arrive at the crossover valve.

As previously stated, higher temperature hot water will be more immediate when using a dedicated return line as no crossover valves will be needed. With no crossover valves, there will be nothing to prevent circulation flow and so full temperature hot water directly from the WH can continue to circulate nonstop if desired.

 

[Sonny goldstone]

Although the specs indicate the crossover valve will stop recirculation flow at 95F, it does not state the temperature at which the valve will reopen. If perhaps the valve reopens at 90F, although the pump may be running the entire time, no water will circulate until the water in the valve cools to 90F. Any 'warm' water remaining in the supply line before the crossover valve will need to be cleared out before additional 95F water will arrive at the crossover valve.

As previously stated, higher temperature hot water will be more immediate when using a dedicated return line as no crossover valves will be needed. With no crossover valves, there will be nothing to prevent circulation flow and so full temperature hot water directly from the WH can continue to circulate nonstop if desired.

Thanks this is all really helpful...

honestly since I’m on a crossover system and “instant warm” isn’t that helpful to me I’m considering shutting off the pump.

How much additional gas am I using by leaving recirculating on “learning mode” which means it probably fires up 3 times an hour for about a minute?

I guess the better question is how much gas per minute does the heater us when I’m using hot water

 

[Bannerman]

how much gas per minute does the heater us when I’m using hot water

The NRCR111 Specifications indicate 18,000 - 199,900 BTU/hour. 1 cubic foot (ft3) natural gas contains approx 1,000 BTU. Because the heating output is modulated (variable), then the minimum heating output will consume 18 ft3/hr, to any amount up to 199.9 ft3/hr max.

Consumption will be directly conditional on the water flow rate, the temperature of the incoming cold water, and the number of degrees the water will need to be heated to provide the desired hot water temperature (Temperature rise).

 

[Sonny goldstone]

The NRCR111 Specifications indicate 18,000 - 199,900 BTU/hour. 1 cubic foot (ft3) natural gas contains approx 1,000 BTU. Because the heating output is modulated (variable), then the minimum heating output will consume 18 ft3/hr, to any amount up to 199.9 ft3/hr max.

Consumption will be directly conditional on the water flow rate, the temperature of the incoming cold water, and the number of degrees the water will need to be heated to provide the desired hot water temperature (Temperature rise).

If I buy the more advanced remote and set the recirculating times to say 5-6pm - does that mean the heater would be heating water and running the recirc pump for a full hour?

 

[Bannerman]

In your 5-6 pm example, the pump would begin operating at 5 pm and begin circulating water so the WH will activate to heat the outgoing water to the set temperature. Once the crossover valve senses 95℉, the valve will close to stop flow. The hot water pipe feeding the crossiver valve will contain 95℉+ water. Although the pump will continue running, with no circulation path open, the water will not circulate so the WH will shut down until the water in the crossover valve cools to where the valve will open again to allow circulation.

Perhaps Noritz On-Demand kit will be compatible with your WH. The kit described here: https://www.google.com/url?sa=t&source=web&rct=j&url=https://support.noritz.com/download.php?file=Literature%20Page/Installation%20Manual/IHK-NRCP%20IM.pdf&field=InstallationManual&ved=2ahUKEwi7oI-KgrHuAhVJbKwKHf9eDMsQFjAEegQICRAB&usg=AOvVaw232w_fjxojQMNEcx23BH6A

is intended for a dedicated return line, but I anticipate if you can feed a light gauge 2-wire cable (thermostat wire) to where the crossover valve is currently located, the sensor could be located there. The sensor will shut off the pump when sensing 102℉ so 7℉ greater than the crossover valve so removing the crossover valve would be necessary. The crossover valve could be replaced with an H shaped connection you build yourself, with a check-valve and ball valve in the cross over line between hot and cold to ensure flow is one direction only.

A 2-conductor cable routed to each bathroom, kitchen laundry and 2-piece connected to a momentary contact switch (door bell button) will activate the pump any time hot water use is anticipated. The Noritz manual linked above specifies On-Demand activation will allow the pump to run until the sensor senses 102℉ or 5-minutes, whichever is first.

Increasing the water temp to 102℉ will of course increase the temp of the cold water past the sensor, but 102℉ should continue to be reasonable.

https://www.homedepot.com/p/NORITZ-...ect-Tankless-Water-Heaters-IHK-NRCP/314025957

 

[Sonny goldstone]

In your 5-6 pm example, the pump would begin operating at 5 pm and begin circulating water so the WH will activate to heat the outgoing water to the set temperature. Once the crossover valve senses 95℉, the valve will close to stop flow. The hot water pipe feeding the crossiver valve will contain 95℉+ water. Although the pump will continue running, with no circulation path open, the water will not circulate so the WH will shut down until the water in the crossover valve cools to where the valve will open again to allow circulation.

Perhaps Noritz On-Demand kit will be comparable with your WH. The kit described here: https://www.google.com/url?sa=t&source=web&rct=j&url=https://support.noritz.com/download.php?file=Literature%20Page/Installation%20Manual/IHK-NRCP%20IM.pdf&field=InstallationManual&ved=2ahUKEwi7oI-KgrHuAhVJbKwKHf9eDMsQFjAEegQICRAB&usg=AOvVaw232w_fjxojQMNEcx23BH6A

is intended for a dedicated return line, but I anticipate if you can feed a light gauge 2-wire cable (thermostat wire) to where the crossover valve is currently located, the sensor could be located there. The sensor will shut off the pump when sensing 102℉ so 7℉ greater than the crossover valve so removing the crossover valve would be necessary. The crossover valve could be replaced with an H shaped connection you build yourself, with a check-valve and ball valve in the cross over line between hot and cold to ensure flow is one direction only.

A 2-conductor cable routed to each bathroom, kitchen laundry and 2-piece connected to a momentary contact switch (door bell button) will activate the pump any time hot water use is anticipated. The Noritz manual linked above specifies On-Demand activation will allow the pump to run until the sensor senses 102℉ or 5-minutes, whichever is first.

Increasing the water temp to 102℉ will of course increase the temp of the cold water past the sensor, but 102℉ should continue to be reasonable.

https://www.homedepot.com/p/NORITZ-...ect-Tankless-Water-Heaters-IHK-NRCP/314025957

This would be a great solution though I would need to hire someone - how are you able to run the button wire across the house to the water heater?

 

[Reach4]

This would be a great solution though I would need to hire someone - how are you able to run the button wire across the house to the water heater?

There are ways to run concealed wires. Your installer may be skilled in that. If you have an unfinished basement, that should be simple.

There are ways to go wireless for the button. If nothing else, there are third party remote buttons that close a set of "dry contacts" that can be located at the control box, whenever you push a button. I don't have a device to suggest, but there are many available.

 

[Bannerman]

While the sensor located at the point of return would need to be hardwired, because the WH in On-Demand recirculation mode has a 5-minute limit when activated with a button, perhaps the sensor would not be required. Without a sensor to shut off the pump when 102F is sensed, I could not predict the temperature of hot water entering the cold line in 5-minutes circulation if no thermostatically controlled cross-over valve was used to limit the temperature.

If you have a Google Home or Alexa device, you maybe able to activate recirculation by voice. The smart switch listed below is connected by WIFI. Although usually used for controlling an electric garage door operator, the switch offers a momentary contact relay so I anticipate it could be wired as an On-Demand button if wired to the appropriate terminals within the WH.

https://www.amazon.com/dp/B0752P57ZG/ref=as_li_ss_tl?keywords=ewelink+module&language=en_US&ie=UTF8&sr=8-1&linkCode=gs2&linkId=7b93392fcd98392bd94c34a45a30dfb2&tag=twhomeshow07-20