Question about Rinnai RL75iP Interior, 7.5 GPM, Liquid Propane, 82% Efficiency Tankle

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Why does the unit come on for 1 or 2 seconds when I shut the cold water off in the kitchen

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It may just be something it does when you happen to turn on the sink. I don't think there is a problem with the water heater coming on when you use cold water. It may just be heating the water back because the water is much colder than normal. You could talk to an HVAC guy and see what kinds of things they can do to help the situation. SERVICES Marv Plumbing Bellingham WA

Posted on Jun 16, 2015

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1 Answer

Which is cold water connection on the boiler


Incoming cold water usually connects to nipple marked with C, and/or the nipple that feeds into water filter (if unit has built in filter)
If unit has shut-off valve, then shut off is located on cold line.
If unit is operable, then turn on hot water and see which pipe gets hot ... and then cold is other pipe.
read your product manual.
Search your brand and model on internet to locate product manual.
Otherwise re-post question and include brand and model number so product manual can be located and information can seen first-hand.
Gene

Jul 18, 2013 | Water Heaters

1 Answer

Heater takes more than 1 minute to get water to kit faucet , then temp fluctuates


1) Guesses: Sounds like a bad single-handled faucet cartridge, or low water flow at faucet, or clogged water filter.
Replace faucet cartridge, clean the aerator, and/or clean sediment out of pipes below sink, and clean water filter at tankless unit each month.

2) For exact measure of problem:
Typical faucet can have 2 gallon per minute flow rate.
2 gpm flow rate means faucet fills 1 gallon container in 30 seconds. Test faucet using 1 gallon container and a cooking timer to get flow rate.
Clean aerator to improve flow rate. Compare kitchen flow rate with other faucets in home.
http://waterheatertimer.org/Low-hot-water-pressure.html

Most homes have 1/2" diameter pipe running to kitchen faucet.
100 feet of 1/2" diameter pipe holds 1.2 gallons of water. This assumes no sediment build-up inside pipes.
http://waterheatertimer.org/Water-heater-recirculation-system.html

Assuming only hot is turned on: If faucet is 100 feet away from water heater, and pipe diameter is unobstructed 1/2" diameter, and faucet has 2 gallon per minute water flow, then hot water should arrive in 36 seconds.
50 feet away, and hot water should arrive in 18 seconds.

If kitchen has single handled faucet, and the handle is raised in the middle, then equal amounts of hot and cold water are drawn at same time. This doubles amount of time for hot water to arrive.

If single handle faucet has a bad cartridge, then faucet can have crossover.
Crossover means that cold water can enter the faucet even if faucet is turned to hot.
Bad single-handled faucet cartridge can delay or stop the arrival of hot water.
http://waterheatertimer.org/Crossover.html

Tankless require maintenance including cleaning combustion parts yearly, de-lime heat exchanger frequently, and clean water filter each month.
http://waterheatertimer.org/pdf/Tankless-maintenance.pdf
http://waterheatertimer.org/pdf/Bosch_Overcoming_fluctuating_temps.pdf
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

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Sep 15, 2011 | Rheem Direct Vent Natural Gas Tankless...

1 Answer

I have powerstar model # 45557701- what causes the cracking noises when water is heating? what will make the unit slow to start to heat? how can i change the heating units?


The crackling noises is just from air in the water and should be of no concern. If you are having a problem of heating up the water with the unit it is most likely do to water moving too fast through the lines. Ideally, there should be a shutoff valve installed on both sides of your heater (makes for easy removal if it needs to be serviced). But if you turn off the valve about 1/4 to 1/2 way on the one on the "in" side of the heater (where the cold water enters) then you will slow down the water going through the heater and this will give the water a better chance to heat up. This should alleviate the heating problems you are having. If you do have a shutoff valve on the cold (in) side of the heater, shut it off about 1/4 to 1/2 way and then go to your shower and turn the hot on all the way (no cold). Wait for the water to warm and test the water by hand to see if it is the temp you want. If it is still not warm enough, turn the hot on the shower DOWN just a little. This will actually make the water hotter. I know this doesnt seem right but it will. On the other hand, if the water coming out with the hot water fully turned on is too hot, then just turn on a little cold water at a time until the water is the temp you want. Remember, always give the water plenty of time to get from the heater to the shower before you decideof its the right temp. Ideally, you should be able to turn the hot water on all the way and get the hot temp that you want and if you want to cool it down, just turn the cold on just a little bit until it is where you want. I'm fairly sure the problems you are having are due to the water going too fast through the unit and once you adjust that and understand better how these tankless heaters work, you wont have any more trouble. They are difficult to get used to after using conventional water heaters and the manufacturers arent very good about giving you these hints so they will work properly. You will need a professional to uninstall and hopefully this will work and you want have to. But if you do, it requires shutting off the water to the unit. Shutting off the pwer to the unit. Unattaching the water lines to the unit and then unattaching the electric lines from the junction box or wherever they are attached. The heater then can be removed from the wall by unscrewing the screws from the hangers which hold it to the wall.

Feb 21, 2011 | Bosch PowerStar AE115 Tankless Water...

1 Answer

Heats up the rapidly decreases within in minutes.


Problem new or old? How long you have unit? Sounds like not enough flow to keep burner on. Tankless need at least .6 gpm to keep hot water flowing or else the burner fires then shuts fires then shuts and you get a sandwich effect...hot cold hot cold. If you have new diverter valve in shower -vs- old two handle type try turning hot water ALL the way ON and see if hot stays hot. If it does stay hot then slowly adjust to cool and see if you maintain a good MIX for proper temp. If it goes cold again try this......LOWER control pad setting to a comfortable 105 degrees (ladies) 100 degrees(men) and turn shower valve all the way to HOT. See if your temp remains consistant now and if it does then problem solved. Tankless mindset...set temp on control pad and stop trying to MIX at shower valve. Thats how these things work. Thats why I install a control pad in each bath and one in the kitchen for adjusting ash temp during dishwasher on time. ditto for wash machine. You should never need to turn on cold water if your unit is set to proper temp at controller. Hope this helps

May 17, 2010 | Rheem Tankless Hot Water Heater...

2 Answers

We have a customer that has a 751od who says at times thier water gets cold for a few seconds. No error codes on the remote. They claim it does it at different fixtures. Everything checks out from water...


A few things you should check:

1. Cross Connections - this occurs when cold water leaks into the hot water system through a fixture. In order to check for a cross connection: 1) turn off the cold water to the tankless 2) open up hot water fixtures in the home. The water should shut off at all hot water fixtures; if there is a continuous flow of cold water, then you have a cross connection. The most common place to find a cross connection is on old shower cartridges.

2. Ask the customer to check to see if the burner indicator is continuously lit during operation.

3. When the water goes cold at one fixture, try another near by fixture to confirm it is also cold there. If its hot at one fixture but not the other, then you have some issue with you plumbing. Tankless heaters can't pick and choose which fixtures to deliver hot water to.

4. Tankless water heaters all have a minimum flow rate that must be maintained in order to continually fire (.5 gpm for Noritz). Ensure their hot water fixtures flow at least this amount, or that the customer isn't mixing too little hot water at their fixture.

5. If they see the cold spurt during initial firing, they may be experiencing a cold water sandwich. When the heater moves from a standing state to a firing state it takes a short period to ignite and heat water. During this time it will be passing cold water through the system. Usually this cold water mixes with hot water in the line as it travels through the plumbing system, but if their fixture is very close to the heater, there won't be enough time to mix.

6. If debris has gotten into the flow sensor, this can prevent the unit from registering flow and cause intermittent firing.

Aug 27, 2009 | Noritz 7.1 Gpm Natural Ng Gas Tankless Hot...

1 Answer

No hot water


check the flue and make sure nothing is in it, nothing can be obstucting the flue or it will shut down on carbon monixide make sure nothing is in it if you have to take it apart do so it just slips together

Jun 07, 2009 | Rheem Tankless Hot Water Heater...

2 Answers

Hot Water Heater in 1991 Pace Arrow RV is not working


If you look on the outside of the RV, you will find the vent for the water heater behind and access door. There usually is a drain plug and valve located as well. Generally they will be tucked away under the kitchen sink area with internal access as well. You will need to find where the valve that shuts the water off to the unit is and turn it on. Most times the water heater is either electric or propane. But sometimes they are only propane. Once your find the access door, you will know where the water heater is. You can also contact Fleetwood who makes the Pace Arrow to see if they have any information on your unit. Usually your unit info or trim number will be located on a little plaque right by the entrance to the RV. You will need this when you contact them. Hope this helps.

Mar 31, 2009 | Water Heaters

2 Answers

Runs out of hot water


I wonder if you have this problem below caused by a drop in water pressure from someone flushing a toilet or a washing machine. I would call the company to remedy this issue.

17. What is a cold water sandwich effect? The term “cold water sandwich effect” is a term that is used to describe the introduction of cold water into the hot water supply line during frequent on/off operation of an instantaneous water heater. The cold water sandwich effect, when present, appears as a momentary drop in hot water temperature as it is discharged from a hot water supply outlet (i.e. shower, tub, or faucet). This phenomenon is present in the operation of all instantaneous, tankless style, water heaters, but is minimized with the high tech design of Rinnai water heaters.
The technology built into the Rinnai water heaters is designed to minimize the cold water sandwich effect. Rinnai water heaters are microprocessor controlled and when water flow through them ceases, they remain in a “ready to fire state” for approximately 1 minute. If water flow through a Rinnai water heater begins within the first minute following water flow stoppage, the water heater will fire back up within 1 to 2 seconds. This minimizes the cold water sandwich effect that would otherwise be experienced with a low tech tankless water heater. It should be noted that the cold water sandwich effect cannot be removed completely from tankless style water heaters. The safety standards developed to insure the safe operation of water heaters require a delay in the ignition sequence of all gas water heaters.
While the cold water sandwich effect cannot be completely eliminated from standard plumbing systems, it can be eliminated from plumbing systems that have a supply and return hot water circulating system. Rinnai has developed 2 methods to eliminate the cold water sandwich effect in residential hot water circulating systems.
The first (and preferred) method to remove the cold water sandwich from circulating systems utilizes a small electric tank water heater (powered up) that is used with a dual purpose. The small water heater acts as a mixing tank to eliminate the cold water sandwich effect from the Rinnai water heater and it uses its electric heating element to offset the heat losses from the hot water circulating system.
The second method to remove the cold water sandwich from circulating systems utilizes a small 2 to 6 gallon storage tank installed on the hot water outlet of the Rinnai water heater. This tank acts as a mixing tank to blend the cold water sandwich with hot water and eliminating its effect at fixtures.

Mar 11, 2009 | Rinnai Water Heaters

2 Answers

Scalding hot water


If your water is too hot, then either the water tank thermostat or the wiring to the indoor unit is defective. When the water reaches the set temperature, then the tank thermostat contacts should open up and shut off the combustion unit. If the combustion unit does not shut off, then check all wiring and relays. A manual is located at http://www.scribd.com/doc/29550374/Amana-HTM-Plus-Manual

Dec 03, 2008 | Water Heaters

3 Answers

Water is either hot or cold - no in between.


I found a way to get warm water in the shower, but I'm not sure it qualifies as a solution. After trying everything else I thought that maybe when I was feathering the faucet in the shower toward the cold side so I would get warm water that at a certain point it blocked the flow on the hot water side enough so that the sensor in the hot water heater sensed there was no demand in the line and it shut the water heater off. To test this, I went to the kitchen and turned the kitchen sink faucet all the way to the hot side and then turned it on so that I got a small flow of water. I waited for the water to get hot to be sure the hot water heater was working. Once it was hot, I left it running to keep demand in the line and then I went to the shower and turned the faucet on. When the water got hot I started feathering the control towards the cold side and soon I had warm water. So I think I'm right in that the sensor in the hot water heater was shutting the water heater off when the demand in the shower was lowered to a certain point when I was trying to adjust the water temp in the shower.

So now I can get warm water, but it means I have to leave the hot water running at another fixture in the house to create a false demand in the system so the hot water heater doesn't shut down. Is there a way to adjust the senor in the hot water heater so that it will stay on when I'm using the shower only, so I don't have to waste water by running another faucet when I want to take a shower?

Nov 28, 2008 | Water Heaters

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