I have a Rinnai tankless. The temperature fluctuates wildly
I suffer occasional loss of heat in the sinks but the basement shower is the worst. Temperature will fluctuate from burning hot to icy cold withing seconds with touching the controls. This will last for months, and then not happen again for a while. First my serviceman thought our pipes might be clogged with sediment, but they are pretty new. Then he thought there wasn’t enough gas coming into the house, so now we have enough for an apartment building.
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Re: I have a Rinnai tankless. The temperature fluctuates...
I think the dip tube in your water heater has failed, this is a plastic tube that goes in the cold side of your tank and forces incoming cold water to the bottom of the tank allowing hot water out at the top. When this tube deteiorates the incoming cold water mixes at the top of the tank causing the problem you have. the dip tube runs about 5 bucks but takes someone with pluming skills to install.
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A lot depends on the size of the tank. And when it heats some systems only heat at night , this is ok if the system is large , on most heaters there is a thermostat on the side that can be used to set to a higher temp. the thermostat on your heater may be faulty.
Have you ever tried to pump water for a fountain... It is so tough and you need larger and larger pumps to get it to go 7 feet high to let's say 10 feet high. Having the on demand water heater in the attic dramatically drops it's pressure. It's best to feed it with a 1 inch or at least 3/4 inch pipe downstairs before it splits the hot and the cold to get the best pressure everywhere then the least pressure will be when it reaches the 2nd floor. but the heater won't cut out because the pressure it even greater downstairs.
Water heaters by Rheem have not changed that much over the years. the link below will give you some good information about electric water heaters in general. As water heaters age, the heating element will lose efficiency due to deposits and general build-up of minerals in the tank. Turning up the temp may not be a good idea since the problem is actually caused by a coating on the element. Also make sure that cold water is not bleeding into shower valves thru other single lever faucets. While shower is running, listen to and feel the water lines connected to sink faucets in other rooms for water transferring thru valve. You can actually hear water running at faucet while shower is on if faulty. If other vaucet valves are leaking thru, repair those first before you do anything to the water heater as that is cause of loss of hot water. Good luck.
Ok i intall tankless water heaters and sell them and repair them . The trouble your are hving is more than likely ,the mixing valve on your shower has a ajustment on it to prevent you from burning your self . that is the number one reason in showers when water never get to temp . What it is doing is addng cold water to your shower for you bummer . Take handle off and adjust water temp to your hottest setting . Some times you have to remove the low flow washer in shower head to get the right flow . also every time you start up your hot water it shouldbe set all the way ot other wise withe the battery 2 D models the unit will not sence flow and shut off the unit ,with some units it is a fine balancing act to get them adjusted right. If your buying a tankless water heater always buy a blower type unit that has a computer that runs it . You will be happy . If the Battery operated unit is for a cottage or a smallcabin then your just going to have to fix the pumbing to make it work right many of the safety features of the newer showers are not made to work well with tankless water heaters .
Tankless heater are a little frustrating sometimes but this is generally an issue of waterflow I believe. The fluctuations are do probably to the amount of water and rate of water going through the heater. If you have a shut off valve on the cold side of the heater, shut it back about half way. This will slow the water going through the heater and allow the heater to heat it up more efficiently. Then go to the shower, turn the hot on all the way (no cold) and allow it to heat up. Once it has heated up, test it by hand for a good temperature that you like. If it is too hot, turn the cold on just a bit until it comes to the temp you like. If it is too cold turn the hot down just a little (still no cold) and it will warm up. Ideally you should be able to turn the hot on full blast and then just turn on a little cold to get the right temp. Once you learn how these work then it makes it easier. You really cant run the water like you do with conventional hot water systems and expect to get the same results. Also, wanted to give you another little tip. Every 6 mos to a year, you should flush you heater with vinegar for about 30-45 minutes using a small cheap submerible pump like for a water feature in a garde. Just put in a bucket of vinegar and and run a hose to the "in" side of the heater and another from the "out' side of the heater and then back into the bucket. This will circulate the vinegar inside the heater and clean all the deposits that will DOA your heater. Funny how the manufacturer wont tell you this but these deposits will ruin the connectiosn on the heating elements. You can make your heater last for a long time if you do this.
COLD MIX, HEATER DEACTIVATES If inlet water temperature is over 70°F due to geographic location, water maybe very hot out of the tap. This requires a lot of cold water to be added with it in order to attain a useable hot water temperature. The addition of too much cold water will overpower hot water demand from the tankless water heater. This slows the flow within the tankless water heater, decreasing it below activation point, which shuts off the heater. The end result is nothing but cold water coming out of the outlet. See: TWH E2-04 Overcoming fluctuating temperatures [PDF].
FLUCTUATING WATER PRESSURE If the water pressure in the home is erratic and the water flow is not consistent while a tap is opened, then the temperature of hot water will fluctuate. The minimum water pressure for the home should be 30psi or greater. For people on well systems the minimum pressure range is 30-50psi. The use of a pressure reducing/regulating valve is an effective way to maintain constant water pressure to the water heater. Watts brand 25AUB- ¾" or N35B-¾" pressure reducing/regulating valves or equivalent is suggested.
CHANGING FLOW RATE Major changes in flow rate can adversely affect the output water temperature of the heater. Increases from one major fixture running to multiple fixtures running at one time can cause the temperature to fluctuate. Stay within the heater's specifications. See: TWH E2-03 Outlet temperature vs. flow rate [PDF].
lower the output temp on the unit. the tap water could be too cold coming in. The bosche units don't like a large temperature difference between tap water and the water at your shower head. Condensation becomes a real problem. I run my water thru my basement slab to heat it up and that made all the difference, but you probably didn't buy your house with a dirt basement did you?
This is a great heater. It is however crucial that it be installed to every detail of the manual. If there is trouble send pictures to Bosch tankless you can call 1-800-283-3787 ask for Bosch Tech support or go to boschhotwater.com click find a contractor and call the closest Bosch Service Provider most will travel.