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Troubleshooting
Greentherm T9800 SE 160/199 – 6 720 816 815 (2022/01)
58
8.4 Water is not hot enough
1. Selected temperature on the unit is too low. To raise output
temperature, see chapter 6.4, page 6.4.
2. Confirm the heater's gas type coincides with the type of gas
being supplied. See fig. 2, page 12 for location of rating
plate.
3. Verify gas pressure is in accordance with specifications in
chapter 4.13, page 43. A gas pressure reading is needed to
proceed further. Contact your original installer or a local
certified gas technician to obtain this reading.
4. Check inlet gas particle screen/filter for blockage at inlet
gas valve. Need to remove gas valve from the appliance.
5. Cold water is mixing into the hot water lines (plumbing
crossover). A plumbing crossover can unintentionally mix
cold water with the hot water leaving the heater. The end
result is a cooler water temperature than desired. To check
for a plumbing crossover, shut off the cold water supply to
the water heater. Then open all of the hot water faucets
served by the heater. Wait 10 minutes and check all faucets
for water flow. There should be no water flowing. Any
continuous flow of water, small or large, indicates a
crossover and must be corrected. Consult a professional
plumber for help in correcting a crossover. Failing single
lever faucet mixing valves are common causes of plumbing
crossovers.
8.5 Low water flow/pressure
1. Too many hot water applications are being used
simultaneously or too much flow is demanded. The water
heater will effectively support two 2.0-2.5 GPM shower
heads simultaneously or multiple sink applications. Greater
draws will result in a water pressure drop and reduced flow
at faucets.
2. If the selected temperature on the unit is set too high for the
demanded flow rate, the water heater will close its
motorized water valve, reducing the hot water flow rate in
an attempt to reach the selected output temperature.
Lowering the selected temperature will allow the motorized
water valve to open up for increased water flow rate.
3. Clean inlet filter screen as instructed in chapter 7.1,
page 55 to increase flow through the heater.
4. Inspect the water path for obstructions. Make sure all
shower heads, faucet aerators and whole house filters are
clear of debris. It may be necessary to upgrade to higher
flow rate shower heads if allowed by local code.
5. In areas where the water has a high mineral content,
periodic descaling may necessary. See chapter 7.3,
page 56 for directions.
8.6 Hot water temperature fluctuates at faucet
1. If the water heater set point temperature is high, mixing at
the faucet could deactivate the water heater. The addition
of too much cold will overpower hot water flow from the
tankless water heater reducing its flow below the activation
point.
If this slows the flow through the tankless water heater
below its deactivation point, it will shut off the burner.
2. Unbalanced pressure in water lines. Any restriction in the
water heater, such as a clogged inlet water filter screen, can
result in unequal pressures between the cold and hot water
lines. In such cases, when mixing in the higher pressure
cold water at the faucet, the lower pressure hot water can
be overpowered. This will shut down the burners because
the hot water flow rate falls below the minimum flow rate
required for activation. Verify that the inlet water filter
screen is clean and clear of debris. See chapter 7.1,
page 55 for inlet water filter cleaning instructions.
3. The water heater may be deactivated by temperature
balancing shower valves. If the water heater's set point
temperature is set too high, the temperature balance
shower valve will automatically mix in cold water to reduce
the hot water temperature. An adjustment should be made
to minimize the amount of cold water the valve is adding.
Additionally, the temperature setting on the water heater
can be lowered to reduce the amount of cold water that the
temperature balance valve mixes in.
4. Inlet water pressure is erratic due to fluctuating supply
water pressure. For installation on a private well system
with the use of a pressure tank, the lowest pressure range
setting recommended is 30 - 45 psi (2.06 - 3.1 bar).
Consult your installer or local plumber for effective ways to
maintain constant water pressure to the appliance when on
a well system.
8.7 Noisy burner/heater during operation
Burner noises can be heard if combustion is not properly set.
This could be caused by improper gas supply conditions (gas
pressure and/or gas composition).
Two types of noise can be heard: low pitch noise/vibration
(rumbling) and high pitch noise/vibration (whistling).
8.7.1 High pitch noise
1. Verify if correct gas type is selected (see section 6.8).
2. Verify is gas pressure is within specified range (see
section 3.2).
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