Delta single faucet shower temperature

[MasterPlumbersKeymaster]

We have a combination tankless water heater and a Delta single knob shower. In the beginning of the shower you can adjust the temperature, but after a couple of minutes the temperature goes cold!! You must work the knob to again adjust the water temperature from Hot to OK. This process occurs throughout the shower. We replaced the internal pieces of the Delta knob (it was not leaking) but this did not alliviate the situation. FYI we just moved in!!
Is it the heater?? All other faucets deliver a steady stream of hot/warm water. If not, how to fix it??

[SylvanLMPParticipant]

A lot of times the tankless heater cannot make up the volume being used from a shower (GPM DEMAND as per GPM make up)

The easiest way to alleviate this condition is installing a flow restrictor ON THE outlet from the coil. This will give you a more uniform flow say 4-6 GPM etc.

The reason it shows up on the shower part is the volume your using compared to a basin or kitchen sink is much less.

Most tankless heaters are
relatively small and cannot keep up to demands placed on it from showers and dishwashing machines.

Try either 1- using less volume in your shower 2- Installing the flow restrictor at the coil outlet.

The reason I detest flow restrictors at the shower head is
1-They can clog up
2- If someone flushes a toilet you could get seriously scalded by the sudden loss in VOLUME of the C/W

Most folks today are trying to get away from the tankless heater for the simple fact you don’t have enough stand by volume and your also using a BIG BOILER to make a little H/W not very energy efficient during the non heating months.

A hot water heater has its own limitations such as stand by losses and the severe water removal (LEAKS) when they give up the ghost.

Another major draw back on the tankless heater is the temperature fluctuations of the water leaving the coil. Most CHEAP IDIOT installers use a manual globe valve to throttle the temperature of the mixed water instead of using a QUALITY Holby mixing valve with 2 Gauges.

1 gauge of the inlet H/W water one gauge of the mixed water tempered water.

The globe valve not only offers lots of restriction it has a washer that WILL fail in time rendering the tempering useless.

A lot of these coils on steam boilers are installed just below the water level and relies on the heat transfer from the VERY hot water to the coil and the temperature does fluctuate all over the place and this in turn causes the thermostatic showerbodies to open the cold side more to prevent scalding conditions, so it is doing its job.

Have a great week end

[Edited by SylvanLMP on 04 June 2000]

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