Hot water cylinder does not seem as hot

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mb82

223 posts

Master Geek

#318300 5-Jan-2025 12:14

Thermostat is set at 77c thermal camera shows cylinder at about 45c. Cylinder has power to it (if ripple control was off the power would not be going to the cylinder at all? Or would power be going to the cylinder but not to the element?).

Saw power going to element decided to see what it heats up to, has heated to less than 50c and turned off again. If it is set at 77c what temperature should it turn on at?

Power meter is landis e350 but don't know how to tell if ripple control is on or off?

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2837 posts

Uber Geek

Subscriber

#3327794 5-Jan-2025 12:50

How old is the clylinder?

Sounds like the thermostat needs replacing.

k1w1k1d

1530 posts

Uber Geek

#3327798 5-Jan-2025 13:08

Thermal camera aimed at outside of cylinder will read very low due to insulation between inner and outer.

Will be more accurate if you can get at the water outlet fitting at the top of the cylinder.

Is the water coming from your taps too low?

RunningMan

8963 posts

Uber Geek

#3327800 5-Jan-2025 13:10

Where is the temp being measured? 45 degrees surface temp sounds very high.

mentalinc

3243 posts

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Trusted

#3327801 5-Jan-2025 13:11

Do you have a meat thermometer to test the tap temperature with?

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mb82

223 posts

Master Geek

#3327808 5-Jan-2025 13:18

k1w1k1d:
Thermal camera aimed at outside of cylinder will read very low due to insulation between inner and outer.

Will be more accurate if you can get at the water outlet fitting at the top of the cylinder.

Is the water coming from your taps too low?

I aimed the thermal camera around the element area and on the outlet pipe with the tap running

mb82

223 posts

Master Geek

#3327809 5-Jan-2025 13:19

RunningMan:
Where is the temp being measured? 45 degrees surface temp sounds very high.

Around the element / thermostat (unisulated) and on top outlet pipe with tap running

mb82

223 posts

Master Geek

#3327810 5-Jan-2025 13:20

mentalinc: Do you have a meat thermometer to test the tap temperature with?

No but running tap into sink showed circa 40c on thermal

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mb82

223 posts

Master Geek

#3327816 5-Jan-2025 13:28

I know hot taps are not allowed to be as hot as they used to be but this is controlled by a tempering valve set about 50c. Problem is hot water seems to run out quickly I am guessing because cylinder is heating to about 50c instead of 75c

tweake

2394 posts

Uber Geek

#3327824 5-Jan-2025 14:02

i think you might be tripping up over your own feet a bit here.

thermo cameras etc only show radiated heat. what temp you get depends a lot on the material its radiating from. it in no way will show the water temp accurately. you need a thermometer you can put in the hot water.

the other thing is a lot of newer cylinders have a thermal overload cut out as well. so you could well be reading temps low (because of the camera etc) and your hitting the thermal cutout temp before its hitting the thermostat temp.

or you have faulty thermostat or cutout.

btw a lot of multi meters these days can take a thermo probe.

MadEngineer

4298 posts

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Trusted

#3327825 5-Jan-2025 14:11

The thermostat should be set to 60degrees C plus or minus adjustments required to get the temperature at the tap to be 60 degrees C.

You should be able to adjust the thermostat up and down through its range and find a point where it is clicking on and off. This will give you an approximate temperature of the water.

You can also check if the element is drawing power by checking your meters between turning off the switch to your HWC and having it on whilst at a high setting on your thermostat or after a shower.

If you end up getting a sparky and if you don't know the age or history of the element and thermostat it may be worth getting them replaced as preventative maintenance. Some parts of the country require them changed yearly

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mb82

223 posts

Master Geek

#3327827 5-Jan-2025 14:33

tweake:
i think you might be tripping up over your own feet a bit here.

thermo cameras etc only show radiated heat. what temp you get depends a lot on the material its radiating from. it in no way will show the water temp accurately. you need a thermometer you can put in the hot water.

the other thing is a lot of newer cylinders have a thermal overload cut out as well. so you could well be reading temps low (because of the camera etc) and your hitting the thermal cutout temp before its hitting the thermostat temp.

or you have faulty thermostat or cutout.

btw a lot of multi meters these days can take a thermo probe.

Confident cylinder temp is about 50c, shiny surfaces can throw off the thermal camera and I can hold my hand on the pipe.

mb82

223 posts

Master Geek

#3327828 5-Jan-2025 14:37

MadEngineer:
The thermostat should be set to 60degrees C plus or minus adjustments required to get the temperature at the tap to be 60 degrees C.

You should be able to adjust the thermostat up and down through its range and find a point where it is clicking on and off. This will give you an approximate temperature of the water.

You can also check if the element is drawing power by checking your meters between turning off the switch to your HWC and having it on whilst at a high setting on your thermostat or after a shower.

If you end up getting a sparky and if you don't know the age or history of the element and thermostat it may be worth getting them replaced as preventative maintenance. Some parts of the country require them changed yearly

Thermostat is at 77c, cylinder is about 50c, no voltage to the element. Didn't know some areas require them to be changed yearly? I bet nobody does

tweake

2394 posts

Uber Geek

#3327830 5-Jan-2025 14:45

mb82:
Confident cylinder temp is about 50c, shiny surfaces can throw off the thermal camera and I can hold my hand on the pipe.

thats something i missed. if you can hold your hand on then its low temp.

i would follow the wiring and see if there is another thermo cutout. otherwise its a bad thermostat, which is not common. they usually burn the contacts or weld themselves together. don't often get the bimetal strip failing. at least a thermostat is typically an easy fix.

tweake

2394 posts

Uber Geek

#3327833 5-Jan-2025 14:48

btw i assume its not a dual element cylinder. those can have two thermostats.

WWHB

38 posts

Geek

#3327899 5-Jan-2025 19:09

A faulty thermostat works 2 ways. On an older cylinder a faulty thermostat boils the water as it never shuts off, On a modern cylinder they fail to the off position and don’t heat the water at all.
A faulty element wouldn’t heat you water to 50c.
You may have a tempering valve that is on its way out, hence the water isn’t getting hot enough.
Water should be heated to 60c at least one day per week inside a cylinder to avoid legionella.

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