Hot water unit not working

[KVJ]

We moved to a new house and installed our basic Fujika hot water unit from our old house. It was working fine in the old place but had troubles with it from the get go in the new place. The hot water would work intermittedly and often it would cut out after a short period or if the knob got turned past a certain point. I took it to a repair shop and they said the switch was buggered and replaced it. Took it home, installed it again, and still not working. Took it back to the shop, they tested it in front of me and it was fine.

I'm guessing this is some kind of water pressure problem? Our old house was single story whereas we are on the second floor of the new place. The pressure doesn't seem that bad though - it wasn't great at the old place either but had no problems there. The other thing now is that it's just stopped working period now. No light comes on at all whereas before it would come on and off if it was reset. I don't even get the green test light come when I press the test button.

Any ideas before I try taking back to the store again?

Cheers for any advice.

[Crossy]

Intermittent hot and tripping if turned up too far does seem like a pressure problem, how's the shower pressure with the power off?

No lights at all I would be looking at its electrical supply. Do you have a multimeter?

Check that the breaker feeding the heater is not tripped (turn it off and back on).

[KVJ]

Thanks for that.

We have a well and pump so if the power is off there's no water.

Don't have a multimeter I'm afraid.

Yes it does seem that something has tripped out seeing as there is no light at all now. The fuse box is fine. Have swtiched it on and off a few times.

Everything looks fine inside the unit too.

[Crossy]

Actually I just meant the power to the heater so your pump works

With no meter you're really in trouble I'm afraid.

As the unit has a 'test' button, have you made sure its internal RCD trip is properly reset?

[MaeJoMTB]

Inlet and shower hose the wrong way round?

Easy to do (I did it).

Neutral and live wires connected the wrong way round?

25bht for a screwdriver with a 'live' light in it, how can you work on anything electrical and not have one?

Suicidal!

[RichCor]

Instant, on-demand (tankless) water heaters will typically have

Water Flow reed switch

High-Temperature bi-metallic sensor

On-board RCD

Water flow rate must be adequate enough to keep an internal reed-style switch closed to allow the unit to power the heater element

Water flow rate must be adequate enough to prevent the water from super-heating, when measured by a bi-metallic sensor

Unit must not allow any Live/Neutral current to pass to Earth-Ground, as measured by an instant-off sensor.

If the issue is intermittent, I would suggest you look at the water flow rate.

You can check the water flow rate minimum requirement in the manual (usually can be found online). Many units will list a "Switch-on flow rate of 3.0L/min / No Pressure Needed"

On ours, you can hear the flow switch engage/disengage when adjusting the water valve.

Otherwise, it could be variable control circuits corrosion, a failing circuit board, heating element or Triac.

[KVJ]

Thanks for the useful info guys.

It's definitely hooked up right and I've reset the RCD trip.

It's strange that before it would intermittedly work but now there's nothing which seems to indicate another problem has surfaced.

Time to take it back to the repair shop

[Crossy]

Does the built-in RCD trip when you press the test button, if it does that's an indication the unit is getting power.

If not, time to get the meter out. Go and buy one, simple digital meters are cheap and invaluable, get a neon screwdriver whilst in the shop.

[KVJ]

OK. Just had another look and it turns out the jack for the RCD wasn't in quite right. So, now we're back to the hot water dropping in and out.

The unit has been checked over in the repair shop and it worked fine there. Seems to be the water pressure. I'll speak to the landlord about turning up the pressure. Failing that I guess I'm looking at a gravity fed tank or somthing? Don't really want to be spending much money on this. Personally, I love cold showers but the rest of the family don't unfortunately!

[Crossy]

A gravity tank won't give you the pressure unless very high. Look at adjusting or uprating the pump.

Hows the pressure at the shower head, does it seem low?

[KVJ]

Pressure at the shower head seems fine. The water pressure in the shower in general seems fine - it's not great but it wasn't anything flash at the old place either and it worked fine there.

The water pressure elseswhere in the house upstairs is OK too. The pressure downstairs is very strong.

Will look at getting the pressure adjusted at the pump.