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Electric Hot Water System


MADOG & JENNY
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I have recently installed a new electric boiler, however, after about an hour the pressure release valve kicks in & starts to drip water from the overflow pipe. I have installed a new pressure water regulator & adjusted it so the pressure is quite low going into the hot water tank. I have even changed the pressure relief valve thinking it might be faulty, to no avail. The only observation I have made is when you turn the hot tap on, the water comes out white, cloudy- & these millions of air bubbles clear in a few seconds. I can only assume that the bubbles expanding in the tank, as the water is heating, are causing the pressure overload. Water dripping out the overflow all the time & the excess pressure in the tank is not good, but I am at a loss as what to do next.
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HI

It is normal for the tank to 'overflow' as you put it, as the water expands when heated....

You could try turning down the thermostat, often it is set far too hot, if you cannot wash your hands with it without adding cold, then its too hot and also costing you more than neccessary.

The bubbles are probably being caused by the taps mesh washer, give the appearance of much more flow/ pressure than actually exists.

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The next question is "where is the thermostat ?". It is under the cover at the bottom of the tank and you need to stand on your head to adjust it [8-)]. It usually has a little knurled knob and/or a slot for a screwdriver. As one has to fumble for it, strongly recommend turning the power off before attempting this manouevre.
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When we asked the plumber/electrician who installed our electric hot water cylinder about turning down the thermostat, he said it was a factory pre-set (at I think 58 degrees - very hot, anyway) and could not be changed - that is, there was no way of changing it. This might, of course, be incorrect, but it it is probably worth asking before trying to alter something that is fixed.

Our pressure relief valve only drips occasionally - every week or so. We were told to open it to let a little water out on a regular basis - every month - to make sure it doesn't seize up. A subsequent plumber said that was the correct advice to give but no-one normally does it!

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[quote user="tj"]HI

You could try turning down the thermostat, often it is set far too hot, if you cannot wash your hands with it without adding cold, then its too hot and also costing you more than neccessary.

[/quote]

Don't turn down the 'stat (even if an adjustable one is fitted). Regs require the water to be heated to a certain temp (63 deg), to kill off (very) nasties - most of which I can't spell so won't try.

The thermostat will have been set at the correct temp in the factory.

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Listen to the above good advice, the water is set to that high temperature for a reason. Very nasty bugs breed at lower temperatures.

Our plumber also told us to release the pressure valve now and again as they have a tendancy to stick.

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If that's the case, then the entire population of the UK, with our indirect water heaters running at around 50°C, should have died out. The moral is to not drink from the hot water tap!

When I moved in to my chalet, I spent a week tracking down a "wiring fault", because my water was stone cold. It turned out that the previous owner had turned the thermostat down to minimum.

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Thanks to everyone for writing in. However, this still leaves me with the question as to why my pressure valve is constantly dripping. The instructions on the packet, the new valves came in, says to test it every month. Both of the new valves I`ve tried should read - test if you notice it ever stops dripping!!   One drip every second = at least 10ltrs per day depending how long it is switched on, would add up nicely over a year.
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One drip every second = at least 10ltrs per day depending how long it is switched on, would add up nicely over a year.

If the above is true, then the valve seating is dirty, normally opening and closing it a couple of times would clear it.

Do you know how old it is? Maybe a good move to change it !

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The truth about the chauffe eau

Can be single phase, three phase or some can be wired for either supply

Some have thermostats, fitted under the removable cover, some do not

Those that have thermostats have a limited range of temperature adjustment

Some have elements that can be replaced, some do not

The correct way to obtain the water temperature you require is by installing a simple adjustable mixing valve on the hot water outlet from the chauffe eau

The groupe de secuity should not drip, if it does this should only be for a very short period of time as the heater reaches maximum temperature

Water expands as it is heated and system pressure increases, the groupe de security is a safety device ( amongst it's other functions ) and it will open when the system pressure reaches 7 bar

Normally there is no problem with the GDS valve, unless it is very old and bunged up with calcaire because it has been dribbling all the time

The problem is almost always caused by an excessive cold water pressure

You should have a pressure reducing valve on your incoming water supply to restrict the water pressure in you property to a maximum of 3 bar

If this is installed then your hot water system pressure has to more than double before the GDS will open

Operation of the GDS once a month is recommended, not to check the valve performance but to prime the trap with water, left unattended for a long period this trap can dry out with the result of drain smells in the house

Le Plombier

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Le Plom, please excuse me for my ignorance, but I was under the impression that the ballon took up the pressure increase when the water heated and the only time that the 'over pressure' valve operated was when you had an over pressure and not during normal operation?

We have lived in our present house for almost 4 years now and have not had any dripping from the pressure relief valve or the solar coil that also operates in the hot water tank. I have never tested the valve and have not been advised to do so. There is no problem as far as the trap is concerned because it is shared with our condensing boiler and as you know that is sending distilled water into it all the time it is running.his trap is installed inside the house and is plumbed to an underground soakaway so no smells anyway.

The one thing that I want to do is to instal a time switch that will cut the overnight feed for the imersion heater. There are only 2 of us here most of the time and we don't get to use most of the hot water provided from the day time cheep elleky or solar heating. Mind you, the electric imersion heater will be switched off soon because the solar will provide all that we will need till about late October!

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Jonzjob

Looks to me that you installation has been done correctly

The chauffe eau can withstand the pressure increase up to a limit, that is why the pressure relief is set to 7 bar in order to protect the equipment

It cannot absorb the increased volume of water caused by expansion due to heating, therefore the system pressure increases

To absorb the increased water volume and maintain a stable pressure you would need to fit an expansion vessel

Your solar coil circuit will be an independant sealed system and have no influence on the hot water system pressure

I see a lot of installations with this problem and the vast majority are simply solved by installing a pressure reducing valve on the incoming mains water supply

The dripping GDS is normally the symptom and not the problem

Le Plombier

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