Discuss Verifying/confirmation if Horstmann Economy7 Timeswitch needs replacing. in the DIY Electrical Advice area at ElectriciansForums.net

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J

JoC

Hope I've got the right section of the forum for this question (please redirect me if not).

I'm looking at a Horstmann Economy 7 timeswitch which appears to need replacing.

However the timer (24 section is still turning) and the boost timer winds itself down properly, so the timer parts of it are still working fine - but neither of them trigger the orange lights to come on or the immersion to start actually doing it's job of heating water.

Before I replace the box I wanted to be sure that it is the timerswitch which needs replacing and
that I'm not going to replace it and then find that I need to replace the element in the immersion
(again - it was replaced about 2-3 years ago) or the thermostat (currently set to 50).


Extra background info in case it's useful:
It's an old system in an ex-council house which used to share the immersion tank with a back boiler system (long since mostly disconnected from the actual back boiler - a plumber has removed connecting pipes so that shouldn't be interfering). For the last few years it's tripped it's main fuse box switch every few nights (almost as if the fuse is acting as a thermostat trip) but it's still working fine so long as the trip is reset.

I'm about 85% sure that it is the timer switch and that the switches in it have probably just burnt out,
I'm just after reassurance that if the thermostat or element were dead then the timerswitch would still have it's orange light on and be trying to heat and so the current symptoms are definitely a dead Timerswitch.

Also any recommendations of the best source for really cheap second hand Hortsmann Economy 7 Quartz welcome..

Thanks

Jo
in Devon
 
Initially it would be best to test to see if when the switch operates the output terminals are powered. If they are not then the timer switch replacement sounds likely.
If they are then this eliminates the timer switch as the problem.
Generally timer switches do not cause faults that cause circuit breakers to trip, although they may cause faults that cause an RCD to trip.
It is more likely that the element in the immersion is breaking down, however this hypothesis could only be determined by testing.
 
As Richard said, put a permanent supply through the contacts and see if this switches the relays/output terminals, if not then there is a fault with them!
 
Thanks for that, I had a feeling it'd be worth not just replacing it.

It's the RCD in the main consumer unit which trips,
I was thinking more the other way round, not that the unit necessarily causes the trips,
but that the regular tripping might have damaged the TimerSwitch.

Though i guess it would be useful to eventually work out what it is that causes
the RCD to trip every third day or so sometime around 3-4am.
 
Thanks again for the valuable help. As I was in the process of getting the right bits to do the job (should have mentioned i'm not a pro, just DIYer trying to learn properly, so don't yet have my own multimeter etc) then i remembered i had insurance cover and so instead I saved time and created paid work for someone and the insurance got a sparks out who checked and established although there was current to the switch it wasn't actually enough to power anything but the timer, not even the light, and I had a damaged MCB in the consumer unit which was just not passing enough current through. That's now replaced and everything is working again, well one element is.

At the same time we did a quick check and confirmed that the second immersion element didn't appear to be working at the time and may be the cause of the MCB regularly tripping, though with our usually very hot water temperature it might be the thermostat. Lastly he happened to check the Test button on the RCB, I haven't done that for a while, and it's apparently dead, ineffective, duff too and needs replacing. He said he couldn't do it as part of the job at at the time (shame), he also said I'm not going to die from not replacing it, that it's safe enough, so not to panic, but I'd rather it were fixed asap, but don't have the funds to pay someone to do it for the moment. So I'm trying to find out if it's a job that i can legally do myself. I've had a search and there doesn't appear to be a definitive answer.

I'm smart enough and confident having watched him change the MCB that unless it's significantly different I should be absolutely fine doing it, if I have fairly straightforward notes/instructions for it then if it's like-with-like replacement am i okay doing it. It appears to be remove cover of unit being careful not to touch anything, unscrew the top of the RCB, clip it off, clip the new one one, tighten the screw, and replace the units cover... or is the RCD significantly different to an MCB to replace?

or is it just that anything inside the consumer unit have to be done by someone certified/qualified?

I hope to do the immersion replacement fairly soon and want to check whether I might as well try to get the RCD at the same time and fit that too or if I'll just have to live with it until I have rather more ÂŁÂŁ to get someone else to do it. I'm willing to study notes and videos and learn how to do it myself if it's more complex than the MCB, but only so long as it's legal and safe to do so. I'm calm, confident and learn well, not stupid, foolhardy and illegal.

My to do list is now:
- find out how to test the thermostat and check the actual element
-order the part needing replacing
- do replacement of whichever one is duff (fingers crossed it's the thermostat but fairly confident it's the element breaking down) the other element was replaced a couple of years ago. (whilst praying the tank holds togehter and doesn't need replacing)

-find out if I can fit my own RCD
- order and fit it if I can.

If anyone can even just help with the "am I allowed to do it myself?" bit that would be brilliant.
Thanks

Jo
 
You may be taking on more than you are competent to do.
Legally Any one competent could change an RCD for one of the same make and model, however the key is competence.
I am afraid I wouldn't feel safe providing a step by step guide to changing an RCD.
If you want to attempt this the first thing I would say is SWITCH OFF THE POWER and TEST to ensure that the item you are working on and any adjacent items are off before you start work.

The MCB probably failed due to the immersion fault and it is possible that the immersion fault is also masking the correct operation of the RCD (though this would need to be checked).
A high water temperature might indicate that the element is partially shorted somewhere and overheating because of the rate it is heating the water, however the thermostat could also well be faulty.

In order to test the thermostat and element you would need a test meter, one that can do continuity, resistance and voltage measurements.
Verifying/confirmation if Horstmann Economy7 Timeswitch needs replacing. Immersion heater - EletriciansForums.netwith the power off and water cold test continuity from line to neutral, should show 17-20 ohms, if it is not continuous at all move on from incoming line to the other side of the thermostat and then onto the element itself. leaving the other probe on neutral. where continuity stops is the "off" item.
If the resistance of the element is less than or more than 17-20 ohms there is probably something wrong with the element.

If this testing is comprehensible to you then you should be able to move on from there and test independent items, if you are not sure how this works then it is best to get more trained assistance.
 

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