Just to give an update chaps still not entirely sure if have diagnosed things correctly? Got to property and first thing checked was connections from spur to immersion. Turned out polarity reversed by previous spark so live supply through neutral load and vice versa. Did all tests and got 19 ohms through coil so that all good and no short between live and earth. I tested the thermostat itself which didn't have any reset button and was getting complete open circuit 0.00 ohms and when changing temp setting the resistance wasn't changing at all and staying at zero at no point did it go to open position. So give advice next cheapest thing to do change thermostat now corrected polarity.....sound about right??
Heads up on Immersion heater fault?
- Thread starter DaveS79
- Start date
Help Support Talk Electrician Forum:
- Joined
- Nov 28, 2009
- Messages
- 14,782
- Reaction score
- 968
Open circuit is infinity ohms, often shown as OL or OR or similar depending on your meter. 0.00 ohms means the thermostat is closed. It may not be possible to turn it down low enough for it to open if the water is cold.
So you have 19 ohms at the heater. What do you get between L and N at the isolator switch where the flex comes from? If that is also 19 ohms then all good. Keep following it back through any timers or other switches. Eventually you should get back to the mcb in the off peak fuse box showing 19 ohms and then you know it will come on when the off peak supply comes on at night.
Sorry Dave my terminology mistake meant 0.00 ohms so totally closed and didn't increase with turning of dial which it should of right? Also from vid see if turned full distance it should eventually click into open position which it didn't. I didn't trace the 19ohms reading back to spur and then to mcb hadn't been suggested to do that previously will defo do in future. Does my readings suggest dogey thermostat most likely?
- Joined
- Oct 22, 2010
- Messages
- 14,621
- Reaction score
- 1,171
Was the water in the tank hot, warm or cold whilst you were doing this?
Sharpend
"It Just Is"
Is the spur even switched on if flat is unoccupied?
Sharpend
"It Just Is"
Has the meter been changed?
Doc Hudson
Well-known member
- Joined
- Oct 21, 2008
- Messages
- 5,619
- Reaction score
- 230
If the tank is below the minimum temperature setting of the thermostat it will never "click to the open position". As it thinks the water is too cold and needs to be heated up. It will only click open once the tank is up to temperature. Fault finding any switched item, be it a light/fan/immersion heater/storage heater/etc. is fundamentally the same. (1) Start at the source, is there a supply Y/N. (If it is a timed supply try putting a temp supply via a 13A plug & fly-lead). (2) Once you have established a supply, trace it though all switches/timers/programmers/thermostats to verify it is getting to the load. (3) If you have proved a supply is getting to the load, then verify the load also has a neutral. (4) When you have proved Live & Neutral are reaching the load, put a clamp meter around the supply to see if the load is drawing the expected current. If you do all of the above you will establish if the cause is due to failed, Live/Neutral/or Load.
Doc H.
Last edited by a moderator:
Thanks Doc very helpful. So even if thermostat disconnected from any power source it will still not click into open position because of the cold water? If this is the case how can the thermostat be effectively tested. Can this only be done by like you say putting a temp supply through it by 13amp plug and fly lead.
- Joined
- Nov 28, 2009
- Messages
- 14,782
- Reaction score
- 968
Your immediate concern is to get the heater to turn on, so that is all you need to concentrate on to start with.
I would not personally then wait a couple of hours for the cylinder to heat up to make sure the thermostat does actually turn off. I let the customer test that. If it heats up too hot or more likely trips the over heat thermostat then I would go back when called.
Alternatively a new thermostat is under £10 so why not just fit a new one for peace of mind and certainty that you won't get called back?
Dave - you have enough posts ... could you not post a photo or two as some of your descriptions seem a bit odd
DaveS79 the thermostat should as you say " Click into the CLOSED position " with cold water . It should be " calling for heat "
Sorry guys I know my terminology been using and explanations been lettuced to say the least. Obviously next time for sake of doubts with the thermostat just need to have one on board and do quick change. Thing that threw me when went to job was expecting thermo to click into open position like in vid below at 13:20. It never did and stayed at 0.00 ohms with no variation in resistance with turning of dial. This is why I diagnosed thermo change which he is going to do himself. I don't however feel I 100% proved this and if I had followed all the other testing procedures you lot have explained I would of been able to be a lot more certain of the problem...live and learn
Why did you let the customer change the thermostat?
next he’ll be refusing to pay your bill
top tip : do it all or nothing
- Joined
- Nov 28, 2009
- Messages
- 14,782
- Reaction score
- 968
Not all thermostats are the same, not all allow the temperature to go down that low, if the lowest setting is say 40 degrees and the water is cold, then it will never turn off.
But you were there to diagnose why it was not heating up. So why would you think the thermostat being stuck on and not opening would be the reason for the water not heating up?
But you were there to diagnose why it was not heating up. So why would you think the thermostat being stuck on and not opening would be the reason for the water not heating up?
Last edited by a moderator:
- Joined
- Oct 22, 2010
- Messages
- 14,621
- Reaction score
- 1,171
Take stat out
multimeter
kettle
rocket science
multimeter
kettle
If the Thermostat was reading 00.00 it means it was switched ON so the problem is elsewhere . Did you actually put your mains testers on the heater terminals ?
Last edited by a moderator:
Doc Hudson
Well-known member
- Joined
- Oct 21, 2008
- Messages
- 5,619
- Reaction score
- 230
Sorry Sir Kerch, AKA 'Forum Grand Lord Of Common Sense', I fear that health & safety may no longer allow the use of a kettle due to the risk of scalding, or taking an unscheduled break for Tea or Coffee! Possibly one of the last EU directives before the Boris Brexit Bus reached its terminus at the end of Jan. Common sense appears to be superseded by Googling YouTube for the correct answer. How hard is it to evaluate the operation of a manual switch - Timer controlled switch - Movement controlled switch - Darkness controlled switch - Temperature controlled switch - Or any combination thereof?
Doc H.
I said in my previous posts I identified incorrect polarity at switched spur which I corrected. And i also proved element was good. As I had wrongly expected thermo to click into open position at some point I maybe wrongly suggested thermo change. As I have said already if I had new thermo on board and provided a supply I could of proved things 100%. I'd rather be someone that holds hands up and learns from stupid mistakes.
