Controller overheating ??

[peweuk]

I have the old type of off-peak supply (ie one meter for standard supply and a separate one for off-peak supply overnight.)

Originally the off-peak was used for storage heaters which are no longer present, and it is now used soley (at present) for an immersion heater.

A year or so ago I had a Horstmann BX controller fitted which is wired between the supply and immersion. This automatically turns on the immersion overnight using a feed from the off-peak Cu, but is also wired to the standard supply CU so a 'boost' switch allows top up any time during the day.

The BX is wired directly back to the CU's and there are no other electrics on the circuits - just the immersion heater.

Recently I noticed that there were some 'brown stains' on the front of the controller, and on investigation discovered that the box was getting very warm on the front (there are two seperate stains - one in front of the internal relay, and one in front of an internal control unit). None of the connecting cable gets warm.

I spoke to Horstmann who said this was not normal for the unit and it sounded as if there was something in the circuit drawing too much current.

As the immersion is the only item in the circuit - could this be the problem, and if so what fault could have developed to cause this??

I would say that I have a second BX unit, and when I swapped them over the second unit was getting warm too.

 

[electronicsuk]

Without a clamp ammeter or a multimeter that will measure relatively high currents, there is little you can do to check the true consumption of the immersion heater. However, if it's protected by a suitably sized fuse and/or MCB then it seems unlikely that a significant overload would go unnoticed.

Assuming the immersion heater is rated at no more than 3kW (the E7BX contacts are rated to 13A, right?) then I'd be more inclined to suspect the timer itself. Many run warm, so if you've had this old one for a number of years and it gets used a lot, I wouldn't be all that surprised about heat damage.

 

[peweuk]

Thanks Matt.

The BX2000 that was being used is only about 2 years old and was used about 3 nights a week for the last 12 -15 months.
The second unit I replaced it with is brand new never used.

Thats why I was surprised at the severity of the marks.

The fuse in the CU is 15a and the BX has a rating of 16a on the relay and 13a on the control circuit box.

I take your point about long term used generating marks, but what I am concerned about is the degree of heat being generated on a plastic box - hence the potential for fire.

An EDF engineer had a quick look at the box when he was here the other day to replace our meter, and he agreed that the burn marks were unusual and suggested it could be a bad connection, that's why I replaced the box to test, as well as checking all the connections - but found the same heat problem.

I guess I need to get an electrician with the proper equipment to look at it.

 

[electronicsuk]

Well, you can get a clamp ammeter for about £10 on eBay. I wouldn't expect it to last long or be very accurate, but it should be good enough to get an idea of whether or not the element is drawing the amount of current that it should. That said, I still think a continuous overload would have led to the fuse protecting the circuit getting rather warm, which I think you might have noticed by now.

You mention a 13A control circuit box. Do you mean a Fused Connection Unit? If so, is that getting warm too?

 

[nozspark]

I have the old type of off-peak supply (ie one meter for standard supply and a separate one for off-peak supply overnight.)

Originally the off-peak was used for storage heaters which are no longer present, and it is now used soley (at present) for an immersion heater.

You really need to think about getting your tarrif changed as an E7 tarrif will be costing you a fortune, then you can use a standard immersion timer instead of an expensive "Horstman" type one you are using now.

and yes, over time they can overheat

 

[peweuk]

I have checked the current drawn by the immersion and it appears to be 11.5 amps, so both the DX units are getting warm within their rated current.

I guess another call to Horstmann is in order.

Nozspark - the 'off-peak' tariff is currently the cheapest way of using our consumption. The extra cost off daytime units with E7 is no where near compensated for by the cheaper nightime rate - we would have to be using over 40% of our current consumption overnight to break even on the extra cost.

 

[electronicsuk]

Nozspark - the 'off-peak' tariff is currently the cheapest way of using our consumption. The extra cost off daytime units with E7 is no where near compensated for by the cheaper nightime rate - we would have to be using over 40% of our current consumption overnight to break even on the extra cost.

Eh? You seem to contradict yourself there! You say you have an off-peak supply, so you must be on an E7 or similar tariff, yet less than 40% of your energy demand over 24 hours is during the night

 

[peweuk]

I have two meters feeding 2 seperate consumer units - the most comon way used in the past when Night Storage radiators were first introduced.

Most of these types of installation were ripped out years ago when E7 came in, but our cottage still had it when we bought it 12 years ago - and we still have it now.

One meter is for a 24 hour supply at standard rate of 0.12p per unit, the other is a radio controlled meter which offers no supply until 12pm, at which time the supply goes live and the useage is charged at 4.5p per unit until 7am.

If I go E7, then my daytime charge goes up to 15p and the night time is 5.8p (over 1p more than we currently pay for night time use)

Apart from the immersion heater most of our consumption is during the day and early evening. At night we are asleep and use no electricity apart from heating water for the morning.

I worked it out that based on our annual consumption we would have to change our lifestyle considerably to use more electricity at night to benefit from getting rid of the 'off-peak' system and going to E7, E10 or Eco20/20.

 

[nozspark]

Makes sense now..

I must admit I thought you had E7 from a single meter & (timeclock or teleswitch).. this would be more expensive than std rate..

although you seem to have a hybrid!

 

[nozspark]

I have two meters feeding 2 seperate consumer units - the most comon way used in the past when Night Storage radiators were first introduced.

Most of these types of installation were ripped out years ago when E7 came in, but our cottage still had it when we bought it 12 years ago - and we still have it now.

One meter is for a 24 hour supply at standard rate of 0.12p per unit, the other is a radio controlled meter which offers no supply until 12pm, at which time the supply goes live and the useage is charged at 4.5p per unit until 7am.

If I go E7, then my daytime charge goes up to 15p and the night time is 5.8p (over 1p more than we currently pay for night time use)

Apart from the immersion heater most of our consumption is during the day and early evening. At night we are asleep and use no electricity apart from heating water for the morning.

I worked it out that based on our annual consumption we would have to change our lifestyle considerably to use more electricity at night to benefit from getting rid of the 'off-peak' system and going to E7, E10 or Eco20/20.

So if I read the highlighted bit correctly your immersion heater will only ever get a supply between 12am and 7am.. if that's the case then you don't need the horstmann timer, just replace it with a DP switch?!?!

 

[ban-all-sheds]

I must admit I thought you had E7 from a single meter & (timeclock or teleswitch)

I have the old type of off-peak supply (ie one meter for standard supply and a separate one for off-peak supply overnight.)

So if I read the highlighted bit correctly your immersion heater will only ever get a supply between 12am and 7am.. if that's the case then you don't need the horstmann timer, just replace it with a DP switch?!?!

A year or so ago I had a Horstmann BX controller fitted which is wired between the supply and immersion. This automatically turns on the immersion overnight using a feed from the off-peak Cu, but is also wired to the standard supply CU so a 'boost' switch allows top up any time during the day.

 

[ban-all-sheds]

Originally the off-peak was used for storage heaters which are no longer present, and it is now used soley (at present) for an immersion heater.

Ever thought about using it to run the washing machine/tumble drier/dishwasher overnight?

 

[peweuk]

Yes - it is a 'hybrid'. It was the first 'off-peak' supply - and is no longer available for new supplies.

The Horstman DX is designed specifically for this type of supply and uses the Off-Peak supply at night, but is also wired to the standard supply to allow use during the day using a 'boost' button.

We are building an extension at present and when it is complete I will re-wire the utility room to allow use of the washing machine etc using the off-peak at night.
Using the BX would allow me to have only one socket for each appliance and use the 'boost' (it has 1 hour and 2 hour boost options) to use them during the day if needed.
That's why I want to sort out the overheating problem.

 

[ban-all-sheds]

A quick google shows the BX to be in the £60-70 range, and you'd need 1 per socket, plus 2 FCUs per socket. It'll take a long time to recover that in electricity savings.

Why not just install 2 socket circuits in the utility room, one standard, one off peak, and plug the appliances into the appropriate ones as and when?

 

[peweuk]

A quick google shows the BX to be in the £60-70 range, and you'd need 1 per socket, plus 2 FCUs per socket. It'll take a long time to recover that in electricity savings.

Why not just install 2 socket circuits in the utility room, one standard, one off peak, and plug the appliances into the appropriate ones as and when?

I have 3 of these that I bought at £10 each last year at a 'closing down' sale.

But you are right, I was considering a two socket system for the utility room for the appliances, but that's not an urgent project so I have not given it thorough consideration yet.

By the way - forgive my ignorance - what are FCU's.