power usage

[mikeg]

Can anybody tell me how much power a transformer uses when plugged in but not used?

 

After two to three hours the case gets warm but it is not enough to show up on a household thermometer when placed on the unit. As there is heat I assume that power is being used although there is no draw on the secondary, as I need to leave it on, there is no switch on the socket, and I do not want to keep plugging in & out. I don't want to waste money if it is likely to be using a lot of energy.

 

I have been told that standby on most electrical goods cost over £1 a week! so hence my question.

 

regards

 

mike g

[cliff park]

OK, I'll stick my neck out. I would guess maybe 5 to 10 watts. Based on how hot transformers get under no-load, think about a 15W iron and how hot that much smaller mass gets. !0 W, worst case, at 16p per Kw/H would give an approximate 30p per week ! Anybody like to test my mental maths ?

[34theletterbetweenB&D]

The consumption is minimal as transformers are very efficient, key to the whole business of AC power transmission. But wouldn't you rather have the money in your account rather than some energy suppliers? A simple in line switch in the mains lead and you can have the power off without unplugging.

[Suzie]

You should only use a transformer nowadays if you absolutely need AC. A switchmode PSU is cheaper, smaller, lighter and much, much more efficient, but has the 'drawback' of only producing regulated DC.

 

I would have thought that a transformer would consume about a watt or so off load, nothing significant. If a transformer gets to be more than warm then it may be faulty - it should never get hot off load.

 

There are very few items in the model railway world that absolutely need AC and I can only think of two, a motorised windmill from a continental supplier, and the Lenz LS150 accessory decoder!

 

Mains transformers for the most part can now be considered a historical artefact, about as useful as a steam engine in the home. Still quite handy if you are a power distribution company though.

[CourthsVeil]

...

There are very few items in the model railway world that absolutely need AC and I can only think of two, a motorised windmill from a continental supplier, and the Lenz LS150 accessory decoder!

.

 

Suzie, only add to your two-items list the Gaugemaster controllers and all other controllers relying on thyristor tech. Plus them old school throttles using half waves to overcome inertia and magnetic momentum at the start.

All of them won't work with regulated DC coming off these PSUs.

Regards

   Armin 

[Kylestrome]

For the non-electricians amongst us, could someone please explain what a PSU is? Is it the sort of thing that comes with modern devices such as laptops and mobile phones (so-called dongles)?

 

TIA

 

Edit: I've just realised that was a silly question. A quick Google revealed PSU = Power Supply Unit, doh!

Please disregard.  

[DCB]

It depends on what you define as a transformer, some power supply units are described as transformers even when they have controllers built in. 

 

Morleys and OnTrack controllers such as I use have no reliable off position ion the speed control and I suspect very many other controllers using potentiometers for speed regulation don't have an of position either so it has to be a good idea to switch off the unit at the mains every time.

 

In my experience computer PSUs giving 12 volts don't supply enough volts for a realistic top speed on 00 scale locos, the Bachmann std 5 being particularly slow mine needs 16 volts for a scale 65.  19 volts off load or max power is about typical for "12 volt" model railway power supplies.

[Suzie]

...In my experience computer PSUs giving 12 volts don't supply enough volts for a realistic top speed on 00 scale locos, the Bachmann std 5 being particularly slow mine needs 16 volts for a scale 65.  19 volts off load or max power is about typical for "12 volt" model railway power supplies.

 

"12 Volt DC" in practice is nearer 18V and often more. If buying a regulated supply as a replacement for a 12V DC railway item, an 18V PSU is a better choice.

 

 

 

Suzie, only add to your two-items list the Gaugemaster controllers and all other controllers relying on thyristor tech. Plus them old school throttles using half waves to overcome inertia and magnetic momentum at the start.

All of them won't work with regulated DC coming off these PSUs.

Regards

   Armin 

 

Well spotted. As you say these are all a bit old fashioned now and new quieter technologies have made them obsolete.

 

 

 

For the non-electricians amongst us, could someone please explain what a PSU is? Is it the sort of thing that comes with modern devices such as laptops and mobile phones (so-called dongles)?

 

PSUs are not dongles - dongles are something else entirely!

[Judge Dread]

Speaking as a retired electrician, "if you are not using any piece of electrical equipment and leaving it unattended, switch it off and or unplug it!". I've seen too many fires caused by unattended equipment left switched on and thereby rated "safe". 

[Crosland]

For the non-electricians amongst us, could someone please explain what a PSU is? 

 

On the other side of the pond it seems quite common to refer power supplies as transformers. In strict terms "transformer" should only be used to refer to the (usually large) iron, wound component, even if it's in an enclosure. At a stretch, a transformer alone could be a power supply but If there is anything else attached to rectify, smooth, or regulate the output then it's always a power supply.

 

Transformers or PSUs moulded into plug tops are often called "wall warts". Those that connect via a mains lead are sometime called "power bricks". In some fields "brick" refers to a specific physical form factor so you can get 1/2-bricks, etc. 

 

Those intended for laptops are "switch mode" PSUs usually referred to as "chargers" but most make perfectly good PSUs if a little on the high side voltage wise for the smaller scales.

 

Switch mode PSUs also contain transformers, but they are much smaller and lighter than the kind at issue in this thread.

 

In the lighting field you will find "electronic transformers". These are generally not suitable for our use.

 

Andrew

[Kylestrome]

PSUs are not dongles - dongles are something else entirely!

 

 

I was confusing dongles with Douglas Adams's "Dongly Things"   :

http://www.douglasadams.com/dna/980707-03-a.html

[mikeg]

Well the item in question is a large iron cored TRANSFORMER the out put of which I use attached to a small charger for 'AA' size batteries so often leave it on over night for charging but only disconnect the charger unit, as the 6 & 12 volt regulated supply that is built into the unit is very useful for testing motor etc. The unit is in my workshop and the plug is behind a cabinet hence why I tend to leave it on.

 

The original question has become a bit lost but as I have just fixed my unit rates for the next twelve months I though I would ask the question as power costs seem to be going up at the moment, and the work to put on a longer lead or change the plug position will be quit considerable, the unit is all riveted and the plug is fixed in the dado trunking.

 

regards

 

mike g

 

SO what is the likely cost of leaving it on?

[stewartingram]

Fire is the likely cost if it fails.

 

Stewart

[Suzie]

If it consumes 1W, probably a little under £2 a year assuming you don't use it at all! If it is charging stuff half the time then the cost halves to under £1.

 

That 1W is dissipated as heat, so for the cold parts of the year you get 1W of bonus heating, and that will be saving you a few pennies elsewhere - if you have electric heating you get 50p saved taking your annual running cost down to 50p.

 

This is just an approximation of course making lots of assumptions!

[kevinlms]

Well the item in question is a large iron cored TRANSFORMER the out put of which I use attached to a small charger for 'AA' size batteries so often leave it on over night for charging but only disconnect the charger unit, as the 6 & 12 volt regulated supply that is built into the unit is very useful for testing motor etc. The unit is in my workshop and the plug is behind a cabinet hence why I tend to leave it on.

 

The original question has become a bit lost but as I have just fixed my unit rates for the next twelve months I though I would ask the question as power costs seem to be going up at the moment, and the work to put on a longer lead or change the plug position will be quit considerable, the unit is all riveted and the plug is fixed in the dado trunking.

 

regards

 

mike g

 

SO what is the likely cost of leaving it on?

Don't worry about the costs, there is a 'cost' no matter how small. If it bothers you, just turn if OFF. if your not using it and it won't cost you anything.

[Suzie]

Don't worry about the costs, there is a 'cost' no matter how small. If it bothers you, just turn if OFF. if your not using it and it won't cost you anything.

 

Everything has a cost in the same way that everything has a risk. You cannot take one cost or one risk in isolation and say that is all you have to consider. In this case for cost you have to consider:-

1. The cost of the electricity used if left on.
2. The cost of replacing the switch when it wears out if you turn it on and off every day.
3. The cost of replacing the socket if it wears out because you unplug it every day.

The cost of electricity can be calculated quite easily and will come to about £5 per decade using my sums above that may or may not be correct.

The cost of replacing a switch if it is integrated with a wall socket is probably £50+ if you have to get an electrician to do it so you have to consider that the switch needs to be good for at least 30 000 operations MTBF to stand a one in ten chance of having to replace the socket in a ten year period which will cost you ten times the saving.

 

The risks are similar in approach:-

1. The risk that the transformer will fail and the protection will fail causing a fire.
2. The risk that the switch will fail causing a fire.
3. The risk that the flex will fail causing a fire.

While clearly there are documented cases as described above of transformers failing and causing fire, a properly protected device to modern standards with over temperature and over current protection are very unlikely to result in fire, especially if kept away from anything combustible. This is a very low risk.

 

Fire caused by worn flex which has been flexed too much is probably a much greater risk especially if regular inspection has not been carried out and the device is regularly plugged in and out every day.

 

I suspect the biggest risk is from a worn out switch that has been turned on and off too many times with an inductive load attached. If it goes high impedance but not open circuit there is the potential for heat build up and damage to fixed wiring that could cause a fire.

 

I am not specifically advocating leaving on, switching off, or unplugging - that is for the owner to weigh up the relative merits and make an informed choice, I am just saying that all courses of action carry a risk and a cost, there is no zero cost and zero risk solution and what on the face of it looks to be common sense might not be the best course of action.

 

Landfill is full of televisions that are just fine - apart from the on/off switch has worn out because people thought they were saving money by turning them off rather than using the standby button on the remote! £5 of electricity is a lot cheaper than a £100+ repair of a television. Always look at the bigger picture and quality is often the key to saving money.

[stewartingram]

I wonder what the rating of the fuse is in the plug?

 

(......13A....?)

 

 

 

Stewart

[brigo]

My daughter's bedroom suffers a similar problem to the OP, the sockets are placed just where you need to put furniture, in her case a chest of draws. Simply used one of those extension leads that have 4 switched sockets on the end of a 2m cable, available from Argos, Wilkinsons or most supermarkets. Obviously don't put it trailing over the floor but place it along the skirting board. They can also be wall mounted with a couple of screws if you want.

 

Brian

[kevinlms]

Everything has a cost in the same way that everything has a risk. You cannot take one cost or one risk in isolation and say that is all you have to consider. In this case for cost you have to consider:-

1. The cost of the electricity used if left on.
2. The cost of replacing the switch when it wears out if you turn it on and off every day.
3. The cost of replacing the socket if it wears out because you unplug it every day.

The cost of electricity can be calculated quite easily and will come to about £5 per decade using my sums above that may or may not be correct.

The cost of replacing a switch if it is integrated with a wall socket is probably £50+ if you have to get an electrician to do it so you have to consider that the switch needs to be good for at least 30 000 operations MTBF to stand a one in ten chance of having to replace the socket in a ten year period which will cost you ten times the saving.

 

The risks are similar in approach:-

1. The risk that the transformer will fail and the protection will fail causing a fire.
2. The risk that the switch will fail causing a fire.
3. The risk that the flex will fail causing a fire.

While clearly there are documented cases as described above of transformers failing and causing fire, a properly protected device to modern standards with over temperature and over current protection are very unlikely to result in fire, especially if kept away from anything combustible. This is a very low risk.

 

Fire caused by worn flex which has been flexed too much is probably a much greater risk especially if regular inspection has not been carried out and the device is regularly plugged in and out every day.

 

I suspect the biggest risk is from a worn out switch that has been turned on and off too many times with an inductive load attached. If it goes high impedance but not open circuit there is the potential for heat build up and damage to fixed wiring that could cause a fire.

 

I am not specifically advocating leaving on, switching off, or unplugging - that is for the owner to weigh up the relative merits and make an informed choice, I am just saying that all courses of action carry a risk and a cost, there is no zero cost and zero risk solution and what on the face of it looks to be common sense might not be the best course of action.

 

Landfill is full of televisions that are just fine - apart from the on/off switch has worn out because people thought they were saving money by turning them off rather than using the standby button on the remote! £5 of electricity is a lot cheaper than a £100+ repair of a television. Always look at the bigger picture and quality is often the key to saving money.

Since you started talking about risks, there is also a risk of damaging your knees & back, by constantly getting on all fours to turn the thing on & off!

 

Kids these days won't bother to pick up low value coins, makes sense, because they can't buy anything worthwhile with it!

[bertiedog]

Golden Rule, if out of use unplug it, (or switch off), never trust any standby in long term, even for TV's. The running cost does come into it, the cost of the risk is of fire..........unplugging is also beneficial, as the action cleans the pins on the plug.

 

About all you can leave on are fridges and freezers, fans, and domestic heating control, the rest should be shut off when unattended.

Personally I find Switched mode power supplies a fraction risky as the capacitors can blow. Having said that I have only had one fail like that.

 

Stephen.

[kevinlms]

My daughter's bedroom suffers a similar problem to the OP, the sockets are placed just where you need to put furniture, in her case a chest of draws. Simply used one of those extension leads that have 4 switched sockets on the end of a 2m cable, available from Argos, Wilkinsons or most supermarkets. Obviously don't put it trailing over the floor but place it along the skirting board. They can also be wall mounted with a couple of screws if you want.

 

Brian

Easily fixed! Do it once then control it remotely.

 

Typically, since I cannot comment on the UK market.

 

https://www.amazon.co.uk/dp/B01FSAFFYC?psc=1

 

Only thing is you need to check is the maximum ratings, many won't supply an electric heater for example.

[kevinlms]

Golden Rule, if out of use unplug it, (or switch off), never trust any standby in long term, even for TV's. The running cost does come into it, the cost of the risk is of fire..........unplugging is also beneficial, as the action cleans the pins on the plug.

 

About all you can leave on are fridges and freezers, fans, and domestic heating control, the rest should be shut off when unattended.

Personally I find Switched mode power supplies a fraction risky as the capacitors can blow. Having said that I have only had one fail like that.

 

Stephen.

I would add modems to the list, as sometimes you can get synchronising problems as the PC can be ready before the modem, as so cannot 'phone home' for updates.

[Crosland]

I would add modems to the list, as sometimes you can get synchronising problems as the PC can be ready before the modem, as so cannot 'phone home' for updates.

ADSL routers should always be left powered on and connected as the exchange can downgrade your line speed if it sees frequent dropouts, mistaking these for a bad line.

 

No one turns their burglar alarms or central heating boilers off every night do they? Boiler PCBs are especially renowned for developing faults.

 

Really, the risk of leaving modern TVs, etc., on standby is vanishingly small, compared to to other risks you are likely to face every day.

 

Andrew

[bertiedog]

With modems, if on a BT line,(or sub contracted other supplier like Sky), then, yes, there may be issues with powering up etc., but on cable, Virgin for instance, prefer the modems and Tivo to be turned of completely to go through full set up, were updates can be applied. They do not advise every time, just say, once a month. I leave the cable modem live whilst in occupancy, but when not here it is off.

The current Tivo will auto update whilst connected, and as it records stuff whilst away, it is safe to leave in standby.

The biggest cost saving in domestic power is to change the lighting to all LED, slashes the bills right down, but only after initial cost.

Stephen.

[kevinlms]

The biggest cost saving in domestic power is to change the lighting to all LED, slashes the bills right down, but only after initial cost.

Stephen.

Especially if it means getting rid of the Quartz-Halogen lights. What a blind alley they were.