Jump to content

Amps On a Narrowboat


Featured Posts

13 hours ago, Loddon said:

Er no it wont trip immediately or even within a few minutes A 16amp mcb will easily pass 20amps for a surprisingly long time. On Parglena when washing machine, tumble dryer, batrery charger, aircon etc were all on it was not unusual to see 25amps being drawn off a 16amp supply!

If you are able to draw 25amps off a 16amp supply, it is one of two things. 1. It's not a 16amp supply, or 2. If it is a 16amp supply, it's faulty. If you attempt draw over 16amps off a "serviceable" 16amp supply it will trip, every time. 

Link to comment
Share on other sites

16 minutes ago, Mikexx said:

Calor gas prices seem to be around the £38 - £40 mark for the 19kg cylinder which works out at 14p/kWhr, more expensive than the 13kg.

It is also a whopping 43kg which means handling is awkward for many.

There are quite strict rules on the price of reselling electricity so it sounds a little strange you're paying more than this.

25 quid for 19kg at my local, same price as 13Kg. 

Its not the unit cost, but the service charge that makes it an expensive option 

Edited by rusty69
Link to comment
Share on other sites

2 minutes ago, Mark May said:

If you are able to draw 25amps off a 16amp supply, it is one of two things. 1. It's not a 16amp supply, or 2. If it is a 16amp supply, it's faulty. If you attempt draw over 16amps off a "serviceable" 16amp supply it will trip, every time. 

 

25amps is a 55% overcurrent wrt 16amps.

According to:

  https://www.tlc-direct.co.uk/Technical/DataSheets/Wylex/WylexTech.pdf

it will take anything from 1 to 10 minutes to trip.

If you're passing 25 amps for longer than 10 minutes then I would regard the MCB suspect.

The sole purpose of the MCB is to protect the cable. Its rated temperature is usually taken as 70degsC.

 

5 minutes ago, rusty69 said:

25 quid for 19kg at my local, same price as 13Kg

You're lucky to have a local at that price, obviously not Calor and works out at a little under 10p/kWhr.

If you assume a boiler efficiency of 80%, your talking of a comparable cost of 12p/kWhr.

I'm not sure if the mischief caused by lugging a 43kg cylinder is really worth it.

Link to comment
Share on other sites

Diesel capacity -

That depends on how good the builder is. Some make an effort to provide at least 70 gallons - or (roughly) 300 litres. At half a litre per heating hour that's 600 hours of heating. Probably a full winter season's worth of heating. That was the point of my suggestion as you were concerned about fuel running out while you both are at work. If you check the fuel level with a pointed-stick every fortnight until you can see a pattern of usage, then at monthly intervals, that will give you a gauge as to how long a tank lasts in reality.

It's inconceivable to me that you want to live on a boat but don't want to use it as such, but -hey - times change. You never know, suddenly you might want a change of scenery and go out to potter up your local canals!!

Link to comment
Share on other sites

8 minutes ago, Mikexx said:

 

25amps is a 55% overcurrent wrt 16amps.

According to:

  https://www.tlc-direct.co.uk/Technical/DataSheets/Wylex/WylexTech.pdf

it will take anything from 1 to 10 minutes to trip.

If you're passing 25 amps for longer than 10 minutes then I would regard the MCB suspect.

The sole purpose of the MCB is to protect the cable. Its rated temperature is usually taken as 70degsC.

 

You're lucky to have a local at that price, obviously not Calor and works out at a little under 10p/kWhr.

If you assume a boiler efficiency of 80%, your talking of a comparable cost of 12p/kWhr.

I'm not sure if the mischief caused by lugging a 43kg cylinder is really worth it.

It is Calor. Not very far to move bottles either, although I may give up when I get too old to lift them m

Link to comment
Share on other sites

3 hours ago, Tony Brooks said:

An 800 watt microwave is unlikely to be anything of the sort. *00 watts look very much like cooking power to me, not electrical consumption. Without seeing the consumption data assume its around 1600 watts.

As Bruce said, the 10 assume an inverter efficiency of 80% and its very easy to use in mental calculations. You can bet the inverter efficiencies published were measured under the most favourable conditions and load so 80% will sometimes be pessimistic but with a large inverter supplying a small load like a phone charger it is likely to be optimistic. Again, as Bruce said, for long battery life when away from shore power its est to overestimate your consumption and also  vastly  overestimate what you think the charging time will be.

Yeah no worries champ, I understand all that. I just enquired what your thought process was in using 10 when the correct calculation is 12. You didn't say you were factoring in any loss in efficiency, estimation of power consumption or safety factor . The microwave I used as an example, was just that, an example of the correct calculation (watts / 12Volts) of converting watts to amps. I didn't say that is what it draws in real life. You don't know what it draws until you personally measure it under load. Until you do so all you have to go on is what the manufacturer tells you and a best guess. 

Link to comment
Share on other sites

23 minutes ago, Mark May said:

If you are able to draw 25amps off a 16amp supply, it is one of two things. 1. It's not a 16amp supply, or 2. If it is a 16amp supply, it's faulty. If you attempt draw over 16amps off a "serviceable" 16amp supply it will trip, every time. 

No you are wrong.  It is a 16amp supply and the mcb is not faulty.  I design build and test power distribution up to 2400amps 3phase  for a living so might just realise if it was faulty. I will admit that the mcb is a k- type that has the capability of handling functional peak currents up to 8xln and not the run of the mill b-type.........

 

 

Link to comment
Share on other sites

2 hours ago, Alan de Enfield said:

 

Just to reinforce what Tony has explained

The  COOKING POWER of the microwave is 800w.

You 'don't get owt for nowt' so the actual input power of the microwave will be much higher. The manufacturers rarely quote this figure but as a guide assume the input power is 2 times the output power, so your input is around 1600 w (max)

Working on the basis of inverter losses (you dont get owt for nowt, and nothing is 100% efficient) the microwave will be drawing 160amps (max) from your batteries.

 

Real Life Test Results : my 700w microwave. Powered by the inverter - it draws around 120 amps (but the readings may be slightly affected if the fridge is running or not)

No need to reinforce anything. the microwave was an example of the correct calculation: watts / volts (12) = amps. Not a statement of what a 800w microwave draws in real time

4 minutes ago, rusty69 said:

But the best guess should include inefficiencies in the system. 

I know I would!

Link to comment
Share on other sites

14 minutes ago, Mark May said:

No need to reinforce anything. the microwave was an example of the correct calculation: watts / volts (12) = amps. Not a statement of what a 800w microwave draws in real time

I know I would!

 

Sorry, but when you say

   " Example: 800w microwave oven in a boat or caravan (800w / 12 volts = 66 amps) "

without any qualification it can be read as implying that would be the battery current at 12V.

Hopefully we have now established that in reality, taking into account the efficiencies we might expect, that the actual current is going to be circa 160amps.

Link to comment
Share on other sites

2 minutes ago, Mikexx said:

 

Sorry, but when you say

   " Example: 800w microwave oven in a boat or caravan (800w / 12 volts = 66 amps) "

without any qualification it can be read as implying that would be the battery current at 12V.

Hopefully we have now established that in reality, taking into account the efficiencies we might expect, that the actual current is going to be circa 160amps.

Yep,my 700W. Microwave draws IIRC Approx. 130 AMPS.

Link to comment
Share on other sites

Your mooring will NOT be your permanent home. Even if it's a formal residential mooring it's only on a 12 month "lease" or licence. Should you ever move, the 16A socket on another mooring may or may not be fully rated at 16a. You need to consider that your boat should have two or three methods of heating, including something that you keep on board! So oil, coal and wood are obvious fuels that you can take with you, and have in store. Electricity is essential -usually for lighting, electric heaters are usually good but expensive and can only be fed from a shore line.

With electricity you must consider how many things will be on at one time and how long things will be on for, then you can do the diversity calculations -calculating the maximum current realistically likely to be drawn.

Your boat WILL need to be moved for cruising, repairs, servicing and hull blacking 

At a guess most residential boaters spend at least an hour per day working on things that just flow in a land home -water, foul waste, gas/coal/oil -Yes you have to carry toilet waste to a disposal place.

On top of that your boat will need engine maintenance, hull maintenance, painting and blacking regularly. 

There are aps and timers for Eberspacher heaters to turn them on as you leave work, so there will likely be similar for the other oil heaters.

  • Greenie 1
Link to comment
Share on other sites

1 hour ago, Mark May said:

No need to reinforce anything. the microwave was an example of the correct calculation: watts / volts (12) = amps. Not a statement of what a 800w microwave draws in real time

I know I would!

But the microwave output of 800w is at a 'radio frequency' of 2400 Mhz and not at a voltage, if you are using a microwave as an example of converting watts to amps / volts then it is totally meaningless  unless you wish me to say that my 25w Marine VHF radio at 156 Mhz is putting out just over 2 amps at 12v

Link to comment
Share on other sites

3 hours ago, Mark May said:

the microwave was an example of the correct calculation: watts / volts (12) = amps.

But it's not a 'correct' calculation unless it's a 12V device. Any 230V device being fed by an inverter needs the inverter inefficiencies accounted for. That is why we always use 10 as the nominal voltage for such calculations; it not only accounts for inefficiencies but will probably be slightly pessimistic to boot. 

If you want to be 'correct' then divide the mains power consumption by 230, then look up the inverter inefficiency, multiply your result by that, then divide by 12.4. You'll find that the result is close to dividing by 10. 

Link to comment
Share on other sites

21 hours ago, Chewbacka said:

I just had a look at the Schneider MCB trip curves and it shows that a 16A mcb passing a 25A current will trip between 90 and 400 seconds, which is a fair bit slower than I expected.  Surprisingly a 16A mcb at 16A could trip as soon as 1000 seconds, though it can also be much longer, up to never.

As a rule of thumb,  miniature circuit breakers will require 3-20 times their rated current to trip instantaneously depending on type, (type B is about 3-5 times whilst type D is 10-20 times rated current).

BS88 fuses will blow at twice their rated current, which is why fuses are often preferred to protect sensitive equipment even though they need changing say every 5 years to avoid random blowing due to ageing.

Edited by cuthound
Spillung
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.