Inverters

[Eastern]

Firstly, modified sinewave and quasi sinewave are usually the same thing. There are however three types of inverter. Some of the really low cost ones are just square wave types and are best avoided. These may also be described as "modified sinewave".

 

The only devices that won't run properly on a quasi inverter are devices for whom the shape of the sinewave is important. These are mainly motor control circuits that use a "light dimmer" type circuit to vary motor speed in washing machines etc.

 

Other devices like TV's, computers, hairdryers, radios, chargers couldn't "give a damn" because they operate from switched mode power supplies nowadays and the AC input waveform is totally unimportant. So if you are told they don't run on it then that is misleading information.

 

Ergo, if you don't have a washing machine/tumble dryer on board you don't need a pure sine wave inverter which will be at least twice the price and will consume more power than a quasi inverter. If price and power are no issue, then by all means go for it but in 90% of cases it's not necessary.

 

Mathematically, the distortion on a quasi (multistep) sine wave inverter is 6.5% compared to a stepped waveform version at around 23% distortion so the quasi version is a good approximation of a sinewave anyway.

 

Chris

 

PS: our local marina/chandler is a Victron agent but hates Victron PSW inverter/chargers because he has so many returns due to faulty operation in the field. I have no personal experience with them myself. The additional issue with a combined inverter/charger is that if one part fails you lose your inverter AND your charger while it's being repaired. Bit like combi washer/tumble dryer. Sounds a great idea till it goes wrong.

 

Sorry Chris - You say that "The only devices that won't run properly on a quasi inverter are devices for whom the shape of the sinewave is important"

 

Surely a sine wave is defined by its shape i.e. its sinusoidal. A different shape sine wave cannot and does not exsist - its either a sine wave or it isn't.

 

Eastern

[chris w]

Sorry Chris - You say that "The only devices that won't run properly on a quasi inverter are devices for whom the shape of the sinewave is important"

 

Surely a sine wave is defined by its shape i.e. its sinusoidal. A different shape sine wave cannot and does not exsist - its either a sine wave or it isn't.

 

Eastern

 

Of course, but most devices don't care too much, or at all, about the shape of the incoming mains. A lamp doesn't give a hoot what the shape is for example. So long as the RMS value of the incoming mains is 240v it will glow just as brightly as inputting "normal" 240v 50Hz regardless of the shape. Even DC at 240v through a mains lamp will glow at exactly the same brightness.

 

This is true for a whole plethora of devices. Most motors don't care providing the frequency is 50Hz eg: a hairdryer motor. Modern switched-mode laptop/phone chargers don't care because they convert the incoming mains to high voltage DC immediately and then regenerate their own internal AC signal.

 

The only devices that do care are those that specifically use the shape of the incoming wave for some function. Normal domestic mains lamp dimmers use specific timings on the mains input wave to enable dimming. They won't work properly or at all on a modified sinewave. So too for many motor speed controllers which essentially are dimmers.

 

Chris

[carlt]

Sorry Chris - You say that "The only devices that won't run properly on a quasi inverter are devices for whom the shape of the sinewave is important"

 

Surely a sine wave is defined by its shape i.e. its sinusoidal. A different shape sine wave cannot and does not exsist - its either a sine wave or it isn't.

 

Eastern

I'm sure Chris meant "the shape of the wave purporting to be a sinewave".

Of course even a square wave is merely made up of sinusoidal components.

I could start talking about Fourier analysis but I'd end up sounding like Chris (no offence, etc.).

[Theo]

Phone chargers, cordless tool chargers, camera chargers, laptop chargers, even toothbrush chargers!

 

They al seem to work OK on my Sterling 1800W MSW.

 

N

[chris w]

I'm sure Chris meant "the shape of the wave purporting to be a sinewave".

Of course even a square wave is merely made up of sinusoidal components.

I could start talking about Fourier analysis but I'd end up sounding like Chris (no offence, etc.).

 

...............and a good MSW inverter (and I include my 1800W Sterling in this 'cos I've measured it on a scope) has a harmonic distortion (as compared to a true sinewave) of only 6%.

 

Chris

[magnetman]

I find a msw inverter has a far lower 'wallet distortion' than a psw and as it runs most devices okay i believe this is a Good Thing.I find a msw inverter has a far lower 'wallet distortion' than a psw and as it runs most devices okay i believe this is a Good Thing.

[Pav]

I find a msw inverter has a far lower 'wallet distortion' than a psw and as it runs most devices okay i believe this is a Good Thing.I find a msw inverter has a far lower 'wallet distortion' than a psw and as it runs most devices okay i believe this is a Good Thing.

 

 

Hi everyone, Being the starter of this thread, I thank all for your replies.

 

After giving much thought, I feel that Magnetman hits the nail on the head..................The extra money required to go PSW seems quite hard to justify, especially when a lot of feedback seems to sugest that a MSW will more or less do the job.

 

So I have decided (i think!!) to keep with a MSW, but to upsize from the originally proposed Sterling 1.8kw to a Sterling 2.5kw and will hope that I do not regret my decision once it is put to the test.

 

I will let you know how I get on with it when the narrowboat is eventually/finally completed and handed over to me.

After many delays, this should hopefully be sometime in December.

 

Bye for now,

Pav.

[dor]

Good idea to uprate your inverter if you are sticking to a MSW as many of them degrade considerably as they come up towards full load, both in waveform and RMS voltage.

[anhar]

Hi everyone, Being the starter of this thread, I thank all for your replies.

 

After giving much thought, I feel that Magnetman hits the nail on the head..................The extra money required to go PSW seems quite hard to justify, especially when a lot of feedback seems to sugest that a MSW will more or less do the job.

 

So I have decided (i think!!) to keep with a MSW, but to upsize from the originally proposed Sterling 1.8kw to a Sterling 2.5kw and will hope that I do not regret my decision once it is put to the test.

 

I will let you know how I get on with it when the narrowboat is eventually/finally completed and handed over to me.

After many delays, this should hopefully be sometime in December.

 

Bye for now,

Pav.

 

Why are you happy with "more or less" on a new boat Pav? Don't you want it to do the job every time without doubt? As you are having a new boat built, the money saved by buying an MSW unit from a less than satisfactory maker must be relatively very small so you should want only the best. People advocating MSW are mostly those trying to save small amounts of money, Magnetman's approach. That's okay if you don't got any money and have no choice but for someone with a new boat who must be able to afford the difference I can't see it.

 

One of the common habits of the canal boater having a new build is to be penny wise and pound foolish, skimping on essential equipment, making do with second best to save small amounts that often, later, they will come to regret. Read Gary Peacock's blog, he wrote an excellent feature on just this attitude within the last few weeks.

 

regards

Steve

Edited November 16, 2007 by anhar

[carlt]

Why are you happy with "more or less" on a new boat Pav? Don't you want it to do the job every time without doubt? As you are having a new boat built, the money saved by buying an MSW unit from a less than satisfactory maker must be relatively very small so you should want only the best. People advocating MSW are mostly those trying to save small amounts of money, Magnetman's approach. That's okay if you don't got any money and have no choice but for someone with a new boat who must be able to afford the difference I can't see it.

 

One of the common habits of the canal boater having a new build is to be penny wise and pound foolish, skimping on essential equipment, making do with second best to save small amounts that often, later, they will come to regret. Read Gary Peacock's blog, he wrote an excellent feature on just this attitude within the last few weeks.

 

regards

Steve

But if someone says "I've had a msw inverter on my liveaboard for 10 years and still haven't found anything it wouldn't run", I think that it is a reasonable case for saving money.

[anhar]

But if someone says "I've had a msw inverter on my liveaboard for 10 years and still haven't found anything it wouldn't run", I think that it is a reasonable case for saving money.

Read the thread Carl if you're really interested in the subject. There are many examples of things that won't run. You have to read about when msw doesn't work, not when it does, to form a worthwhile opinion of what to do, particularly when the difference in cost is unlikely to be a problem as with a new boat.

 

It all depends on what appliances will be used but you can never be sure exactly what they might be in future. Things change, not only the kind of appliances one might want to run, but their electrical construction. So even if you think you know now that you will have only appliances that run on msw, that may not hold true in future. Thus buying an inverter that may not always function correctly is just not the way to proceed in my view. A new boat buyer wants certainty, or I would have thought they do.

 

regards

Steve

Edited November 16, 2007 by anhar

[carlt]

Read the thread Carl if you're really interested in the subject. There are many examples of things that won't run. You have to read about when msw doesn't work, not when it does, to form a worthwhile opinion of what to do, particularly when the difference in cost is unlikely to be a problem as with a new boat.

 

It all depends on what appliances will be used but you can never be sure exactly what they might be in future. Things change, not only the kind of appliances one might want to run, but their electrical construction. So buying an inverter that may not always function correctly is just not the way to proceed in my view. A new boat buyer wants certainty, or I would have thought they do.

 

regards

Steve

Thank you Steve, for those patronising words of advice. I've read the thread. After living aboard for 10 years I'm obviously interested, and not inexperienced in the subject and my opinion is as worthwhile as somebody who has not got any experience of MSW inverters.

 

Regards

Carl

[magnetman]

I admit I'm not the best person to ask because I don't run anything technical in my 3 shedroom boat, for me part of the joy of it is not being swept along with the newest most fashionable electronic kit etc etc . If you are building a boat to try to be as similar as possible to a house/flat then a psw inverter is probably best as it will run all the plastic encased winking led stuff.

[anhar]

Thank you Steve, for those patronising words of advice. I've read the thread. After living aboard for 10 years I'm obviously interested, and not inexperienced in the subject and my opinion is as worthwhile as somebody who has not got any experience of MSW inverters.

 

Regards

Carl

I didn't claim or imply your opinion was not worthwhile. You said:

 

But if someone says "I've had a msw inverter on my liveaboard for 10 years and still haven't found anything it wouldn't run", I think that it is a reasonable case for saving money.

 

My response was to counter this argument. In my view it is not a reasonable case for saving money because maybe you just didn't have those appliances which don't work properly. Others have had poor experiences as the thread shows, hence my suggestion to read it because it appeared from your comments that you think msw doesn't cause problems. What you meant is that it didn't cause you problems but it is not right to argue from that, as you have, that it won't cause others to have problems because they have, as stated here and elsewhere. You appeared not to have taken notice of that fact hence my saying you should read the thread.

 

In any case I couldn't have known you were talking about yourself because the word "someone" suggests that you were not. You should have made it clear that it was your own experience if that was what you wanted people to understand by your message, not that it would have altered the gist of my reply though I probably would have worded it differently.

 

Either way, whether you meant yourself or not, I don't see that I was being patronising. I simply don't agree that your comments are necessarily good advice to others. Any ostensible patronisation in your mind arises from your poorly worded message which gave the clear impression that you hadn't read the thread and that you were not referring to your own personal experience.

 

regards

Steve

Edited November 16, 2007 by anhar

[RobinJ]

I don't know the technical difference between the two Pav but it doesn't matter because in my view you should go for full sine wave and moreover stick to Victron or Mastervolt. I understand that fsw consumes more electricity when running than the cheaper types but you have to design your electrical system to allow for that.

In theory quasi sine wave are better than modified sine wave, since they are supposed to have a more digitally accurately impersonation of a sine wave (for the techies quasi is supposed to have more bits than modified), typically 2V steps instead of 50V steps. However many people confuse to two and there is no guarantee that a quasi isn't modified!

Only mains equipment that utilises switched mode type supplies will notice the difference, dimmers, computers etc., as they will fail or be unable to regulate the power properly (this incidently includes some types of flashing christmas lights!). If in doubt go for the pure sine, but is is more expensive and uses more power.

[carlt]

My reason is so that you are certain that any appliances you may purchase will work including the more sensitive ones such as computers, TVs, 'waves with electronic control, drills with electronic speed control and so on.

I've reread the post following your advice, Steve, and, taking your list, one item at a time:

 

computers: Ran a desk top, and lap top with no problems.

Tv's: never any problems

'waves with electronic control: not sure what you mean?

Drills: all my power tools are top of the range (Hitachi, mainly) and I've never had any trouble.

and so on: you'd have to be more specific.

[chris w]

In theory quasi sine wave are better than modified sine wave, since they are supposed to have a more digitally accurately impersonation of a sine wave (for the techies quasi is supposed to have more bits than modified), typically 2V steps instead of 50V steps. However many people confuse to two and there is no guarantee that a quasi isn't modified!

Only mains equipment that utilises switched mode type supplies will notice the difference, dimmers, computers etc., as they will fail or be unable to regulate the power properly (this incidently includes some types of flashing christmas lights!). If in doubt go for the pure sine, but is is more expensive and uses more power.

 

Robin.... with respect what you have written is mainly nonsense. There is no offical definition of "quasi" or "modified". They may be different, they may be the same. I have never seen a non-pure-sinewave (NPSW) inverter with 2v steps and don't believe one exists. Even with 50v steps you will only get around 6% wave distortion if you run the maths.

 

Further your statement that "Only mains equipment that utilises switched mode type supplies will notice the difference, ..................................... as they will fail or be unable to regulate the power properly."

 

This is totally wrong. It is switched-mode power supplies (SMPS) that will work best on a NPSW inverter because SMPS's don't care what the input wave looks like and will also work automatically over a very wide input voltage range. If you knew how they worked, you would realise they don't care about wave shape. Old fashioned 50Hz transformer charges may object because square waves contain many high frequency harmonics which might cause the transformer to overheat.

 

I agree with your statement about (mains) dimmers as the "shape" of the wave is important for them.

 

Chris

Edited November 16, 2007 by chris w

[Pav]

Why are you happy with "more or less" on a new boat Pav? Don't you want it to do the job every time without doubt? As you are having a new boat built, the money saved by buying an MSW unit from a less than satisfactory maker must be relatively very small so you should want only the best. People advocating MSW are mostly those trying to save small amounts of money, Magnetman's approach. That's okay if you don't got any money and have no choice but for someone with a new boat who must be able to afford the difference I can't see it.

 

One of the common habits of the canal boater having a new build is to be penny wise and pound foolish, skimping on essential equipment, making do with second best to save small amounts that often, later, they will come to regret. Read Gary Peacock's blog, he wrote an excellent feature on just this attitude within the last few weeks.

 

regards

Steve

 

Hi Steve, I take your point, and I really would like to have the best I can afford to be fitted, included within the build. The trouble is my pockets are only so deep and, as everyone is aware, the cost of a newbuild is not cheap. I have already exceeded my original budget by some way, and although I agree with you about being penny wise and pound foolish, the fact is that the additional £800 or so needed to go down the PSW route would buy an awful lot of food and provisions in the future when money will be tight. Our boat builder is aware of the concerns over choosing the correct inverter and is is adamant that the MSW will be more than up to the job, and that the the 1.8kw model, make up the majority of what his company installs on their boats, which are mainly built for livaboard use. I thought upping to the 2.5kw would be prudent, particularly for the price difference between the 1.8kw and 2.5kw units. I have also queried the surveyor on this matter, who is overseeing the build, and he is also of the opinion that the MSW will be fine. The feedback from this forums members and also from boaters whom I have spoken with is a real mixed bag of opinions, and I have been very glad to hear the various pros and cons from each camp. Reading the 'Valerie' blog regarding inverters recently, made me think that a 3kw PSW is probably something I can do without. Although on the face of it, it would seem that someone who has ordered a new build narrowboat, is going to be in a position of not having to worry about the odd few hundred quid here or there, I can assure you this will not be the situation I find myself in (unfortunately!) When my wife and I move onto the boat, we will be continuous cruisers and will no longer have the luxury of salaries coming in from our jobs, but neither will we have the pressures and stress of work. It is our choice, but we have decided we would rather be poorer and happy, than richer and miserable. However, we will need to cut our cloth accordingly and live within our means, so not having to spend £800 now, where it may not be needed, is a definate consideration.

Regards,

Pav.

[denboy]

i installed one of these 1800 watt 3 years ago and ive been happy with it ever since we havehad it

 

 

http://www.powermastersystems.com/index.htm

 

runs everything we have (dont have microwave )

[Radiomariner]

Why are you happy with "more or less" on a new boat Pav? Don't you want it to do the job every time without doubt? As you are having a new boat built, the money saved by buying an MSW unit from a less than satisfactory maker must be relatively very small so you should want only the best. ....

 

Unrelistic philosophy Steve. If a new build was to be constructed and fitted with "nothing but the best" in equipment and materials the cost will be foolishly astronimical considering that the end product will still be just another narrowboat.

Pav is right, he must cut his suit to according to his cloth.

I used italics for the word 'best'. Replace the word "best" with the expression "most suitable for purpose".

Take for example a pocket calculator; a £25 model or £2 model, which is best? The word best is meaningless.

If all you want is a few basic functions then the £2 model is the most suitable for purpose, the £25 model is probably too complex and definately unsuitably expensive.

Pav has sensibly demonstrated his desire to find the most suitable inverter for his requirements, simply by making enquiries. He has like most of us a budget to work to and he simply needs information so he may weigh the cost against functionality.

It is a pity enough that so much advice should be contradictive, but that is the nature of a forum. However I am sure he will be able to seperate the "information" from the "advice" and make a suitable descision.

 

Edited by radiomariner to remove possibly offensive content.

Edited November 17, 2007 by Radiomariner

[magnetman]

I am a bit disturbed by the tendency to rely on inverters for so much onboard equipment. Most domestic type stuff can be run on 12v anyway. Anything with high electric consumption should be run on a genny. It's 'old school' but seperate generator and main engine may become popular again with the rise in diesel costs coming. I would buy a Honda EU20i genny rather than a big inverter for £1000.

[anhar]

Unrelistic philosophy Steve. If a new build was to be constructed and fitted with "nothing but the best" in equipment and materials the cost will be foolishly astronimical considering that the end product will still be just another narrowboat.

Pav is right, he must cut his suit to according to his cloth.

I used italics for the word 'best'. Replace the word "best" with the expression "most suitable for purpose".

Take for example a pocket calculator; a £25 model or £2 model, which is best? The word best is meaningless.

If all you want is a few basic functions then the £2 model is the most suitable for purpose, the £25 model is probably too complex and definately unsuitably expensive.

Pav has sensibly demonstrated his desire to find the most suitable inverter for his requirements, simply by making enquiries. He has like most of us a budget to work to and he simply needs information so he may weigh the cost against functionality.

It is a pity enough that so much advice should be contradictive, but that is the nature of a forum. However I am sure he will be able to seperate the "information" from the "advice" and make a suitable descision.

 

Edited by radiomariner to remove possibly offensive content.

When I referred to buying "best", this was about inverters, not necessarily every single aspect of a boat. As I've said the additional cost of a psw inverter over msw compared with the cost of a new boat build must be of virtually no consequence. There can be no argument about that really.

 

I agree that there is no point in buying an item possessing features that are wholly unnecessary for the user, like the calculator you mention. But the analogy is flawed because we're not talking about paying for unnecessary features. Ensuring the inverter will run any possible type of appliance is hardly something the user may not need, it is of genuine practicality. Well it is in my view but clearly some disagree. I think it's short sighted penny pinching.

 

There is evidence in this thread and others to demonstrate that msw just doesn't properly with everything. We don't actually know how Pav intends to use his inverter system, what kind of appliances and so on. It may well work on msw who knows? But I'm talking about buying certainty that it will work on present and future appliances. Peoples' requirements and technological designs of equipment change over time.

 

Why risk having something inferior given the relatively modest cost of going for the best? And yes, psw is the best. Isn't it better to err on the side of caution with a new build, within one's financial constraints.

 

regards

Steve

Edited November 17, 2007 by anhar

[chris w]

I understand where you're coming from Steve but you have freely admitted on previous threads that you have no technical knowledge. Therefore your thoughts on the suitability or otherwise of MSW inverters don't really carry any weight. If you understood how they worked, you wouldn't be so critical of them. MSW's will run everything except equipment that have electronic timers and/or motor speed control.

 

The cost difference alone for an equivalent PSW is a factor of two and they are less efficient than MSWs. On a previous thread you said that you designed your battery/charging system around efficiency factors like this (inter alia), but when you listed your set up some time ago, it didn't seem well matched to what you have installed, in terms of battery life.

 

I believe that once you start cruising properly and spend a few days away and need to rely on an alternator to recharge the batteries you will understand the need for as high an efficiency as possible.

 

I had a new boat this year and selected an MSW because I know it will do the job. I could have afforded a PSW but IMHO it's nuts to throw away money and efficiency for no gain.

 

Chris

[anhar]

I understand where you're coming from Steve but you have freely admitted on previous threads that you have no technical knowledge. Therefore your thoughts on the suitability or otherwise of MSW inverters don't really carry any weight. If you understood how they worked, you wouldn't be so critical of them. MSW's will run everything except equipment that have electronic timers and/or motor speed control.

 

The cost difference alone for an equivalent PSW is a factor of two and they are less efficient than MSWs. On a previous thread you said that you designed your battery/charging system around efficiency factors like this (inter alia), but when you listed your set up some time ago, it didn't seem well matched to what you have installed, in terms of battery life.

 

I believe that once you start cruising properly and spend a few days away and need to rely on an alternator to recharge the batteries you will understand the need for as high an efficiency as possible.

 

I had a new boat this year and selected an MSW because I know it will do the job. I could have afforded a PSW but IMHO it's nuts to throw away money and efficiency for no gain.

 

Chris

This argument seems to arise regularly Chris. I guess we'll just have to agree to disagree. I confirm having no technical knowledge. But I don't need it.

 

Bottom line is, I want an inverter that will work with anything no question. I don't want to have to worry every time I use some appliance whether it will work properly. It is perhaps precisely because I don't have technical knowledge that I see it this way. I don't want to know, I want simply to plug and play. You and some others are satisfied with msw even though it will not function correctly with certain equipment. The latter appears to be wider than just electronic timers and speed controls according to some readers but whatever, you admit that msw will not function universally. That's unacceptable for me and I would have thought for most people spending what must be a large sum on a new boat given the relatively small additional cost of psw.

 

For example I presume you can't even run something as simple as, say, a mains clock radio to listen to whilst falling asleep on timer and wake you up. You may not want to but my point is that it is valuable to have the capacity to do so.

 

Then there's the future issue. Two points. A boater with a new boat may not know what appliances they would like in future. Secondly, technology changes in that new things are available and old things are redesigned. You know that better than me. Far as I know it is as certain as it gets that psw will power anything in future. It is not certain that msw will do so if it can't even power everything now.

 

As for the higher power consumption of psw it simply requires the correct system design as I've said often which you mention. This isn't about my particular boat, it is a general comment for anyone having a new build or refitting, which is what the original query was about.

 

Some of the responses have ignored the fact that this query is about a new build. It's not about someone sticking an inverter into an old boat who probably isn't the type to have a range of modern appliance anyway. As I keep saying on a new build it makes no sense, to me, to save a relatively minuscule amount of money for something that just doesn't work universally. On top of that, Sterling is an inferior brand anyway as Chris Gibson and Gary Peacock, who ought to know because they see large numbers, have confirmed.

 

regards

Steve

Edited November 17, 2007 by anhar

[magnetman]

My pure 'bug' DAB radio has two seperate wake up' alarms settable to a particular day or everyday or weekdays only and a sleep option and it runs on 12v.