Generator Decision

[robertager1962]

We are planning a liveaboard trip later this summer and I have decided to buy a small generator instead of installing an inverter. I have purchased a small microwave that shows an input rating of 1000w. The generator I am looking at is the IMPEX range from Screwfix and undecided whether I can get away with the 1200w version. The next size up is the 2200w. I would like to keep the size down to a minimum so would prefer the smaller unit. Trouble is you can't try these (relatively high priced) out and I am worried that if I buy the smaller version it won't power the microwave. Can I ask for advice please.

 

[Tillsbury]

Modern microwaves need a good supply. My new 1000W microwave was cooked running from an old 1200W inverter. It works fine running from a new Victron 1600W, which reports it pulling 1550W peak. I would suggest having some headroom.

 

[jiris]

I went through a few generators already and all had one thing in common: The rated power was always over-stated - big time in some cases. I wouldn't risk the 1,200 W. Even if rated right, it would be making it only just and working very hard.

 

[sailaboutvic]

I think you need to ask your self how offen will you be using the Gen , plus if it one of them noisy once you be hard push to use it on a quay side or harbour wall and even in a crowed anchorage if you use it long enough someone will come over and complain.
We full time liveaboard we have a suite type Gen inside ,
Which you can't hardly hear it out side but before then for 7years we used an inverter for the microwave the little time we used it and for power tools and so on ,
Unless you need a Gen for say AC or water maker I wouldn't go that route , but then your not me .

 

[KellysEye]

IMPEX range from Screwfix

They are Impax and I tried to check whether they are 3,000 rpm and couldn't find the answer they have a life of 500 to 1,000 hours ours, fitted by the previous owner, committed suicide after 550 hours and was not repairable. I suggest you check with Screwfix what the rpm is. I changed to a 1,500 rpm generator that has a life the same as diesel engines 8,000+ hours if serviced properly. If it is 3,000 rpm I would walk away.

 

[RichardS]

We are planning a liveaboard trip later this summer and I have decided to buy a small generator instead of installing an inverter. I have purchased a small microwave that shows an input rating of 1000w. The generator I am looking at is the IMPEX range from Screwfix and undecided whether I can get away with the 1200w version. The next size up is the 2200w. I would like to keep the size down to a minimum so would prefer the smaller unit. Trouble is you can't try these (relatively high priced) out and I am worried that if I buy the smaller version it won't power the microwave. Can I ask for advice please.

If the smaller generator can power the microwave, and it will be marginal, it will be deafening.

We have a 2kW suitcase generator and an 800W microwave so probably could power the microwave but have never actually tried to do so except when connected to shore power as there's always another way when at anchor.

Richard

 

[Mistroma]

IMPEX range from Screwfix

They are Impax and I tried to check whether they are 3,000 rpm and couldn't find the answer they have a life of 500 to 1,000 hours ours, fitted by the previous owner, committed suicide after 550 hours and was not repairable. I suggest you check with Screwfix what the rpm is. I changed to a 1,500 rpm generator that has a life the same as diesel engines 8,000+ hours if serviced properly. If it is 3,000 rpm I would walk away.

These rpm and lifespan figures look oddly similar to stuff I saw many years ago about built-in diesel gen-sets.

OP is talking about a small £280 petrol suitcase generator. I don't believe I have seen one of those with normal rpm of 1,500. Pretty certain the Honda 20EUi runs at around 4,300-5,000 rpm. It is a pretty safe bet that the Impax model won't run at 1,500 rpm unless it's at tickover (assuming it has a variable throttle).

I would be very interested in the make and model of your suitcase generator in case I need to buy one. It is bound to be quieter than a high revving screamer. I'll certainly keep a note of it for future reference.

Others have covereed microwave ovens. My 800W microwave will probably use around 1200W and could be higher with some inverters. I think that our microwave cooking times are about 25% longer with Honda 20EUi than on shore supply. Surprising as the Honda 20EUi is considered to give a pretty good output, not at all like a cheap square wave type inverter.

I agree that the small Impax model might struggle a bit unless OP has a very small microwave. At least microwave ovens are usually only run for a few minutes, unlike battery charging. Earplugs might be an acceptable solution but it will take a while to row round the anchorage distributing them.

 

[LadyInBed]

One good thing with Screwfix is their no quibble return policy, so why not buy and try at home. If it's not up to the job, take it back.

 

[mattnj]

the larger one is what you want, they are all inverter/variable speed, and relatively quite at lower output and pretty loud when near flat out.

 

[robertager1962]

Thanks so much to all for your very helpful advice. Lots of food for thought. I had originally planned to fit an inverter, but the helpful chaps on the Solar on a Boat FB forum gave me some alarming figures at what draw I could expect and no way are my batteries up to this. By the time I have increased the battery compartment, bought the inverter and all the ancilliary wiring, it will have cost me twice the price of a generator. I only really want the generator for for short periods when off shore power and need to use the microwave to cook. I have considerable solar charging and also a wind generator, so not worried about battery charging. Where we are going, I can see gas supply may be an issue and 10 mins in a microwave for jacket spuds and the like, will save us a whole heap of issues in rationalising the use of gas. The microwave is rated at 1kw electrical input , not actual cooking power as some have mentioned. It is actually rated at 600 watt. (I purposely bought a small one suitable for a caravan/boat.)
It is such a difficult issue rationalising whether to buy a cheap generator at 1/3rd price of a Honda. I like to get good gear but as it won't be used that much, do I really want to spend £1,200 on something that
may just sit in a locker most of the time. Shame I couldn't find a decent 12V microwave which would have saved me a deal of trouble.

 

[Mistroma]

Thanks so much to all for your very helpful advice. Lots of food for thought. I had originally planned to fit an inverter, but the helpful chaps on the Solar on a Boat FB forum gave me some alarming figures at what draw I could expect and no way are my batteries up to this. By the time I have increased the battery compartment, bought the inverter and all the ancilliary wiring, it will have cost me twice the price of a generator. I only really want the generator for for short periods when off shore power and need to use the microwave to cook. I have considerable solar charging and also a wind generator, so not worried about battery charging. Where we are going, I can see gas supply may be an issue and 10 mins in a microwave for jacket spuds and the like, will save us a whole heap of issues in rationalising the use of gas. The microwave is rated at 1kw electrical input , not actual cooking power as some have mentioned. It is actually rated at 600 watt. (I purposely bought a small one suitable for a caravan/boat.)
It is such a difficult issue rationalising whether to buy a cheap generator at 1/3rd price of a Honda. I like to get good gear but as it won't be used that much, do I really want to spend £1,200 on something that
may just sit in a locker most of the time. Shame I couldn't find a decent 12V microwave which would have saved me a deal of trouble.

Pretty much what we do with our suitcase generator. It is used to run a mains hair drier and sometimes charging on dull days. Microwave rarely used and usually when the Honda has been out earlier for something else.

A 600W microwave is still going to use something around 900-1,000W. Perhaps a bit more efficient running a 12V microwave instead of 240V generator and mains microwave. However, you don't get something for nothing and a 12V microwave is still going to use about 90-100A. Unless there's a tiny 300-400W version.

1) Buy a quite a big, good quality (not square wave) inverter (and run engine when needed).
2) Go for a 12V microwave instead, still have similar high current draw but save on inverter purchase.
3) Get a small generator with a decent integral inverter

The generator also provides an extra way to charge batteries via mains charger. Useful backup if you have a failure of solar or alternator. I'd bet 12V microwave ovens will usually be pretty expensive and difficult to find.

My main concern would be the inverter in the Screwfix generator as you want to run a microwave. I'm guessing it would be quite difficult to discover what the output was like (either close to Honda or more like a staircase, perhaps with only one step ).

 

[robertager1962]

Screwfix are saying that these are fitted with a Pure Sine wave output inverter (and suitable for electrical equipment) so I am hoping it will be suitable. I like the idea that one poster mentioned about trying it out and if it doesn't work, return it. I can also check out the noise level.

 

[Mistroma]

Screwfix are saying that these are fitted with a Pure Sine wave output inverter (and suitable for electrical equipment) so I am hoping it will be suitable. I like the idea that one poster mentioned about trying it out and if it doesn't work, return it. I can also check out the noise level.

Yes, I thought that was a particularly good idea. I would say, just before paying, that the only reason to buy it is to run a microwave. Comment that it's good they say it has pure sine wave output. I like to weigh things in my favour, even with no quibble guarantees.

Can you try it out on the small microwave to prove it is OK? I would use the same oven on mains and then on 12V to do a couple of quick tests.

Just heat a known volume of water and time how long it takes to get the same temp. increase, say from 15C to 50C. It will let you if it works well also how much to adjust cooking times. I guess someone will come along and tell you to put a wooden stick in the cup to avoid super-heating. I tend not to drink distilled water from utterly clean containers and have been lucky enough to avoid the problem by some fluke.

 

[LadyInBed]

I carry a 2kW (continuous output) Gen. If you go for a 2kW Gen, one thing that you should bare in mind is their weight. Moving it from a storage locker to the deck and stowing it can be hard work on your back.

 

[robertager1962]

Just an update on my generator question. Funny how all of a sudden all the 2kw generators (even Honda) have gone out of stock and no deliveries till April - Screwfix included. I wonder if they are not replacing stock till after Brexit. Maybe being paranoid. I looked into it lots and in the end bought a Honda 22i. An agricultural supplier had one in stock. The great benefit is that we have a microwave and electric hotplate on board so if we ever do run out of gas, we can still cook and eat. More than I wanted to pay and in an ideal world I would have liked to use an inverter and my solar panels, but this seemed to be a much more complicated setup than I had anticipated. (If I wanted to set it up safely.)

 

[Mistroma]

Just an update on my generator question. Funny how all of a sudden all the 2kw generators (even Honda) have gone out of stock and no deliveries till April - Screwfix included. I wonder if they are not replacing stock till after Brexit. Maybe being paranoid. I looked into it lots and in the end bought a Honda 22i. An agricultural supplier had one in stock. The great benefit is that we have a microwave and electric hotplate on board so if we ever do run out of gas, we can still cook and eat. More than I wanted to pay and in an ideal world I would have liked to use an inverter and my solar panels, but this seemed to be a much more complicated setup than I had anticipated. (If I wanted to set it up safely.)

Forgot to turn off mobile view and last post was immediately deleted.

Same here, no 2kw version in stock for miles. I thought they might have had a problem with that particular model. Unlikely, as 2kw Stanley frame model is also unavailable.

At least the Honda is likely to be reliable and keep a decent resale value.

It looks as if people might be preparing for armageddon.

Time to dig out my spare generator. It's only a 30 year old Yamaha 650 rated at 500W. It will run central heating, fridge or freezer, TV and 2 lights, just enough to keep comfortable when the lights go out. Planning to be in Greece by mid-April and not stockpiling on assumption planes won't be grounded. Maybe I'm getting too complacent in my old age?

 

[Graham376]

I would be wary of anything from Screwfix that isn't available elsewhere as they aren't interested in parts or service once warranty has run out. If going cruising, it's worth paying more for something like Honda for which parts are available worldwide. Our 2.0i runs the microwave fine although use is restricted in quiet anchorages for occasional battery charging when necessary.

 

[DuncanHall]

I have an microwave on board and have a replacement model at home. Although both are rated at 700W. They draw about 1.2kW. This is measured a power meter attached to test them. I have a 2KW Honda generator linked to a victron multiplus which has a 1.6KW inverter which can combine the generator and inverter output. This works fine without the generator and is not a significant load as the multiplus only takes about 1% of battery capacity (390AH) per minute of use. If you use the multiplus to limit the generator output you can maintain a low noise level. In fact a 1KW honda generator would do as the multiplus can top up the output.

Regards

Duncan

 

[Mistroma]

I have an microwave on board and have a replacement model at home. Although both are rated at 700W. They draw about 1.2kW. This is measured a power meter attached to test them. I have a 2KW Honda generator linked to a victron multiplus which has a 1.6KW inverter which can combine the generator and inverter output. This works fine without the generator and is not a significant load as the multiplus only takes about 1% of battery capacity (390AH) per minute of use. If you use the multiplus to limit the generator output you can maintain a low noise level. In fact a 1KW honda generator would do as the multiplus can top up the output.

Regards

Duncan

I was a little confused initially and thought you meant 3.9A draw but quickly realised that wasn't the case. I read your post again and think I see what you mean.

You did specifically say capacity so you mean 3.9Ah of 390Ah capacity used for every minute in use.

1% per minute sounds about right. 100A for 10 minutes would be about 17Ah which is about 4.3% of 390Ah. However, the actual impact on capacity could well be around 10% with such a high current.

Finally got there, 10-15minutes cooking is about 10-15% of your battery capacity and 20-30% of usable capacity. Getting to sound more like figures I'd expect.

 

[DuncanHall]

I was a little confused initially and thought you meant 3.9A draw but quickly realised that wasn't the case. I read your post again and think I see what you mean.

You did specifically say capacity so you mean 3.9Ah of 390Ah capacity used for every minute in use.

1% per minute sounds about right. 100A for 10 minutes would be about 17Ah which is about 4.3% of 390Ah. However, the actual impact on capacity could well be around 10% with such a high current.

Finally got there, 10-15minutes cooking is about 10-15% of your battery capacity and 20-30% of usable capacity. Getting to sound more like figures I'd expect.

Yes

Its 1% of capacity as measured by the victron BVM which takes current rate and capacity into account. However the real point is one does not need a generator. A decent inverter and a bit more battery capacity is much less expensive.