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We are looking at getting our first boat ,but as im a Air conditioning eng would like to fit a/c in the boat so would need 5/6 amps to run a 2.5kw unit ....so can this been done.  ? just looking for pitfalls for doing this ..cheers 

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2 minutes ago, jaime66 said:

We are looking at getting our first boat ,but as im a Air conditioning eng would like to fit a/c in the boat so would need 5/6 amps to run a 2.5kw unit ....so can this been done.  ? just looking for pitfalls for doing this ..cheers 

Will the boat always have access to shore power?  That's a heck of a load to try and run off a battery bank.

 

 

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1 minute ago, jaime66 said:

We are looking at getting our first boat ,but as im a Air conditioning eng would like to fit a/c in the boat so would need 5/6 amps to run a 2.5kw unit ....so can this been done.  ? just looking for pitfalls for doing this ..cheers 

5 amps at 230v will be about 50amps out of your batteries via an inverter.

@ 12 hours per day that 600Ah, you will need at least an 1800Ah battery bank, but more importantly a method of keeping it fully re-charged EVERY DAY

 

Basically it is not possible unless you run a 230v generator full time. A quiet inboard diesel generator will be about £10,000 installed.

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Just now, robtheplod said:

Maybe best to open the windows?

I had a car that had an early Air-con system, it was apparently a "4WD" system (which I thought referred to a Land Rover) it turned out to be "4 Windows Down"

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18 minutes ago, Alan de Enfield said:

5 amps at 230v will be about 50amps out of your batteries via an inverter.

@ 12 hours per day that 600Ah, you will need at least an 1800Ah battery bank, but more importantly a method of keeping it fully re-charged EVERY DAY

 

No, 5A at 230v is over 100A at 12v, allowing for some inefficiency. 96A if you assume an impossible 100% efficiency.

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19 minutes ago, Alan de Enfield said:

5 amps at 230v will be about 50amps out of your batteries via an inverter.

@ 12 hours per day that 600Ah, you will need at least an 1800Ah battery bank, but more importantly a method of keeping it fully re-charged EVERY DAY

 

Basically it is not possible unless you run a 230v generator full time. A quiet inboard diesel generator will be about £10,000 installed.

If its 12v batteries, its over 100 Amps!

2.5kw is 10 Amps @250v AC, off an inverter that will exceed 200 Amps!

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20 minutes ago, Alan de Enfield said:

5 amps at 230v will be about 50amps out of your batteries via an inverter.

@ 12 hours per day that 600Ah, you will need at least an 1800Ah battery bank, but more importantly a method of keeping it fully re-charged EVERY DAY

 

Basically it is not possible unless you run a 230v generator full time. A quiet inboard diesel generator will be about £10,000 installed.

I think your sums may be a little out there

 

Unless you are on shore supply I wouldn't bother

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25 minutes ago, jaime66 said:

We are looking at getting our first boat ,but as im a Air conditioning eng would like to fit a/c in the boat so would need 5/6 amps to run a 2.5kw unit ....so can this been done.  ? just looking for pitfalls for doing this ..cheers 

I think you need to reassess what your narrowboat is about.

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24 minutes ago, jaime66 said:

We are looking at getting our first boat ,but as im a Air conditioning eng would like to fit a/c in the boat so would need 5/6 amps to run a 2.5kw unit ....so can this been done.  ? just looking for pitfalls for doing this ..cheers 

I think you are falling into a common trap of trying to do things differently from everyone else on your first boat. People generally do things in much the same way because that is what works. And surely a 2.5kw unit will take around 11A at 230v?

 

it simply isn’t feasible to have this sort of power available on a boat for anything other than short durations (eg boiling an electric kettle) or with the engine running and something like a travelpower, unless you are plugged into shore power.
 

You would do better with good ventilation and maybe some fans, or how about a heat exchanger that uses canal water to cool the air?

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3 minutes ago, Tracy D'arth said:

If its 12v batteries, its over 100 Amps!

2.5kw is 10 Amps @250v AC, off an inverter that will exceed 200 Amps!

 

Air Con unit though, so the 2.5kW is cooling power, not electrical input.

 

It's a big heat pump, not an electric coldmaker ...

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Most shore line bollards inland are only 16A at most. Some only 6A. Only a couple of days a year when air con would be nice on a boat. The rest of the time you can open all the windows and doors. Fly screens can keep the bugs out.

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7 minutes ago, nicknorman said:

No, 5A at 230v is over 100A at 12v, allowing for some inefficiency. 96A if you assume an impossible 100% efficiency.

 

6 minutes ago, Tracy D'arth said:

If its 12v batteries, its over 100 Amps!

 

6 minutes ago, ditchcrawler said:

I think your sums may be a little out there

 

I've not been well you know !!!

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1 minute ago, TheBiscuits said:

 

Air Con unit though, so the 2.5kW is cooling power, not electrical input.

 

It's a big heat pump, not an electric coldmaker ...

I did wonder about that. Anyway, shouldn’t it be -2.5kw as it is extracting heat, not delivering it?!

 

 I wouldn’t like to be moored next to that on a hot day, pumping 2.5kw of heat in my direction!

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1 hour ago, jaime66 said:

We are looking at getting our first boat ,but as im a Air conditioning eng would like to fit a/c in the boat so would need 5/6 amps to run a 2.5kw unit ....so can this been done.  ? just looking for pitfalls for doing this ..cheers 

There is a boat on the cut called Anonimity which was once owned by an A/C man.  I believe it had an onboard whisper generator [Onan or summat] but the main donkey was an RN DM2.  PM me and I may be able to put you in touch with the owner

 

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Sorry  should have said unit would only run when engine is running not off battery also 2.5kw a/c unit would be drawing 4/5 amps and would make unit water cooled so no hot air blowing on anyone ....

1 hour ago, nicknorman said:

I did wonder about that. Anyway, shouldn’t it be -2.5kw as it is extracting heat, not delivering it?!

 

 I wouldn’t like to be moored next to that on a hot day, pumping 2.5kw of heat in my direction!

Would make the unit water-cooled  so no hot air blowing on anyone 

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4 minutes ago, jaime66 said:

Sorry  should have said unit would only run when engine is running not off battery

 

If you are doing that, you might as well fit a vehicle A/C to the boat engine and not bother with the electric version.

 

Your other alternative is a Travelpower on the engine so you have mains power available all the time the engine is running, but you will soon find out why most of us don't even try to run electrically powered A/C. 

 

I just use a couple of computer fans blowing cooler air up from the bilge!

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10 minutes ago, jaime66 said:

Sorry  should have said unit would only run when engine is running not off battery also 2.5kw a/c unit would be drawing 4/5 amps and would make unit water cooled so no hot air blowing on anyone ....

Would make the unit water-cooled  so no hot air blowing on anyone 

Modern engines like Beta 43 have a 12v 175A or greater domestic alternator, that equates to around 7 or 8 A at 230v having been put through an inverter. However these types of alternators are automotive ones and not really designed to produce a high output for a long time - they run too hot and fail prematurely.

 

A better idea is a TravelPower (as just mentioned). This is a high voltage alternator feeding a “magic box” out of which comes up to 3.5kW at 230v 50Hz. Because the alternator is running at around 300v the current is low and so even though it is a similar physical size to a 175A 12v alternator, it runs much cooler and can easily produce your 4 or 5 amps at 230v.

 

Oh and the only other thing to consider is the startup current of the aircon compressor. Whilst it may only take 4A when it’s running, I bet the start up current will be much, much higher, maybe approaching 10 times higher. Just for an instant, but if the Inverter or Travelpower can’t start the motor without cutting out from overload, it ain’t going to work!

 

We have a 2.5kw inverter but it struggled to start up our small dyson vacuum cleaner due to the startup current surge.

 

More generally, I would concentrate mostly on getting the best insulation. The roof will be far too hot to touch on a hot sunny day and the less of that heat that gets through to the cabin ceiling, the better. Light coloured paint makes a big difference as well. I’ve always thought about a sprinkler system that pumps canal water over the roof to keep it cool, but never actually tried it.
 

Finally, boating is about calm and relaxation and if you have your engine running all the time it will be a nuisance not only to you, but also to anyone else within earshot. Fine when you are cruising, not fine when you are moored up in the company of other boats or moored outside someone’s house on lovely summer’s day.

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I agree with Nick above. Conventional A/C is too power hungry.

 

One possibility would be to make a homemade system of a Swedish system sometimes used to cool telecoms equipment.

 

Basically this system used a mains driven compressor to chill water, which was then stored in insulated tanks and when the mains failed, used battery driven pumps to circulate the chilled water through ceiling mounted "radiators" to rain cold air down onto the equipment.

 

The compressor could be engine driven and make chilled water for when you stop cruising.

 

I can see two issues, but at least it will keep the roof clean, unlike Nick's evaporative cooling using canal water 😁.

 

1. Room to accommodate sufficient chilled water.

 

2. Limited run time until the pump batteries go flat.

 

Ask why virtually no one has A/C on their boats.

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2 hours ago, TheBiscuits said:

Air Con unit though, so the 2.5kW is cooling power, not electrical input.

This is something I've never understood with the aircon industry. If a unit has 2.5kW of cooling power, how come it only draws 1kW? Where does the other 1.5kW come from?

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1 hour ago, nicknorman said:

Modern engines like Beta 43 have a 12v 175A or greater domestic alternator, that equates to around 7 or 8 A at 230v having been put through an inverter. However these types of alternators are automotive ones and not really designed to produce a high output for a long time - they run too hot and fail prematurely.

 

A better idea is a TravelPower (as just mentioned). This is a high voltage alternator feeding a “magic box” out of which comes up to 3.5kW at 230v 50Hz. Because the alternator is running at around 300v the current is low and so even though it is a similar physical size to a 175A 12v alternator, it runs much cooler and can easily produce your 4 or 5 amps at 230v.

 

Oh and the only other thing to consider is the startup current of the aircon compressor. Whilst it may only take 4A when it’s running, I bet the start up current will be much, much higher, maybe approaching 10 times higher. Just for an instant, but if the Inverter or Travelpower can’t start the motor without cutting out from overload, it ain’t going to work!

 

We have a 2.5kw inverter but it struggled to start up our small dyson vacuum cleaner due to the startup current surge.

 

More generally, I would concentrate mostly on getting the best insulation. The roof will be far too hot to touch on a hot sunny day and the less of that heat that gets through to the cabin ceiling, the better. Light coloured paint makes a big difference as well. I’ve always thought about a sprinkler system that pumps canal water over the roof to keep it cool, but never actually tried it.
 

Finally, boating is about calm and relaxation and if you have your engine running all the time it will be a nuisance not only to you, but also to anyone else within earshot. Fine when you are cruising, not fine when you are moored up in the company of other boats or moored outside someone’s house on lovely summer’s day.

All modern AC units run with inverter to power the compressor so no high amp draw on start up ....if they can build Pyramids  sure we can get a AC unit to work lol 

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5 minutes ago, WotEver said:

This is something I've never understood with the aircon industry. If a unit has 2.5kW of cooling power, how come it only draws 1kW? Where does the other 1.5kW come from?

Surely this is just basic heat pump stuff (in reverse)? and why a lot of people are now fitting heat pumps in place of central heating boilers. A good heatpump installation can put about 3kW of heat into a house for each 1kW of electricity that it uses.   An A/C just sends the heat the other way, in fact I believe some can work in either direction.

 

..................Dave

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10 minutes ago, WotEver said:

This is something I've never understood with the aircon industry. If a unit has 2.5kW of cooling power, how come it only draws 1kW? Where does the other 1.5kW come from?

Its green energy ....you need 1kw to run compressor 

 

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