Electrical Question

[shanson 0]

My Brain hurts! (thats not the question!)

 

I'm thinking of buying a 2KW inverter to run tools and a water heater.

 

So at it's maximum it's outputting around 8amps at 240Volts.

 

What I'm trying to work out is how many AMPS it would draw from my batteries and whether a generator would be a better (read cheaper!) option?

 

Cheers

 

SHANE

[Absolution 7]

A good inverter will be roughly 94% efficient so to get 2kW output you'll need to be able to supply 2.128kW at the input.

 

Then all you need to know is: Volts x Amps = Watts

 

..so you'll need roughly 177A from your batteries. Unless you have a shitload of batteries they'll be flat before the water even gets warm. The next problem becomes charging the batteries so you'll probably need the genset anyway.

 

If I were you I'd buy a califont and some battery powered tools with a few spare batteries.

[shanson 0]

Thanks Fineline.

 

SHANE

[wheels 543]

And to add, unless you can afford one of those very expensive very efficient inverters, you aremore than likely going to be using one with only an 80% efficiency. So the problem is compounded.

The other trick is to pull up along side a boat with a genset/inverter and one of the spring lines needs to be a camoflage power lead.

[Guest]

The hotwater cylinders that are available now that use 240v and/or engine heat exchanger are an option too.

If you are running your engine every day to charge batteries, you get enough hot water for the day for free.

If you are alongside a berth or gin palace the 240v gives hot showers all day long.

Someone on here was extolling the virtue of these things awhile ago.

They are a bit more pricey than a gas califont, but don't suck down the gas bottle and you don't have flames and exhaust gases inside the boat (definite positive).

[shanson 0]

yea It's on of those cylinders that I've got, however my heat exchanger only has two circuits, so does this mean the HW cylinder replaces the existing heat exchanger or should I install a BYPASS valve then route the return back through the engines heat exchanger?

 

I think the next best option is a small Gene, I've got the space in the aft cabin which can be well insultated to reduce noise.

 

Cheers

 

SHANE

[wheels 543]

The hot water usually comes off a different point again Shane. You hopefully will find a couple of 1/2" screw bungs in the head somewhere that it normally connects too.

If you are happy with Petrol, I highly recommend the inverter gensets. They rev to the load. So no load, they idle. Small load and they ramp up a little and if you turn on something big, they ramo up to full noise. This makes them very economical to run as they only only use the fuel related to load.

If you go diesel, which I like as it tends to be a little safer fuel wise, then they will run fullnoise all the time. So with any that run full noise, you want to load them up and work them so as you are getting as much from them as you can. Yes that means they use a little more fuel, but the difference is not that great. So run the hot water heater and a charger and maybe fridge/freezer or whatever.

Also remember, if you ever want to run a Microwave, you need three times the Microwaves wattage to start it. So a 600W microwave will need a genset capable of peak supplying 1800W. Once it starts, it will come back to 600W.

[shanson 0]

Thanks Wheels

 

Looking at the specification of the cylinder it draws 4.5Kw!

 

This puts a genset out of my price range, not to mention size!

 

So its back to a gas califont I think!

 

SHANE

[wheels 543]

Yikes, that's huge. You sure??? Nah that can't be right. At 230V that's over 20 amps. Even home cylinders aren't that big.

I can't think it being a 12 or 24V element. you would have to have huge battery cables going to the thing.

Can the element be removed?? (hmmm, seem to have a faint memory you telling me something about not being able to). Anyway if it could and it should be able to, then a much smaller element could be fitted.

[shanson 0]

yea that what I thought, Here's a section from the manual...

 

 

Raritan Water Heaters ....or 17200203 with

4500 watt/ 240V heating element). ....

 

It does heat up REALLY quick! The element can be removed, originally is was 120V, can you get a 12v element?

 

SHANE

[shanson 0]

Ahh I see what's happened.

 

There is a 4.5kw element available, I assume that I have the standard one which is 1.25kw!

 

Which is a little more realistic! I'll check next time I'm on a pontoon.

 

SHANE

[wheels 543]

Arrr yes, makes more sense.

[Grinna 2]

The other option is to go with a diesel water heater like the ones Eberspacher make. They do air heaters and water heaters .... the latter ones have the advantage of heating the water up and using that to then heat air which is blown around the cabin (if you desire it).

 

http://www.eberspacher.com/products/wat ... nic-4.html

 

They use about 0.5 litres of diesel per hour.

 

Just a thought.

[shanson 0]

Thanks Grinna

 

That would be sweet, however I'm what you might call "Fiscally Challenged"! at the moment. (Well at every moment!)

 

 

SHANE

[Grinna 2]

That would be sweet, however I'm what you might call "Fiscally Challenged"! at the moment. (Well at every moment!)

 

I would have thought the diesel heater option is at least comparable in cost to an electric water heater + genset (if not cheaper)?

[Guest]

Do the engine powered heaters put the heat exchanger in the freshwater circuit for the engine as this will be hotter once up to temperature?

You could plumb it in circuit before the seawater cooling coil to pull the best heat out of it.

Is yours set up like this at present Shanson?

[wheels 543]

Grinna, Shane already has the cylinder in the boat. You would be correct if he was buying new.

Slacko, you have to take the cylinder heat exchange unit from the engine, not the engine heat exchanger circuit. it is important to get the engine to temperature ASAP, so you don't want to mess with that part of the circuit. Most engines have additional plumbing points on either the head or the block that you connect such a unit into.

[shanson 0]

Wheels

 

I've found the connections into the engine. The flow is after the water pump and before the thermostat and the return is around the end of the engines heat exchanger.

 

Just have to check my HW cylinder now!

 

Cheers

 

SHANE

[wheels 543]

Cool. I have heaps of plumbing fittings in brass and SST between my shed here and at work, so yell if you need anything or need a hand.

[Guest]

Surely the freshwater hose from the engine to the seawater cooling coil is after the thermostat, so no hot water will flow through the circuit until after the engine is up to temperature. I'm only assuming this as this is how a car radiator circuit works.