Power inverters

Is anyone using a power inverter to run a heat pump? I'm exploring different options but due to limited space I'm trying to eliminate a generator. I have twin perkins T6 354.4's and also am looking at a pair of belt driven generators. Any info in this regard would be appreciated

What size is the "heat pump". The knee jerk reaction is "it wont work". Inverters are great for small loads and intermittent large loads, not so much for large continous loads.

10000 btu. Runs on a 15amp circuit so will spike on startup but settle down to around 1200 watts running

No

Well, my boat and many like it is set up so I could run the reverse cycle A/C system from its Freedom 20 inverter/charger. But it would run down my batteries very quickly. Just like trying to run the A/C in the summer from the inverter.

My 12,000 BTU unit uses 12 amps A/C to run. That will take about 120 amps DC to power the inverter. That will kill my 200 AH house battery in about an hour.

You would need a 2,000 watt inverter and at least 800 amp hours of batteries to do this for even a few hours. And then you have to recharge the 400 amphours that you withdrew from your battery. That will take 6 hours of genset running time. Why bother, run the genset if you have one. If not then consider a propane or diesel heater.

David

Thanks for your input. I'll have to go to plan "B"

UNDERWAY , with a large enough alternator it would not be any problem (besides mounting the alt).

Buses use 12V 250A or 24V 300A alts that are available used , rebuilt.

The problem cones when NOT powering the alt , fine if you are dockside and plug in the power hose.

At 120A (12v) draw most battsets wont last 1 hour.

Prior to all the suggestions I was planning on installing a 4000w inverter connected to three deep cycle batteries. I was told that there are high output alternators that work at low rpm as well and planned one for each engine. These would be in addition to alternators presently installed which would only be used for the 12v supply.
When trolling only one engine is used and was hoping the alternator would be able to keep up. I guess I won't know until I get it together.

It will be expensive and difficult to do what you propose to power an inverter from a large frame alternator underway.

You will need a big alternator, an external regulator and an engine mounting system. You can certainly install a 200+ amp alternator that will do what you want. Even at trolling speeds- 1,000 rpm, this alternator will put out enough at 2.5:1 pulley ratio to do the job: page69-97EHDinformation

But why not install a $300-800 bus heater and connect it to your boat's cooling system to give you heat undeway. Heatercraft makes them in all sizes.

David

djmarchand said:

It will be expensive and difficult to do what you propose to power an inverter from a large frame alternator underway.

You will need a big alternator, an external regulator and an engine mounting system. You can certainly install a 200+ amp alternator that will do what you want. Even at trolling speeds- 1,000 rpm, this alternator will put out enough at 2.5:1 pulley ratio to do the job: page69-97EHDinformation

But why not install a $300-800 bus heater and connect it to your boat's cooling system to give you heat undeway. Heatercraft makes them in all sizes.

David

Click to expand...

Wow...did I miss that one......I thought he meant for cooling....good suggestion.

Hands down a bus heater is the ticket for heat....not simple but in the long run compared to the electrical demands and costs....nothing really is.....

For dual use on the heat pump....can be done....but get ready to super size a lot of wiring, etc....

It's not for heating its for air conditioning. 90 degree heat and windless days are the issue with humidity at near 100 percent.
The engines idle at 700 and my sons and I can manufacture the mounting hardware needed. I have the electrical panel and the transfer switch. Two 8D deep cycle 240 amp hour each should do it and the alternator I'm looking at has the voltage regulator built in.

Be careful!!

If you want to put out 120 A to drive your inverter while your engine is running at 700 rpm you will need a greater pulley ratio than is typical- at least 3:1 and not the more typical 2.5:1. This will require a bigger pulley on the flywheel than your existing alternator. And it may over speed the alternator at cruising engine rpms. Most small frame alternators are rated to 10,000 max and the big Balmar one referenced is rated at 6,500 rpm max.

Don't even think about an alternator with an internal regulator. Those use a constant voltage regulator that are typically set at 13.5 V. You need an external regulator to push enough current to do what you want.

And don't skimp on the alternator. Look at the Balmar's cold and hot ratings that was attached to my previous posting. You need one that will put out 120 A at 2,100 alternator rpm while hot. Most truck alternators like the Leece Nevilles won't stand up to that kind of continuous low speed load. You need lots of cooling, heavy windings and heavy diodes to do that.

David

GE-Series | Electrodyne | Brushless Automotive Alternators

40SI High Output Brushless Heavy Duty Alternator | 240, 275, 300 Amp Alternators | Delco Remy | Delco Remy

Alternator Cross Reference

MEPS // Products

50 DN Heavy Duty Transit/Coach Alternator | Brushless Alternator | Delco Remy | Delco Remy

High Output Alternators manufactured in the USA by ZENA, Incorporated


Several possibilites as sources are above. No recommendation.

You MUST pay attention:
-- to the OUTPUT CURVE of any alternator you consider so there is sufficient current at the rpm of the engine that you want to run/cruise at. Some are designed to produce a quite large output at lower alternator rpm than others.
--pay attention to the ratio between the engine and the alternator or you may destroy/overspeed the alternator. Not just the trolling rpm.
--pay attention to the maximum speed of the alternator rotor
--pay attention to cooling.
--mounting must be rock solid
--belt drive must be big enough to transmit the HP from the engine to the alternator. Small sheaves and belts will not do the job
--consider the effect on the engine front cranksahft bearing if belt drive is your means of drive
-- D Marchand points should be taken seriously
It's possible but all must be considered or not only will the installation fail but you could cause engine damage.


--this is just a suggestion but two dedicated alternators to drive the heat pump, one alt, on each engine may be a possibility also. It adds some complication in many ways yet it splits the load to the two engines instead of a very heavy load on the one. Front crankshaft loading.

--

Thank you all for your input. I am a couple of months away from doing this so I have time for research.
Thanks again and safe boating
Gord

Seems like the cost to do all this could be approaching that of an inexpensive generator. I know there are debates on using portable generators, but I have plenty of friends who use the small Honda gennies to run AC (taking reasonable CO precautions).

Carolena:

The Delco Remy 40SI referenced by C Lectric above lists for more than $2000 and sells for above $1,000. So does the Balmar that I referenced. Either of these will do the job but the D-R's 8,000 rpm max speed makes it just work at a 3:1 pulley ratio on the Perkins, whereas the Balmar won't.

A good regulator will cost $300+. A two groove pulley or serpentine belt system will cost hundreds. You will need a bank of batteries to dampen DC useage. Total cost- at least $2,000.

I think that a Honda EU2000 is the best solution for the OP's needs.

David

It's possible, but not with off the shelf retail knowledge. You need somebody who understands the whole thing front to back and those people are rare if its not you yourself. Advisable?

For a charter, I would knee jerk and say no. Once reliability, duty cycle and serviceability are considered, I think it would be hands down against such a thing. I would go with a high reliability generator without question.

Once there, I might consider adding the high output alternators very correctly sized belts and mounting, while considering belt speeds at both trolling and max speeds. You can then look at some specialty level inverters more than capable of handling the startup loads, with an appropriately sized battery bank to buffer this kind of high amperage.

Ultimately that would arrive at the kind of reliability to typically run with the generator, but be able to fall back on the inverter if needed. Charter boats need to do one thing right and that's to leave the dock without giving the guests the slightest hint at any kind of problem. I don't believe you always have the luxury of being able to wait and schedule a specialist around the specialists schedule.

Oh...and electronics is very much in my comfort zone and I'm otherwise predisposed to want to do it. I'm just seasoned enough to understand the true value of practicality.

I would like to thank all of you for your input. Originally I was thinking generator and due to the added noise and vibration thought I would explore the inverter route. Fish get spooked from vibration. But since then and considering the information that everyone has supplied I am now thinking generator once again. The cost was not the issue only performance and reliability once I was satisfied the system would work.

A small generator that can carry the running load of the aircon tied together with a Victron inverter with the load assist feature to help with the LR (startup) of the compressor would be ideal for your situation.

You're trolling so you're already sending vibrations into the water. What's a little genset vibe added to the mix?

Just my uneducated opinion but I think there's a difference between sharp noises and vibrations vs. the constant RPM drone of main or genset engines. The sharp noises can be more alarming whereas the engines fade in and out with distance.

Just my free opinion...but worth every penny.

I run a 16K btu ac unit off a Leece Neville 220 alternator on my charter boat. The inverter and alternator totaled about $1K and you could spend $300 or more on installation materials. Works great at cruising speeds, fuctions at 1,200 rpm, and not below a 1,000 rpm. The big issue for long term use at slower engine speeds is adequate cooling of the alternator. My 16K btu unit requires between 100 and 120 amps at 14 volts. This alternator is only running the ac unit, everthing else runs off the primary alternator.

Ted

The other option is to purchase an auto refit air cond unit as used in hot rods and custom cars.

These are quite powerful probably double what a single boat unit would put out.

With a place to blow the hot air about $1400 should do it.

A sea water to freon heat exchanger is not that expensive and an electric sea water pump would work just fine.

If its cooling underway only , this probably would be the cheapest , easiest option.

Why make electric , convert the electric to run a pump, when a belt will run a far bigger pump OTS>

Fred has a good idea. It won't be any harder to fabricate a mount for a compressor than a big alternator. The seawater condenser may be a bit tricky. But if you are handy you could cobble one together with a length of cupronickel tubing inside copper tubing. Or take one from a defunct marine unit.

David

While an automotive system is certainly worth exploring and would likely work ok at cruising rpm, you're still only going to spin the compressor at 1/4 to 1/2 the rpm needed when trolling. My guess is that the automotive compressor may seem much more powerful when cruising, sitting idling at a traffic light, not so much. Also, the inside of a sedan is much smaller than the cabin of a charter fishing boat.

Ted

Well, I'm back to the generator again after all the comments and suggestions. This is where I began almost 3 years ago. Since I have twin diesels the Kubota generator will work ok other than access for maintenance. We are planning on building a special hoist that attaches to the deck to set in and lift out this unit. I changed the rear deck to 1/4" aluminum plate last year so mounting the hoist is a nonissue. We will make disconnects for the exhaust, raw water and electrical easily accessible so this process will be fairly simple and fast. Again, thank you all for your input. It was what I needed to hear.
I'll try and keep you posted as things go.
Gord

Footnote

At anchor we run our forward stateroom A/C, set to 68F, on a 5KW inverter at night off 600 amps of Li-ion batteries. It is probably at 30% duty cycle at night. Also, the frig and whatever else is on during the night. Depleted batteries by morning. You can do this with Li-Ion batteries for 3000 cycles. Cant prove it because we'll never get there but the electric car literature seems to back it up. The OP was trying to do it during a hot day which is a whole nother story and everybodies' advice was right on.

Cost of the batteries is 2800 plus freight and inverter circa 400. I used a cheap one (square wave) but no AC device seems to notice. I even tried it on the salon unit and it started and ran just fine, not simultaneously with forward of course. The big units of 10000 watts would probably run both but then you are talking serious draws and the genset better be running or on dockside power, so no point.

It appears that the battery banks are the weak link in all this but still have to recharge them from shore, alternator, solar etc. This is more work and monitoring than it may be worth for my application. The Kubota gen set will be going in and with 7kw I'll have plenty of power.