Anybody know if you can run inverters in parallel?

[SB118]

Been pricing up an inverter for a project, and it seems that "economy of scale" doesn't seem to apply here.

600w units go for just over £30, but 1000w units are £70.

If i could get the 600w units to run in parallel, i could save a few quid.

So..... any clever begger out there want to enlighten me?

cheers

 

[SB118]

Correct, 10 points, have a badge.

I'd also have an additional 200w capacity to play with.

And if i CAN run in parallel, i could run 3 600w units and have nearly the same capacity as a pair of 1000w units. 3 x 30 quid vs 2 x 70 quid, now does the query make sense?

edit, and i might learn to type faster too!

 

[SB118]

That would work, but what are you going to spin it with?

This do ya? (just the green bit!)

 

[SB118]

The only thing you can do is divide up your loads so that you can put some on one inverter and the rest on the other. Then the two inverters CAN be hooked up to the same power source.

Just remember that 1000W @ 12V = 831/3 amps. That'll draw a standard car battery down in a little over 21/2 hours (455CCA batery dropping below minimum voltage, not completely dead). And even if your car is running at the time, most cars only run a 35 - 55 Amp alternator. So all you've done is delayed the inevitable.

As I found out the hard way. I was running my 1600W inverter off my truck, which was idling. Now, it has a GM 105A alternator, but with the truck idling the alternator couldn't put out full power. So after running my saw for a couple hours, my truck sputtered to a stop. I thought I'd run out of petrol. Come to find out the battery had gone so flat it didn't have enough power to fire the ignition coil. I had to take the battery out of the truck and carry it back to the garage to put it on the charger (for 24 hours it was so dead).

So please be careful as to what you hook a 1000W inverter up to.

Looks like i'll have to make do with a single 1000w unit then, going to have a half dozen or so batteries, so hopefully they shouldn't run flat overnight. Going to need a bigass charger to get juice into them during the day though, or i could even push a couple of car alternators into the loop, if i could find a way to stop them overcharging the batteries.

 

[SB118]

I'm looking at going "off grid", 6hp Lister engine (got!), 5kw alternator (need), pile-o-batteries & a nice big inverter.

 

[SB118]

Yup, and the Lister engines love the veggie too = free leccy and depending on the heat output i can use the coolant circuit to heat a couple of rooms in the flat, doing away with our portable calor fire = more savings

 

[SB118]

I hope you understand the implications of connecting stuff to something like this, if you are using more than just say a single appliance, you should tie the supply down to physical earth, then you have to make sure its adiquately protected against indirect contact, over current devices are unlikely to be sufficent as the fault current will be limited from such a set up, and you'll likely to need to protect against indirect contact via way of RCD.

Anyway, what you thinking of doing, fitting a changeover switch before your CU, and having it switch between the supply from the grid and a ceeform inlet socket?

I'm planning on using the exsisting earth curcuit, along with a chuffing great big spike into the back yard. Looking for a CU to put along with the genny, coupled with an RCD. Hoping to completly disconect the mains and feed the current CU from the "shed supply" of either the genny or battery stack.

What power consumption are you expecting to need to meet?

Jokester

I'm planing to cover everything in the flat, the only failing point is the electric shower which has a higher load than the rest of the flat put together Might have to leave that one running from the mains until i can sort something out.

 

[SB118]

Capacity is about 350cc i think, dimensions are, umm, BIG (restored engine of similar type, you can see a dog in the background, bit of scale )

For the amount of arsing around to run a set of lights n shi you'd be better off with a cheapo b&q 850 genny i'd think.

 

[SB118]

No worries, the inverter outputed stuff was just to run overnight (fridge, etc), the main generator output would be used during the day. Nice to get somebody who has done similar stuff into the fray

 

[SB118]

Yup, the altenator has a 240v output, looking at a sincro 6kva unit for just over £100 (then allow a bucket load for drivebelt fittings, etc)

 

[SB118]

Is that a dizzy i can see? spits on floor, throws salt over shoulder and kicks the cat

Bolt it to a frame, chuck some gogo juice in and you're laughing, it's not like you couldn't fit two or three 12v alternators into the space, one for the batteries, one to use and one for a charging circuit for anything you happen to be working on ... (i have come to love having a healthy 12v boost with the van in the manky weather!)

 

[SB118]

Although i admire the project from an engineering point of view, i have to wonder how much do you realistically expect to save from this - or is this not the point of it?

I only ask as my experience of utility bills is that they are not really very large, i run a 2 bedroom detached cottage in the middle of nowhere, the boiler runs on oil, and everything else is electric (cooker etc), so i'd imagine my house has to be less economical than a flat in a town? I just cant see that your costs are going to be re-couped, plus you have the added hassle of having to think about what load you are putting on your invertors all the time.

Once i've got the heat exchange side of things sorted, it's an immediate saving of £15/week as we won't need to run our calor gas fire. Not running this fire will also solve a LOT of the damp problems we have here (not nice to wake up and find water running down the windows of both bedrooms) Allow another £10-£15/week for electricity, maybe more when it's piddling down with rain all week and we use the tumble drier more.

Minimum saving of £25/week, the engine will be paid for in under a month, 5 weeks to cover the alternator (just grabbed an 8kva unit), allow another 5-6 weeks to pay off the inverter, then i'm hopefully putting money in the bank (or at least not taking so much out) Should all be done in under 4 months.

Most painful part is looking at the price difference between true sinewave and "modified" sinewave inverters (prolly cheaper to get a couple of bigass UPS units and daisychain a load of deep soak batteries to them, only things that will need higher end power of an evening will be the telly and the fridge, hopefully the lights will be happy with cheapo inverter electric. It's a steep learning curve, i've already ordered the flowers for when she gets hacked off with the noise, not done any soundproofing yet!)

 

[SB118]

Thanks for the tips, collant system heating will be when i get the next engine (she'll give in to shut me up in the end ), this one is aircooled, so i need to either knock up and exhaust heatexchanger or just dip a big chunk of exhaust into a big tank of water and pump that through some radiators in the flat.

It's going into a concrete shed, but i'm going to pad out the interior to pacify the locals (it's great telling 'em to bogoff until they show up with the local council and a noise meter )

I'm still planning on running the genny during the day for all the household stuff, and then falling back on the inverter based kit for the evenings (fridge, telly, router and lappy chargers, looking to minimise all the current use), if we do all the domestic stuff during the day, we have to spend more quality time together in the evenings

 

[SB118]

Holy hell i wish i lived nearer to the guy selling me the alternator, going to be £33.50 + vat to get it delvered, damn thing is 45 kilos

 

[SB118]

Veg oil fumes are less "smelly" than diesel, it doesn't choke you as much. I've got a social club (with all day cafe) on one side and deli with friers two door in the other direction.

The noise is fixable, i'm wondering how much oil i have to burn before anybody actually notices!

 

[SB118]

Soft start?

Been looking at more inverters on the bay, some of them are listed as "soft start", umm, wassat?

Been nosing in my CU and the flat runs 1 x 6A, 3 x 32A & 1 x 40A trips, so i need to find out which 32A circuit runs which areas of the flat, been considering a handful of inverters, but using one per circuit (thinking big unit for kitchen/utility room, one for living area, then one for the bedrooms, HOPEFULLY the circuits will be broken down that way!, aslong as the cowboys that built this place didn't share neutrals and other clever things )

Of to that highstreet electronics place (lets be honest, you've seen their prices, i don't see how they can call them a "competitor" ) later to get my hands on a litle pluggin item called a "kill-a-watt", useful for measuring the kwh consumption of whatever item is plugged into it, ie, total running power of all the telly kit, or the fridge, or the utility room, etc)

So far so good. Nearly killed myself getting Dave out of the van though, not the lightest of things!