Generator for 190m2 house - All ideas please

GeorgieVa

Hi all,

We are looking for a budget friendly generator for a 190m2 detached house.

To keep mechanical aeration system going, as well as the water well pump and kitchen.

All ideas welcome

Irish Steve

You need to write down all the items that you have to run, and then add to that list the items it would be nice to run, and then determine how much power they draw. Once you have that list, you can get an idea of the capacity you need the generator to supply. There needs to be a % uplift to cover the startup surge of the essentials, some items can take quite a bit of extra current to kick start them, and after that, decide how much of the "nice to have" items will be running at the same time, and that's then a guide to the sort of capacity you need. You then need to determine how long you might need to be able to run for in the event of a failure of the incoming supply, while there's no way to be sure, previous experience will hopefully give you an idea.

It's unlikely that you will be able to look at renewable power for the sort of load I think you will end up with, and the realistic option will most likely be diesel powered, while there are petrol powered generators available, they tend to be relatively low power, and run at 3000 rpm, so noisier than a diesel set, and also petrol gen sets are much dearer to run than diesel, as you can legitimately use green diesel. If going diesel, try to get one that runs at 1500 rpm, they are quieter and less stressed mechanically. If you're urban, it would be better to get one in an acoustic enclosure to reduce the noise, and that will also help protect the unit when it's outdoors. Electric start is almost essential for diesel, due to the compression ratio, unless you are in to serious fitness training. Battery start will also mean a trickle charger to ensure that the battery remains viable to start the rig. Ideally, it needs to be run regularly, even if not on load, to keep everthing reliable.

Your next decision will be how it is connected to the house, there are some very specific rules about connection, to protect workers outside of your house if the generator is live, and the choices are manual switching or automatic change over, which will depend on the size, and the degree of automation, it's totally feasible to have it set up to automatically start when the incoming supply fails, then switch over to generator, and shut down when the supply returns, with options to allow a "settle" period to avoid nuisance switching, I have mine set up that it doesn't even start until the incoming has been off for 10 seconds, and then it monitors the supply and doesn't drop the generator until the supply has been back on for a minute.

After that, it's down to buying new or used, and that's down to what's available, and how quickly, and without knowing the size you end up with, that's not something I can comment on yet.

Mike2006

Hi,

I have a generator on a changeover switch (manual).
It is a 3.6kW petrol generator which cost ~€300.
It covers the following:
Lights, circulation pump for heating (oil boiler), TVs, charging of devices, electric gates etc.. and a little bit more. Importantly, it keeps the fridge and freezer going also.

It will not power the oven or hob and with everything else on it would struggle to boil a kettle on top of it..

It is only used a handful of times a year but very handy when it is needed.

I have the MCBs marked in the main board for the 'generator' circuits and turn the rest off to avoid overloading and tripping out the generator.

Couple of tips: run it under load for 30 mins every 3 months to ensure that it will start when you need it. Mine seems to be sensitive to 'dead' petrol so I keep it low and top it up with fresh petrol when I need it.

Most important: Fit an under/over voltage relay to the output of the generator. Cheaper generators will not have automatic voltage regulation and if the regulator fails, it will feed your main board with 'dirty' voltage and will kill lots of appliances across the house. I fit one after this happened to a neighbour of mine... Blew varistors rated at 300VAC, blew sky box, laptop PSUs, portable phones, bell transformer, and lots more.... I would not risk hooking up a 'cheap' generator to my house without this protection in place.

Mike

Pasteur.

If you put it into the distribution board it might save you on DSO supply under/overvoltage as
well ,if it ever happened

Not a fan of cheap generators hooked up to installations

Pasteur.

Another issue with the small generators is fault disconnection and trip times when hooked up to a house

It's mad to hook these things up to a house imo

alan4cult

Question:

Where does one put the changeover switch i.e. where does one connect the generator feed ultimately? Is it after the main fuse on the tails to the main board or do you put it closer to the main board.

How does the earthing need to be done at this point, as the earth will no longer be bonded to the neutral?

Pasteur.

alan4cult wrote: »

Question:

Where does one put the changeover switch i.e. where does one connect the generator feed ultimately? Is it after the main fuse on the tails to the main board or do you put it closer to the main board.

How does the earthing need to be done at this point, as the earth will no longer be bonded to the neutral?

After a main protective device I would say, that would be a main fuse on old houses

Be risky otherwise, the new meter cabinets will have one fitted too


Earthing I think the recommended is only to break one pole for changeover so I don't think there's a problem

Maybe a spike and an RCD for fault disconnection of a small generator

I'm not too well up someone else probably knows more

Irish Steve

Concur with the thoughts about smaller generators, the biggest issue is petrol generators that are governed by a device in the airflow of the cooling, they are not exactly sensitive, and even the slightly better centrifugal regulators tend to be a bit of a lottery, so voltage and frequency stability can be a problem, as smaller units may not have a separate voltage regulation board, they rely on the speed being right to keep the voltage right.

The worst issue I came across with smaller petrol units is when they are used on devices that take a significant start current, and the set bogs down as it can't provide the current, and at that point, the voltage and frequency goes haywire, which as mentioned above, can cause significant problems to some devices. Things like compressors on freezers can take a surprising load on start up. On an older petrol unit we had at one time, the trick was to start the generator, and then get the freezer running with nothing else connected, and once it was running, put it into fast freeze, which meant it didn't switch out on the thermostat, so no load surges from that device. Not a viable plan if the power is out for many hours, but it was a way to use a small gen set for short term problems. For long faults, if the freezer is well down to temperature, if it's not opened, it can be left for a number of hours without affecting the contents, then brought down to temperature again by using the same technique to start the compressor.

I'm lucky, the gen set I have here came in over 20 years ago originally to provide back up power for a (pre server days) computer system that lived on a special area in the garage, so it's a lot larger than the normal domestic unit, (3 phase 30 Kva, driven by a big 6 cylinder 5 Ltr air cooled diesel engine), so I can run just about anything in the house without having to worry about what that's doing to the gen set.

Due to the nature of it, there's a specific control panel that monitors everything, (voltage, current, frequency, engine oil pressure, engine temperature) and if it goes out of spec, the load is dropped and the set shuts down. If ESB goes off, it waits a few seconds to ensure that it's not just a system switch over, then automatically starts the unit and brings it on line, then when ESB returns, it waits for a minute to make sure it's staying on, then shuts down and restores ESB. The panel is completely parameter driven, so the limits can be set by the user, and it can be remotely monitored and operated by a remote PC, (or smart phone on the newer versions), which makes for a very flexible system. The switch over is managed by the panel using mechanically interlocked contactors, ensuring that only one contactor can be closed at any time. Needs a trickle charger to keep the battery fully charged, but that's easy enough to set up.

I kept it when the computers went as it meant I had backup power for emergency flood prevention pumps that we had to install, and it's done exactly what is needed over the years.
Back in the day, there were no issues with "domestic" or "commercial", and it was pre the new rules about what can and can't be done, so once ESB were happy with what I was planning, it was easy enough to install, though ESB's area manager no less came over to sign it off and prove that there was no risk to their operatives when it was running. Now, for a domestic installation, it all has to be done by a registered electrician, which can get interesting, choose your electrician with care for something like this, to be sure that you get all the right information and operational procedures after it's up and running.

You only do something like this once, so do it right, and it will give you the back up and peace of mind you expect it to. Ours certainly has done so.