voltage optimisation development - are you looking for a more reliable unit?

[Gavin A]

We've got a problem with a VO unit we've fitted, and after speaking with all the manufacturers of full house domestic VO units (ie not Vphase), we've realised that they're all far from ideal, and this is the sort of glitch we're going to be coming across time and again if we keep installing these units.

Essentially the problem is a house where the voltage swings so much that while we measured it at 242V on 2 occasions prior to fitting the VO unit, it actually turns out that it spends a fair amount of the time in the evenings hovering around the 230-233V range on the incoming side. The apex unit we've fitted is a fixed ratio VO unit, as are all the other offerings (Voltis, and VO4Home), with an 18V voltage reduction. It switches to bypass at 232V incoming, meaning that when the incoming voltage slips below 232V the actual voltage in the house swings immediately from 216V to 231V, and then back again as soon as the voltage rises above 232V.

This is happening several times an hour at the worst points, causing the lights to change noticably, and the cooker heat to vary by ~10% etc, as well as meaning the unit isn't going to last too long due to the number of switching cycles it's doing per hour... needless to say the customer isn't best pleased.

So I've rung around all the manufacturers tech departments, the best offering seems to be VO4Home that allows the installer to set the voltage reduction to 12V, which would give 228 as the switching point... but they're only a 60amp rated unit with no bypass capability, so I can imagine we could be in trouble on Christmas day as it's an electric cooker and fairly big house, which I'd expect would draw enough to trip a 60amp MCB under peak load conditions. Voltis allow you to adjust the incoming voltage to as low as 227V, but it's fixed ratio 20V reduction (possibly 9%, I couldn't quite get a straight answer on that) reduction, meaning that the outgoing voltage would be 207V. Voltis say this is within the regs limits, which it just about is, however the voltage at the far end of a ring circuit would be several volts below this limit, and therefore outside of the limits appliances are rated for... as well as it not actually being an efficient voltage point for most appliances.


Potential Solution
So I've been back to Apex, and have essentially been told that their engineers have a solution on the test bed, but are struggling to convince management to bring it to market as the management don't understand the problem, and don't think there'd be a market for a product that was a little more expensive but actually worked properly.

The solution they've come up with is for a unit with 3 tappings of 6, 12 and 18 V reduction, and automatic 0V switching between the tappings when the incoming voltage drops below certain set points (which could potentially be installer adjustable).

This unit would be rated at 40amp continuous, 60 amp for half an hour, then would bypass upto 100amps, so would be a whole house unit that splits the incoming tails.

Essentially the point with this is to come up with a unit that is suitable for virtually all situations to minimise the potential for any call backs from customers such as here where the voltage swing on the grid is greater than usual, and end up with a unit that can basically cope with anything thrown at it, and actually maintain the voltage at somewhere in the optimal region instead of potentially ending up with the voltage significantly lower than optimal for much of the time.

Costings
The current none adjustable Apex unit comes in around £250-275+vat.
Depending on volumes, we think the auto switching 3 tapping unit would come in at something like £300-325+ vat trade prices, possibly less with bulk discounts.

For comparison Voltis reckoned they'd be around £327, and VO4Home significantly more than that, but maybe less via CEF with our trade discount, so the APex unit would still be pretty much price competitive with these units.

Obviously they're all more expensive than the Vphase unit, but personally I think the whole house unit is a much better solution than just pulling a few low load circuits out and running them through an 8 / 20 amp unit.


Expressions of interest sought
The Apex guys have asked me to get some expressions of interest from any companies who think they'd be interested in offering the improved VO unit even if it did cost an additional £50 or so per unit.

They've got a meeting with management on Thursday, and basically just want some evidence to take with them to back up their views that they should develop this improved unit and demonstrate that there would be a viable market for this unit.

If you're interested could you please tick the appropriate box on the survey, and if you want an email notification if / when the product is going to be available, please leave you email addy on a post or via PM. It'd be useful to also get an idea of roughly how many units you might expect to fit per month if anyone wants to volunteer that info

I'm also going to ask them about the potential for discount rates for buying direct in pallet quantities eg 5-8, as apart from anything else we've had some issues with these units getting damaged in the standard post due to their uneven weight distribution. Apex don't really want to deal direct, but I suspect it'd be worth it for them and us in those sort of quantities, which I;d think could equate to a monthly order level for many of us.






PS - I ain't getting commission for this, I'm just acting out of frustration that a better product is sitting on a test bed and we can't get access to it because Apex management don't think there's a market for it.

 

[Gavin A]

Just to add a bit more info on my thinking re paying a bit more for a unit that will always work...

Essentially these units only make sense to the customers if they're installed at relatively low installation fees / margins of eg £150-250 a unit.

This is just about doable if there's minimal need for site surveys, and the call back rate for them is in the 1% region, but not if you need to either take time installing a proper voltage recorder to check the voltage range over a period of days, or risk call backs in the range of 10-20% of cases because the unit is going into bypass to often and causing the lights to dim and brighten noticeably too frequently.

I'm not suggesting that it's sensible to be installing in situations where you know the grid voltage is usually around 230V - obviously it isn't, I'm more talking about protecting ourselves from call backs for situations where the grid voltage can vary from 245+ to under 230, which is impossible to know about during a brief site survey. In these situations the customer will still benefit from the lower voltages at the higher incoming voltages, but just won't have to cope with sudden 20V voltage swings at times of peak load (which is usually going to be early evening, just when it's most annoying for them).

To my mind it's worth paying £50 extra up front to reduce the call back rate down towards the 1% range, otherwise we'll rapidly see that the call backs and occasional replacement of entire units are going to mean we probably end up losing money overall, whereas we can build the extra £50 per unit into our upfront costings for the customer, or even partially absorb them because of he improved reliability - especially if we can order direct and reduce the postage costs etc.

 

[Gavin A]

not a vast amount of interest then?

 

[sedgy34]

ive got a voltis HD had no problems so im happy

 

[Marvo]

I'm not an expert on these domestic voltage optimization units although I've had several brushes with the industrial variety. I think there's just too many problems to make them an attractive option for someone looking to save money.

Firstly the installation can be complicated. In order to prevent the thing frequently running in bypass mode you need to split up the CU so it doesn't have circuits like the shower and cooker running through it. This might involve a complete new CU in certain cases.

Secondly a high percentage of domestic load doesn't benefit from voltage optimisation. Obviously if you drop the voltage it just means the kettle runs for longer to make the water boil or the immersion heater also runs longer to reach it's set temperature on the thermostat. These are obvious cases but there's also more subtle cases such as airconditioning or air source heat pumps compressors will run hotter due to reduced voltage. This effects the superheat characteristics of the unit and results in reduced overall efficiency. The air con will take longer to bring the room temp down meaning it's running time is longer, likewise a heat pump would need to run longer to raise the water temperature.

Also it's very difficult to conclusively prove how much money you're saving with voltage optimisation. The domestic load is very organic, appliances are added and removed very frequently and usage patterns are not constant. It's not like installing solar pv where the exact generation can be metered and extrapolated into a financial savings figure. This leads to suspicion on behalf of potential customers and also fantastical or misleading claims by some of the manufacturers.

So I would answer your opening question with another question. Wouldn't retrofitting or redesigning the VO unit to reduce lighting flicker just be re-arranging the deckchairs on the Titanic so to speak?

 

[Gavin A]

there's loads of other threads to discuss the merits or otherwise of VO units.

Let's just assume there are customers out there who want the things fitted, and that this thread is aimed at them, and trying to come up with better units that will actually do the job as advertised while minimising the potential adverse side effects of possible extreme under voltage, and / or regular 18-20V voltage swings as the unit bypasses while the incoming voltage hovers around the lower voltage limit.


fwiw though, the units do offer additional benefits even on resistive load heating circuits in situations where solar PV systems have been fitted, as they effectively spread that load out over a 10% longer period, so 10% more of it can be powered directly from the PV generation on site instead of being imported.

I fully recognise the issues with these units and difficulty calculating savings, and we're only fitting them in the houses of high energy users with relatively high incoming voltage levels where in our judgement we believe savings are likely to make it worthwhile. They're certainly not something we'd recommend for everyone.