Pv solar install the inverter in loft or garage

zeupater

larkim wrote: »

Don - sometimes I wonder why you bother to carry on arguing. Then again, sometimes I do argue continually just for the sake of it, so I suppose I can understand it!

I would have thought that the situation, without the technicalities, is fairly readily summed up:-
- inverters work better cooler than hotter
- inverters will generally last longer in cooler rather than hotter conditions
- inverters (it seems) automatically de-rate themselves when they detect it getting "too" hot (i.e. >40degC ambient it seems)
- lofts, in general as an area directly exposed to solar radiation more than the rest of the house, may well get hotter than most other areas of the house in the summer; potentially exceeding 40degC
- garages (or any other room in a house, perhaps with an exception of a conservatory) are likely, on average, to have a cooler ambient temperature than the loft
- therefore garages make more sense than lofts to install inverters purely when weighed up on an ambient temperature basis
- there are other issues such as cable run lengths which might need to be considered, but they probably don't outweigh the de-rating effect of an inverter running in high ambient temperatures

I'm not entirely sure what there is to argue about?

Matt

Hi Matt

Agree with the summary ....

One other point which seems to have been missed is that a loft with increased insulation at rafter level will generally become hotter than one without due to insulating the thermal mass of the house from the air temperature in the loft.

For example, we have >500mm of loft insulation which made a considerable difference to the upstairs temperatures during summer when compared to when there was the standard 4" fitted. Another consideration is that massively increasing the insulation around loft tanks reduces the heatsink effect of cold water storage too, our ~1/2 tonne of cold water now stays cold whereas it used to be what could be classified as slightly 'mild' in high summer. As previously posted, we have ~200sqm of loft space, therefore our array has very little overall shading/cooling effect with loft temperatures above 40C being noted regularly since we have owned the house ....

HTH
Z

larkim

Loft insulation is one of those things that I really need to sort one of these days. Having said that, you draw out a salient point for me - one of the things I love about our 1905-built, single skin, high ceiling'ed house is that in the summer when it is hot outside, it is actually cooler inside.

We used to live in a 1990s, cavity wall, double glazed, properly insulated house, and in the summer we just couldn't get rid of the heat upstairs - all of the windows upstairs were "awning windows", so the rising heat simply couldn't escape in sufficient volumes.

A combination of a badly insulated house, plus nice sash windows that allow an upward flow of air from one room to the next, means it is nice and cool in the summer.

If I did have a "hot" house, it would be nice to have the option to lift (easily) the loft insulation to remove its effect in the summer, if possible.

However, we're in winter at the moment, and all of the above means we're no doubt using more gas than we really should!!

Matt

Martyn1981

larkim wrote: »

Loft insulation is one of those things that I really need to sort one of these days. Having said that, you draw out a salient point for me - one of the things I love about our 1905-built, single skin, high ceiling'ed house is that in the summer when it is hot outside, it is actually cooler inside.

If I did have a "hot" house, it would be nice to have the option to lift (easily) the loft insulation to remove its effect in the summer, if possible.

However, we're in winter at the moment, and all of the above means we're no doubt using more gas than we really should!!

Matt

Matt, possible solution, which I did for 2 years, was to pop the loft hatch up and swivel 45 degrees (the hatch, not me), so heat could escape up. Only works in late evening when the loft is cooling down, but allows a lot of hot air from upstairs to escape.

Longer term solution was to convert the loft. Which I did myself (back when my back worked), though I did commission a staircase, and had to hire in muscle to help lift the 7by2 joists up. Then I insulated against the slates with 75mm fibreglass. This stopped the bulk of the solar gain. Next I fitted a Velux, and that's when it gets interesting. If the house gets hot (April to Sept) wifey or I 'crack' the Velux, i.e. leave it open about 1 inch. Doesn't sound like much, but this creates a chimney effect, as the hot air leaves the loft, it sucks in cool air downstairs and creates a strong(ish) draft. Obviously can open further, but 1 inch prevents any rain coming in, so can leave it. Also prevents cats jumping out - seriously, this did happen!

PV now covers 90% of ESE roof so presumably less hot in future, but as stated insulation reduced that dramatically already.

Z - 200m2 bloody hell, where do you live, the O2? My 1930's semi loft is 40m2 (if I'm generous). Took me nearly a month to stain, wax, cut and install the T&G for my loft (was pulling short hours by then), your place would be like the Forth Bridge!

Mart.

zeupater

larkim wrote: »

Loft insulation is one of those things that I really need to sort one of these days. ...

Hi

In our case the extra loft insulation has cooled the upstairs at night by reducing the heat transfer from the loft into the house through a warm ceiling ......

I know what you mean about sash windows .... for bedroom cooling in the summer, simply opening both the top&bottom of the window creates a pretty efficient ventilation system ...

Z

zeupater

Martyn1981 wrote: »

... Z - 200m2 bloody hell, where do you live, the O2? My 1930's semi loft is 40m2 (if I'm generous). Took me nearly a month to stain, wax, cut and install the T&G for my loft (was pulling short hours by then), your place would be like the Forth Bridge! ...

... and yet the whole place is being heated by a logburner on tickover at the moment, GCH has only been used for around 18 days so far this winter, most of that being this month and no, according to our high-tech Galilean thermometer on the other side of the room, it's not cold .... all we need at this time of year is some solar gain and the log burner can go for days without being fired-up too.

Regarding the property being like the Forth Bridge, you're not far wrong, you try cleaning all of these pesky window pains (deliberate word substitution)...

Z

don0301

larkim wrote: »

Don - sometimes I wonder why you bother to carry on arguing. Then again, sometimes I do argue continually just for the sake of it, so I suppose I can understand it!

I would have thought that the situation, without the technicalities, is fairly readily summed up:-
- inverters work better cooler than hotter

do they? within normal operating conditions?

- inverters will generally last longer in cooler rather than hotter conditions

really? proof? within normal operating conditions?

- inverters (it seems) automatically de-rate themselves when they detect it getting "too" hot (i.e. >40degC ambient it seems)

and how often does that happen?

- lofts, in general as an area directly exposed to solar radiation more than the rest of the house, may well get hotter than most other areas of the house in the summer; potentially exceeding 40degC

wow, more 'facts'

- garages (or any other room in a house, perhaps with an exception of a conservatory) are likely, on average, to have a cooler ambient temperature than the loft

wow, more 'facts'

- therefore garages make more sense than lofts to install inverters purely when weighed up on an ambient temperature basis

your logic is inescapable!!!!!

- there are other issues such as cable run lengths which might need to be considered, but they probably don't outweigh the de-rating effect of an inverter running in high ambient temperatures


I'm not entirely sure what there is to argue about?

no, you probably don't......

Matt

I've stated my view, counter arguments of pearlers like 'errhenius equation' (still rofl) and garages may be cooler than a loft are well......

larkim

Don

Not sure why you persist with this. I caveated all of what I said with "it seems" and "may" precisely because I agree with you that there is not a blanket rule which can apply to each and every situation. Clearly all houses, garages, lofts, under-the-stairs, basements, cloakrooms, meter cupboards etc have different characteristics which make them more or less suitable locations for inverters.

Surely its blindingly obvious that if you have the choice to locate a piece of electronic equipment somewhere cooler (assuming no other compromises) then that is the better place to locate it? If there is even only a small chance of an inverter beginning to de-rate its output at some point during the year, the surely you more than anyone (given your enthusiasm for the output that you are getting) would appreciate squeezing a little more juice out of the system? I know I would.

I personally don't understand in the slightest how inverters work. I don't understand arrhenius equations at all (I'd never heard of them before this week), I don't know how to calculate cable losses, and I've no idea what temperature my loft gets up to in the summer.

But I do know that the manufacturers describe themselves that the ambient temperature may trigger de-rating, I understand that de-rating means you get less out of your inverter (partly to help maintain longeivity of the inverter), I know I've got a black roof and that the loft feels hotter than the rest of my house (including my out-building garage) in the summer (I don't know whether it will be the same now that I have PV panels shading most of my roof).

In short, I can't for the life of me work out what you are arguing (let alone why!)? Are you saying that inverters don't reduce output when its over a certain temp? Are you saying that most lofts are cooler (in summer) than the rest of people's houses? Are you saying that most people's garages are hotter than their loft?

Remember, I'm a PV supporter here - I'm not "nay-sayer" or opponent of either the tech or the current subsidising regime as I'm benefiting from it myself. I've also got an inverter in the loft, and never even thought about the temperature issues. But now I've learnt a little I'm better informed. I wouldn't be able to change the location of the inverter due to the layout of my house anyway.

As I said, I like a good argument as much as anyone, and all I want to do is offer you some advice that you should either clearly state what position you are arguing for, and then provide clear, cogent counter-arguments why other people are wrong. From my perspective, you seem to be failing to do this, but I'm more than willing to engage in a healthy discussion if you want to clarify things a little.

Matt

don0301

larkim wrote: »

Don

Not sure why you persist with this. I caveated all of what I said with "it seems" and "may" precisely because I agree with you that there is not a blanket rule which can apply to each and every situation. Clearly all houses, garages, lofts, under-the-stairs, basements, cloakrooms, meter cupboards etc have different characteristics which make them more or less suitable locations for inverters.

agreed.

Surely its blindingly obvious that if you have the choice to locate a piece of electronic equipment somewhere cooler (assuming no other compromises) then that is the better place to locate it?

read your first paragraph again.....

cooler when? and for how long?

If there is even only a small chance of an inverter beginning to de-rate its output at some point during the year, the surely you more than anyone (given your enthusiasm for the output that you are getting) would appreciate squeezing a little more juice out of the system? I know I would.

the point is about failure, not 'squeezing more juice'....

no i dont agree. for example my inverter gets pretty close to max now, or are you cherry picking the time of year?

and again, I'll point out no-one has proved that an inverter within normal operating temperature is so badly affected.

I personally don't understand in the slightest how inverters work. I don't understand arrhenius equations at all (I'd never heard of them before this week), I don't know how to calculate cable losses, and I've no idea what temperature my loft gets up to in the summer.

But I do know that the manufacturers describe themselves that the ambient temperature may trigger de-rating, I understand that de-rating means you get less out of your inverter (partly to help maintain longeivity of the inverter), I know I've got a black roof and that the loft feels hotter than the rest of my house (including my out-building garage) in the summer (I don't know whether it will be the same now that I have PV panels shading most of my roof).

at last, something i can agree on.

In short, I can't for the life of me work out what you are arguing (let alone why!)? Are you saying that inverters don't reduce output when its over a certain temp? Are you saying that most lofts are cooler (in summer) than the rest of people's houses? Are you saying that most people's garages are hotter than their loft?

Remember, I'm a PV supporter here - I'm not "nay-sayer" or opponent of either the tech or the current subsidising regime as I'm benefiting from it myself. I've also got an inverter in the loft, and never even thought about the temperature issues. But now I've learnt a little I'm better informed. I wouldn't be able to change the location of the inverter due to the layout of my house anyway.

As I said, I like a good argument as much as anyone, and all I want to do is offer you some advice that you should either clearly state what position you are arguing for, and then provide clear, cogent counter-arguments why other people are wrong. From my perspective, you seem to be failing to do this, but I'm more than willing to engage in a healthy discussion if you want to clarify things a little.

Matt

I'm saying no-one has proved an inverter working within it's operating temp. window is more likely to fail in the loft than elsewhere.

Dave_Fowler

don0301 wrote: »

I'm saying no-one has proved an inverter working within it's operating temp. window is more likely to fail in the loft than elsewhere.

I absolutely agree with you, Don. In fact I wouldn't want to put my inverter in the garage because of the mice and squirrels which frequent there.

I think what most people are saying is that they believe an average loft is more likely to be hotter than an average garage and that the temperature could be above the derating temperature and the manufacturers only derate the inverters to minimise damage to the circuit.

Perhaps we should drop this argument until we have some actual figures for our lofts / garages taken during the forthcoming (hoped for) summer.

Dave F

larkim

We agree!!

I thought the whole point of this discussion was to highlight that inverter manufacturers themselves recommend avoiding a situation where de-rating occurs, and to recognise that de-rating in several situations, one of which is where the ambient temp prevents the inverter from cooling itself sufficiently.

You'll notice that I jumped into this discussion early on because I had, in the past, sought objective commentary on "hot" components, as I was fed up with people saying "ooh, that CPU was too hot to touch, it must be damaging the components" as I couldn't see why hand temperature mattered for CPU operations. It seemed to me that no-one looked for the specification which said, for example, all an AMD Athlon XP2100+ should be operated at xdegC or cooler, rather than "don't let CPUs burn your hand, that's bad".

Some people's lofts (not all, otherwise there'd be something of a blanket ban on it!) do get very hot in the summer (and equally very cold in the winter), and this might push inverters outside of their normal operating range. "Some" and "might". So therefore, something to think about when siting your inverter should be "am I likely to have a very hot loft in the summer" and "is there a nice, cool, convenient location for my inverter". If the answer to both is "yes", then why wouldn't you choose the nice cool alternative.

If you can't, like me, then you simply put the inverter in the loft anyway and accept that there is some risk (not large, and for me completely unquantified) that your inverter might have some hot days of lower output due to the fact that the inverter itself will force de-rating to happen in certain circumstances.

Matt