Annex heating choices

[simond]

Do you really think that an oil combi would be cheaper to run than an LPG Combi running off bottles?

Yes.

Of course it would. Oil is 17% cheaper than Natural Gas at the moment. Clearly this might not always be the case, but....

LPG Bulk is very expensive and always priced way ahead of NG and Oil for domestic use; buying it in bottles it is ruinously expensive. You would never use LPG bottles for home heating unless there was no alternative.

It would give peak rate LX a run for its money, cost wise. This is the stuff used by those 'clever*' electric heaters, which are 100% efficient.

So's my toaster, by the way.

Please, remind yourself that Electric heating uses a fuel that costs at least 14p a Kw, oil is around 5p a Kw. The clay cores and German design don't make any difference, they are still 100% efficient. Like my kettle. You may not know that mains electricity is significantly cheaper in Germany than here.

The modulation ratio point is a misconception often thrown into the ring by gas installers with only limited knowledge of heating technology, the training schools only teach the basics (pipes, and how to recognise them); oil boilers have a high water content and can tolerate small loads. An oil boiler easily reaches 90% efficiency. Gas boilers need clever tricks like modulation to get there.

A Worcester Heatslave MkII nozzled down to 12Kw would be my solution, or failing that, last resort, bulk LPG. But never LPG bottles, it'll ruin you. And electric radiators! You'll have to sell the Porsche.

*only if you are a mug, who has forgotten O level physics.


http://www.oftec.org.uk/news_and_press_releases/oil-now-cheaper-than-mains-gas-for-home-heating

 

[vulcancontinental]

I'm not sure I follow the reasoning here.

I followed the link to find the report stating that oil in a three bedroom house (usually10-12KW htg load max but 2-3KW when warm and maintaining comfoprt levels) would be £119 a year cheaper to run or £2.20 a week on average. The new annexe in question is smaller and better insulated than a three bed semi so loads would be much less. LPG is of course much more expensive than either oil or NG.

The £2000+ Worcester you suggest I assume cannot reduce it's output below 12KW compared to a £700 gas boiler and that 12KW would only be necessary during the worse weather conditions and they form a minimal part of the heating season. It simply will have to cycle often and although the Riello burners, which I believe are fitted to some Worcesters can withstand numerous operating cycles; Riello being the owner of Vokera boilers.

I may well, have indeed, forgotten O level physics if I ever understood it but a condensing boiler does not need modulation at all to condense, simply a low return temperature, something attainable on either appliance but much more sustainable on one that can match it's output to the load placed upon it. Being 4 times oversized for the vast majority of the time of the job at hand does not seem a good starting point.

I am ready to be corrected but underline your point that the cost of bottled LPG is horrendous, absolutely horrendously expensive.

If I can add a pet hate of mine regarding the 100% electricity. There is relatively very little fuel lost during the tranmission of any type of gas (or oil) from source to point of use where it is burned at a reasonable efficiency. 49% of our electricity is generated by burning gas in power stations that operate at between 35 and 55% efficiency and of the electricity thus generated a further 38% is lost in transmission between the generator and the property. To say it is an efficient use of energy is only looking at part of the issue.

 

[simond]

I agree with most of your points apart from the cycling one. This does waste a small amount of energy but remember nearly every oil boiler is at least 50% oversized or more for most of the year. That does not significantly impair their efficiency compared to a gas boiler.

If the cycling wastes a lot of energy, where do you suppose that wasted energy goes? And most modern stats only fire 6 times an hour. Oil has a lower dew point too.

Riello are now fitted to all floor standing Worcesters.

 

[simond]

Also worth reminding that Evohome type zoning systems typically run just one or two rads at a time.

Under the forum obsession with range rating and modulation, surely a multiple zone system like Evo would use more energy? Just trying to get the modulation fetishists thinking......

 

[vulcancontinental]

You are making me think here though not agreeing.

First I must express my personal misgivings about published boiler efficiency, I do not see it as representitive of real life useage. Boilers are run constantly at high temp and low temp max load and then at 30% load on a test rig. An EU body in the early 2000's reckoned it lead to a 10-13% overestimation of efficiency, never mind the gross/nett malarky. Another survey in Germany canculated that the system efficiencies were overstated by around 12% simply due to boiler oversizing. Oil I don't know about but gas; each time the boiler cycles there is a tiny pre and post purge of unburnt gas which has passed through the meter, rejected energy, something I'd not heard of before. More cycles, more waste.

I suppose I just like the idea of 'if you need 2KW over an hour, burn 2KW for an hour'. Putting it in in 12 KW bursts with the boiler shutting off seems like accelerating and braking hard to maintain an average 30mph when a set throttle is more efficient.

Not really obsessed or fetishist (I think) just trying to apply my logic to the situation presented.

 

[Agile]

49% of our electricity is generated by burning gas in power stations that operate at between 35 and 55% efficiency and of the electricity thus generated a further 38% is lost in transmission between the generator and the property. To say it is an efficient use of energy is only looking at part of the issue.

I find it hard to believe that 38% of electricity is lost in transmission.

I would have expected about 5-6%.

Can you quote any source of that figure?

Tony

 

[andytw]

http://www2.nationalgrid.com/WorkArea/DownloadAsset.aspx?id=43615

 

[vulcancontinental]

http://electrical-engineering-portal.com/total-losses-in-power-distribution-and-transmission-lines-1

http://electrical-engineering-portal.com/total-losses-in-power-distribution-and-transmission-lines-2


I couldn't quote my source as it was given in a lecture I attended for the company and I always remembered it as it was so huge. Before seeing andytw link I quickly googled and found the above. Will look further later.

 

[whiskeyfrank]

Thanks for all the replies but i have to say ive lost the plot a little of what the best option would be - give me a gearbox and ill tell you the ratios in my head but plumbing and heating is not my thing.

The main house is heated by oil and i cant get oil to the new property as its too far to take the tanker hose, but im guessing that a combi oil boiler with a feed off the main tank is going to be the best option. But have no idea what boiler?

 

[simond]

Since you are in Worcestershire, and since Worcester Bosch will give you a 7 year warranty if certain conditions are followed, I know what I would do.

The oil boiler high water content acts as a buffer store, whereas some modern gas boilers only have around 2 litres of water in them. This lends the oil boiler to a non modulating application.

Also, the oil boiler condenses at a higher water temperature than gas versions, increasing efficiency.

Try comparing current oil and gas SEDBUK efficiency figures and you will see what I mean.

Worcester 12/18ERp System (oil) 91.1%
Worcester 15i System ERp (gas) 88.8%

and for Dan
Intergas 18ov Gas 88.9%

 

[muggles]

Since you are in Worcestershire, and since Worcester Bosch will give you a 7 year warranty if certain conditions are followed, I know what I would do.

The oil boiler high water content acts as a buffer store, whereas some modern gas boilers only have around 2 litres of water in them. This lends the oil boiler to a non modulating application.

Also, the oil boiler condenses at a higher water temperature than gas versions, increasing efficiency.

Try comparing current oil and gas SEDBUK efficiency figures and you will see what I mean.

Worcester 12/18ERp System (oil) 91.1%
Worcester 15i System ERp (gas) 88.8%

and for Dan
Intergas 18ov Gas 88.9%

You seem to have missed the bit where he specified a combi...

 

[simond]

Have I? I thought he wanted a combi?

Here's the combi figures Andrew........

Worcester 24i Junior Greenstar NG Combi 89.1%
Worcester Heatslave MkII Oil 12/18 Combi 89.4%

 

[muggles]

Have I? I thought he wanted a combi?

He does, but in your last post you were talking about system boilers...

You're also out of date. SEDBUK is dead, welcome to ErP, where you'll note that your Heatslave is rated B/A and your Greenstar i (the Junior is also dead) is rated A/A, so a higher efficiency. If you'd like to talk about efficiency figures though, you might be interested to note that at 30% output the Greenstar i ErP LPG is rated at 99.4% efficient (Heatslave 96.8%), and the quoted seasonal efficiency is 94% (Heatslave ErP 91%). Whichever way you look at it, according to WB's own stats, gas beats oil on efficiency on their current models

 

[simond]

Bosch have stated that;

The modulation of oil-fired boilers
The major stumbling block is on the modulation of an oil-fired boiler. Generally speaking, certainly in the UK, a domestic oil-fired boiler typically has a fixed burner, a non-modulated burner.

It simply cycles on and off when it reaches its required temperature.

However in the current proposals, manufacturers would incur a penalty of 7% on the overall efficiency of the boiler.

We consider this notion to be very unfair as we don't see any great difference in efficiency between an on/ off burner and a modulating burner.

As a result we believe, a penalty which takes 7% off the efficiency of, for example, one of our oil-fired boiler will make it difficult, if not impossible, for oil-fired boiler to continue in the UK without changing to a modulating burner.

A modulating burner would cost almost double the price of the present burner used in oil burners and also require an increase in controls complexity.

All of which are relatively untried and tested so as a result we think it could signal the end of oil-fired boiler.

In what is generally a price-sensitive market, the price of an oil-fired boiler would increase significantly, thereby reducing accessibility and meaning homeowners would probably be forced to look for other means of heating their homes.

 

[simond]

It's also worth pointing out that the ERp directive has only changed, in the main, the electrical consumption of boilers by altering the pumps. The claimed efficiency changes are cobblers, because it is just yet another way of measuring.

Just like the MPG figures for cars are pure baloney, laughably created in the EU to give us all an accurate idea of likely consumption, so the SAP, SEDBUK and ERp figures bear little relation to what a customer is likely to achieve. Sticking a coloured label on a product does not make it more efficient, it is just another example of Government led nonsense which only serves to confuse the customer further.

In fact I would go as far to say that if a manufacturer were to have dreamt up this very labelling scheme themselves, they could be prosecuted under the Trades Descriptions Act, for misleading potential purchasers. If you believe it, you are as gullible as the rest of them.

Now where can I recharge my carbon zero electric car? Ferrybridge?