A Well Designed Boiler

[GeorgeNewman]

Well, it's gone wrong again! After 30 years service, my Worcester Heaslave 2+ has suffered its second fault. Came home to find no hot water and no heating.

Called my service engineer, who quickly diagnosed a failed Gas Flow Control Valve. Pleasingly some years ago he suggested, because the boiler was getting on a bit, that I keep a spares inventory of the main replaceable components - pump, thermostats, piezo igniter, mechanical timer, etc., etc., and including of course the gas valve - a Honeywell V4600C 1029 Soft Start.

As a result of this he had it up, running and tested within a couple of hours, with no delay obtaining spares. He had a bit of a battle undoing the valve from the burner feed pipe (factory installed, with jointing compound), but otherwise a straighforward piece of work.

Moral of this story - if you have an old boiler, get in a few of the essential components as spares. Saves time, and you don't have to hang around at home feeling chilly!

 

[mysteryman]

Back to the question about boiler efficiency. You can read it straight off a flue gas analyser. Every serviceman will have to have one soon, and the certificates to show he knows how to use it.

 

[Stamina]

the Worcester Heatslave 2+ is 65% seasonal efficiency?

 

[mickyg]

Back to the question about boiler efficiency. You can read it straight off a flue gas analyser. Every serviceman will have to have one soon, and the certificates to show he knows how to use it.

you can read combustion efficiency from an fga not boiler efficiency.

 

[mysteryman]

I thought it would give overall boiler efficiency as well, knowing the air and flue gas temperature, and oxygen content plus type of fuel?

 

[mickyg]

nope

 

[Stamina]

I thought it would give overall boiler efficiency as well, knowing the air and flue gas temperature, and oxygen content plus type of fuel?

burner efficiency and boiler efficiency are entirely different

 

[Agile]

I thought it would give overall boiler efficiency as well, knowing the air and flue gas temperature, and oxygen content plus type of fuel?

That might explain why some boiler manufacturer's seem to quite their boilers as having efficiencies over 100% !

The Ravenheap boiler with a Band B construction and a Band A rating ONLY actually achieves an efficiency within Band A when on LPG. But they still claim its a Band A on NG as well!

Tony

 

[D_Hailsham]

That might explain why some boiler manufacturer's seem to quite their boilers as having efficiencies over 100% !

That is due to the different method of calculating efficiency used in the UK and on the continent.

The Ravenheap boiler with a Band B construction and a Band A rating ONLY actually achieves an efficiency within Band A when on LPG. But they still claim its a Band A on NG as well!

Which model boiler are you thinking of?

Incidentally, the use of Band A, Band B etc has been dropped; percentages are used instead. A boiler has to be over 90% efficient if the formula given in SAP2005 is used but only over 88% efficient if the new formula given in SAP 2009 is used. Boiler manufacturers have to say which method was used.

 

[Agile]

Its totally confusing to customers when different manufacturers quote efficiencies using different criteria.

So is quoting DHW flow rates at 30°C when most quote the lower figure at 35°C.

Tony

 

[muggles]

It's an industry-wide issue though isn't it...look at radiators, there doesn't seem to be a common standard for quoting outputs at a given flow and return temp, so manufacturers can use 85/75, 80/70, 75/65 etc etc, and with different target room temperatures, making comparisons and sizing more difficult. On that subject it's about time they got with the times and started quoting outputs at 20ºC differential temperatures rather than the usual 10.

 

[D_Hailsham]

It's an industry-wide issue though isn't it...look at radiators, there doesn't seem to be a common standard for quoting outputs

Oh yes there is! It's called BS EN 442 which specifies flow temp =75C, Return temp = 65C and Room temp =20C. All reputable manufacturers have their radiators tested by approved independent laboratories.

The output with a 20C differential can be calculated, provided you know what the flow and return temperatures are.

 

[muggles]

Then I stand corrected, but I'm sure I've seen rads quoted at other F/R temps recently.

And yes, I know they can be calculated but it's a load of extra work we shouldn't really have to do, why not go for a nice standard high efficiency 60/40 table, or at least provide it as a supplement.

 

[mehran]

stelrad quote their outputs with for Δ 50 ° C

 

[D_Hailsham]

stelrad quote their outputs with for Δ 50 ° C

That's correct for BS EN442

The mean water temperature is 70°C {(75+65)/2} and the room temperature is 20°C, so ΔT =70-20 = 50°C.