R
Ray Stafford
0k = -298c point at which all molecules stop moving so no thermal energy. Theoretically coldest temp possible
I thought that absolute zero was - 273.15 C?
Discuss under sized boiler ??? in the Plumbing Jobs | The Job-board area at PlumbersForums.net
0k = -298c point at which all molecules stop moving so no thermal energy. Theoretically coldest temp possible
I thought that absolute zero was - 273.15 C?
He taught me everything I know Paul, & then some !!!Bugger me Erm have you been knocking about with Chris Watkins
Perhaps a few more of you should also pay heed to what he has to say cos from where I am sitting there are some big miss understandings on boiler / system load sizing.He taught me everything I know Paul, & then some !!!
Not so I am afraid happy & it is a common misconception. If you look at modern boilers they only modulate down so far, to around 8kWs depending on their size (I can't remember the exact radio). Added to this the internal controls which have the boiler firing full burn for around five cycles when they are first turned on, presumably as it knows it has to put heat into the system. Only then does it look at the return water temp to decide the level of modulation, if this is <20 degC Δt it may stay off & they have anti-cycling routines built-in which can hold the boiler off for 20 mins once the returning water is up to temperature.But Chris correct me if I am wrong modern boilers will try and match the load connect they do't just bang it at full power, do they, so over size
massively by the size of the will just cost more to buy, or is there something more finite going on. I don't know that anyone here would size boiler like this:
Boiler size to be fitted 45Kwh, that isn't gong to happen Chris, is it??? Most people will do like you say, but what sort of calculation is that, rule of thumb, I don't think
over sizing can do any harm, big old lofty house, big rads, long heat up time, big boiler rules OK???
He taught me everything I know Paul, & then some !!!
OL stop it :blush5:sorry chris for dropping your name,trying to think of a clever chap and your name came up first
Most boilers can turn down on a 4:1 ratio so a 28kw could wind down to a minimum of about 7kw. The ideal vogue has a 7:1 ratio .
This is my pet hate with combis. Whack a 40kw in for hot water then the boiler cycles like mad on heating as the min output is 10kw!
U can set the load on some of the better boilers.
The new Vokeras have a 1:10 modulation
From Vokera
The Unica i range boasts an enviable modulation ratio of 10: 1, this high ratio enables the boiler output to be reduced to as little as 10%. For example the 28kW Unica i can reduce its output to just 2.8kW, so when the home only requires 3kW, the boiler will modulate itself down to 3kW. Boilers with an inferior ratio, for example 4:1 would only reduce to 7kW, resulting in wasteful ON/OFF cycling and reduced efficiency. A high modulation ratio can significantly reduce wasteful on/off cycles, which in turn, will increase component longevity and helps to ensure stable domestic hot water temperatures.
In simple terms; 10:1 modulation = better fuel efficiency, increased component longevity, optimal comfort.
So there you go, this is why boilers shouldn't be oversized.
Oh, but I still wouldn't fit a Vokera..
I worked for Hamworthy 40 years back on the Dual fuel Rotary Cup burners up to 20,000,000 Bthus in old money, flame length up to 15ft long, turn-down about 30 to 1, in the days before GSR and Corgi when men were men, the noise from the burner caused most of my tinnitus 99dB+ , we used 50 gallon oil barrels as the outer core for the silencers on the main air intake, a client was posh if they had silencers fitted, now you would get drummed off the plant, at hamworthy we perfected an excess oxygen cell, it controlled excess oxygen in the flue gases perfectly, the burner air damper had a small slave damper on it this was operated by the cell, you guys with your 25 kws gas boiler meeeow.
Now you're talking my language.
Thought I loathed and despised rotary cup burners with a deep and abiding passion, was glad to see my last one go a few years back.
Alright you condescending old git!
Go and learn how the remote control for your video recorder works!
:83:
Alright you condescending old git!
Go and learn how the remote control for your video recorder works!
:83:
Haven't seen one for years but I would bet a lot of money there a load still going in India at lot when out there in the 60s, a real engineering job. I worked as Area Manager for Selectos for 3 year went over to Dublin to service potato crisp oil heaters they were the size of a London bus, we would fire it from one end and the flame would be about 2ft in dia and 12-15ft long oil only in Dublin there was no gas then.... lads don't know there born, used a fork lift truck to take the burner off it was that heavy.
Still a few rotary cups going at sea, last ship i was on had 2 down firing running on 360cst fuel, the ignitors used 4.5 gal nozzles to get the things going., they were a major pain for the cups getting clagged up with crud especialy if they were firing for a prolonged period (i.e when you most needed them). I also sailed on a ship with the same burners but firing from the bottom, never had any issues so can only put it down to the extra heat they were exposed to.
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