by Perry525 »
Mon Apr 05, 2010 3:01 pm
When your boiler was made, it was probably sold as 80% efficient, a modern boiler will be sold as about 90 to 95%. The problem here is that none of these boilers is checked by any one, they are merely self certified by the manufacturer. The so called improvements, are basically that some of the heat that would otherwise be lost, is captured and recycled.....but, this only happens during start up and the benefit disappears once the system is up to running temperature.
Thermocouples are made of copper, they are subject to a lot of heat (being in the flames) and the copper does evaporate. What he says is rubbish.
Some boilers, fitted with cast iron heat exchangers go on for over thirty years and as long as spares are available I advise people to keep them, as they are better made than today's.
The servicing of a boiler is like anything else, it depends on how well it was made and how hard and how long it works each year.
The pipe to and from the hot water tank on a gravity feed system should be at least 28mm.
How well it will work depends on how many bends and what temperature, how well insulated, the internal friction being the main consideration.
Gravity systems are old technology, they were OK 50-70 years ago when people had more time, today a pumped system produces hot water so much quicker. Switching the pipe work so that the hot tank is part of the central heating system will resolve this for you at little to no cost.
It is true that whenever a boiler gives up, its a disaster, but modern systems, usually fail on their exhaust/heat exchanger fan, or computer control system. Older ones are so much simpler.
If you merely T off the existing central heating with a 22mm pipe and a tank thermostat, for a few pounds you will immediately see and feel the difference. If later you decide to change the boiler, then the existing system will work.
Your existing boiler is a floor level on the ground floor? The cold water expansion tank is in the loft, the difference in feet between the bottom of the boiler and the surface of the water in the expansion tank is about 18 to 20 feet?
Most modern pressurized boilers are expected to run at one bar or thereabouts, this equals a column of water 30 feet high, they do run at half a bar = 15 feet. From this you can see that there is very little difference between what you have and a new boiler. By all means measure the height of the water in your system and compare it with the boiler of your choice.