old crap boiler - help please!

[johnnyrod]

How to get more efficiency from an old boiler? I know we have some good plumbers on here, so any words of advice would be appreciated. It goes like this...

Just moved into a new and quite large house. It's got an old Potterton boiler from about 1985, gas-fired floor-mounted jobby of something like 25kW though not too sure (it can modulate around 75-100% of rated power). Rads all over the place (no TRVs), all bled and all get hot. When it's running the house does get warm, but by God it's eating gas. The hot water bit is switched off due to a duff cylinder stat (using an immersion heater instead).

I know the best answer is to replace this with a new boiler but that's a job for summertime. For now how can I optimise its efficiency? I've got a temperature probe and am going to start by setting all the rads to a 20C inlet/oulet difference. What (else) can I do? Is this a good start?

Many thanks in advance

uncover the radiators. put foil down the back of them. thats it i guess? dont know how you would increase the boiler efficiency.

Not a plumber but a few thoughts....

1) Daft question, but I'm a southerner. What's the water hardness up there? If you're in a hard water area then there's a chance that the heat exchanger pipes in the boiler are furred up and impacting the ability of the boiler to heat the water. Our old boiler was so bad it used to take 24 hrs to heat up the hot water cylinder, the new boiler takes 20minutes. If you can still get the bits you can replace the exchanger rather than the whole boiler.

2) What's the inside of the pump like? The vanes slowly clog up with the crap that ends up in the water. The more clogged up the vanes, the less water gets moved about, typical symptom of this is that the boiler stops burning quite quickly as the water in the boiler is getting too hot as it isn't being moved through fast enough.

[johnnyrod]

1) hard as hell, it's got a load of papers about some compound that's been added to it to prevent corrosion etc. but who knows when of course.

2) again no idea, it's fairly quiet (though was noisy when heating the HW tank) and is on setting 2 out of 3 for speed (well-known red Grundfoss jobby) so I guess if need be I can crank it up to 3. I presume I'd see a large temp rise of the water across the boiler if the flow wqas low? Not had any problems with it shutting off that I know of. Boiler water temp is on setting 2 of 6 which I think is about 62C according to the manual.

[embee]

This is probably not in the realms of what you want to do, but I'll throw it in FWIW.

I too have an old Potterton, same era as yours. Next year it'll get replaced but in the meantime I did a few simple mods last year.

I zoned the upstairs/downstairs heating, got all the Honeywell stuff off ebay around half retail prices. Zone valves for up/down, and used wireless programmable room stats (CMT927). With a decent programmer (ST9400C) the combination allows me to effectively get up to 7 or so break points per day (on/off settings, plus dropping stat demand temp down to 5C effectively turns it off). That made quite a big reduction in last winter's gas bill.

Possibly a simpler and reasonably cost effective alternative is to use Pegler programmable TRVs . I installed a couple for a friend and they seem very reliable (Pegler is well respected). Effectively you get individual room programming. I found the programming a bit clumsy, but just follow the instructions and it works. You do need to change to a TRV valve body so some draining required. They come as either a complete TRV+programmable head or just a head to fit to an existing TRV, also in horizontal or vertical orientation, check the part details carefully before ordering.

Most cost effective thing is loft insulation, by a mile.

Make sure your loft insulation is at least 250mm thick. That will save a fortune, and you can get a grant to do it.

yeah turn up the pump speed, turn down the roomstat if you have one gravity hot water maybe?, if so totally inefficient and the only real saving would be to fit a new boiler, you could powerflush the system rads etc, but costs £.
How much is the gas bill per month? mines £22, but i'm a tight git , yeah, make sure you is on a internet dual fuel account, is way cheaper, paying by direct debit.