Boiler Woes - repair or replace?

dfarry

I would appreciate any initial advice as I am struggling to decide the best way forward.

Basically our 13 year old Vaillant 242 Combi boiler has a number of problems and I am now considering whether it is uneconomical to repair. However the costs associated with fitting a new condensing boiler are making my decision difficult.

The problems are as follows:-

About 18 months ago the black plastic secondary heat exchanger started leaking, this was replaced with a smaller chromed unit. Although the hot water temperature dial has scaled up and cannot be moved (another though minor problem) the water temperature and flow rate were constant and quite acceptable.

Over the past few months the water temperature has fluctuated, also in heating water the boiler seems to light and then shortly after stop then start again - therefore the water temperature is at best luke warm. This did seem to improve for a few weeks but now other problems have surfaced.

The water temperature continues to be very low but also I noticed that the water pressure had increased. I therefore released some water using the right side pressure release valve. This released the water but then seemed to stick in place and drained much of the water out of the system. I managed to stem the flow of water by gently tapping the valve tap spindle but the the water still trickles from the outside drainpipe from the valve. I'm not sure if it should still be fitted but there is a braided hose (with a inline valve) that allows me to refill the boiler with fresh water and I have needed to do this.

In addition to the constant flow of water outside (which appears quite rusty and is filling a watering can each day) the pressure within the boiler still seems to be rising, even when the boiler is not in use. This pressure increase happens over a day or two and will rise to over 2 bar until I manually release water from the pressure valve.

It has been suggested to me that the secondary heat exchanger may have been scaled, to cause the initial fluctuation in temperature but may now be leaking internally to cause I assume water to pass from the mains supply into the heating system and increase the pressure in the system. I assume that the pressure release valve is also faulty to constantly let the water escape unless it is designed to do this (though it has never done so before).

The temperature selector being scaled is less of a problem, however the earache I am getting from the females in the house who are bathing in luke warm water means I need to get this fixed asap

However, I don't want to throw money at the boiler if it is beyond economical repair, just replacing the secondary heat exchanger 18 months ago was costly enough and has apparently not lasted. For replacement, I know that new condensing boilers such as the Vaillant EcoTec 824 and 831 condensing boilers are not far short of £800-£900 incl. retail, plus the fitting etc... This may not be correct, but I have been told that these high efficiency boilers can also be unreliable and expensive to maintain despite the considerable fuel efficiency savings - so I am concerned about that too.

I'd welcome you comments and thoughts, basically what I am saying is I need to get this fixed as quickly and cheaply as possible, any idea's please fellow MSE'ers?

Russ66

Hi,

I'm unable to help you, but these guys helped solve a problem I had last year. :T

http://www.diynot.com/forums/viewforum.php?f=7

HTH

dfarry

Yes they are very helpful and have replied to similar posts by me.... I was just looking for extra opinions especially those from general customers I guess.

Thanks for your help/suggestion though.

billycasper_2

Hi there, just a thought but the new condensing boilers will have to have a 22mm pipe from your gas meter not a 15mm. If your boiler is 13yrs old then you may have the 15mm pipe. i only mention this because it comes into the cost of fitting the boiler. It may not be a simple "swap"
I'd recommend getting some quotes on a new boiler and let the finances make the decision

dfarry

Yup it is 15mm and is Tee'd off our gas cooker supply (which is currently not being used as the oven/hob is electric)

Steve_PS

You should not use your pressure relief valve to dump pressure if at all possible. It is actually a safety valve and will release system pressure if it rises above 3bar. Using it raises a rubber seal off it's seat and they rarely re seal completely, especially with all the crude circulating around a CH system. Use a hose pipe on a drain down point, usually on radiator valves. You are correct, safety valves should not 'leak'. If your pressure is continually rising it could be a leak from mains pressure through your plate heat exchanger into your pressurised system as you have assumed. FYI I have had an Ideal Icos condensing boiler fitted for 5 years now without once going wrong...touch wood. Dont touch a Ravenheat, cheap and nasty B&Q rubbish.

dfarry

Thanks Steve...yes the PRV remains a problem and problem for the reasons you have mentioned...the pressure is still on the increase though.

I have found a local fitter (away at the moment) but he should be around to fix us up, in the next week. :T

bob_a_builder

Hi there, just a thought but the new condensing boilers will have to have a 22mm pipe from your gas meter not a 15mm

Does that only apply to Condensing Combi boilers and not to normal condensing boilers ? (just checking for my own info)

billycasper_2

bob_a_builder wrote:

Does that only apply to Condensing Combi boilers and not to normal condensing boilers ?

I think and i'm sure someone will correct me if i'm wrong but it applies to all new boilers.
i Had a normal combi boiler fitted and had to have the 22ml pipe

Razor

Actually it doesn't matter which sort of boiler fitted, gas pipe sizing is down to how powerful the boiler is. usually measured in kw and how far from the meter it is combined with how many bends are in the pipe, often a 24kw combi can be run on 15mm pipe, anything larger is normally 22mm but if u want a 40kw combi then u may need a 28mm pipe!! System boilers tend to have lower outputs so can run small pipes more often, however if your gaspipe is 15mm from the meter BEFORE it splits at the cooker it is unlikely to be man enough.