Odd Bolier/Heating problem (not DIY)

Angilion

First up - I'm not looking for DIY advice on my boiler. I'd rather pay an expert than risk killing myself and/or others by making a mistake. I'm making this post to try to get information which will let me spend my money more efficiently.

I'm thinking that there are 3 possibilities:

i) It's nothing to do with the boiler, so I can fix it myself. Free.
ii) It's a simple fault with the boiler that requires no parts or a cheap part. Hire an engineer on a parts and labour basis, cost to me about £70.
iii) Could be various things, some expensive. Hire a company on a flat fee basis, cost to me £165.

My rather old boiler (Vokera Maxin 24e) doesn't have precise temperature control. The control for the central heating is simply a marked dial (as is the control for hot water temperature).

If I have the heating on more than about 40%, it's fine. It'll run until I turn it off, no problems.

If I have the heating on less than about 40%, the boiler will lock out after some time, at least a couple of hours.

The boiler does not indicate the reason for a lockout, so I have nothing to go on there.

Pressure is fine - 1.2 bar when cold, manual states 1 to 1.5 bar is the right range. Pressure rises to about 2.3 bar in use, which is also fine. Besides, if it was overpressure, it would happen when the boiler was on higher, not lower. Ditto for overheating.

There isn't any emergency venting outside (which occurs at 3 bar, according to the manual).

The boiler restarts perfectly when I press the lockout reset button. This is true immediately after lockout (I happened to be in the kitchen one time when it locked out). This also makes me think it isn't overheating.

I'm prompted to ask because the last time I got someone out on a £165 flat fee, the faulty component was a switch that cost pennies and took under a minute to replace. I have the same switches at work, so I could have got one for nothing. If it's something similar, I'd obviously be better off paying parts and labour rather than a flat fee, which would save me £100 and still have the job done by an engineer.

keystone

TBH it could be ANY one of these:

Fan Venturi
Dirty main heat exchanger
Air Pressure switch/tubes
Gas Valve
Ignition control module
Boiler overheating.

I'd get someone in on a no fix, no fee basis although you'll prolly have to pay the call-out in any event.

As a matter of interest was the switch he replaced previously the domestic microswitch?

Cheers

roger196

Get the manufacturers instructions ( about 50 pages) from their website. At the back there are fault finding guides. This should give you guideance as to the likley fault. Don't try the repair yourself but get a competent gas bloke in to fix that.
When did you last have boiler serviced. Was the inhibitor level checked. When the inhibitor has been in a number of years it gets less efficient. Boiler will scale up inside leaving to overheating and lockout. Boiler descaler eg Sentinel X 200 is readily available from www.screwfix.com part no 43140 or B&Q etc.

keystone

roger196 wrote: »

Get the manufacturers instructions ( about 50 pages) from their website. At the back there are fault finding guides. This should give you guideance as to the likley fault. Don't try the repair yourself but get a competent gas bloke in to fix that.

Sorry a quick question if I may? If you have to get someone in anyway whats the point wasting a whole stack of a valuable Sunday trying to fault find yourself?

Cheers

Angilion

roger196 wrote: »

Get the manufacturers instructions ( about 50 pages) from their website. At the back there are fault finding guides. This should give you guideance as to the likley fault. Don't try the repair yourself but get a competent gas bloke in to fix that.

I have a full service manual, complete with fault-finding flowcharts. What I don't have is the knowledge. Flowcharts are no substitute for that.

When did you last have boiler serviced. Was the inhibitor level checked. When the inhibitor has been in a number of years it gets less efficient. Boiler will scale up inside leaving to overheating and lockout. Boiler descaler eg Sentinel X 200 is readily available from www.screwfix.com part no 43140 or B&Q etc.

The boiler was serviced a few months ago, along with the latest repair. I have no idea whether they checked the inhibitor. As for overheating...why would that occur at low temperature settings and not at high temperature settings?

keystone

Angilion wrote: »

I have a full service manual, complete with fault-finding flowcharts. What I don't have is the knowledge. Flowcharts are no substitute for that.

Yep and even if you had the inclination to do it the man you will call out will do it all over anyway.

Your problem with this beastie lies somewhere in the areas I highlighted in my initial reply. It isn't possible to remote diagnose. You need to get someone hands on it IMO.

Cheers

Angilion

keystone wrote: »

TBH it could be ANY one of these:

Fan Venturi
Dirty main heat exchanger
Air Pressure switch/tubes
Gas Valve
Ignition control module
Boiler overheating.

I'd get someone in on a no fix, no fee basis although you'll prolly have to pay the call-out in any event.

It's looking like I'd be better playing it safe with the £165 flat fee. That covers me for parts and labour up to £600. If I recall correctly, British Gas flat fee is no fix no fee. Obviously, they make their profit on it because most faults cost far less than £165 to fix.

As a matter of interest was the switch he replaced previously the domestic microswitch?

Cheers

Yes, it was. He also gave me half a dozen for my work, which was nice of him because my employement is set up so bizarrely that I can't have them delivered by post. I have to call a mobile engineer to deliver them. Seriously, some guy has to drive maybe 100 miles to deliver a microswitch. There are about 400 of them in machines at work, so it would make far more sense to just post me some.

gas4you

If it only does it when the temp is low, there is a chance that it could simply be the minimum burner pressure needs adjusting.

heating-eng

keystone response was spot on but i would just get bg to do it and if its a boiler that tends to be breaking down quite a lot .then i would get on the 3star cover .others offer the same sort of cover now as well

Angilion

heating-eng wrote: »

keystone response was spot on but i would just get bg to do it and if its a boiler that tends to be breaking down quite a lot .then i would get on the 3star cover .others offer the same sort of cover now as well

Yes, but it's a matter of betting how often the boiler will fail. The cheapest Homecare service from BG (they changed the name from 3 star cover a while ago) is £11 a month and that doesn't cover much.

I might buy a new boiler. It might be cheaper in the long run. This one was cheap 12 years ago. A good new one would break down less and use less gas, so it might work out cheaper over time.

I am unwilling to scrap this boiler for an unknown fault that might be trivial to repair, but I have to consider the fact that it's breaking down more often. Repairs to it over the next few years might cost me more than a new boiler.

I was hoping that someone would say "Oh yeah, that's always caused by X. An engineer can fix it in half an hour."