Boiler Woes

[neil]

Hi Guys

I'm having a bit of a nightmare with my heating system and need help! Symptoms are lots of hydrogen in the loft radiator and lots of bubbling through the various radiators as the system warms up but little bleeding needed in those radiators (?), so after a few checks it appears that the system 'pumps over' AFTER the system goes off and this last bit is a relatively new event (< year). Other oddities are the thermocouple appears to have a short-circuit to the front case (but it all still works and nothing ever seems to be live), the cover has possible smoke and abrasion marks in proximity to the capillary which definitely have what look like spark erosion marks! - this worries me! A google appears to indicate that this boiler may not have an overrun (unless it is a standard feature of the gas valve?) so I'm unsure why it is now 'pumping over' when off - from heat soak and steam splurge?, or is it a overrun going wrong, but why now? It is probably this pumping over that is causing the system to rot and gas but how much damage will have been done, I assume the pumping over has long since removed the fernox protection as the F+E has a nice jelly layer!

I can't really afford to replace the boiler even though the fuel savings could be large with a high tech new one, so could I just install a high temp. pipe stat to make a DIY overrun, but I feel this is just treating the symptom rather than the cause, I could also put a pressure vessel in but is that just hiding the problem too?

System details:-

System pipework is perhaps 35 years old, all copper, 22mm circs with 10mm microbore so a bit noisy.

Baxi Solo WM50/4RS (65% SEDBUK) installed new but now 20 years old (ish). Grundfoss pump.

3 port mid position valve (Y-plan), new foamed cylinder/stat and RF roomstat and an upstairs zone with a 2 port valve running from an ordinary wall stat.

All but one rad has TRV's, and all but one are new in the last 3 years. One Myson fan convector that doesn't like being fed by 10mm pipework (or is crap...)

House has a loft conversion (with the gassy rad), the hipped roof means little head for the F+E tank with the expansion actually being through the tank wall, so only 3" space over the water and that being 3" deep in the tank so difficult to improve without maybe swapping to a pressure vessel.

Ideas?

Thanks

[DIY]

Hi Guys

I'm having a bit of a nightmare with my heating system and need help! Symptoms are lots of hydrogen in the loft radiator and lots of bubbling through the various radiators as the system warms up but little bleeding needed in those radiators (?), so after a few checks it appears that the system 'pumps over' AFTER the system goes off and this last bit is a relatively new event (< year). Other oddities are the thermocouple appears to have a short-circuit to the front case (but it all still works and nothing ever seems to be live), the cover has possible smoke and abrasion marks in proximity to the capillary which definitely have what look like spark erosion marks! - this worries me! A google appears to indicate that this boiler may not have an overrun (unless it is a standard feature of the gas valve?) so I'm unsure why it is now 'pumping over' when off - from heat soak and steam splurge?, or is it a overrun going wrong, but why now? It is probably this pumping over that is causing the system to rot and gas but how much damage will have been done, I assume the pumping over has long since removed the fernox protection as the F+E has a nice jelly layer!

I can't really afford to replace the boiler even though the fuel savings could be large with a high tech new one, so could I just install a high temp. pipe stat to make a DIY overrun, but I feel this is just treating the symptom rather than the cause, I could also put a pressure vessel in but is that just hiding the problem too?

System details:-

System pipework is perhaps 35 years old, all copper, 22mm circs with 10mm microbore so a bit noisy.

Baxi Solo WM50/4RS (65% SEDBUK) installed new but now 20 years old (ish). Grundfoss pump.

3 port mid position valve (Y-plan), new foamed cylinder/stat and RF roomstat and an upstairs zone with a 2 port valve running from an ordinary wall stat.

All but one rad has TRV's, and all but one are new in the last 3 years. One Myson fan convector that doesn't like being fed by 10mm pipework (or is crap...)

House has a loft conversion (with the gassy rad), the hipped roof means little head for the F+E tank with the expansion actually being through the tank wall, so only 3" space over the water and that being 3" deep in the tank so difficult to improve without maybe swapping to a pressure vessel.

Ideas?

Thanks

[Graham.]

front case (but it all still works and nothing ever

This sounds like a red herring, when hot the thermocouple produces a current that directly energises a low impedance coil in the gas-valve, so it is normal for it to read virtually short-circuit on a meter.

If you have any doubts about it unscrew it from the valve while the boiler is running, the flame should shut down instantly, including the pilot.

[Graham.]

What again?

[geoff]

In message , Graham. writes

There is no thermocouple, the Baxi Solo Mk 1 has electronic ignition.

Also, there IS no pump overrun. The pcb only controls the fan and gas valves

[DIY]

Hi Graham

It was the fact that it looks like mains voltage has been arcing to the access flap from the thermocouple (as if something shorts every now and then) - I've only tested for the case being live not any of the bits which seem to work just fine.

Sorry about the double post I'm having mail trouble too :-(

[Graham.]

I was right about the fish then ;-)

[Graham.]

front case (but it all still works and nothing ever

that directly energises

virtually short-circuit on a meter.

flap from the thermocouple (as if something shorts

bits which seem to work just fine.

Mains voltage arcs in air are less than 1 mm. are you sure the component you identified as a thermocouple isn't an ignition electrode, and the HT lead to it is arcing to the caseing?

[DIY]

Erm this one has a thermocouple and a pilot light (and no fan), the boiler is GC 41-077-49 does this have an overrun? The manual I downloaded indicates an overrun in the text but it doesn't appear to have a seperate part listed but googling generally suggests the gas valve has a built in one ?.

[DIY]

The thermocouple is a standard universal (Screwfix 44909), the coil of spare capillary is very close to the case so it could arc easily. Being piezo ignition I'm fairly sure it isn't stray sparking. I'll try and get a decent photo and post it somewhere over the weekend.

[DIY]

The (F+E) expansion pipe splurges for a short period after the system has gone off, so it is either an extra vigourous overrun (if it has one) or a heat soak induced steam surge - not sure which but it is after the system has gone off!

[DIY]

It pumps over/splurges just after the programmer goes off and is probably boiling up with heat (or else the pump overrun if it exists is a bit keen!) this effect only lasts at most a minute or two from start to finish, I have not been able to establish how soon after programmer goes off, it isn't every time, and I haven't got a patient enough assistant to help diagnosis at the moment, but she wants it fixed all the same :-(

The header tank is in a frequently used loft conversion and quite audible and sounds like gurgling rather than anything more dramatic. Tonight I was quick enough to feel the expansion spluttering, and whilst initially the water was cold it became warm (but never hot) before all gurgling and spluttering ceased. The audible bit was only noticed recently, but as the F+E is very slimy and crusty it is perhaps a longer standing fault that has been unnoticed, but in any case is only at most 14 months as that is when the system was drained and refilled with inhibitor after a swapped 3 way valve.

Expansion pipe is 4" above water surface and the water level is 4" deep, the base of the tank is 10" above the radiator in the loft conversion. The F+E is original so 30 odd years old but apppears fine with no sign of overflowing or other problems.