Do I need a new boiler? (Possible HEX blockage) (Ed.)

[jchasty]

Hi

Per some of my other threads, I have an issue with a BG 330+ Heat Only conventional boiler.

I've managed to get into the diagnostic menu and double checked Flow & Return Temps.

Despite the Flow Temp being set at 75C, it NEVER gets above c.53C even after 4 to 5 hours of the boiler firing away at full pelt. Return Temp is about 7C lower than Flow Temp.

It is 9 years old and to be honest, only serviced once in that time. What put me off servicing again was the fact that the guy took the front cover off, had a look inside, sniffed and charged me £120....

Anyway, a plumber who I now trust, says that the Flow Temp should try to get as close to the Flow Setting as possible and more than likely the heat exchanger is blocked and f***ed. As mentioned in another thread, it's fed from the Header tank with softened water, despite being an alloy heat exchanger (thanks BG!).

Pro Plumbers on here, would you come to the same conclusion that I need a new boiler?

Thanks in advance!

John

 

[cross thread]

Be surprised if it’s the boiler,what setup have you regarding the cold feed / expansion connection

 

[fixitflav]

Despite the Flow Temp being set at 75C, it NEVER gets above c.53C even after 4 to 5 hours of the boiler firing away at full pelt. Return Temp is about 7C lower than Flow Temp.

That's possible if you have loads of rad area. Are the rooms heated adequately? You could check gas flow by reading the meter over say a 10 minute interval and see if it agrees with the manual.

 

[Harry Bloomfield]

Despite the Flow Temp being set at 75C, it NEVER gets above c.53C even after 4 to 5 hours of the boiler firing away at full pelt. Return Temp is about 7C lower than Flow Temp.

The 75C is a target, it will only reach that, if either the flow through the boiler allows it, or the return temperature is closer to 75C. To ensure the boiler is running flat out to achieve it, check the gas consumption, at the meter, matches the 'flat out' consumption.

The Indoor Display of a smart meter, if you have one - allows for an instantaneous reading of Kwh of gas. Making it easy to compare that against your boilers spec..

If it is really running flat out, and never reaching 75C, then it must be dissipating all that Kw into the radiators etc..

 

[Johntheo5]

Hi

Per some of my other threads, I have an issue with a BG 330+ Heat Only conventional boiler.

I've managed to get into the diagnostic menu and double checked Flow & Return Temps.

Despite the Flow Temp being set at 75C, it NEVER gets above c.53C even after 4 to 5 hours of the boiler firing away at full pelt. Return Temp is about 7C lower than Flow Temp.

It is 9 years old and to be honest, only serviced once in that time. What put me off servicing again was the fact that the guy took the front cover off, had a look inside, sniffed and charged me £120....

Anyway, a plumber who I now trust, says that the Flow Temp should try to get as close to the Flow Setting as possible and more than likely the heat exchanger is blocked and f***ed. As mentioned in another thread, it's fed from the Header tank with softened water, despite being an alloy heat exchanger (thanks BG!).

Pro Plumbers on here, would you come to the same conclusion that I need a new boiler?

Thanks in advance!

John

I'd be very surprised if the heat demand is too big for that boiler because rads with flow/return temps of 53C/46C will only emit just 50% of their normal (T50) rating, so except they are massively oversized then that's not the problem IMO , OR the boiler is range rated, I think these boilers are similar or are a rebadged Vaillant, if so, check, d.0, part load setting, and d.5, target flow temperature and d.71, maximum target flow temperature.

 

[jchasty]

Thanks

Some interesting developments to report.....

I set the DHW cylinder to 60C and the boiler to 60C Flow and hey presto this morning, I have toasty hot water and the boiler display says 60C! This is progress!

In the diags menu, D0 (Partial Load) was set to 18 (KW I assume?), so I have put that up to 30. I'm about to put the CH up to its highest to see what happens......

Moments later.....

.....the rads were proper hot within minutes - which has not happened for a good few months.....however....the boiler is screaming. horrible mid-pitched whistling sound and vibration.

I've now turned the heating down to 18 and the boiler has gone off....

So, progress of sorts (HOT rads & water), but horrible noises from the boiler.....

 

[Johntheo5]

The boiler flow temperature should be at least 5C higher than the HW cylinder (usually 60C) otherwise the boiler will never cut out, suggest setting the boiler to 65C and maybe d.0 to 20/22kw.

 

[jchasty]

OK, thank you!

 

[Mister Banks]

Thanks

Some interesting developments to report.....

I set the DHW cylinder to 60C and the boiler to 60C Flow and hey presto this morning, I have toasty hot water and the boiler display says 60C! This is progress!

In the diags menu, D0 (Partial Load) was set to 18 (KW I assume?), so I have put that up to 30. I'm about to put the CH up to its highest to see what happens......

Moments later.....

.....the rads were proper hot within minutes - which has not happened for a good few months.....however....the boiler is screaming. horrible mid-pitched whistling sound and vibration.

I've now turned the heating down to 18 and the boiler has gone off....

So, progress of sorts (HOT rads & water), but horrible noises from the boiler.....

On some boilers the load is measured in percentage not kw.

 

[Johntheo5]

On some boilers the load is measured in percentage not kw.

 

[fixitflav]

.....the rads were proper hot within minutes - which has not happened for a good few months.....however....the boiler is screaming. horrible mid-pitched whistling sound and vibration.

I've now turned the heating down to 18 and the boiler has gone off....

So, progress of sorts (HOT rads & water), but horrible noises from the boiler.....

What setting is the pump on? Maybe increasing it would help.
Some years ago my system was slightly noisy but I didn't suspect the pump, till it started vibrating badly. I replaced it and the noise disappeared, on minimum pump speed. The impeller of the old pump was clogged with crud, so the flow was reduced, causing the boiler noise. Might be worth checking your pump.

 

[jchasty]

Thanks - what does the "Part Load" setting do please?

 

[Johntheo5]

Thanks - what does the "Part Load" setting do please?

Part Load setting is the maximum output that the boiler will deliver, it normally comes set to its maximum, 30kw? on your boiler, you or someone had it set to 18kw which means the boiler cant deliver more than 18kw no matter what the demand is, it actually controls its output based on the target or setpoint flow temperature so if the demand is > than the part load setting then the flow temperature will start falling. The part load setting is often referred to as range rating.

 

[Harry Bloomfield]

Thanks - what does the "Part Load" setting do please?

It restricts, or limits the Kw output of the boiler, to less than the maximum.

 

[fixitflav]

Thanks - what does the "Part Load" setting do please?

How big is your house/number of rads? To give the symptoms in #1 at 18 kW, I'd guess it's BIG. A more typical house needs a boiler rating ~ 15 kW.