Riello 40 red light problem

robe501

I use the controller, usually manually not timer, to call for central heating and generally the burner fires up. The stat on the boiler is set at 3 ( dial can go up to 5 max). It will run continuously for whatever time it takes to get the boiler stat to turn off the burner…maybe an hour on a cold day.

Sometimes the boiler will re-fire when the water temperature drops below the boiler stat setting but often when it tries to re-fire it hums a bit and then the red-light on the button comes on. Press the button in and it will re-fire straight away (generally jut one push is enough)..it will then go again until the boiler stat temperature is reached…then the same thing happens.

Just once or twice I have switched the CH off at the controller manually before bed while running fine..and next day when switching on at the controller I get the red light..and have to press the button in..it will go every time.

It has been serviced fairly recently and the pressure is correct (8 bar) and the flue gas is also correct ,so say, at 11.8% CO2. New nozzle fitted recently at service (.75 with 80 degree W)

I'm wondering if this could be as straightforward as a capacitor issue. Burner unit has been excellent over the years..installed as far back as 2000 with only a piston damper replaced (and nozzles off course) in that time. The capacitor is therefore 25 years old!

Thanks for reading..any thoughts/suggestions welcomed.

Grallert

Those burners are pretty trouble free once set up correctly. I forget if that capacitor is a start for the motor? I think it is. Is there ever a puff when it starts?

Big Ed_4

The red button on the Riello is the burner reset . That button will trip if that control senses no fire .. If the capacitor were bad , it would not run at all.. You are talking about controller and switch at the thermostat ? The thermostat will not trip the safety ..

Best way to see when the relay drops out is to sit and watch and wait . You need to narrow down the problem or issue ..

robe501

thanks ..

>Grallert ..I believe it is just a start capacitor for the motor..no puff/no smell.

>Ed ..the controller I refer to (maybe I used the wrong word) is a Horstmann ..maybe I should have said "Programmer". Although it can control hot water (HW) and Central Heating (CH) I only use the CH part..and I normally use it manually (not using the timer functions) by pressing the CH button til it scrolls around to "CH All Day). I switch it to "OFF" manually too.

The boiler itself has a thermostat with a dial from 1-5 and I use it on 3. My understanding is that when the temperature of the return pipe water is high enough (as per setting "3") it tells the burner to stop firing..then as the water circulating through the rads gradually gives out its heat and the water on return side becomes cool enough (i.e.below setting "3" level)..then that stat senses that cooler water in the boiler and tells the burner to fire up again.

I have been at the boiler (front facia/cover panel off) when it cuts off and some 10 mins later, say, tries to fire again. You just hear it humming..for maybe 10 seconds..then it goes to red light instead of firing. However, sometimes the burner will do 3 or 4 such on/off cycles and it does re-fire without me pushing the reset button.

mattmia2

easy enough for a burner tech to reproduce and figure out why it won't fire when it is hot and has more draft or the components are hot and something like the ignition is failing. or the centrifugal switch on the motor or the combustion is off and that extra draft keeps it from lighting off or the motor is sticking or a number of other tings. A primary control with some diagnostics would tell you which part of the sequence is failing.

robe501

thanks Mattmia..yes that make sense..maybe Ill have to call the engineer back.

One thing though , as I said sometimes it "goes to red light" from stone cold ..some 12 hours or even more after having been switched off at the programmer the night before.

mattmia2

whatever is failing could also fail when it is cold but seems to be more likely to fail when it is hot

robe501

good point Mattmia.. that couldn’t be the (start) capacitor? Ed, above, states that it either works or doesn’t.. if it was the culprit the burner would never fire.

mattmia2

It could be but if it is weak it is more likely to be randomly intermittent rather than reliably when the boiler is hot.

Grallert

If the capacitor fails the motor won't start, the pump won't pump. The trial for ignition is so short on Riello burners you're not likely to hear the ignitor. What kind of boiler is it? if it's tight you might not notice a puff but my guess is there is no puff and you motor is not starting. You can test if you like by installing a jumper. With the service switch off remove the control and jump from the power in L1 to the motor terminal. turn the power back on. the oil valve will remain off as will any ignition. does the motor run?

robe501

thanks both..will have a longer look in the morning..(UK) bedtime for me (yes..early)..- 2C outside tonight..first frost of Winter.

btw..its a Mistral boiler btw..made in UK & an excellent bit of kit. I installed it in 1988 and replaced the Mectron burner unit in 2000 with a near identical one badged as Riello40. Bearings issue on the Mectron..didn't have the time..in deepest Winter to replace them. No real issues since then .

Never had an engineer look at it until this year. I'm getting pretty old now so got one in to do the annual "service" 3 weeks or so ago. Maybe I should be looking at a new boiler!?

Just wondering if the photocell might be playing up?

BDR529

A hum indicates a dead spot on the motor.It sends back low voltage to the control to complete start procedure

New flame dector is not a cad-cell but diode based.

Replace motor and do the cap, Cheap insurance.

SuperTech

I don't think the cad cell flame detector is the culprit. From what you described the problem is either the capacitor or the burner motor itself. If you don't have a multimeter to test the capacitor you could just buy a new one and see if it solves your problem. The capacitor is inexpensive and easy to to replace.

I wouldn't think about replacing the boiler, this burner problem should be a simple repair once you get it figured out.

robe501

thanks BDR529 & SuperTech..

first stop then I think is to test the capacitor. How careful does one have to be with these on a burner unit? (240volts here in UK). Presumably worth using an insulated screwdriver across the 2 connections to release any charge..or is it?..can that cause damage to the capacitor..I dont have a spare right now and its' damn cold today.

mattmia2

You should short it to make sure it is discharged just to be safe but in most applications at dc it is shorted through the start and run wingdings when it is in circuit anyhow.

robe501

thanks for that mattmia..had to go out all day so will have a look tomorrow.

mattmia2

knowing at which point in the process it fails would help you narrow down which part is failing

robe501

indeed… I’m clearly no expert and all I can say is that the problem manifests itself when the burner has been on for a while, typically over an hour, and shuts off as boiler water temperature has been reached. As the CH water cools as it dissipates heat through the rads it tries to start up the burner again.. that’s where it goes to red light.
I do realise that’s not the degree of precision you allude to

Tonight .. it’s a bit cool in UK .. switched on at programmer at about 6pm.. now over 2.5 hours later it has switched itself (via boiler stat) off about 3 times.. and restarted on its own twice.. just once J had to intervene to press the red button.

mattmia2

find the manual for the primary control and read it. it will tell you the sequence of operations. When the boiler cools and calls the primary control for heat again, look at how far in that process it gets. It is possible the aquastat or whatever calls the boiler to fire isn't making the call or there is a loose connection or something too.

robe501

update - just for the record:

Iv'e been very busy since last my last post so have done nothing more with the boiler except keep some notes on events with it.

Probably be the kiss of death writing this but for the last 9 days there has not been a single glitch/red light event and the boiler has been on 3-4 hours a day on average in the evenings.

One thing I had not stated in my original post and now I think it may be relevant (?).

I had a new oil tank connected and a boiler service done. This included new 0.75/80nozzle, pressure test and adjustment due to pre-existing mix being a bit lean under flue gas analysis. This was just before the issue I wrote about initially.

I had pumped about 1200 litres of oil into the new tank from my old one. (200l left from last season and 1000l I had delivered in September before the new tank arrived).

I am wondering if my issues were to do with either air or water or some dirt in the new line which has gradually worked through? Hope I'm right..fingers crossed.