Pump speed and boiler cut out

[oldskoo1]

I am having a problem with our boiler which is rapidly clicking and cutting out. It is an ideal classic ff380. The pump is a grundfos 16-50 (130) and this system serves 20 radiators, 70% of the radiators have trvs.

If I set the pump to 3 it rarely cycles, system gets up to temp but occasionally the boiler will rapidly click and turn off. This can be frequent which sometimes means hot water doesn't heat up correctly.

If I use pump speed 2, it doesn't click and cut out but instead it cycles a lot after being on for around 20 mins. It will cycle every 3-5 mins by turning off for around 30 seconds to a minute.

It is a 3 storey fairly new town house so I assumed with the number of radiators and 3 floors it would need to be on 3. However the same thing happens when heating hot water.

Neither setting seems ideal. Should I expect a non modulating boiler like mine to cycle like it does, if so should I leave it on speed 2?

Thanks

 

[D_Hailsham]

Yes, your boiler will cycle; it's the only way it can control the water temperature!

What number do you have set on the boiler's temperature control?

Do you have a thermostat on the wall?

Do you have a bypass valve?

You boiler is probably over-sized for your house. Use Whole House Boiler Size Calculator to find out what size boiler you really need.

Production of your boiler stopped in 2004, so I wouldn't call your house "fairly new"!

 

[dcawkwell]

It sounds like you have an old cylinder with big coil that takes little heat away from the boiler. This will be easy to spot if it has 28mm connections.
If the boiler is just heating hot water it will heat the water in the pipes quickly and then have to shut down.
New cylinder need.

 

[oldskoo1]

Boiler temp is on 6 to prevent it from cycling as much, which is max. Actually slightly below max incase there is play in the old stat.

I do have a wall stat but no bypass valve and yes house is 10 years old.

I did the size calculation after checking all the measurements and it came out at 20.35kw boiler output, the ff380 is rated at 23.4kw.

I had to choose the unfilled cavity wall option as it's empty, the walls and all dividing rooms use that celcon block stuff, so there is some sort of insulation.

I can't decide whether it's a pump / flow problem or a burnt out relay on the pcb for which i need to call someone out.

 

[dcawkwell]

Boiler temp is on 6 to prevent it from cycling as much, which is max. Actually slightly below max incase there is play in the old stat.

I do have a wall stat but no bypass valve and yes house is 10 years old.

I did the size calculation after checking all the measurements and it came out at 20.35kw boiler output, the ff380 is rated at 23.4kw.

I had to choose the unfilled cavity wall option as it's empty, the walls and all dividing rooms use that celcon block stuff, so there is some sort of insulation.

I can't decide whether it's a pump / flow problem or a burnt out relay on the pcb for which i need to call someone out.

Try or medium setting for the thermostat.

 

[D_Hailsham]

It sounds like you have an old cylinder with big coil that takes little heat away from the boiler. This will be easy to spot if it has 28mm connections.

The house is only 10 years old!! Were they still installing gravity HW systems then?

 

[D_Hailsham]

Boiler temp is on 6 to prevent it from cycling as much, which is max.

I assume from that, that you have tried a lower temperature and found that the cycling increases.

I did the size calculation after checking all the measurements and it came out at 20.35kw boiler output, the ff380 is rated at 23.4kw.

I had to choose the unfilled cavity wall option as it's empty, the walls and all dividing rooms use that celcon block stuff, so there is some sort of insulation.

The insulation requirement were fairly good 10 years ago, so it might be worth rechecking assuming a filled cavity. However, the boiler does not appear to be massively oversized.

I can't decide whether it's a pump / flow problem or a burnt out relay on the pcb for which i need to call someone out.

What happens if you remove all TRV heads? Do you still get cycling?

Do you know if the system has ever been balanced?

 

[bathjobby]

I am having a problem with our boiler which is rapidly clicking and cutting out.

Is it a single click and then a thermal cut out which has to be reset ? because you then go onto say its cycling....

 

[oldskoo1]

thank you all

yes cycling increases at a lower stat temp on the boiler.

Shocked but when extractor was being fitted i checked cavity and nothing, same when i changed the bathroom extractor.

I thought it was flow too, but it does it on hot water heating only too so i ruled out TRVs throttled flow.

It was horribly balanced when i moved in. but spent hours perfecting the balancing and its now pretty good.

Unfortunately the click isn't the stat trip as the red nipple on the side isn't sticking out so the stat isn't tripping. It is very much a rapid clicking but i'm totally confused why it doesn't seem to happen at pump speed 2. I think i could hear a slight clicking but it is no where near as bad as speed 3 and on speed 2 never cuts out (apart from cycling).

1 more very bizarre thing is, if its cut out after rapidly clicking i can get it back on by simply pressing inwards the bottom panel external casing (where pcb is housed).

 

[Agile]

Your boiler needs to cycle.

We would needs temps to give any further advice but it seems you have focussed on the cycling and somehow think its wrong.

Why not get cavity wall insulation?

Tony

 

[oldskoo1]

I agree this old boiler does need to cycle but due to having to use the slower pump speed it begins cycling prematurely i feel because the output is quite high and the pump isn't moving the heat away quickly enough.

But on speed 3 it clicks rapidly and cuts out which is just as bad.

Afaik its still on its original return stat which is old and possibly slightly out. It begins cycling due to max temp (book level of 82c) at around 10-15mins. On speed 3 it would go nearly 25-30 mins despite the trip offs. When it trips off from clicking i can force it back on by touching the bottom panel or it tries itself and usually comes back.

About cavity wall insulation, our bills are pretty reasonable and i was concerned if we filled it we would get more condensation problems. Allowing the building to breath would probably cost us 10% in energy bills but it might improve airflow. Our old cavity filled house constantly had bad condensation on the windows even with vents, this house is always dry.

 

[Agile]

Cavity insulation usually saves 25% of the gas bill. More even heating too which makes it more comfortable.

Condensation results from inadequate ventilation!

Tony

 

[bathjobby]

I had what sounds like very similar symptoms some years ago on a Potterton, the clicking (very loud and sometimes erratic - so difficult to pin down a scenario) turned out to be the gas valve opening, closing, opening. Could be a single drop off and on again, or a rapid 'stutter'. Fault was a dry joint on the PCB on the power line to the term/res istor that powered the gas valve. It was visibly dry so easily fixed - not a prompt for the Corgi / GasSafe brigade to hijack this with their commandments......
Difficult to tell if yours is anything like that but thought I'd just pass on my own 'similar' experience as it may help.

 

[oldskoo1]

Thanks guys

I'm good with electronics but as it's a case off job, time to ring my gas man.

I'm just puzzled why it doesn't happen at lower pump speed.

10 years of heat and I wouldn't be surprised if the pcb had dry joints. I did think it's either the relay that has carbon on the contacts or a faulty gas valve solenoid.

I think we must be only the right lines with the pcb.