Ferroli 901 short cycle

[NEILC25]

good evening, I've got an issue with my ancient however well maintained ferroli 901 boiler, it short cycles, it stays on for 35 seconds, then shuts off for approx 10 seconds and repeats all day, this never happened last winter, just this winter since turning it back on.

When turned on is fine, however after approx 10 minutes when up to temp issue starts

This is what I have done so far,

2 new thermisters.
New pcb
New flow meter

Water runs hot / cold, however this is due to the short cycling

I have been told as soft water area unlikely to be heat exchanger.

All rads are warm all over,

No airlocks in rads or taps.

Pump is working well because rads get hot quickly.

Any ideas please, I would appreciate any advice,

I appreciate ferrolis aren't the best
Thanks

 

[oz-plumber]

Changing the thermisters was probably your best stab.
If that didn't work, I wouldn't have changed the PCB or Flow Meter.

I would have started to look elsewhere and determined what was causing the problem.
Gas rates, pressure switches, flame rods, flame sensors, pump capacitor, gas valve, gas valve modulation, heat exchanger.
Most of these things can be checked within a very small amount of time.

 

[Gasmk1]

Pump ? Is it performing correctly

 

[SJB060685]

What’s the ΔT across the boiler after this ten minutes?

 

[NEILC25]

ive figured it out, however I need a bit of advice, it's the pump, it's got to the point now where it's not even starting up, I've tried to remove the old pump, however the switch and casing come of but how do you get the actual fan bit out, thr shaft with the rotating part won't come out of the cast iron casing, how do I get it out?

 

[NEILC25]

ive figured it out, however I need a bit of advice, it's the pump, it's got to the point now where it's not even starting up, I've tried to remove the old pump, however the switch and casing come of but how do you get the actual fan bit out, thr shaft with the rotating part won't come out of the cast iron casing, how do I get it out?

 

[ShaunCorbs]

Have you drained the system?

 

[NEILC25]

yep, systems empty, is this part supposed to come off, I don't want to have to buy the whole cast-iron part unless I have to, can I tap this with a rubber hammer, surely this should come out, there's nothing on backside of It securing it. The replacement part has it all as one piece

 

[NEILC25]

Here is the specific part

 

[SJB060685]

It could be a weak capacitor, alternatively the whole pump could do with replacing.

 

[ShaunCorbs]

Yes if empty / drained Waco with a hammer

 

[NEILC25]

It could be a weak capacitor, alternatively the whole pump could do with replacing.

it turns freely with a screwdriver, however when I make a mark on the spindle and turn it on to the point where it shuts down again and remove the metal disk I can see that it hasn't moved.

It could be a weak capacitor, alternatively the whole pump could do with replacing.

 

[NEILC25]

I've bought a new pump for £50 which seems OK, I'll give this one a gentle whack with a hammer and see how it goes, thanks.

 

[NEILC25]

afternoon, I've got a further query, I managed to get the original pump off, it was rusty and the plastic parts looked like rusted metal there's what appears to be a ceramic collar in there which had bits chipped off, I've cleaned it all up, bearings have gone I think, however it still spins, I've put it back in until new one arrives and no more short cycling, however, ( sigh) the heating comes on and the water is now at a constant heat but it is a lot lower that before. I imagine that the current pump isn't woring to full capacity, could that be responsible for this, I haven't replaced aw nything else. I'm hoping that the new pump will spin more freely and solve this, although I thought the pump had little to do with water temp, any advice would be appreciated. Thanks

 

[NEILC25]

Ok. I've got a problem, I'm hoping it's just a faulty part, my new pump came today, I installed it ( I've done a few before with no issues) it ran for about 5 minutes and then started smoking, ( literally) and then blew the fuse I took it out again and it's literally melted. The inside of it has burnt out, any idea why this would have happened?, even the previous one I took out didn't melt? I am hoping it's faulty, I can't see how I can be at fault with this?

Thanks in advance

 

[SJB060685]

Loose wires could cause this. What make of pump is it? They should replace under warranty.

 

[NEILC25]

It's a grundfos, the same as the original one

 

[SJB060685]

It's a grundfos, the same as the original one

If you’re confident you wired it up correctly and with no loose connections then they will replace under warranty

 

[Chuck]

It's a grundfos, the same as the original one

Was it the correct voltage rating? (A 120V motor on a 240V supply behaves rather like you described...)

 

[SJB060685]

Was it the correct voltage rating? (A 120V motor on a 240V supply behaves rather like you described...)

I’d imagine the OP would be aware of that. I could be wrong though

 

[NEILC25]

If you’re confident you wired it up correctly and with no loose connections then they will replace under warranty

Was it the correct voltage rating? (A 120V motor on a 240V supply behaves rather like you described...)

They were both 230v, I've complained to the company and they want me to send it back at my expense to be inspected, I've asked them if they can send another for tomorrow and I'll send the other back, they said, " no"!! . So I've bought another one from someone else and am going to ask for a refund, I hope they don't give me any nonsense or I'll go down the route of "my house could have burnt down "

 

[Gasmk1]

Did you fully change the pump or just the head. You didn’t leave the old rotor in and just change the windings part ?

 

[NEILC25]

Did you fully change the pump or just the head. You didn’t leave the old rotor in and just change the windings part ?

No I did the lot, the whole pump.

 

[Gasmk1]

No I did the lot, the whole pump.

Good was the new pump a brand new one or second hand

 

[NEILC25]

Thanks for reply. It was a brand new pump

 

[Gasmk1]

Thanks for reply. It was a brand new pump

For 50 that’s very cheap

 

[oz-plumber]

FWIW, I never been able to claim a warranty on a pump replacement in a system and I've been in the game 25 years.

The only pumps I've ever managed warranty on are new boilers on new systems.

Pump warranties on existing systems - no chance

 

[NEILC25]

new pump went in no problem, solved issue, just a case of getting refund on damaged one now.

 

[NEILC25]

new pump went in no problem, solved issue, just a case of getting refund on damaged one now.

OK, this is a new development, it's still short cycling, however the period of time between it switching off and on again ids shorter so water is actually hotter because by the time it starts getting cold it starts warming up again. However ive just replaced a sink in the bathroom and when I turned off the water and drained taps the last of the water in the cold tap was warm, I read this may be something to do with thermostat in boiler being constantly in on position, could this have been the problem all along?

 

[Winnywood]

This sounds like a faulty venturi causing the pressure to the pressure switch to fluctuate. On some models this is a hard high temperature plastic and goes very brittle with age. Worth a check as they're quite cheap.