Boiler and CH problems

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Hi all,

This issue has been on-going for a while now but with the weather getting colder, I really need it sorted.

I have an Ideal Classic FF250 boiler. It's worked ok'ish for the past 10 years that I've lived in my current house with the odd problem here or there. The CH pump was changed about 8 years ago and is now working fine too.

Initially, it stopped working and a boiler engineer replaced a broken fan inside it. Then in approx. November 2020, The heating and water would be switched on but before the radiators got up to temperature and before the water got really hot, the boiler would switch off. It'd then come back on again for a few minutes and then switch off again - would keep cycling in this way.

The same engineer changed the gas valve on it and it seemed to work better and get up to temperature.

Recently though, it's happening again. i.e. cycling.

I had another boiler engineer come over as the previous one has moved away. He looked at the boiler, (without opening anything) for a second then went up to where the tank is. He checked it with a magnet and told me that the boiler was fine and that they system was full of gunk and would need a chemical clean out and a new pump.

He said he couldn't do it there and then and that I would have to book it in with the office. On calling the office, they said the work would cost around £600 and that they couldn't do it till March time.

I wanted to ask if this is the going rate in East London and if changing the pump and the chemical clean sounds like the right thing to do for this issue? How would this fix the boiler cycling in this way? I can't see the connection? I asked the 'office' the same question but the lady on the phone couldn't answer it?
 
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Possibly the water is not circulating as fast as it should be and the boiler trips out on overheat although this usually means the re button on the side of the control unit popping out and having to be reset. What number have your got your heat dial set at on the control unit, and what speed is the pump set at. If you look in the tank is the vent pipe discharging hot water into it.
 
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Thanks for that - the boiler is at heat setting 5. The manual says to leave at this and so it's never been changed. It hasn't been reset or needed to be reset either.

Are you asking if hot water is discharging back into the expansion tank in the loft? I'm not too sure to be honest. The pipe is quite hot, and one of the tanks (either water or CH) is definitely overflowing as there is always water outside where the overflow pipe comes out but I can't tell which one it is?
 
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As above, but the boiler is reaching its temperature as set by the control knob on the front of the boiler. If the heat cannot be distributed to the radiators (by the pump) quickly enough the boiler will shut off the burner, re-igniting it when the boiler temperature cools a little (not so hot that the overheat button pops out).
Feel the incoming and outgoing pipes above the boiler. The outgoing (flow) should be about 10C hotter than the incoming (return); if the differential is larger than this then the heat isn't being taken away fast enough, and you'll need to increase the circulation speed.

1. Is the pump set to maximum speed? It shouldn't be for a 15kW boiler, but having it at max speed will disguise the problem.

The solution could well be to have the system cleared of sludge, including the pump, but not necessarily by a full 'power-flush'. With average skills you should be capable of draining your own system, refilling with a sludge removing cleaner such as Sentinel X400, leaving to circulate for several days, then re-draining, and filling again.
With a few extra DIY skills you should be able to remove the circulating pump head and mechanically clear out the impellor (using a copper wire or similar), and restore pump performance.
Once that's done, balance the system (search for the procedure), and reduce the pump speed to get 10C across the boiler.
When satisfied it's working adequately add some Sentinel X100 inhibitor to the system....Fernox and other manufacturer's equivalents are available.
Note: if draining via a drain cock, prepare properly by buying some spare MT-cock washers (rubber seals) - the old ones often crack on removal.

Unfortunately it appears you've had a new gas valve fitted unneccessarily.

MM
 
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....one of the tanks (either water or CH) is definitely overflowing as there is always water outside where the overflow pipe comes out but I can't tell which one it is?

You should stop that from happening first, it's a major cause of sludge creation. Possible causes; ball-cock passing or a fault within your hot water cylinder where water from the higher tank (it may or may not be the domestic cold water tank) passes into the heating system F&E tank.
 
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As above, but the boiler is reaching its temperature as set by the control knob on the front of the boiler. If the heat cannot be distributed to the radiators (by the pump) quickly enough the boiler will shut off the burner, re-igniting it when the boiler temperature cools a little (not so hot that the overheat button pops out).
Feel the incoming and outgoing pipes above the boiler. The outgoing (flow) should be about 10C hotter than the incoming (return); if the differential is larger than this then the heat isn't being taken away fast enough, and you'll need to increase the circulation speed.

1. Is the pump set to maximum speed? It shouldn't be for a 15kW boiler, but having it at max speed will disguise the problem.

The solution could well be to have the system cleared of sludge, including the pump, but not necessarily by a full 'power-flush'. With average skills you should be capable of draining your own system, refilling with a sludge removing cleaner such as Sentinel X400, leaving to circulate for several days, then re-draining, and filling again.
With a few extra DIY skills you should be able to remove the circulating pump head and mechanically clear out the impellor (using a copper wire or similar), and restore pump performance.
Once that's done, balance the system (search for the procedure), and reduce the pump speed to get 10C across the boiler.
When satisfied it's working adequately add some Sentinel X100 inhibitor to the system....Fernox and other manufacturer's equivalents are available.
Note: if draining via a drain cock, prepare properly by buying some spare MT-cock washers (rubber seals) - the old ones often crack on removal.

Unfortunately it appears you've had a new gas valve fitted unneccessarily.

MM

Thanks for this, makes a lot more sense now.

The pump is at full speed but I can hear it working, hence not too sure why it needs to be changed?

I put some Sentinel X800 into the system yesterday, put the heat right up and let it do it's thing.

I'll try draining it all out and refilling over the weekend.

I was told that the X800 was better than the X400 and so I went for that.

What exactly does this chemical do? As in does it dislodge the gunk or does it dissolve it?

If it dissolves, should the system start to work 'properly' while the chemical is still in the system or does it have to be removed for the system to work correctly?
 
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Thanks for this, makes a lot more sense now.

The pump is at full speed but I can hear it working, hence not too sure why it needs to be changed?

I put some Sentinel X800 into the system yesterday, put the heat right up and let it do it's thing.

I'll try draining it all out and refilling over the weekend.

I was told that the X800 was better than the X400 and so I went for that.

What exactly does this chemical do? As in does it dislodge the gunk or does it dissolve it?

If it dissolves, should the system start to work 'properly' while the chemical is still in the system or does it have to be removed for the system to work correctly?

The difference between X400 and X800? Sentinel Treatment Tips #9 - YouTube

And you really want an Adey Magnaclean or similar setup to help keep the system clear
 
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I was told that the X800 was better than the X400 and so I went for that.

What exactly does this chemical do?
Take it out and flush it right away, it will eat your pump bearings and if you have any weak points on your rads they will pin hole, you should have used X400, X800 should never be left in the system
 
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Not really
Screenshot_20220120-201728.png
 
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Has anyone seen it cause problems when left in systems for a few days?
Yes many of us have, do you really think a manufacturer is going to advertise their product and say, dont use it, it is far too aggressive, I would only use it while doing a power flush now, and no way would I risk leaving it in a system, X 400 is fine
 
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Yes many of us have, do you really think a manufacturer is going to advertise their product and say, dont use it, it is far too aggressive, I would only use it while doing a power flush now, and no way would I risk leaving it in a system, X 400 is fine

Thanks for this, I'd have thought that if the chemical was harmful to the system then the manufacturer would say so? They can't label it as non-harmful when it actually is?

I'll drain it out first thing today in that case though. It's been a total of 48 hours so still within the timeframe that the manufacturer says.

This issue that I have now though is this.....

In the video shared above, the guy says that X800 dissolves the gunk in the system.

If this is how it works, it should dissolve the gunk and start working while it's still in there. But it hasn't. Even with the X800 in the system, the boiler still cycles on and off, never getting up to the temperature set out by the thermostat?

Why is the boiler still doing this?
 
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