Central Heating System. Where to start

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So according to my previous posts asking for advice these seem to be the issues.

Conventional system, tanks in loft, cylinder. We have plenty hot water and heating but the issues seem to be:

Blocked pipes. Magnets stick. Probably need cut out?
Air in system and noisy when starting up having to bleed a few radiators a lot - needs Powerflush due to sludge
Radiators coming on with hot water only - possible 3 port valve needs replaced
Water running in loft or tank overflowing outside occasionally - ballcock?

Now I’ve asked two companies to come out and both have let me down. Do I try British Gas? Do I just live with this till we need a new boiler? The house is roasting tonight as radiators cane in when heating water.
 
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CBW

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You can try British Gas, but be warned: they will probably try to sell you a new boiler, a power flush (which may or may not be needed).

I don’t know from previous posts if you’ve stated your location, as someone on here maybe able to help.
 
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Glasgow. The boiler works ok and has been serviced the company just didn’t phone me back to do the other stuff
 
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You were asked this in your previous thread...... is water flowing from the vent?, especially when the circ pump stops or starts. Also was the circ pump renewed recently and if so did your problems start then?.

Edit.
You could write a small book on vented systems that start drawing air in/vent pump over when a circ pump or new rads are installed or pump mode/speed changed/increased and the systems are perfectly clean, its quite simple to convert these systems to combined vent and cold feed which in my experience will almost guarantee 100% success, I have even seen systems with the much vaunted VCP system (Boiler) Vent, Cold feed, Pump, with the above problems "cured" by converting to the combined vent and cold feed, my > 50 year old system was installed in this fashion and some of my rads are > 40 years old, the system is absolutely spotlessly clean with only the odd drop of inhibitor added over the years.
 

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Thanks. The pump was replaced recently but I can’t tell about the flow. Guess I need to find out if anyone can do this
 
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you most certainly dont need a powerflush if the house is roasting, you do have a few issues and BG is the last place you should look , there are a few good lads on here that cover Glasgow depending where in Glasgow you are, if you narrow it down I might be able to recommend someone
 
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Thank you I just feel companies are only interested in servicing a boiler or fitting a new one. I live in Baillieston in the East End
 
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I sympathise with you, my first house the central heating came on with the DHW, it turned out once the flow was started thermo syphon would keep it running, so even if central heating only switched on for 10 minutes upper floors got warm.

This house also had a problem, two pumps, and if either went on then both zones heated up, the zone with pump not running the radiators heated up with reverse flow.

What was recommended to me was set the TRV's correctly, I didn't, I fitted two zone valves, already commissioned the work before the TRV suggestion was made, however if the TRV is set to 20ºC then that should mean room does not exceed that, with programmable should ensure the room is never heated unless required.

Yes I agree it should not happen, rooms should not heat up when only DHW is called for, but when I fitted programmable TRV heads in 2019 the eQ-3 cost me £15 each for bluetooth version and so easy to fit, no wiring involved, or plumbing, unscrewed the wax one and fitted electronic.
 
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thanks. none of our radiators have TVRs. I’ll look into this
Oh, how unusual, I am an electrician, I don't get evolved with plumbing, but sisters house back in around 1990 had TRV's and it seems odd to find a home without them.

The modern gas boiler is different to old gas and oil boilers in that is can extract the latent heat, to do this the return water must be cool, and to do this the boiler needs to modulate (turn down the flame height) so the TRV sets room temperature, and as it closes it causes first more water to flow though those still open and then for the by-pass valve to lift and as the hot water gets back to boiler the boiler auto turns down, once it can turn down no more the boiler starts to cycle off/on, however it can never turn off completely, so we fit a wall thermostat in a room normally kept cool, with no alternative heating, and no outside doors to turn off system when warm weather arrives, (if such a room exists).

This means the whole system should be controlled in the main by circulating water, only thing the thermostat does is turn it off in summer.

Oil and very old gas however work different, they have a thermostat in the main room, there is also a very modern system where the thermostat does not turn on/off but turns the boiler down, and connects to ebus, but not very common, Opentherm is such a system.

So the old system often had no run on system for boiler to cool, so the Y plan with a three port valve defaulted at DHW, so the boiler cools by heating the DHW rather than heat escaping through the flue, but the three port valves also had faults, main problem was the V3 micro switches sticking in, the complex internal wiring causes all sorts of odd things, but it was found when they stick by latching the valve into the bleed position with the manual lever often the central heating would continue to work of sorts.

However it resulted in summer the radiators would get warm when heating the DHW, may be worth checking if lever latched on.

I will admit as an electrician I was at first tricked by the Y Plan, as it seemed I was getting odd readings, and also found many incorrectly wired, missing DHW off wire from tank thermostat and programmer common, plus using earth wires for live. It seems I was not the only one who found the Y Plan hard to understand.

However if set up correctly it works well, but should not use a type AC RCD when using Y Plan, not that that will bother you.

My own house was such a mess when I moved in, had to go outside walk down a set of steps and plug in the central heating pump when turning it on, reverse turning off, and I still can't believe the previous owners put up with that, seems they used a wood burning fire. The oil heating engineer it seemed had no idea how to wire, due to having two pumps, lucky I did, but it seems in Mid Wales where I now live in the land of the blind the one eyed man is king, and there are a lot of so called tradesman who would not have lasted a couple of months in North Wales.

I did take a careful note of the sticker on the boiler saying call this number for service to ensure I never use them, as clearly they have even less a clue what they are doing, I suppose a plumber is a worker of lead, so does work from sealing roofs to tuning organs as well as pipe work, and with such a range one can excuse them not learning how to do electrics as well, even if we do use leaded solder.
 

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