Keston condensate drain

[Paul Roman]

How good a fit is the condensate drain connection to 22mm overflow tubing supposed to be? The tube itself won't fit and the connector fittings seem too loose.

Thanks

Paul

[Andrew Gabriel]

The instructions suggest you don't glue to the boiler, as you would then have difficulty if you needed to take boiler down for some reason. I originally just used a coupler which was glued on the runaway/lower side only. Later I changed it so first 6" of runaway is a length of clear plastic hose so I could actually see when it was producing condensate, and this is a good tight fit on the boiler outlet and the following 20.5mm pipework.

[Christian McArdle]

Overflow piping is normally 21.5mm, not 22mm. Have you got the right pipe?

Christian.

[Tim Mitchell]

In article , Andrew Gabriel writes

The fitter who put ours in did glue it on (obviously didn't read that bit)

Just to hijack the thread slightly, does yours make a sort of pulsing "swishing" noise when it first starts up on full throttle? We've only had it a few weeks and I don't remember it making that noise to start with, more of a constant sound. It now sounds like the burner modulation is overcompensating, then getting too low and turning up again, and repeating this cycle. Or I could be imagining it and it's always done that.

[Andrew Gabriel]

I fitted my own, precisely so it was done correctly. :-)

What sort of frequency is the pulsing? The description doesn't match anything mine does, but the sound mine makes did change over first few weeks. I've seen reports here of gas meters which generate a pulsating gas pressure at higher outputs, and you can get it changed if that's the cause.

[Tim Mitchell]

In article , Andrew Gabriel writes

About 1Hz, maybe a bit faster. There is no visible effect on the control panel or the flue output and it all works fine. It only does it for the first 30 seconds after igniting, then the sound settles down to a normal gas burner sort of sound.

We enclosed it in a kitchen wall cupboard recently, I'm wondering if that has made it sound different and that's why I've noticed it.

[Andrew Gabriel]

I ran mine a few times before completeing the commissioning, and the factory set burn rate was too low. This had two effects; the boiler was running at about 10% under full power when measuring the gas flow rate, and when it had modulated down to the lowest possible level (typically a minute before it switched off), there was a sound at probably around 5-10Hz which I imagine was the gas ignition jumping back into the gas/air mixer. Keston told me to adjust a screw on the gas valve, and that fixed both issues.

[Ed Sirett]

Since the condensate drain needs to be removed for servicing - to clean it out it is important that you don't weld the condensate drain to the boiler!

I have not measured the OD of the boiler drain but I would expect it to be 21.5mm the same OD as many plastic pushfit overflow piping systems. This is the same OD as the old 3/4" copper pipe.

You may find that a 22mm Speedfit coupling fits securely but easily removed

[Ed Sirett]

I have fitted 2 C25s this year including one in my own home. On both models this hapened. I have nick named this quirk 'buzz-bombing' it is some sort of instability in the combustion system on initial firing - which happens at ignition time. When the boiler is alight only then it spins up to full power.

In the one case Keston had to fit a flow restrictor on the 32mm inlet tube inside the casing and then adjusted the combustion system. On my own it went away after I adjusted the combustion system and refitted the case.

[Ed Sirett]

You also, anyone fitted a C25 where this has NOT happened?

[Andy Hall]

I believe it varies by make. I ran into this and had some incompatibilities.

IIRC Osma is 21.5 and some others (might have been Marley) are 22.....

.andy

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[Paul Roman]

Thanks for all your replies. I've opted to fit 0.5m of 19.5mm clear poly tubing. It makes a good seal but can be twisted off if required and provides a visual check that the condensate is draining OK.

(BTW the overflow tube was Wickes and labelled 22mm - too loose for this application.)

Hopefully I'll have the wiring finished tomorrow and it will be ready for its first firing.

Paul

[Tim Mitchell]

Is this an easy adjustment or requiring a combustion analyser? I could get the installers back if necessary but they were a bit scared of the thing in the first place.

[fred]

In article , Paul Roman writes

If they still use an unconstrained O-ring to seal the condensate plug, lose it & replace with a fibre washer & sealant (I used hermetite golden). Too loose & it leaks, tight enough & the O-ring deforms & pushes out and er . . . leaks ;-/

[Andrew Gabriel]

On the subject of condensate, I suggest you check very thoroughly for no leaks -- it is acidic and will quickly do damage. In my case, the exhaust spiggot was leaking between the stainless steel and the muPVC collar they welded to it, which resulted in a puddle of condensate forming on the top of the casing and it had started running inside. Fortunately, I spotted it very quickly before it had a chance to do any damage, but that was just by chance. The other thing I found when initially assembling it was that I had to enlarge the (mounting) holes in the exhaust and inlet gaskits they provided, as the holes were smaller than the protruding bosses from the case, and this prevented the gasket sealing. (When I had the leak, I assumed I hadn't done this enough, but further investigation showed this wasn't the cause.)

I remade the exhaust spiggot. As a further test, I then left a hose pipe trickling into the end of the exhaust flue for 10 - 20 minutes or so, making sure no more water was leaking out anywhere, and I would suggest doing the same before you fire up the boiler for any period of time. Make sure the water is running out too - nasty things might happen if you start filling up the heat exchanger and combustion chamber - just a tiny trickle from the hose end should be enough to check for water leaks. Someone else here reported finding the flexible exhaust host inside the boiler was not correctly fitted, resulting in a large leakage of condensate into the boiler, which corroded through the casing. The test above would have found that before it did any damage.

One other thing - when I pressure tested the water system (with air), I found there was a leak inside the Keston, in my case where the drain c*ck screwed into the elboe casting. It was easy to fix, but don't assume the water pathway has already been checked for leaks, because it clearly hadn't.

Finally a heads-up - Keston have told me they will no longer attend DIY-installed boilers for commissioning, nor I suspect attend for warantee repairs, unless a CORGI has first checked the installation, although they do give phone support. They used to be OK about doing this when I bought mine, and I believe the Keston C25 has been a popular boiler for DIY install (certainly in this NG) because of Keston's support of DIY installed boilers in the past. However, their change in policy means some people might want cross Keston off their shortlist in the future.

[Ed Sirett]

You absolutely need a combustion analyser (sub 300 including VAT). Essentially you try to get the flue gases at 8-9% CO2 over the entire power range. There is an adjustment screw on the gas valve.

[Ed Sirett]

On a sample of 3 Kestons I have not had the spigot problems or the leaks. I do have a 'beef' that the water connections have to be taper threaded because the seals would other-wise be made on the steel boiler casing.

Should the condensate not drain then the boiler has a sensor for condensate overflow and (should) will lockout.