Help needed on water ingress in boiler flue

[Caroline43bt]

This is a bit of a saga which I hope someone may be able to shed some light on and perhaps suggest a new approach.

Firstly make and model: Camray 5 installed in 1999. Regularly service and currently running perfectly at about 90% efficiency. Have all the servicing and repair invoices and reports going back over the years.

Important to note that this was installed in an existing chimney which had been used by solid fuel stove. Steel liner installed with vermiculite surrounding and capped at top.

Towards end of 2014 the boiler broke down and the engineer replaced the oil pump which he said had failed due to water in the fuel storage tank which we removed. (Since then we have had replaced this with another pump Aug 2016). We have emptied the tank, repositioned and replaced all fittings to ensure no water can enter at any point.

Anyway just over a year ago we noticed a large pool of dirty water coming out around the bottom of the boiler, what was happening was that sooty water was coming down the chimney flue and running out the original soot box set in the wall behind the boiler. The water damage continues up the face of the chimney and is visible in patches in the roof space also.

We removed the flue liner cover on top of the boiler and on closer inspection there was evidence of water ingress with a small hardened river of dried soot coming down the flue pipe into the top of the unit. We cleaned this all up and hoped for the best. We think we may have damaged the flue liner when we did that as the water does not now come down liner, merely exits through the soot box. It is now relatively clear too as we assume the amount of water coming down has cleaned the sooty deposits from the chimney.

So we have gone through a process of elimination to get to the root of the problem. Firstly replacing the cowl on top of the chimney and ensuring there can be no ingress down around the chimney pot. Secondly replacing the chimney cope and re-roughcasting the chimney. We have recently fitted an additional cowl around this to eliminate any wind blown rain water.

But the water still drips out of the soot box even though it has been dry here for nearly two weeks. Usually get about 1/2 to 1 litre a day.

Boiler runs during the day but is off I guess between 11pm and 6am. Can be dry during the day and then gives out at night. Today it's been dripping all day and although there was a small amount of rain last night how it could come in defeats us. The attached image shows how we 'manage' the drip the location of the soot box in relation to the boiler from where water exits.

It's a double chimney with a separate liner serving an open fire in the living room so we've tried not lighting that / using as normal, but there is no pattern with that either.

Come to the conclusion it must be caused by condensation from the boiler but how if it's running correctly?

Next step is to replace with a new boiler and position on the outside of the house which is a fairly drastic course to have to take, so welcome any suggestions from experienced engineers. Needless to say at end of tether.

 

[foxhole]

Any boiler will produce moisture as it's part of combustion, should be a condensation trap in flue to accommodate this.

 

[Caroline43bt]

Thanks for taking the time to respond.

Your response throws up another two questions:

1. Why has this only become an issue in the last 15 months?

2. If a condensation trap were fitted would you expect to collect up to a litre of water a day from it?

 

[oilhead]

If the water were coming down inside the flue liner, it would not exit where your container is placed. If it were coming outside the liner, it would stain the outside of the flue. Collecting the water where you are, it appears to be a leak of primary water. Remove the outer casing and insulation and inspect the boiler body.

 

[Caroline43bt]

The boiler is sound, this was first thing we ruled out.
The water comes out from the soot box which is behind the boiler unit. There are no water pipes in, or near the chimney. There may be a small hole in the liner pipe caused when we cleaned it which could permit water exiting down the inside of liner towards the soot box.
Incidentally it's wet and mild today and there is little water collecting.

 

[oilman]

A 1999 Camray will not be a condensing boiler. If it is not coming from the water side, it must be water condensing from the flue. If that is the case it will need a new liner. This has been in for 17 years, so it's possibly at the end of its life. It would normally go on longer but it would have been a good installation at the time. It could have been fitted upsidedown.

That vintage of Camray did not operate with a high enough flue temperature on occasions, and was running in near condensing mode. Bending a couple of the tabs on the baffle plates to allow more gases through was one way of fixing it. Do you have combustion figures for the net flue gas temperature?

 

[Caroline43bt]

Thanks for take the time to respond Oilman. Appreciate your time. The net recorded in December at last service was 94.9. I notice a marked reduction in flue gas temp over last 3 years coming down from 185 deg to 110 deg but not sure that's relevant. Efficiencies broadly similar.
I imagine relining won't be the easiest but running out of options now.

 

[oilhead]

To give any credence to flue gas temperatures, you need to be sure that you are comparing like for like. The boiler should be run for 10-15 mins before any combustion test. As oilman says, these boilers ran in near condensing mode, and on balanced flue versions where you can see the terminal, it is not unusual to see steam for 5 mins after initial startup. 2 litres a day still seems a lot though.