Heating question - major flood after service, what’s gone wrong here?

[Mottie]

Scalding hot is pretty meaningless.

Only going on what I was told. Regardless, it was a lot hotter than its ever been since it was installed.

 

[DP]

Well, I’m not in a position to dispute anybody as I simply don’t have the knowledge on heating systems. All I can go on is the facts of what has actually happened.

For the record though, the landlady is very good to my son and his fiancée and they don’t like to see her ripped off. Only this week they told her of a fault on the washing machine and she’s having a new one delivered. There is a recording of the plumber saying “Yeah, I left it turned up too high, that’s all it was”. It’s been fine for the last two winters - house is plenty hot enough. Okay, there still may be something wrong with the design of the system but the fact remains that it has been fine since the boiler was installed for a few years right up until it was serviced. 2/3rds power has been fine. Maybe the boiler was overrated for that house in the first place?

The boiler should be able to run at full power, end of. If it was at 2/3 power and has not highlighted any issue does not mean it was correct for two years, more a case of the defect was not apparent for that period.
A condensing boiler left at full tilt should still work, be it the boiler will only condense as long as return water is below 55 degree C.
If you guys feel for the landlady, it is the installation that needs checking instead of assuming Max setting on boiler is the issue, which it should not be as there should be no hot water in the header cistern regardless of the boiler flow temperature UNLESS the water reaches 100 degree C or thereabouts in which case the boiler would shut down safely long before that point is reached and water and steam will discharge into the cistern as it should ( reason why the vent is curved to allow discharge into the cistern)

 

[DP]

Pumping over would not last long.

Pumping over is result of pump creating differential in pipework due to incorrect, result is feed and expansion pipe is at negative pressure and vent at positive pressure, result water is pulled from the cistern and pushed out of the vent pipe.

While Mottie is latched onto high boiler setting, at lower setting, pump over would still have taken place and resulting aeration of system water would accelerate corrosion in the system. It does not take long to perforate the radiators and mud like sediment blocks the system

 

[Mottie]

The boiler should be able to run at full power, end of. If it was at 2/3 power and has not highlighted any issue does not mean it was correct for two years, more a case of the defect was not apparent for that period.
A condensing boiler left at full tilt should still work, be it the boiler will only condense as long as return water is below 55 degree C.
If you guys feel for the landlady, it is the installation that needs checking instead of assuming Max setting on boiler is the issue, which it should not be as there should be no hot water in the header cistern regardless of the boiler flow temperature UNLESS the water reaches 100 degree C or thereabouts in which case the boiler would shut down safely long before that point is reached and water and steam will discharge into the cistern as it should ( reason why the vent is curved to allow discharge into the cistern)

I am not disputing any of the advice given on here. Thanks to all who have replied and as I said, I’ll get my son to get the system layout/installation checked.

 

[DP]

Only going on what I was told. Regardless, it was a lot hotter than its ever been since it was installed.

The Y plan that is fitted should regulate hot water temperature ( cylinder stat does that), ambient temperature ( room thermostat does that) regardless of boiler setting ( boiler has own control system). I wonder if long term pump over has effected the three port valve or the pump. If the system ever gets checked thoroughly, I wonder if the blame would land on visiting lads shoulders or bad installation.

 

[Mottie]

The Y plan that is fitted should regulate hot water temperature ( cylinder stat does that), ambient temperature ( room thermostat does that) regardless of boiler setting ( boiler has own control system). I wonder if long term pump over has effected the three port valve or the pump. If the system ever gets checked thoroughly, I wonder if the blame would land on visiting lads shoulders or bad installation.

My son said that the pump that was replaced looked like it had an old analogue thermostat dial on it?

 

[ianmcd]

My son said that the pump that was replaced looked like it had an old analogue thermostat dial on it?

never seen a domestic pump with any kind of analogue thermostat on it

 

[ianmcd]

My guess and it is simply that as not enough info to go on, the system has a combined cold feed and vent, the cold feed has become blocked, the lad servicing the boiler has turned the boiler stat up to max, this has been enough change in expansion for the system water to push up the combined F&E and has overfilled the F&E tank, hence why it takes a short time when heating or HW turned on before it over flows, I would be checking the over flow pipe in the F&E tank

 

[snb]

looking at the pipework it looks like the feed is before the vent. with a pump on speed 1 this may work ok. I'm guessing when he tried to max rate the boiler it kept overheating so he increased the pump speed, not realising the feed and vent are plumbed the wrong way round and now the extra flow is causing the system to over pump.

If this is the case then it is the installers fault when the new boiler was installed, but when he serviced the boiler he should have also checked it was piped correctly

 

[ianmcd]

but when he serviced the boiler he should have also checked it was piped correctly

in whos world exactly ? Are you saying if you are asked to do a boiler service you check all the pipewwork and controls ? B**llo**s

 

[DP]

looking at the pipework it looks like the feed is before the vent. with a pump on speed 1 this may work ok. I'm guessing when he tried to max rate the boiler it kept overheating so he increased the pump speed, not realising the feed and vent are plumbed the wrong way round and now the extra flow is causing the system to over pump.

If this is the case then it is the installers fault when the new boiler was installed, but when he serviced the boiler he should have also checked it was piped correctly

Page 33-41 details what service entails
What are the chances the outer Case was not removed on the boiler in order to service it, bearing in mind the boiler was installed recently. What are the chances that boiler manual is not on site to furnished the relevant data not realised until the case is removed. I am purposely being vague as you will know what I am implying.
Crux of the matter is, boiler left on Max is not the cause of the flood in my opinion, but then in my wife’s eyes I know nothing about boilers as she threatened to call an engineer to fix our system after I installed two TP 5000 to Y plan on the Vaillant ecotec 831

 

[dilalio]

Is there an overflow connected to this system and did it not show any discharge?
If f&e didn't split how did water spill out?

Still waiting for this answer.

Also, did the install involve modifying any other pipework other than at boiler location?

 

[DP]

Still waiting for this answer.

Also, did the install involve modifying any other pipework other than at boiler location?

The flood thread has lost steam
It would be nice to have visiting “service” engineer’s input on the flood

 

[snb]

in whos world exactly ? Are you saying if you are asked to do a boiler service you check all the pipewwork and controls ? B**llo**s

Are you telling me that you don't cover the basic safety checks on an open vented system

 

[Mottie]

Still waiting for this answer.

Also, did the install involve modifying any other pipework other than at boiler location?

Sorry, I must have missed that. Not sure about the overflow but I imagine that would have been checked as the bloke fitted a new F&E tank and although I’m not sure about the boiler pipework, it’s in the same place where the old boiler was and only has a flow and return to it so I imagine not. Oh, and a mag filter but I don’t know if that was there on the old boiler but looks pretty new.