Grant 26e Vortex Combi Oil Boiler

[pharenheit]

The Grant boiler was installed 4 months ago and seem to function fine with the exception that I have to top it up every 8/9 days.

Normally water pressure is steady at 1 bar and then after 8/9 days drops to zero, over night, during what seems to be, some form of internal process it does to itself at around 4am when the heating is off. The boiler has never failed during working hours (so to speak)

This is not normal compared to other combis I have had and I can't find any form of leak from Rads or piping. I have 15 rads and no external mods to the boiler.

 

[dcawkwell]

There is a chance that the expansion vessel in the boiler has lost it's charge and the water is being dumped outside via the pressure relief pipe.
Tie a plastic bag around the pressure relief pipe. Does the pressure climb to 3 bar when operating on central heating?
Otherwise you have a leak in the central heating pipework somewhere.

 

[Andy4444]

If its not an install problem (leak) then the exp vessel will be covered under warranty providing boiler commissioned and reg card sent to manafacturer.

According to Grant most failures for recently installed boilers are down to installation errors.

Did you get a CD10/11 form from your installer/commissioning engineer?

 

[Boilerman2]

It is possible with 15 Radiators + the large water content of the boiler that the on-board expansion vessel may not be large enough for your system
(See the boiler M.I's for info on vessel sizing) you may need to fit an additional vessel on the system somewhere

 

[Andy4444]

Sgree BM. In terms of exp vessel sizing the MI's spin it out to British Standards....your Installer will hopefully have accounted for the system volume?

 

[pharenheit]

I cant find any leaks anywhere and I don't understand the expansion thing although it does seem to keep coming up. Can someone explain what the expansion vessel does?

Also if I run the boiler on hot water only will the possible problem with the expansion vessel not occur due to the rads not being used??

 

[Boilerman2]

When water is heated it increases in volume(expansion) water cannot be compressed, therefore a means of accepting this expansion has to be employed, otherwise the pressure in the system would rise to destructive levels!

An Expansion vessel is a container with a membrane down the middle one half contains compressed air, the other side is connected to the system, air, unlike water can be compressed, and so the expansion vessel accepts the increased volume of water preventing excessive pressure rise, HOWEVER there are limits to the amount of water that can be absorbed by the vessel, the larger the system (litres) the bigger the vessel needs to be.
The problem with Oil Combi boilers, is that the Thermal Store holds many litres of water, and the biggest vessel that the maker can squeeze into the boiler case is often not large enough to cope with more than say 7 or 8 Radiators capacity.

Hope this explaination helps

 

[Tom1981]

I own exactly the same model of boiler. I've found, somewhat annoyingly that if you fill the boiler with the power ON the DHW pump kicks in a pushes on the pressure gauge.

Try filling the appliance with the power OFF, also best when cool, this will give a real pressure reading rather than one that's been effected by a running pump.

 

[pharenheit]

OK... expansion makes sense.

I'll try the cold top up plan but can I check the expansion pressure myself or is it an specialist engineering type thing?

 

[Andy4444]

Did you get a CD10/11 form from your installer/commissioning engineer?

OP - any chance of an answer to the above question?

 

[pharenheit]

Nope... A guy came round a few days after install and checked the work, offered to do annual servicing. He filled in the back of the booklet with dates and things like nozzle size. There is a 2 part CD10, blank, in the booklet?

 

[Boilerman2]

Next "Leading Question" as the CD10 is blank and you have No CD11 Commissioning Certificate has this Installation been notified to the Local Authority Building Control Department which is a LEGAL REQUIREMENT - try selling your house with out this !!

 

[pharenheit]

errrmmm....??? Who would(should?) do that? I imagine it has been registered; a woman came round from the council to sign off the work. I doubt they would have approved the grant if it wasn’t all dotted and crossed? Should I have a certificate from them too?

 

[Andy4444]

Who installed the appliance? Who organised for the person from the Council to come to your property to sign-off the appliance? Have you registered Warranty with manufacturer?

 

[cider]

Who installed the appliance? Who organised for the person from the Council to come to your property to sign-off the appliance? Have you registered Warranty with manufacturer?

Get real paper shuffler. Hows that helping him sort his problem.

If the waters being dumped through the prv at 4 am it may be the frost stat is kicking in & firing the boiler but the pump isn't running.
With the nature of most boilers but esp oil boilers the unit will overheat before the thermostat kicks in and end up emptying itself through the prv.
However the tell tale sign is the overheat stat would normally trip as well.