Winters coming and here comes the baxi 105 problems

NatB

Hi
I'm experiencing some problems with my Baxi 105e (non condensing)

We had a new expansion tank fitted but now we've started using it again we've a couple of problems.

When the CH is working the pressure jumps about 2 bar and if it's been topped up to around 1.5 (incoming water pressure) then the PRV valve opens due to the pressure going above 3 and water is vented slowly. When the CH is off the pressure guage then has dropped to 0. Carefully filling the boiler to less than 1 bar helps solve this problem but still doesn't seem right.

The boiler heats up ok, rads get heated but then the boiler will shut off for a while before firing back up again. The problem is that the rads have cooled too much so are tepid by the time it kicks back in. Changing the temp doesn't seem to make the boiler fire up any quicker but resetting the boiler does. During this process I've notice the return pipe at the boiler doesn't seem to be anywhere near the same heat as the flow pipe which is really hot at the boiler.

When using the boiler it makes a rather loud humming sound.

A basic balancing of the system was done after the downstairs rads were taken off and cleaned out but to get the heat where we wanted it the lounge rads have had to have their lock valves left more or less wide open.

I'm thinking this may be the symptons of a pump that is not pumping enough in combination with some other pressure problem. I gave the plumber a hand when he installed the expansion vessel (he managed to do it without removing the boiler from the wall) and he installed without adjusting the expansion tank precharge pressure.

Any help appreciated, thanks.

davebgas · Posted: Sat Oct 10, 2009 10:53 am Post Subject:

Hate to say it but first things first, have u checked the new vessel? Has it lost it's charge or is water coming out the valve?

__________________
Incorporated Engineer with IGEM & Registered with the Engineering Council UK

Boilerman2 · Posted: Sat Oct 10, 2009 5:17 pm Post Subject:

How the Hell can you install a new vessel WITHOUT CHECKING THE PRE-
CHARGE?? it beggars belief!!!

It does sound like you may have a number of issues regarding your installation which should be checked out by an Engineer that knows what he is about!

bengasman · Posted: Sat Oct 10, 2009 7:33 pm Post Subject:

I am fairly sure that new expansion vessels have the same pressure when they are sold, as new tyres at that moment.
Was the job done on a friday around 4pm?

__________________
Don't feed the troll.

NatB · Posted: Sun Oct 11, 2009 12:52 pm Post Subject:

Well, just emptied the system and checked the ev which didn't have any pressure (or my car tyre pump isn't showing one!). To be fair, it's noted on the side that it's precharged.

Will charge it up and see how it goes, I've a feeling with the right pressure in the system the pump should be working a bit better.

NatB · Posted: Sun Oct 11, 2009 11:25 pm Post Subject:

Well, after repressuring the EV - thanks to the FAQ I managed to only have to do it twice - and the system is keeping the pressure nice and even. Cheers for the heads up.

Still, it's still switching itself off. Rads are heating up well enough, all runs good but just cuts itself off after a while, I assume when the desired temp is reached, but the temp drops right down again before it fires back up.