Worcester Combi Boiler 28CDi Loss of Pressure

[richardson45]

Help! I've read all the stuff I can find on here about drop in pressure, but have a specific question which I haven't found on any forum.

Last week our boiler leaked, flooding the airing cupboard (great way to spend a sunday swimming in the airing cupboard!) It was found to be the water to water heat exchange part that was leaking, and this was replaced. However, we then noticed that our power shower had no power, and squeaked a lot when the heat was turned up and down and the water wasn't that hot even on maximum temperature, this shower is run through the combi boiler. I then noticed that the pressure gauge on the boiler was well below the usual recommended 1.6 bar. Before the water to water heat exchange was replaced in four years never had a problem with the pressure of water, or temperature of water.

I re-pressurised the system as per the instruction manual and left it overnight. The next morning the pressure had dropped. Again, I re-pressurised it. This morning I have come to check it and it has dropped to zero!

I've checked the pipe outside by taping a bag over it, and no water appears to be coming out.

Also went round yesterday morning and bleed all the radiators and checked for leaks - they didn't need bleeding and there don't appear to be any leaks.

Any ideas gratefully appreciated.

Tina.

 

[gas4you]

Firstly when you say power shower, do you actually mean a 'power shower' or is it your loose terminology for a mixer shower?

Combis cannot have a proper power shower working off them. They ca only give the hot water they want to rather than a pump trying to pull more water out of them.

Have you checked inside the boiler casing for leaks around the plate he, or the auto air vent. Could be small but steady leak that is evaporating in the heat of the boiler. Look for staining.

If not top up boiler pressure and isloate from system with the f & R isolating valves. Leave for as long as possible and check pressure gauge.

If it hasn't dropped then it is a leak elsewhere on your system.

Also try only pressurising to 1.2 cold and whilst your system pressure is at zero with boiler drain open, test expansion vessel pressure. See FAQs.

If low re-charge it, if water in it replace.

 

[bengasman]

You can not run a power shower from a combi, nor an electric shower for that matter.
If your pressure goes from 2 to 0, you have lost a litre, if not 2. This must be visible somewhere. Unless your vessel is flat or dead

 

[richardson45]

okay it must be a mixer shower then, another thing that we were mis sold on it appears when we bought this house!!!!

i agree it should be visible, however, it isn't! we have again re-pressurised it to 1.6 bar, and have had the central heating on for about two hours and already it is down to below one. If that is how much water being lost when it is dropping, i'd love to know where it is going. There are no wet carpets/flooring and the pipes going into the combi boiler are all dry.

as this only started happening after the water to water thing was replaced, is there any views on whether this means the part is faulty? Just find it a coincidence that it all started after this new part was put in last week, although that clearly needed replacing having seen it!

 

[richardson45]

i got it wrong, this is leaking out of the pipe outside the house, have just checked the bag i put over it and it is full of water. What does this mean? I think the reason I thought it wasn't is because there is so much rain today!

 

[bengasman]

this is leaking out of the pipe outside the house

Your prv is letting by. prvs let by after having let out excess pressure and getting dirt on the seat of the valve. If you just had your heat exchanger replaced, it would seem that your system is suffering from build up of limescale and corrosion. I don’t know why your plumber replaced the h/e, as they are easy to remove and clean out, and very rarely are a problem in itself. Your system needs cleaning, otherwise the problem is likely to come back.
Prv on this model very easy to replace or clean. Your boiler is a very good one, and with a bit of maintenance should give you years of reliable use when the necessary work is done.