MCB tripping when hot water or heating switched on

[malibu2606]

Hi, I really hope someone can help as we are currently without hot water or heating.

We have a Grant Euroflame 50/70 External Oil Boiler with a traditional gravity fed combination vented cylinder (small header tank as no loft). I believe we have a Y system and have noted a valve on the pipes under the cylinder.

My husband got up this morning and noticed that the central heating programmer was off completely (no display). He checked the CU and the MCB (marked 'immersion') had tripped (we think most probably when the heating was on timed to come on before he woke up). We have had the hot water and heating working fine up until then.

Now, whenever we flip the MCB back up one of the following happens:
1) RCCB trips along with the MCB immediately
2) The MCB remains okay for a short while and then trips (RCCB stays okay)
3) The MCB remains okay for a short while then trips as well as the RCCB

This is without turning the hot water or heating on.

When we manage to the the MCB back up and have tried the hot water or central heating or both (the display on the programmer came back after the original MCB reset and doesn't go off even when the MCB trips again) - the light comes on the programmer, the boiler can be heard, the pump seems to be running and the pipes start heating up. Then it just trips after several minutes - tripping either just the MCB on its own or the MCB and the RCCB.

I don't understand as up until this morning we have had no problems with the heating or water. I have checked the oil tank and there is plenty of oil in there, the valve on the system seems to be moving from W to H okay and the pump seems to be making all the right noises so assume that's okay too?

There is an immersion element in the cylinder wired in to its own switch, which we don't use and is switched off. I have been out to the boiler and there is some wet on the side of the housing due to an overflow pipe from upstairs dripping down next to it. I've temporarily redirected the overflow (another job to sort!) so that it is not wetting the boiler housing. Inside the boiler housing the floor is a little damp I guess but what I would expect from a housing which is outside. I can't see how this could really be the problem as the boiler housing is out in all the elements and has seen considerable rain before!!

What can I do to try and rectify this problem. I am reasonably handy for a GIRL and having recently moved into the area I haven't got a recommended heating engineer/plumber or electrician I can call....If I can sort it out myself safely then I would prefer to do this.

Can anyone advise where to start to pinpoint the problem?

Thanking you much in advance,

Jeanette

 

[PrenticeBoyofDerry]

It could be a number of issues.
Generally the MCB will trip if overloaded (unlikely in your case) or if you have a short circuit.
The RCD will trip when there is earth leakage.

To narrow the fault down items would required to be taken off load and system run.

It is possible that either a pump or a port valve has become faulty and requires replacing.

Disconnecting these can be complexed if you have little knowledge on how they operate or are wired.

I advice you contact a plumber with electrical knowledge or an electrician with plumbing knowledge.

 

[malibu2606]

Thanks Prentice boy - I had problems with the pump in my old house as it kept jamming but never tripped the electrics. Will check the spindle is spinning freely in the pump shortly when I *try* and turn the heating on. The valve is moving okay from H to M to W okay when I change the programmer options. There is no damp/water around the valve or the pump.

Is it possible it is the programmer itself? I ask, as I have just bought a new one with room stat included (currently we do not have a room stat) - we have not fitted it yet. What I don't want to do is fit the new thermostat and for it to blow.

It was odd that the programmer display was blank the first time the MCB tripped, but since then every time the MCB has blown the display remains.

Do you think it could be the wet coming in to the bottom of the boiler housing, there are wires located lying across the bottom of the boiler housing but don't seem to be wet? Truth is, we are very short of cash at the moment (having just moved in) and will be plucking someone out the Yellow Pages. If there is anything I do to identify the issue, and even resolve it, I am sure that will help.

Panicking slightly as although we are enjoying a mini heatwave right now, my house is normally freezing and I have two small children to think about!!

All replies gratefully received.

Thanks very much,

Jeanette

 

[malibu2606]

Okay - programmer display is blank this morning. I assume that means it has some sort of battery which keeps it going after the electrics have gone.