Britony Combi SE 100 boiler fault

[diamondgas]

Hi Ian ... hmmmm ... re-read again and your conclusion sounds logical. Thing I'd be doing to check that the diverter was operating correctly is, from cold, hand on the return pipe. If it heats rapidly then it isn't shutting off the domestic circuit! Also checking out how rapidly the flow heats up. Ideally it should be gradual rather than rapid.

Regards pipe sizing You do have at least 22mm coming from the boiler yeh?

Now i know you've said you've checked for a filter, the manu instructions say there's one in the return connection furthest right! It may be incorporated in the valve itself! I've only ever worked on one Chaff of this era by-the-way!

Regards the pump, it looks like a grundfoss. You should be able to change the head for a 15/60 no problem. You can purchase the head on it's own, about £60...

You say the first three rads are turned off. Try the circulation with them turned on see if makes any difference just to rule out or in a blockage beyond these three radiators.

I''m edging towards the diverter valve as most likely problem, dislodged pump impeller maybe then beyond that a restriction elsewhere! Temperatures differences can tell a lot about how the boiler is working! Oh, bye the way! When your feeling the return pipe check the return above the pump into the boiler and the heating return under the boiler. If there's a huge difference between them then the diverter comes more to focus once more! The bi-pass is less likely to effect the circulation that much in my opinion!

 

[Gary71]

Until you deal with the movement of water thru the plate heat exchanger you are just messing, change the diverter valve assembly, it comes as a kit, change the bypass while your at it as it's fairly inexpensive, this advice is based on being the manufactures tech(for my sins)

 

[Gregorian]

Many thanks, Gary. I'll do that but the whole right-side hydraulic assy below (including the 3-way (diverter?) valve body P/N 1302411 and the Water Control valve P/N 1305290) was replaced only 2 months ago. I spoke to Ariston and he saide he had never known a new one to be faulty. Nevertheless, I shall clean and/or replace the valves again. He also said that a Combi SE 100 should have a 15-60 pump but this one only has a 15-50. The parts short list in the maint manual suggests the either boiler can have either pump. I plan to upgrade the pump anyway 'cos it is a large system. Is the volute (air separator assy) common to both pumps so that I can just change the pump itself or must I change the volute/air-separator too? The parts shortlist shows they come together (PN 1303461) but I've been advised that I coukld just change the pump itself.


Many thanks,

Ian

 

[ricky1]

The Combi SE was Chaff's replacement for the most unreliable boiler ever made (Brittony 80) and whilst they did away with the original faults the combi se introduced a whole new load. Chaff then got bought out by Ariston, talk about the blind leading the blind

 

[jtsplumbing]

Hi just been reading about your boiler ! Seems the fault is with the system and not the boiler , old style house ,what is the total output of all the radiators ? what is the location of the boiler ? Check the pipe size on the system , sounds like you have to much 15mm and not enough 22mm, meaning that the heat can-not get from the boiler quick enough, on these old style houses the more 22mm on the system the better. You did-not say what type of valves you have on radiators, if TRVs make sure that they are on the flow side of the system (unless bi- directional type)

 

[Gary71]

As you seem to have movement thru the plate heat exchanger then as a guess it's either because the diverter valve assem is defective(less likely as you have replaced it) or as water will take the path of least resistance it's easier to force it's way round the diverter valve than do a circuit of your heating system, pointing at your system design/defects(as posted by others). While you have heat bypassing the heating circuit the boiler is going to achieve temperature before it would do under normal operation and the heat ends up pulsing out.

 

[Gary71]

I coukld just change the pump itself.

Yep, just change the head.

 

[Gregorian]

Thanks everyone. I'm going back to the house next wk (23 Aug) and I'll do the things you've kindly advised. I'll let you know the outcome. I'm really grateful to you. Ian