glowworm 35ci;plastic components spliting

[monster82]

I have recently moved to a new house about three weeks ago and was collared by one of the neighbours to fix his leaking boiler.The dhw flow sensor on the cold inlet had a split in the plastic moulding.I replaced the part and all was good until 8 o clock this morning knock on the door boilers leaking again.This time 3-way valve housing has a split in plastic.I suggested fitting a pressure reducing valve on the first visit due to the high pressure on the incoming main,but these boilers are rated to 10 bar aren't they?Is it common for the plastic to split?
.nb boiler 3 installed 3 years ago

 

[Agile]

I have always been suspicious of plastic boilers after the disastrous problems which the first S-Ds experienced with leaks althought it was usually the seals involved there.

Having said that, the G-W models seem to have very few problems in that respect.

The high water pressure might have affected the DHW flow switch but the diverter valve is only under system pressure.

Perhaps this is just an isolated case or possibly the plastic mix being used was faulty? However in the latter case I would have thought we would have heard of that.

Tony

 

[monster82]

Second leak is not on diverter valve as i earlier described,but on the plastic manifold that the dhw he is connected to.Sorry for confusion having trouble identifing part number.

 

[Agile]

Merely fitting a pressure reducer will not work unless you also fit a PRV as the reducers let by if there is no flow.

What does the mains pressure go up to overnight?

Tony

 

[Gasguru]

Use a Caleffi 535 or 536 pressure reducing valve (and screw in a gauge). With no flow (ie static conditions) the pressure downstream can be set to a maximum rate.

Most boilers are rated up to 10 bar however, in line with ever increasing poor quality and plastic components some manufacturers are now only rating their boilers to perhaps 6 bar.

http://www.altecnic.co.uk/PRV/Series_535.aspx

 

[Agile]

Geoff, you cannot rely those valves to only produce the outlet pressure if there is no flow.

The slightest leakage will increase the static pressure at the outlet.

Also, most of that type of valve do not allow backflow to the supply if any thermal expansion occurs in the boiler.

I would not recommend using one without a PRV or possibly with an expansion vessel ( eg a shock arrestor set as an EXV ).

Tony

 

[superdupergasman]

Glowworm recalled some of there boilers and were replaceing water sections due to this.

Cannot remember exactly which models, would be worth a call to them.

 

[Gasguru]

I would imagine the thermal expansion with plate heat exchangers is negligable (say compared with that expected with bi-thermal primary heat ex.). You have a point there Tony (slight let by especially after some time in use) so maybe say a 4 bar prv in addition. Mini exp. vessel would be useful but I find they are always flat since you need a compressor to re-charge them.

I did see a graph some time ago (perhaps from WRAS) and the pressure increase (due to warmed cold water service pipework being located near heated pipework) was staggering.