Highflow 400: Inhibitor in hot water supply!

[williemsnail]

Hi,

My Highflow 400 is doing something very wierd which has my engineer completely stumped:

1. It is overpressurising to a constant 3 bar, even after I de-pressurise the system. It only does this when the mains cold water isolator valve is open. The filling loop is disconnected. There is only one point of entry for the mains water. Therefore the boiler is somehow being pressurised by the mains supply.

2. I can smell inhibitor in the hot water supply. The domestic hot water and central heating water appears to be combining somewhere in the boiler.

My engineer has replaced the heat exchanger and we are still having the same problem. Worcester say the only place the the two systems can possibly mix is via the heat exchanger - but I have had this replaced!!

Please help....

 

[Dan Robinson]

It can only be the plate heat exchanger.

 

[Onetap]

My engineer has replaced the heat exchanger and we are still having the same problem. Worcester say the only place the the two systems can possibly mix is via the heat exchanger - but I have had this replaced!!

Please help....

The replacement has a hole in it. Get him to replace it at no further charge.

He will be able to get a refund on the one he has fitted. Ensure the one he fits is a new replacement part that is in a sealed box.

 

[williemsnail]

Thanks guys, I'm no expert but that's what I thought.

I guess just because its highly unlikely that a faulty part has been replaced by another faulty part, it doesn't mean it can't happen!

Cheers.

 

[1983]

If he depressurises the heating system and then turns on cold water it may be possible to hear where the water is getting in. The manifolds that connect to the plate heat exchanger would be the only other place. They are plastic and suppose a small crack in the pathways could be the cause.

 

[williemsnail]

He did that and we could definitely hear it coming in. We couldn't distinguish whether it was the manifold or the hear exchanger though. He spoke to Worcester and they were fairly adamant it couldn't be the manifold.

 

[1983]

Could try a mechanics stethoscope, pretty cheap to buy and good for pinpointing noises

 

[nickso]

Theres no chance that he has changed the wrong heat exchanger is there?

 

[williemsnail]

As in put the old one back in? Anything is possible I suppose, but I don't think so!

 

[Dan Robinson]

Done that with PCB's and the odd gas valve, but never a PHE

 

[nickso]

As in put the old one back in? Anything is possible I suppose, but I don't think so!

No I mean has he changed the primary H/E and not the PHE?

 

[williemsnail]

I'm pretty sure he has. It's the one with the plastic manifold, cold water going in, hot water coming out.

 

[Gasop]

I'm pretty sure he has. It's the one with the plastic manifold, cold water going in, hot water coming out.

Plastic manifold?

Are you talking about the diverter valve?

The plate HX is silver coloured rectangular shaped
about 9 x 4 x 1 1/2 inches.

What did the part that your engineer changed look like?

 

[Agile]

Its quite easy to drill a flat plate with the two mounting holes and use it to allow the boiler to be pressurised but no plate in place.

Older Biasi heat only seemed to do that ( unless it was an installers bodge! ).

Tony

 

[williemsnail]

Yes that sounds like the part he replaced.

He's coming back to sort but I will convey your thoughts. I've been considering a new more efficient boiler anyway!

Many thanks for your help everybody.