replacing plate heat exchanger on grant combi 70 mk 2

[jimjones235]

Over the last few weeks we've noticed the pressure in our boiler has been rising and the pressure release valve has been dripping. Its been getting worse : I drained off a bowl of water at the weekend and the pressure was down at 1.5 bar. By the evening it was at 1.8 and back to 3 bar by the following afternoon. This has gotten worse over the last few days, and I'm now draining off 2 bowls ofcwater a day. Obviously the excess water is coming from somewhere, the filling loop is disconnected so the only thing I can think is a leak in the plate heat exchanger letting some water enter the system through the dhw supply. Does that sound a reasonable assumption?

I want to get this sorted asap as its getting worse by the day, and I'm worried it will damage the boiler. I've been let down by 2 plumbers, so decided to order a replacement part (even if/when a plumber does turn up - may as well have the part here!). But it doesn't look like too difficult a job, so am considering doing it myself. I should point out that whilst I'm no heating engineer, I have some plumbing knowledge and a mechanical background - certainly if it was on the oil/burner side of the system I'd not touch it.... So am I missing something, or is it a relatively simple job for a diy'er?

my plan is:

- power off boiler/turn off water supply
- drain system
- remove front cover
- undo nuts on existing plate heat exchanger
- connect up new one
- flush system through couple of times
- add inhibitor and refill system

Sound right? presumably there won't be anything which needs adjusting/balacing? The new part comes with washers, presumably the joints will seal with these washers, and I dont need to use ptfe tape/gasket paste?

 

[muggles]

Sounds like you know what you're doing. No PTFE needed. You shouldn't need to drain your system either, just drop the pressure

 

[leakydave]

Move the burner out of the way and get a paint tray in under the exchanger to catch any water that drips out. It isn't that difficult just hard to get spanners at some of the connections. Use new fibre washers and make sure the mating surfaces are clean of old bits of washer.

Turn on mains water connection and leave for 10 mins to make sure it's not leaking. If all ok refill system pressure and again leave for a while. Only when you are sure all is ok add the inhibitor... saves losing the inhibitor should you subsequently have to drain down again.

Good luck.