removing plate heat exchanger from a performa 28i

[stevelee]

Just waiting for the boiler to cool/drain before removing the plate heat exchanger but it's a tight fit and can't see how it will come out. The manual says to lift it up and to the left of the gas valve but that's where the diverter valve is. Anyone know how you physically get one of these out?

Cheers.

 

[stevelee]

got it out but had to remove the pump.

 

[petit_pablo]

Would have been easier to remove the diverter head as it just clips in

 

[stevelee]

Thanks for the tip. Descaling and flushing it didn't work so I've put it back for the weekend and will fit a new one on Monday. Will try pulling the diverter head out then. Did consider doing it this time but it seemed like the pipework running to the valve would have still been in the way.

 

[bengasman]

Do you realise the problem will be back, possibly within months?

 

[stevelee]

Would you mind elaborating? The boiler and heating system have been in for about 5 years and performed well until now. The heating circuit was treated when first installed but has been drained/refilled a few times since then and, I must admit, not re-treated.

I'm hoping that a new h/e and flush of the system will give me another 5 years as long as I treat the heating circuit properly this time. Actually, part of the reason for doing this myself is that I want to be able to sort it if (when!) it does happen again so I won't be too disappointed if I only get a few years...I would be disappointed with a couple of months though!

 

[bengasman]

Plate hex works as a filter, unless you get all the crap out of the system, it will continue acting as a filter.
I am not aware of this model being particularly sensitive, so probably means system is rather bad.

 

[stevelee]

Thanks for the info. The water didn't appear to be that bad but there were some flakes in the heat exchanger. The replacement is certainly a lot lighter than the one that came out! I've had a read up on system cleaning and am planning to use x400 and fit a magnaclean. Sound right?

Unfortunately, replacing the heat exchanger hasn't fixed the main problem (luke warm hot water). With a hot tap on, the boiler gets up to temp on the primary side and then cycles (firing up for about 20s, cutting out for about 20s). The brass manifold that the inlet to the heat exchanger connects to gets hot but the h/ex itself is cold. Diverter valve seems OK (C/H flow doesn't get hot when hot tap is on). C/H seems to be working fine and flow at the taps is good. Turning the hot tap right down (probably to less than a litre a minute) results in slightly hotter water at the taps.

Am now thinking there must be a partial blockage in a different part of the DHW path. Are there any other components that typically get blocked on these?

The boiler is now drained while I wait for a replacement diaphragm to come in but I seem to remember that I got a small amount of hot at the taps with pre-heat on and the pre-heat recharge cycle was taking longer than it used to. Dunno if this gives any clues.

 

[petit_pablo]

The manifolds can block too although rare.

 

[bengasman]

...The replacement is certainly a lot lighter than the one that came out! I've had a read up on system cleaning and am planning to use x400 and fit a magnaclean. Sound right?...

I suspect a combination of limescale and magnetite have caused blockages somewhere. It is unlikely that x400 will do the job, and no chemical will do much where there is no flow.
If you have to resort to acids, I would strongly recommend to engage a pro as substantial damage is possible when you do it wrong.

 

[stevelee]

Thanks for the quick reply. Do you think this might improve if I add the magnaclean/x400 and wait a bit? If not, are there any other tests that I can do to try and narrow this down before I start pulling the boiler apart?

Cheers.

 

[bengasman]

I am not sure about the specifics of x400, but Hyperflush can be left in as long as you want. If you can live with the performance of the boiler as it is for a month or so, I would try that.
Installing a magnaclean will give you a good way of monitoring what comes out in terms of dirt.

 

[Agile]

Have you checked the eye of the pump for dirt?

Tony

 

[stevelee]

Just seen the additional replies...thanks a lot for your help with this.

I think there is at least some flow round the dhw/pre-heat circuits but probably not much. Since the c/h is OK, it seems like the blockage would either be in one of the manifolds connecting to the h/ex or the expansion vessel (I haven't checked the pump but will do).

Think we can live with it as it is for a month...just need to plan baths well ahead of time

Before I go down that route though, am I jumping to conclusions by assuming this is a blockage? There was certainly some crap in the system but it didn't seem that bad. Could these symptoms be caused by anything else?

Cheers.[/i]

 

[Agile]

Could these symptoms be caused by anything else?

Cheers.[/i]

Check the pump then we will think of other things to look at.

Also do the finger test while its off, see FAQ for details!

Tony