Hi Andy, I've followed your suggestions from other postings regardin
flushing the system, here's what I've done so far:

1. Drained system, noticed water was clean
2. Removed each rad and flushed through with hose pipe
3. Ruined a carpet in the process!
4. Removed pump, inspected, no sludge build-up
5. Checked by-pass circuit, no sludge build-up
6. Half filled system
7. Added heavy duty central heating restorer (sluge, scale remover)
8. Continued to fill, bleed system

Three days later I still have the same problem, the boiler keeps
popping off. The rads get hot really quickly so I don't think that
there is a circulation problem. The by-pass circuit is 15mm with an
isolater valve (b&q 74p!), again no sludge here.

To combat the problem so I can at least have some heat in the house I
have to open by-pass fully and open the 22mm gate valve feeding the HW
coil to 3/4 - full. but the rads don't get to full temp with this
config. I set the HW circuit to approx 1/4 open, rads getting piping
hot, room thermostat pops off, boiler safty cut-out soon follows!!

Could it be the boiler thermostat? If so, can I replace just the
thermostat, and approx how much are they?

BTW, temp of pipes is approx 65 degrees

Regards,

Danny

Andy Hall wrote in message . ..
On 25 Oct 2003 10:54:56 -0700, (Danny)
wrote:

one problem after another! Now I'm back to my orginal problem, CH
valve shuts off, boiler cuts out! Interestingly enough though, when I
fully open the gate valve into the HW storage tank, turning the pump
on full speed, you can hear water rushing through, air being expelled,
and then gushing water into the FE tank? I've heard about
over-pumping (?) but why would this cause water to be expelled though
the FE tank this way?
I would have thought that considering the pump
is sited after the pipe work leading to the FE tank (ie water is being
sucked rather than pumped) that the water would only flow up this pipe
if there were a blockage?


If the feed pipe and the vent pipe are on opposite sides of the pump,
pumping over or sucking down of air will tend to occur depending on
which way round they are. This would in any case be a fault in the
design.

However, you can get the same effect if they are both on one side but
that there is a pressure differential between them - it doesn't have
to be very much.
This can happen if they are connected to points on the circuit that
are too far apart or if there is a flow restriction. Winding up
the pump speed will exacerbate this.

Based on what you've found at the bypass, I suspect that other parts
of the system are full of sludge as well......

I would suggest you drain the system and if you can undo a fitting
near the points that the feed and vent pipes join the system see if
there is more sludge, or take a look at a nearby radiator.

I'd be willing to bet that there is a lot of grot in the system.




.andy

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