On 16 Sep 2003 21:35:53 -0700, charlesward_totalise_co email@example.com
Depending on what the boiler is, it could be a fault there as well -
you don't say what the boiler is. Often the pilot light does not
depend on an electrical supply to the boiler working.
Th other thing to look for is whether there are any places (and it
could be anywhere on the system) where the insulation on a wire might
have been nicked or possibly chafed by it going through a hole in
metal without a rubber or plastic grommet. Boilers can be
favourites for this if the installer was lazy.
The problem as well is that these are intermittent.
You could for the pump, quite easily, and the motorised valve less
easily. These have up to five wires connecting to the motor and an
auxiliiary switch inside. You need to pick the motor wires. Either
you can take the cover off of the valve head and trace the colours to
the motor or look at the manufacturer's data sheet. One thing to
watch with this is that you will be feeding the item under test from a
different power source and this means that it is not isolated at the
same time as the rest of the system if you switch that off.
I don't think that you would be able to diagnose much more than the
pump and possibly the motorised valve this way. The boiler will
typically have multiple connections and you really need to know what
you are doing and have the manufacturer's service information .
One candidate for the fault you are describing is failed insulation
and shorted turns on the motor of the pump or the valve. This can
manifest itself as intermittent - I had a pump that failed that way
once. FOr any of these tests, don't use more than a 3A fuse.
NOTHING other than the correctlhy rated fuse. The 2A and 3A fuses
are there to protect the system and you. The 6 inch nail approach
can result in more damage or even a fire so don't be tempted.
On an intermittent fault, I don't think that you will see all that
It could have been a failure that was an open circuit, a short circuit
or even an insulation breakdown to earth.
You might want to look back through recent posts and find Ed Sirett.
His email address is in his signature and is in North London.
I've had this twice and both times it was a failing synchron motor (not yet
failed) in the zone valve. Might be an idea to get a spare synchron motor
if you havn't got one. Were fairly cheap from BES, now you have to pay
I would first check if you have separate mains feeds to boiler and wiring
box. If separate I would not suspect boiler or pump initially. The
intermittency may just be due to the actual current being drawn. Don't
have the tables to hand but depending on the actual current the fuse may
take some time to blow. If you are confident (and competent) I would
suggest inserting a test meter on ac Amps in series with each load (zone
valve(s), pump, boiler etc). Obligatory health warning - switch-off while
connecting. What I might do in this situation is to fit a 13A plug (3A fuse)
to the feed and plug into a 30mA RCD. Healthy readings should be nowhere
near 3A. OK, won't work if it is genuinely an intermittent, but I would
Cost of Plumber? Sorry d-i-y here, you can buy a lot of pumps, zone valves,
test meters etc for the cost of a plumber.
Had a bit of time today so this is what I did. Got a card of fuse wire
- cheaper than 50p a go fuses, even if a bit fiddly!! I turned off the
power and replaced the fuse.
I disconnected the red wire feed to the pump in the wiring box.
I set the programmer to off for both CH and HW and turned the power
back on. All ok so far.
I then switched the programmer to call for HW, still ok.
I then switched the programmer to also call for CH, still ok.
Eureka I'm thinking...it must be the pump - Grungfos 15-50. Based on a
previous post I tried to get hold of a replacement capacitor but no
luck. Decided I'll replace the pump, on the basis that even if it
isn't the pump this time at least I'll have a replacement next time.
I turned off the gate valves eitherside of the pump and tried to
remove the pump. Unfortunately I didn't have large enough spanners to
remove one side of the pump so reconnected to pipework again. What I
didn't realise was that whilst I had the gate values on either side of
the pump disconnected, the boiler couldn't come on. Presumably this
means I have a fully pumped system?
Anyway I decided to leave the pump disconnected this evening and try
again tomorrow. Bear in mind that at this time I'm still thinking its
the pump. The boiler was on and happily heating water and
approximately 40mins to an hour later the fuse went pop again.
When I was in the plumbers merchants he said if the pump was gone it
would smell of burning - it doesn't.
So now where do I stand? Have I confirmed it ISN'T the pump?
Does the fact that it took 40mins to an hour to blow indicate the
blowout happened when the motorised valve was moving to a different
position once the HW was heated?
Back to you boys ot there.
And it was ok foabout 40minutes. The fuse then
When I opened the inspection at the front of the pump I got quite a
bit of water coming out of it, as opposed to a few drips. Is this
normal or does it indicate a knackered pump?
I put a screw driver in to try and turn it but nothing. Didn't have a
torch so unsure whether I was seating the screwdriver correctly.
Took the motorised valve apart - there is very little movement. when I
turn the valve but about the same as the amount of movement in the
motor. However when the motorised part was off and I slid the manual
overide lever across to manual, I got a consistent amount of
resistence and the lever comes back ALL the way to "Auto". But when
the motor and valve are back together the lever can be moved over and
back by about 1cm without any resistence. Is this normal?
And finally I opened the drain valve to drain the system and
"NOTHING". There doesn't appear to be any water in the system.
Presumably no water would cause overheating of the pump. Could this
blow the 2A fuse in the wiring box or could other parts overheat?
False alarm - there is water in the system - must be an old drain
Tried again today with the red wire feeding the pump switched out and
the valve manually turned on but it blew. Valve obviously kicked in
cos when I checked after the blow the vavle had retiurned to the auto
position. Tried with the valve feeds all out also also blew. Did
manage to get it going for a short while but then the boiler went out.
Managed to restart the pilot ok.
I've given up!!!
Had the Electrician in. None of my components had gone!!! It turned
out there is a break in the cable running from under the stairs to the
kitchen. About 15 metres of cable nicely boxed and hidden. I did it
myself around 15 years ago so I can't complain too much!!
Now my problem is do I run a new cable in some sticky back trunking
along the skirting and behind the kitchen cupboards where it can be
seen (concrete floors unfortunately) or do I try and pull a new cable
thru the existing boxing which also contains the pipework? I
previously used twin and earth lighting cable. Electrician suggested I
use 4 core as a replacement as any future boiler is likely to have
live in addition to switched live. Will the new cable be up to being
pulled through about 15metres of boxing, 2 walls and 3 corners.
No to both questions, I'm afraid! For the first, it's not accepted
practice to run mains-carrying cable in the same compartment as
pipework, on grounds both of heat (presumably the pipework includes
the boiler output - 70-80 degrees?) and of what-happens-if-there's-a-
fault-exposing-conductors (like, we're pretty sure the pipework's
earthed, but just *how* sure are we?)
For the second, pulling cable round three corners, expecially with
other pipework in their, is pretty much doomed to failure; and likely
even if you manage to damage the insulation.
But hey, maybe you can use this as an excuse to buy a nice new SDS drill
so you can channel the 4-core neatly ;-)
Pipework as in CH pipes to from boiler? Ordinary PVC cable doesn't
have a particulary high temperature rating. 80C+ from boiler pipework
probably exceeds it. I don't think we need be concerned about heating
from the load if you use 2.5mm.
If you can get clear straight runs you should be able to do it. No
chance around a corner, let alone 3.
Dave. pam is missing e-mail
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