Dingdongler

Thanks. I will try that tomorrow. I wish they would put some sort of indicator on the pump to let you know whether it's working to full capacity or not.

greatgonzo

iTrader: (1)

Yeah that would help. The pump to hot to touch when only running 50 degrees doesn't sound right to me

mart360

The banging is kettling. whereby the water in the heat exchanger is being

boiled dry, rather than heated and moved on through the system.

if your pumps are borked, its a bit of a suck it and see process, you may

have burnt the pump tips out,

This is usually accompanyied by the pump getting hot ( over hand hot)

but no heat in the pipes either side.

if the pump is shot, the boiler will normally shut down, as it should detect

no flow through the heat exchanger, (which is what yours is doing by all

accounts)

Looking at your pumps from the piccys, budget £40-50 each,

fitting is a 10 minute job, once the system is drained, providing you have

waterpump pliers


Mart

Dingdongler

Interesting. The pipes either side are hot. Does that mean the pump is definitely working?

mart360

How far either side? if the pump is fubarred, it will still spin, in turn it will

generate heat, and by capillary means the heat will radiate from the pump.

If the pipes are hot all the way to the rads, then the pump/s sounf like there

ok. the next place to look would be for sludging or air leaks.

Mart

ALi-B

iTrader: (1)

I agree, its sounding like one of the pumps are foobared.

I can't see how the boiler heat exchanger should sludge up, its not an old gravity system which has next to zero flow rate; the velocity of water should be as such that sludge deposits should never build up; sludge builds up in areas of low flow, i.e the tank and radiators. Unless the system has been disturbned (drained down, power flushed/additives, pump speeds messed with etc.).

As mentioned, removeing the bleed screw in the centre of the pump will reveal the pump shaft, which can be tuned with a screwdriver - turn off the power first (you'll need a tray to catch some water that leaks out - quite normal). However a worn pump that spins freely can still jam intermittantly (our "really" old boiler used to do this....sounded like someone was kicking the radiators, as the boiler was overheating and the thermal cut-out was a bit slow to react ).

Seeing you have two pumps which look identical, as long as the gate valves work ok you could swap them over (including the wiring, of course). It unlikely both have failed (unless its a wiring/controller fault).

Also it goes without saying, just check and make sure there is water in the storage tank (lift the lid on the top, that should be the header tank).

Dingdongler

Mart, the pump on the left is getting hot. As far as I can gather that's the one to the boiler, not the rads. The other pump is to the rads, and that's not spinning as the heating is switched off because the heating doesn't work!

Going back to the first pump. There is a short pipe that connects it to the tank, that is hot, even though the tank isn't. Not sure if the tank should feel hot from the outside as it must be insulated. Then there is a second pipe from the pump that dives between the joists and goes downstairs (see photos on page 1) The amount visible/accesible is short, and that is hot.

Now, if that pump pushes water from the cylinder to the boiler then which pipe brings the hot water back from the boiler to the cylinder? If the pump, and its inlet and outflow pipe are hotter than the pipe returning from the boiler the this can only mean one of two things

1) The pump is knackered, and it, along with its inlet/outlet pipe are only hot because its malfunctioned.

2) There is severe restriction to flow through the boiler, hence it's heating up the pipework back from it to that pump, but not the water leaving it and going to the cylinder (as much).

My best course of action is

1) Try and change the pump first and see what happens.

2) If that doesn't solve the problem then change the heat exchanger (or entire boiler) + powerflush+ check cylinder for debris.

Do we agree?

Thanks

500

The hot water in to the cyl (circs) should be directly above the outlet (nearer to the top though)

Best bet is to bleed the pipework at the highest point and see if you have any air there as it looks to be a sealed(unvented) system. Do you have a pressure gauge and a braided hose anywhere (to fill the system) This will more than likely be near the boiler or in a cupboard where the pipes run through.

If no joy, swap the pumps around and see if that helps then report back

mart360

Do you know if its an indirect or direct thermal store?

how many immersion elements does it have 1 or 2?


if its an indirect, it will have a cold tank ontop of the unit,

a direct does not

see the attached link to work out which it which

Thermal Store Copper Cylinders | Newark Copper Cylinders

dark/ blackish water...hmm

on a standard HW system it would indicate sludge.....with fernox in it

should be a very pale yellow (almost like wee lol).

Before you go down the parts replacement route,

you could try a drain & flush, and run for a few days if possible with a

cleaner/ descaler, to see if that works.

however if your pump/s are allready borked, then its not going to make any

differance.
?


the problem is i'm not savvy on how this system works, so i cant tell readily

which pump has failed.

On a standard system, the boiler heats water in the heat exchanger, which

circulates through a coil in the cylinder, this hot water then flows through

a 3 way valve, and depending on what is set to either returns straight to

the boiler, or goes round the rad system and provides heating before

returning to the boiler. The Hot water is provided by the heat radiated

from the coil in the tank heateing up the cold water around it, this water is

drawn off by a seperate HW circuit, to prevent cross contamination (sorry

if you allready know this).

So as we only have one pump, if you dont get heating or HW then its easy

to fix.

You could always grab a pump from screwfix, close the gate valves either

side, and change one pump.

Makes sure you turn off the mains before you start, control boxes are more

often than not perminantly live due to the need for the pumps to overun .

Turning the mains off at circuit box is the only way to ensure its off

Then restart the sytem, bleed the system to check no air leaks, and run it

and see what happens. if its still defective, it could be the other pump.

Then swap the (now spare pump) for the other pump, and see what

happens. if its ok, then job done , if its still nok, you have 2 options,

buy another pump to check the one thats still potentially defective (you

may have 2 nok pumps). Or get some professional help in, as it could be

the heatexchanger/ associated piping


hth


mart

Dingdongler

Thanks.

As far as I can gather its a direct system.

No place for filling, I think its a self fill system with ball **** in the cylinder.

A couple of questsions

1) In one of the pics you can see a pipe coming out of thhe top of the cylinder with a metal canister on it. What is that canister?

2) No plumber who has had a look, can say for sure whata it is. Heatexch comes up tops. I will try the pump change today, if that doesn't fix it, do we think its reasonable to ask a plumber to change the heatexc(or boiler) +powerflush system+ service cylinder?

Thanks again

ALi-B

iTrader: (1)

Had a fresh look today, think its a bit clearer:

Dingdongs, I think the tank is as per this which is an indirect (or indirect - doesn't really matter) thermal store with built-in header/expansion tank.




The pump on the left in the previous pictures is the critcal one, as that circulates water throughout the whole tank (connection points F in the diagram), it MUST work for any hot water or central heating. The pump in the forefront of the picture serves the lower heat exchanger coil (connections G in the diagram )and is only critical for heating the rads, as such it can be disabled without any effect on hot water.

Actually, shutting off a gate valve on the CH pump will prevent any heat lost via convectional currents or if the CH pump decide to turn on for any reason, such as a frost stat in the garage etc. This will aid the immersion heater - a 2.8kw element with at a guess, a 150ltr tank, providing it works without interuption by pumps running and convectional loses will take well over 3 hours to reach useful temperature. You may also need to shut off/adjust the blending valve (Labelled B above) on the hot water supply to better compensate for the reduced tank temperature.

It goes without saying that for any of this to work (especially teh HW heating) the tank must have water in it....you still have not said if you've checked the header tank on the top (lift the lid).

The small stainless steel canister to the side of the main tank looks like a surge arrester to prevent water hammer. (or a very large auto air vent, never seen one that big though ). Its connected to mains cold water feed, so its at mains pressure.

alcazar

iTrader: (2)

The last time I had a pump that got hot, it was knackered.
Have you tried taking the silver cover off the centre of the pump to SEE if it's running, yet?

Dingdongler

Thanks Alcazar.

Mart, yes there is water in the cylinder and ball **** working.

In the user manual to the cylinder they show two diagrams. One is the same as yours, but that is marked 'indirect'. The other diagram is marked 'direct', and that's the system I've got. Rather than two coils there is one.

Pump on the left pumps water from the bottom of cylinder to the boiler. The water from the boiler returns to the top of the cylinder somewhere. This main body of water is for the rads, and is passed to the rads by pump2.

Mains cold comes into the cylinder through the coil, gets heated up, and then is blended with more cold mains to be fed to the hot water taps.

So one coil, and two pumps.

Thanks

greatgonzo

iTrader: (1)

Dingdongler
Answer to question no. 2
Its a expansion vessel ! this will take up expansion in the system or cold mains.

Dingdongler

Thanks Gonzo.

Well changed the pump for a brand new one, that my bro in law had spare. No luck. same problem, the boiler very quickly goes up in temp to about 50-55 degrees and then starts banging like a *****!

so, I've decided to change the boiler for a Worcestor Bosch and have the whole system serviced/powerflushed.

I tried to get a list of approved local installers from the W-B website, and that facility isn't working! I'm really not having much luck these days.

Anyway, do we agree that we've eliminated all the other potential causes, and the boiler must be fooked in some way or another?

Thanks

mart360

did you swap both pumps?

have you esablished that you actually have enough water in the system?

you may have more air than water another reason for the kettling


Do a complete drain from the lowest point, leave the drain open and refill,

once you establish water is pulling through the system then drain / vent

each rad in turn from the ground up


Mart

Dingdongler

Mart, no I didn't swap both pumps. The second pump is for the heating, and hence is not working. The water never reaches a temp to be able to drive the heating, so heating is off. To me that means the second pump is irrelevant to this problem.

Yes, there is water in system.

I have another plumber coming around today, so will see what he comes up with and post back.

ALi-B

iTrader: (1)

Only other possible scienario I can think of is the outlet on the tank to the boiler is blocked, thus restricting flow and causing the boiler to kettle/overheat.

Dingdongler

Yes, thats a possibility, but the pipework is only 4 years old and the pipes are big. Most be quite unusual for them to block

ALi-B

iTrader: (1)

I was thinking more of the outlet at the bottom of the tank more so than the pipes.