PLEASE HELP! OIL FIRED HEATING GONE MAD!

[jacquioh]

hi,
Hoping someone can help as I waited 10 days for a plumber who justleft and says he doesn't know what the problem is!

We have an oil fired central heating system, it does not heat the water, just the rads (of which there are 16) We have an aga which heats the water. When we switch on heating, only 4 rads get hot, and only at the top, the bottom stays luke warm. (rads have been checked for sludge - there is none). system is 3 years old & worked perfectly last winter. Have tried bleeding all rads, no air. Have tried turning off all rads and then, one by one, turn them on again starting with furthest away. this seemed to do the trick...until more and more rads got turned on...then the ones switched on first just got cold again! Have tried balancing the system too, this had very little effect.
the boiler is only coming on for about 5 mins each time, even though the temperature clearly has not been reached, then it goes off again for about 20 mins. This seems to be the problem as it can't possibly heat 16 rads if it is only coming on for 5 mins....but why is it doing that?
It may be worth mentioning that we had a new bathroom fitted in the summer, and a pressure pump was added to increase the water flow to the shower. however, the ftter told me that he didn't touch anything to do with the heating system and the hot water for the new bathroom comes off the aga.
So basically....we can have SOME of the rads on, but only if we turn others off and we can't understand why the boiler is only on for 5 mins at a time?
Could it have been the bathroom fitter?
any help would be greatly appreciated as there is zero chance of getting a heating engineer out now
Jacqui

 

[spraggo]

The water is not being pumped through the radiators fast enough, hence the boiler reaching temp and shutting down. The culprit is the central heating pump. Try altering the settings on it and listen for a change in the tone of it, are the isolating valves fully open either side of it. If no joy you will need a new pump.

 

[jacquioh]

The water is not being pumped through the radiators fast enough, hence the boiler reaching temp and shutting down. The culprit is the central heating pump. Try altering the settings on it and listen for a change in the tone of it, are the isolating valves fully open either side of it. If no joy you will need a new pump.

Hi,
thank you for such a fast response! The pump is switched on fully and yes I think the valves are both open, no-one has touched it since last year when it was working fine. At least we now know what the problem is...not sure why the plummer couldn't figure it out?
Can you tell me how much it may cost to replace the pump? and it is something we can do ourselves or must we get a specialist in?
Jacqui

 

[spraggo]

The water is not being pumped through the radiators fast enough, hence the boiler reaching temp and shutting down. The culprit is the central heating pump. Try altering the settings on it and listen for a change in the tone of it, are the isolating valves fully open either side of it. If no joy you will need a new pump.

Hi,
thank you for such a fast response! The pump is switched on fully and yes I think the valves are both open, no-one has touched it since last year when it was working fine. At least we now know what the problem is...not sure why the plummer couldn't figure it out?
Can you tell me how much it may cost to replace the pump? and it is something we can do ourselves or must we get a specialist in?
Jacqui

What sort/make pump is it?.

 

[jacquioh]

The water is not being pumped through the radiators fast enough, hence the boiler reaching temp and shutting down. The culprit is the central heating pump. Try altering the settings on it and listen for a change in the tone of it, are the isolating valves fully open either side of it. If no joy you will need a new pump.

Hi,
thank you for such a fast response! The pump is switched on fully and yes I think the valves are both open, no-one has touched it since last year when it was working fine. At least we now know what the problem is...not sure why the plummer couldn't figure it out?
Can you tell me how much it may cost to replace the pump? and it is something we can do ourselves or must we get a specialist in?
Jacqui

What sort/make pump is it?.

hi again,
it's a "grundfos". I turned it down and then back up again and can hear it whiring, so I'm pretty sure it's working?

 

[Richard C]

The pump may be making whirring noises but the impeller drive may have sheared, so pump will be next to useless; only way to check is remove it.

Also, do you have a motorised valve in the heating circuit? Sometimes these can seize or get jammed; I once removed a 25mm lump of metal swarf from one, god only knows how that got in there.

 

[spraggo]

It may be working but not fast enough, you should hear a definite change of tone as you turn it from one setting to another. Regarding replacing the pump, if you feel confident it will entail isolating the electrics, isolating the pump by turning off the valves either side, (Beware these do not always turn of completely so have plenty of towels at hand, or it could mean that you have to drain the system to get the water level down below the pump). It is then a matter of disconnecting the electrics from the pump and unscrewing the large nuts either side of the pump with suitable spanners. Make sure that the replacement pump is the same, a 15/60 or 15/50. Before fitting new make sure that there is no build up of muck inside the isolating valves. You can get a new pump in B&Q etc cost about 90 quid. The best of luck.

 

[jacquioh]

The pump may be making whirring noises but the impeller drive may have sheared, so pump will be next to useless; only way to check is remove it.

Also, do you have a motorised valve in the heating circuit? Sometimes these can seize or get jammed; I once removed a 25mm lump of metal swarf from one, god only knows how that got in there.

hi!
thank you for your response
Motorised valve, heating circuit, swarf? It's all chinese to me I'm afraid....being a woman and all that!

We have 2 separate systems in the house, one each end, the other end works fantasically! (but the pump is indoors down that end of the house in an airing cupboard and appears to be in pristine condition), where as this one is outside in a brickbuilt shed, checked the pump again and it does appear to have limescale build-up at the base of the pump where it connects to a pipe, but that doesn't mean the pipe is clogged does it?

 

[jacquioh]

It may be working but not fast enough, you should hear a definite change of tone as you turn it from one setting to another. Regarding replacing the pump, if you feel confident it will entail isolating the electrics, isolating the pump by turning off the valves either side, (Beware these do not always turn of completely so have plenty of towels at hand, or it could mean that you have to drain the system to get the water level down below the pump). It is then a matter of disconnecting the electrics from the pump and unscrewing the large nuts either side of the pump with suitable spanners. Make sure that the replacement pump is the same, a 15/60 or 15/50. Before fitting new make sure that there is no build up of muck inside the isolating valves. You can get a new pump in B&Q etc cost about 90 quid. The best of luck.

hi again,
thank you for that info, much appreciated
I did hear a definite change of tone when I turned the pump to a different setting, it got louder and the whiring was faster when it was turned from no 1 to no 3 setting (which is what it currently set at). surely if the pump is not working, I wouldn't get any hot rads at all?

 

[Richard C]

Motorised valve, heating circuit, swarf? It's all chinese to me I'm afraid....being a woman and all that!

Oh I see but don't really see how that's relevant ;

We have 2 separate systems in the house, one each end, the other end works fantasically! (but the pump is indoors down that end of the house in an airing cupboard and appears to be in pristine condition), where as this one is outside in a brickbuilt shed, checked the pump again and it does appear to have limescale build-up at the base of the pump where it connects to a pipe, but that doesn't mean the pipe is clogged does it?

It doesn’t matter what the pump looks like on the outside, it’s what’s going on inside that matters. Unfortunately you will need to call in another heating engineer who actually knows what he’s doing as, from what youve said, you will have less than zero chance of fixing it yourself.

 

[hermetic]

Spraggo is spot on, god only knows why the plumber you got out couldn't suss that in about 5 seconds flat, don't use him again! If you remove the large chrome slotted screw/vent plug from the rear of the pump (there will be a trickle of water, get a bowl or some rags) and put a straight screwdriver in the hole, it will rattle when it touches the shaft of the pump, if it is rotating. If the pump is not rotating (which is my guess) then try to find the slot in the end of the shaft and turn the shaft with a screwdriver. The slot is sometimes not very well formed, but it is possible, use a torch and try to find a screwdriver that fits well and is the same length as the slot. push the shaft in and let it spring back out a couple of times, and then get it turning freely. Switch the pump back on, and check it revolves (turn the speed to max for an hour or so) and all should be well. Refitt the screwed plug,The other possibility is that the boiler or the main circulators are sludged up, and this sludge is preventing circulation and thus the boiler is cutting out on the boilet thermostat. How long since installed/flushed? if its an old system this is a possibility. Is there a drain off at the bottom of the boiler, or on the return near the boiler, if so you could try draining some water out of there to see if there is sludge.......BUT BEWARE!!! the washer on the drain off tap will probably break up and leave you having to drain right down to replace it, so dont try this unless absolutely neccasary AND you have a spare washer!

 

[spraggo]

is not working, I wouldn't get any hot rads at all?

With your latest information is it likely that the system in question is a sealed one, Is ther water supplied by a header tank or have you got a red expansion vessel that needs pressurising?.

 

[hermetic]

You ought to check that there is water in the system!! go into the loft and check that the ball valve on the F/E tank is not stuck and there is water covering the outlet

 

[hermetic]

You ought to check that there is water in the system!! go into the loft and check that the ball valve on the F/E tank is not stuck and there is water covering the outlet

 

[Richard C]

hi!
thank you for your response
Motorised valve, heating circuit, swarf? It's all chinese to me I'm afraid....being a woman and all that!

Great effort lads but given this statement, I think your wasting your time; but who knows the OP may get lucky