Worcester heatslave 25 - no oil pressure

[bruce3]

Hi,

I'm fault finding my Heatslave 25 combi oil boiler.

The problem announced itself by going into lockout and there's no oil pressure showing at the burner head (I fitted an oil pressure meter). The burner is a Electro Oil B11.

So far I've. .

1. Checked the oil supply to the oil pump which is good (I loosened the inlet and there's a good flow).

2. Replaced the oil pump (which includes a new solenoid) - but still no pressure shown on the oil pressure meter. A new pump apparently comes set to 150 psi.

3. Bled the oil pump by loosening the pressure check port next to the pressure adjustment port - there's an oil flow when the boiler's operated.

4. Ensured that the photo cell was clean and well seated in the burner.

5. Changed the burner nozzle (done as part of the annual service).


If I run the boiler with the pressure monitoring point cap on the burner removed I get a little oil if I cover the hole but certainly no real flow which backs up what the oil pressure meter is telling me.

Any advice on what to test next?? I thought that maybe the control box (it's a TF830b) maybe was not supplying enough power to open the solenoid properly but can't work out how to get inside it to check the relay contacts or to test if this is the case.

The other thought was the oil pump coupling to the electric motor (why are they made out of plastic???) - it's worn but I think good enough (I've a new one on order) - but is the coupling likely to cause these symptoms and if so is there any way of verifying that it's indeed the cause.

Fixing this is becoming a priority - any thoughts? - I need a shower . . .

Thanks

 

[Agile]

It sounds as if you dont know if the pump is actually turning ???

Tony

 

[spraggo]

Have you checked that the new pump is set for a one pipe or two pipe supply?.

 

[bruce3]

It sounds as if you dont know if the pump is actually turning ???

Hi Agile - interesting point. The electric motor is certainly turning and I reckon the coupling was in a good enough state to turn the pump - although I guess there could always be slippage. Any thoughts on how to check that it's turning?

Have you checked that the new pump is set for a one pipe or two pipe supply?.

Hi spraggo - I don't think there is a setting - I'd assumed that a single pipe supply (which is what I have) just left the other inlet blocked by the blocking plug. The pump is identical to the last one and connected to the same inlet- you can see it here http://heating.danfoss.com/xxTypex/65397_MNU17379088_SIT54.html

 

[bruce3]

Correction - I've just been following up on the one pipe/two pipe operation and have looked at the pump documentation - quite correct - the setting can be changed - I'll take it off and investigate. . .

 

[bruce3]

OK - I've checked the new pump - it comes as default set to single pipe operation (which is what I want) - conversion to 2 pipe operation requires the removal of a washer - and the washer is in place.

 

[spraggo]

OK - I've checked the new pump - it comes as default set to single pipe operation (which is what I want) - conversion to 2 pipe operation requires the removal of a washer - and the washer is in place.

You say that you have bled the pump and oil comes out of the bleed screw when the pump is working? Oil should flow from this bleed point when the pump is not working. So I suggest you unscrew the bleed screw and remove it, make sure that the oil is turned on and wait for oil to emerge from the bleed hole BEFORE swiching ON THE BOILER, then replace the bleed screw. If no oil is present you have either got a blockeds oil filter on the tank, a massive air lock or the fire valve is not letting oil through

 

[bruce3]

Hi spraggo,

The flow of oil to the pump is good - I removed the inlet hose and it shoots out.

The recommended bleed point for the pump is the pump pressure test point so the exit hole is small. I uncrewed the plug totally as suggested and the oil drips out slowly which presumerbly is normal as it's on the pressure side of the pump. So unless I'm miss-understanding something it implies that the pump is already bled?

 

[bruce3]

Also - following your exact instructions (which I miss-read first time around) - with the bleed screw removed when the pump is turned on, the heating oil shoots out. So I'm wondering if the solenoid is being activated. Any suggestions on how to check that it is being activated?

 

[spraggo]

Hi spraggo,

The flow of oil to the pump is good - I removed the inlet hose and it shoots out.

The recommended bleed point for the pump is the pump pressure test point so the exit hole is small. I uncrewed the plug totally as suggested and the oil drips out slowly which presumerbly is normal as it's on the pressure side of the pump. So unless I'm miss-understanding something it implies that the pump is already bled?

OK. The next thing to do is to get the boiler going and then loosen the outlet pipe connection from the pump to the burner nozzle before it goes to lockout and you should get oil spurting out at high pressure, so be prepared to tighten the connection quickly. If this is the case you have a blocked nozzle. If this is not the case it would indicate that the pump dog is slipping and the motor is not spinning the pump

 

[spraggo]

Also - following your exact instructions (which I miss-read first time around) - with the bleed screw removed when the pump is turned on, the heating oil shoots out. So I'm wondering is the solenoid is being activated. Any suggestions on checking that it is being activated?

This does indicate that the solenoid valve is working

 

[bruce3]

This does indicate that the solenoid valve is working

So just to clarify - the integral solenoid stops the flow to the non-pressured side of the pump rather than to the pressured side (ie it does not interrupt the flow between the pressured side and the outlet to the burner)?

 

[bruce3]

Re solenoid - just done an experiment - I disconnected power to the solanoid and ran the previous test (bleed screw out and boiler turned on) and oil still shot out of the bleed screw which makes me think that the solenoid must be on the pressure side of the pump.

 

[spraggo]

This does indicate that the solenoid valve is working

So just to clarify - the integral solenoid stops the flow to the non-pressured side of the pump rather than to the pressured side (ie it does not interrupt the flow between the pressured side and the outlet to the burner)?

This is not correct, the selenoid valve stops the high pressure outlet from the pump, hence when the pump is working it opens to let oil go through to the nozzle. If the photocell does not pick up that the flame has established within seconds it will shut off and the boiler will go to lockout

 

[spraggo]

Re solenoid - just done an experiment - I disconnected power to the solanoid and ran the previous test (bleed screw out and boiler turned on) and oil still shot out of the bleed screw which makes me think that the solenoid must be on the pressure side of the pump.

As already stated, the selenoid valve only interrupts the the oil supply to the nozzle. It has no effect on the bleed hole.