Vokera compact 28

[bellairaphon]

need to pick brains here. i was told to go have a look at this job simple routine or so i thought. tenant said she had no heating but hot water fine. I checked the hot water fine Then i selected heating. The boiler fired as it should high modulation then low. the kettling sound appeared and the boiler shut off however no lock out after 5 mins restarted it did the same. the pump impeller was spinning. the house has just been re occupied after a house fire ( council house ) so i just checked to not look stupid the valves on the flow/return both open took them off and checked. so curiosity got to me n i changed the pump same thing still kettling. swapped the pump back and got a new heat xchanger (common fault when no pressure reducing valve fitted ) and put new thermistor in. still same thing. so now i was gettin frustrated so i took the hydraulic block completely checked all the flexy hoses the bypass valve was on its seating. so i thgought perhaps dhw flow switch stuck so i linked it out and still the same!! it is just like a one pipe convection. i just felt like crying any thoughts out there??

 

[nickso]

pipework blockage?

 

[bellairaphon]

thought so myself. piped a loop a meter from the boiler but its like theres nothing coming down the flow.. but checked the block new heat exchanger. tell ya mate im stumped. i even used a meter cap n blocked the auto bypass on the boiler cos a mate suggested the bypass

 

[nickso]

slap me for asking this but the F+R valves are open yes?

 

[bellairaphon]

haha if i could only reached. physically removed the valves n checked yes

 

[nickso]

ill consider myself slapped. dunno what else to suggest. if theres no blockages and a new or proven pump on it and no airlocks should work.

 

[mickyg]

do they have any filters on these boilers? I don't know enough about the model, but some boilers have gauze filters fitted on heating return, sometimes in some bizarre places.

 

[bellairaphon]

i know its a total mystery to me. i thought i was a good engineer but that kind broke my spirit. even the hand on the casing n the WORK BOILER WORK didnt help haha

 

[HarrogateGas]

do they have any filters on these boilers? I don't know enough about the model, but some boilers have gauze filters fitted on heating return, sometimes in some bizarre places.

Isnt the filter on these on the left hand side of the plastic manifold. Held in on an oring and a clip?

 

[bellairaphon]

yeah i know what u mean the cap i checked in there all fine

 

[bellairaphon]

they leak sometimes

 

[Derrick B]

To Bellairaphon

did you ever resolve the vokera compact 28 problem. I have a customer (a church) with the same situation. Boiler ignites, pump is circulating water, I feel heat build up on the flow, and then the boiler shuts off flame due to excessive heat. It takes a good 8 seconds or so for that high heat to move a four or so down the flow pipe which indicated to me a slow flow. Yet there is no restriction in the flow to return (I even tried a cross pipe short). What was your solution in the end?

 

[CBW]

Would have been better starting a new thread rather than hijack a 13 year old one. Are your flow and return valves open? How short did you do the small loop of pipe?

 

[DP]

Wondered if Nichso was back.

 

[Derrick B]

To cbw

Yes valves open. My power flusher can push water through the boiler from flow to return or return to flow as if it was an open 15 mm pipe, hardly any pressure difference between the two implying no flow restriction, blockage or similar flow inhibited. When I shorted flow to return it was a 22 mm flex pipe 300 mm in length and about 400 mm down from the boiler below the magnetic sludge trap and feed in Tee. So about 1.2 metres of pipe from flow to return take offs on the boiler underside.

The power flusher blasted out any air traps, the AAV is definitely clearing the pump rotor chamber. The only thing I have not yet tested is the bypass valve and taken the pump out to look at the rotor itself (I have experienced one pump which, when I removed it, had no blades on the rotor, it was just a circular hub on the shaft. Goodness knows how they disappeared, grit?).