Hi All,
I have a problem with a late 80's Worcester Bosch Hiflow 400. (Manual heating knobs on the left) analog controls. We attempted to have it serviced a few weeks ago and the engineer that came, capped off the gas due to a fault gas valve on the first test. Then refused to repair as didn't want to fix an old boiler. Fair enough. We're selling the property so wanted to fix rather than replace.
Sourced a new gas valve, had a local engineer come and fit. Hot water back on, however no central heating. Asked him to service the boiler as we are selling the property and noted the expansion vessel was full of water and pump was weak and this might be cause of the central heating not working. Spent a good few hours trying to get the CH working no avail.
Came back again, fitted vessel and pump - still no CH. Another 4 hours odd spent fault finding and still no CH. When the rads are switched on, demand LED is lit and boiler fires up but shuts back down again within a minute or less. Suspect control board now as only getting 20v to diverter valve I think he said rather than 240v.
We have 2 rooms under floor heating and the rest of the house is rads. Pipework and radiators, UFH is sub 5 years old. 3 separate stats, 2 for UFH and one for Rads, we are using a Honeywell valve to isolate the radiator and UFH circuit and they are fed by the same flow pipe.
Oddly I have been attempting to look myself today as the boiler worked perfectly before capped off (was about 8-10 days ago now) and it seems we are in the realm of throwing parts at it with uncertainty. I've noticed today that the boiler will run perfectly, with the flow pipe hot and staying hot with demand if it's activated via the UFH and the UFH pump is set to max and rad valve is OFF. If we try to activate via the rads, it fires up and cuts out pretty quickly. I have added automatic bleed valves to the lines at the highest point of the circuits on after the honeywell rad valve and the return flow highest point. There are bleed valves on both the vertical flow + returns off the boiler - to ensure the possibility of air is removed from the system - this was my initial hunch and made the most sense. After fitting the bleed valves, it's still the same.
Today we have tried tricking the boiler into activating via the UFH to create and sustain the demand for CH and opening the honeywell valve manually using the overide to add in the radiator circuit, but still the boiler flow just goes cold quickly after. We have then tried locking off the all the rads apart from 1 (there are 6 in total), to see if this helped. We can get the closest rad semi hot. If you add any more rads in after this, same again, flow output from the boiler goes cold.
If you reduce the speed of the UFH pump, with the rads isolated closed, the flow from the boiler sometimes goes cold. If you reduce the temperature for the UFH, with rads isolated, the boiler flow sometimes goes cold.
It's almost as if the boiler needs to a lot of flow to stay hot, as you make the circuit bigger by opening up the rads the flow is reduced and the boiler just cuts out.
I'm from a very technical background in automotive, and competent with electrics/plumbing on vehicles so aware enough that something doesn't quite stack up here. Particularly as the boiler operation, rad & UFH circuit was working perfectly some 9 days ago, I'm in disbelief there are this many issues from turning the boiler off for 9 days however I don't understand boilers. I have tried two engineers now who have both struggled, 1 who is very busy is still trying to help us but we have been without heating for coming on 10 days now and due to personal circumstances really need it back in action. I've now got manuals of the boilers to aid fault finding but hoped someone may have an idea to point me in the correct direction.
My next steps from research (within this forum) are to check a small pipe for blockages from the diverter valve and a potential filter in the manifold that can also be blocked.
Thanks in advance.
I have a problem with a late 80's Worcester Bosch Hiflow 400. (Manual heating knobs on the left) analog controls. We attempted to have it serviced a few weeks ago and the engineer that came, capped off the gas due to a fault gas valve on the first test. Then refused to repair as didn't want to fix an old boiler. Fair enough. We're selling the property so wanted to fix rather than replace.
Sourced a new gas valve, had a local engineer come and fit. Hot water back on, however no central heating. Asked him to service the boiler as we are selling the property and noted the expansion vessel was full of water and pump was weak and this might be cause of the central heating not working. Spent a good few hours trying to get the CH working no avail.
Came back again, fitted vessel and pump - still no CH. Another 4 hours odd spent fault finding and still no CH. When the rads are switched on, demand LED is lit and boiler fires up but shuts back down again within a minute or less. Suspect control board now as only getting 20v to diverter valve I think he said rather than 240v.
We have 2 rooms under floor heating and the rest of the house is rads. Pipework and radiators, UFH is sub 5 years old. 3 separate stats, 2 for UFH and one for Rads, we are using a Honeywell valve to isolate the radiator and UFH circuit and they are fed by the same flow pipe.
Oddly I have been attempting to look myself today as the boiler worked perfectly before capped off (was about 8-10 days ago now) and it seems we are in the realm of throwing parts at it with uncertainty. I've noticed today that the boiler will run perfectly, with the flow pipe hot and staying hot with demand if it's activated via the UFH and the UFH pump is set to max and rad valve is OFF. If we try to activate via the rads, it fires up and cuts out pretty quickly. I have added automatic bleed valves to the lines at the highest point of the circuits on after the honeywell rad valve and the return flow highest point. There are bleed valves on both the vertical flow + returns off the boiler - to ensure the possibility of air is removed from the system - this was my initial hunch and made the most sense. After fitting the bleed valves, it's still the same.
Today we have tried tricking the boiler into activating via the UFH to create and sustain the demand for CH and opening the honeywell valve manually using the overide to add in the radiator circuit, but still the boiler flow just goes cold quickly after. We have then tried locking off the all the rads apart from 1 (there are 6 in total), to see if this helped. We can get the closest rad semi hot. If you add any more rads in after this, same again, flow output from the boiler goes cold.
If you reduce the speed of the UFH pump, with the rads isolated closed, the flow from the boiler sometimes goes cold. If you reduce the temperature for the UFH, with rads isolated, the boiler flow sometimes goes cold.
It's almost as if the boiler needs to a lot of flow to stay hot, as you make the circuit bigger by opening up the rads the flow is reduced and the boiler just cuts out.
I'm from a very technical background in automotive, and competent with electrics/plumbing on vehicles so aware enough that something doesn't quite stack up here. Particularly as the boiler operation, rad & UFH circuit was working perfectly some 9 days ago, I'm in disbelief there are this many issues from turning the boiler off for 9 days however I don't understand boilers. I have tried two engineers now who have both struggled, 1 who is very busy is still trying to help us but we have been without heating for coming on 10 days now and due to personal circumstances really need it back in action. I've now got manuals of the boilers to aid fault finding but hoped someone may have an idea to point me in the correct direction.
My next steps from research (within this forum) are to check a small pipe for blockages from the diverter valve and a potential filter in the manifold that can also be blocked.
Thanks in advance.
