radiators not heating up/no circulating CH hot waters

[thomasj]

hi all,

moved in to brand new house 5 years ago. gas central heating (GCH): Potterton Suprima 30 boiler, Flowmax tank within the airing cabinet, and what looks like two identical "Grundfos Selectric" vertically installed pumps on either side of the tank. CH controlled by timer below the boiler and wall thermostat in the hallway. a few of the radiators have TRV control.

GCH was switched off for about three months what with good summer. decided to switch it on briefly day before yesterday but it would not come on. although i could hear the click on the wall thermostat, i could not hear the usual 'rush' of hot water circulating around the house to the radiators (if this make sense). in fact all the radiators were cold as were all the pipes leading to the radiators.

initially i thought it may be huge 'trapped air' though deep down i had thought that this quite unlikely but the alternative a more serious problem would be hard to bear. so tried bleeding the radiators - well no surprises there, no air trapped!

reading around british gas website suggests that this could be due to 'jammed circulating pump' as a result of me not switching on the GCH in the summer months. but i don't know whether this is the problem or there are other problem(s). are the two Grundfos Selectric pumps the so-called circulating pumps that moved the hot water around the central heating radiators? could both of them be 'jammed' simultaneously or could this be a blown fused problem (i noticed two electric cables leading to somekind of covered circuit box with a written warning to switch off mains before opening the cover)?

my possible course of actions:

1. call an engineer out
2. attempt to diagnose and pin-point the problem, subsequently either have a go rectifying it myself or if advised to the contrary, get an engineer to carry out any repair work

with everyone's advice/help in this forum i am hoping to undertake the second course of action (2) if nothing else i would learn something about GCH and at the very least, if i have to call an engineer, i would not be taken for a ride (i hope). i do not have an insurance cover for GCH so any possible ways to save money (but sensibly) would be considered.

would appreciate advice/help direction to take with regards to my GCH problems. please do let me know if you need any further information to help me solve my GCH problem.

thank you,
thomas

ps: btw, there is no problem with the timer and timing - boiler would come on at the programmed times and there is hot water supply for showers, baths, and taps.

 

[ChrisR]

One of the pumps will be for the CH. Probably the one on the left.

They will probably be 3 speed pumps. Lever for switch is on black plastic part. See where it is. Set CH controls to on , and room thermostat up. If pump is running you can feel it stop and start as you switch between speeds.

If apparently not running, get a towel or bowl
(leave the power ON)
remove the big central chrome screw from the pump - might dribble.
Insert a flat screwdriver with a 4-5mm thin blade. There's a (rather poor) slot in the end of the pump shaft.
Feel for it, and turn the pump spindle. Might be hard - you're trying to unseize it. If the pump's already running, it'll just rattle the screwdriver - replace screw.
If you can't turn it, you need a new pump.
If it turns freely, remove the top of the black plastic part of the pump and you'll see the connections - check for mains present.
If mains present and pump not turning - new pump needed.
If no mains, check system controls.

 

[thomasj]

hi chris,

many thanks for your advice. i switched on the boiler, turned on CH and turned up all the thermostat. i turned the selection switch on the side of each of the Selectron pump. the one on the right started and stopped - so i presumed this one was to circulate the domestic hot water supply. there was no reaction on from the left Selectron pump. so i worked on the assumption that the left one must be the CH pump as suggested by you.

after i switched off the boiler but leaving the power and CH on, i unscrewed the big central chrome screw on the left Selectron pump, bowl and towel prepared whilst leaving the power on (but definitely was not prepared on how hot the water that dribbled out though). found the spindle - dead on in front of the opening. it was not running/spinning. i did as suggested - it was really stucked and a bit of torque was required but when it gave, suddenly it just came to life as was the CH!

i have left the CH running for about couple of hours and even tried it on the timer. the CH seems to be ok now - finger crossed.

again, thank you for your advice.

thomas