- Messages
- 11
Hi I am a keen dIYer of 40 odd years and can deal with general plumbing jobs of all types but need some opinions on a course of action.
The bungalow we have lived in for over 7 years has a low wall mounted balanced flue Gloworm gas boiler now over 30 years old in the ground floor pantry but still going well apart from very occassional pump/programmer and valve replacements over the years. Until we moved in it was serviced annually by BG.
The system is neat simple/basic but seems unusual in that the indirect HW cylinder is in the roof space and is permanantly pumped, ie only boiler stat and programmer controlled and no gravity circulation, via 15mm pipe off a 15mm tee just before the single port zone valve in the 19mm heating flow next to the boiler (which then goes straight up into the roof space to drop down again after 10 foot horizontal run so as to feed all rads from under the ground floor wooden floors). The large attic is very warm!
The 15mm HW flow T off is just after the pump in the 19mm flow. At the cylinder the 3/4" cylinder coil is reduced via a 15mm tee to accept the 15mm cylinder flow and a 19mm single pipe rises upwards to the CW CH feed/exp tank and on to the U vent - all in the one pipe run. The cylinder coil return is immediately reduced and just drops back down in 15mm pipe to connect to the 19mm heating return near to the boiler. There is a redundant stub on the 19mm heating return which passes close to the cylinder coil so it clearly did not circulate originally!
Recently the hot water failed to circulate and part draining and refilling took ages to eliminate the air from the heating circuit so only in the warm weather did I decide to find what seemed to me to be a blockage.
I fortunatley found this quite quickly by cutting the feed/expansion 19mm pipe just above the cylinder return and its 15mm tee off flow down to the boiler.
It was blocked solid for about the first 6" from the reducing T with the black oxide which was quite hard and scaly. I removed this by ppoking it out by a stiff wire and flushed though. Thus full circulation and venting was restored - it must have been venting via the 15mm coil return which is free flowing. The water in the system was mostly clear in past removal of rads for redecoration/valve renewal did not show up that much of the black stuff in the bottom and the system rarely got air in it and alwaysfilled up quickly and was easily vented.
Three points arise:
We are not keen to go combi given the poor reliability and high maintenace that these suffer and want to keep this going a long as possible
The bungalow we have lived in for over 7 years has a low wall mounted balanced flue Gloworm gas boiler now over 30 years old in the ground floor pantry but still going well apart from very occassional pump/programmer and valve replacements over the years. Until we moved in it was serviced annually by BG.
The system is neat simple/basic but seems unusual in that the indirect HW cylinder is in the roof space and is permanantly pumped, ie only boiler stat and programmer controlled and no gravity circulation, via 15mm pipe off a 15mm tee just before the single port zone valve in the 19mm heating flow next to the boiler (which then goes straight up into the roof space to drop down again after 10 foot horizontal run so as to feed all rads from under the ground floor wooden floors). The large attic is very warm!
The 15mm HW flow T off is just after the pump in the 19mm flow. At the cylinder the 3/4" cylinder coil is reduced via a 15mm tee to accept the 15mm cylinder flow and a 19mm single pipe rises upwards to the CW CH feed/exp tank and on to the U vent - all in the one pipe run. The cylinder coil return is immediately reduced and just drops back down in 15mm pipe to connect to the 19mm heating return near to the boiler. There is a redundant stub on the 19mm heating return which passes close to the cylinder coil so it clearly did not circulate originally!
Recently the hot water failed to circulate and part draining and refilling took ages to eliminate the air from the heating circuit so only in the warm weather did I decide to find what seemed to me to be a blockage.
I fortunatley found this quite quickly by cutting the feed/expansion 19mm pipe just above the cylinder return and its 15mm tee off flow down to the boiler.
It was blocked solid for about the first 6" from the reducing T with the black oxide which was quite hard and scaly. I removed this by ppoking it out by a stiff wire and flushed though. Thus full circulation and venting was restored - it must have been venting via the 15mm coil return which is free flowing. The water in the system was mostly clear in past removal of rads for redecoration/valve renewal did not show up that much of the black stuff in the bottom and the system rarely got air in it and alwaysfilled up quickly and was easily vented.
Three points arise:
- I would like to fit a zone valve/stat to independently control HW temp which at boiler temp of 180 deg F is far too hot (I run it at 140 deg F in the summer with HW only on) - would this be better in the 15mm Flow or the 15mm Return? Is is safer to leave it uncontrolled, install extra venting or increase bore of HW circuit in whole or part?
- Should the whole system be descaled or would this cause more problems and result in leaks in 30 odd year old steel rads. If so what is the best stuff to use?
- If descaled then inhibitor would be essential I suppose so what is the best type? The boiler is cast iron and all pipe is copper and mainly end feed capilliary soldered fittings.
We are not keen to go combi given the poor reliability and high maintenace that these suffer and want to keep this going a long as possible