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I’m trying to help sort out the heating at my parents’ house and would greatly appreciate some advice. What they really need is a new boiler, but that will have to wait until after winter. Problems are as follows:
Boiler is kettling
Some radiators not getting properly hot
Some rooms remain cold whilst others are roasting
Central heating timer clock no longer working
Shower has very poor flow rate
The boiler is a Gloworm 85/100 and original to the house which was built in 1977. There is a hot water cylinder, radiators (no TRVs), single room thermostat, Gloworm timer controller (clock bust so they have to manual switch between OFF and CONST).
I went to their house yesterday to fix a few other things, install a dishwasher and try to tackle the heating, but didn’t have time to do everything.
I replaced the timer controller with a Honeywell ST699. This took a bit of time as the old timer had 4 control wires plus L+N whereas the wiring diagram(gravity HW, pumped CH) for the new one showed only 2 outputs – one for CH and one for HW. After checking inside the boiler I saw that 2 of the 4 wires ran to a terminal strip, but weren’t connected to anything else. After checking the old switch with a multimeter I established that these two wires are fed with the HW OFF CH OFF signal and so could basically be left unconnected in the new one.
I had brought with me some TRV’s and Fernox boiler restorer. I was planning to drain the system, fit the TRV’s and add the restorer to see if that would sort out the kettling for a while. However, I ran out of time and also was a bit puzzled in the loft as the CH seems to be fed from the same cold tank as the HW.
So the questions –
a) The thermostat is in the lounge so I was planning to fit TRV’s to all rads except there. My only concern is if the lounge warms up and stat turns off whilst a room elsewhere is still cold. I could fit a TRV to the lounge as well and keep the wall stat turned up, but I understand then I will need to fit an automatic bypass valve and the boiler will keep cycling on warmer days. Is there another option where the pump senses that all the valves are closed and so shuts down itself ?
b) I’m wondering if they have a Primatic cylinder – in the loft there are two cold tanks. The first one has a mains feed and ball valve, outlet that goes to bottom of cylinder, cylinder vent pipe goes to top of this tank – all looks fairly normal. The second tank only has an outlet and this goes to a 15mm pipe that looks like it goes down to the boiler; this outlet is also connected via a T to the outlet of the first tank. Coming up from the boiler is another 15mm pipe that looks like it used to T into the cylinder’s vent pipe, but is no longer connected; this pipe looks like it is no longer connected to the boiler either as it lifts up easily – I assume this was the expansion pipe for the CH and it has been cut and sealed at both ends.
I didn’t know anything about Primatic cylinders yesterday, but having read more now I’m pretty sure it is one. What’s puzzling me a bit is why there was ever an expansion pipe from the CH. It looks like a normal cylinder has been replaced with a Primatic one, but I’m pretty sure the cylinder is original.
Anyway the question now is about using the Fernox. The stock answer is NO due to risk of contamination of HW if the air bubble has failed. However is it really that bad –
If the CH water is mixing with the hot, would we not see loads of gunk in the hot water already. Alternatively if it is possible there could be only slight mixing is that really bad – no-one is drinking the HW anyway and the cold taps are all mains fed. If I put the Fernox into a radiator directly and then drain and flush after a couple of weeks is that really a health risk ?
c) Does the fact that it is a Primatic cylinder make the CH draining process and refilling any different (i.e. do you have to do anything special for refilling to make sure the air lock is set up again). What I was planning to do was: unplug boiler, turn off the water (there are no service valves anywhere!), turn on downstairs hot tap until it runs dry to empty the cold tank, open pipe drain valves in garage (there is 1 on the flow and 1 on the return to the lowest rad in the house), open bleed valves on all rads, wait until all water has finished coming out of pipe, replace rad valves with TRVs, close drain valves, inject Fernox into 1 rad, close bleed valves, turn on water, bleed all rads, turn on boiler
d) I was planning to fit a pump for the shower, but was wondering if there are any issues with this and it being a Primatic cylinder
Thanks for taking the time to read this far and I appreciate your advice. In the summer I’ll try to get them to have a professional fit a new boiler and zone valves, etc, but for now I’d like to help them out.
Boiler is kettling
Some radiators not getting properly hot
Some rooms remain cold whilst others are roasting
Central heating timer clock no longer working
Shower has very poor flow rate
The boiler is a Gloworm 85/100 and original to the house which was built in 1977. There is a hot water cylinder, radiators (no TRVs), single room thermostat, Gloworm timer controller (clock bust so they have to manual switch between OFF and CONST).
I went to their house yesterday to fix a few other things, install a dishwasher and try to tackle the heating, but didn’t have time to do everything.
I replaced the timer controller with a Honeywell ST699. This took a bit of time as the old timer had 4 control wires plus L+N whereas the wiring diagram(gravity HW, pumped CH) for the new one showed only 2 outputs – one for CH and one for HW. After checking inside the boiler I saw that 2 of the 4 wires ran to a terminal strip, but weren’t connected to anything else. After checking the old switch with a multimeter I established that these two wires are fed with the HW OFF CH OFF signal and so could basically be left unconnected in the new one.
I had brought with me some TRV’s and Fernox boiler restorer. I was planning to drain the system, fit the TRV’s and add the restorer to see if that would sort out the kettling for a while. However, I ran out of time and also was a bit puzzled in the loft as the CH seems to be fed from the same cold tank as the HW.
So the questions –
a) The thermostat is in the lounge so I was planning to fit TRV’s to all rads except there. My only concern is if the lounge warms up and stat turns off whilst a room elsewhere is still cold. I could fit a TRV to the lounge as well and keep the wall stat turned up, but I understand then I will need to fit an automatic bypass valve and the boiler will keep cycling on warmer days. Is there another option where the pump senses that all the valves are closed and so shuts down itself ?
b) I’m wondering if they have a Primatic cylinder – in the loft there are two cold tanks. The first one has a mains feed and ball valve, outlet that goes to bottom of cylinder, cylinder vent pipe goes to top of this tank – all looks fairly normal. The second tank only has an outlet and this goes to a 15mm pipe that looks like it goes down to the boiler; this outlet is also connected via a T to the outlet of the first tank. Coming up from the boiler is another 15mm pipe that looks like it used to T into the cylinder’s vent pipe, but is no longer connected; this pipe looks like it is no longer connected to the boiler either as it lifts up easily – I assume this was the expansion pipe for the CH and it has been cut and sealed at both ends.
I didn’t know anything about Primatic cylinders yesterday, but having read more now I’m pretty sure it is one. What’s puzzling me a bit is why there was ever an expansion pipe from the CH. It looks like a normal cylinder has been replaced with a Primatic one, but I’m pretty sure the cylinder is original.
Anyway the question now is about using the Fernox. The stock answer is NO due to risk of contamination of HW if the air bubble has failed. However is it really that bad –
If the CH water is mixing with the hot, would we not see loads of gunk in the hot water already. Alternatively if it is possible there could be only slight mixing is that really bad – no-one is drinking the HW anyway and the cold taps are all mains fed. If I put the Fernox into a radiator directly and then drain and flush after a couple of weeks is that really a health risk ?
c) Does the fact that it is a Primatic cylinder make the CH draining process and refilling any different (i.e. do you have to do anything special for refilling to make sure the air lock is set up again). What I was planning to do was: unplug boiler, turn off the water (there are no service valves anywhere!), turn on downstairs hot tap until it runs dry to empty the cold tank, open pipe drain valves in garage (there is 1 on the flow and 1 on the return to the lowest rad in the house), open bleed valves on all rads, wait until all water has finished coming out of pipe, replace rad valves with TRVs, close drain valves, inject Fernox into 1 rad, close bleed valves, turn on water, bleed all rads, turn on boiler
d) I was planning to fit a pump for the shower, but was wondering if there are any issues with this and it being a Primatic cylinder
Thanks for taking the time to read this far and I appreciate your advice. In the summer I’ll try to get them to have a professional fit a new boiler and zone valves, etc, but for now I’d like to help them out.
