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NO Hot Water, but CH OK

I have a Glow Worm Boiler 65/80. There is a single heater unit for the dual purpose of CH and domestic water supply, although the hot water for bathroom and kitchen is provided by pumped circulation. There is a Cylinder (21 Gallons). A corrosion inhibitor was added to the CH installation. I normally have HW even if the CH is off.
Two weeks ago I noticed there was not hot water, but the CH was OK.
As I have BG CH three star cover I requested service. The Engineer came and in a hurry decided there was a blockage from the expansion tank into the system and that this was not covered by the Insurance.The estimate was £318. However he raised the CH to 20 degrees and in one hour I had hot water again.

An independent plumber told me the expansion tank was OK.

But as soon as I switched off the CH, I ceased to have hot water again.

I request a second opinion from BG three star service. The inspector said the reason I did not have hot water was a faulty valve (located in a box outside the cylinder).
A few days later another engineer came to do the job, but the first thing he did was to empty the system. Before even looking at it, he said the system was full of sludge and this was the cause of the problem. However when he emptied the system I noticed that only for a few seconds the water came out dirty - dark grey = after that continued flowing from the system completely clean. The engineer insisted the system needed to be power- flushed, that the system did not replenish when he changed the valve and that this required a work not covered by my insurance. I have been left without CH or Hot water now and an estimate for repairs nearing £700.

Please could you advise whether the fact that the water came clean from the hose after the first bursts is irrelevant, and that indeed the system needs power flushing. I should say that right from the time the CH was installed, the few drops of water that came out from the radiators when there was air in the system were always dark. This engineer told me the system is corroded and that there was no inhibitor in the system despite I have guarantee from BG installer that an approved corrosion inhibitor was duly added.

The system has been serviced every year, it was working perfectly well and I had CH despite not having hot water. I have never been told that the system required cleaning when I had the last service.

I would be grateful for a knowledgeable opinion on this matter.

If the central heating is working and the hot water worked once since the engineer has been I'll be very surprised if there is a blockage. The heating water is normally discoloured and only really need flushing if there's alot of sludge or the bottom of radiators remain cold or radiators don't heat at all.

It sounds to me like the problem is probably the actuator or 3 port valve, but cannot really say without seeing the system or with abit more info:

Tried to find your boiler online but can't - is it a back boiler ? How old is
the heating system.

The sytem probably was installed with inhibitor added but if the heating system has been drained since then for replacing radiators etc the inhibitor will no longer be in the sytem.

from what i can remember this is a system boiler. Do you get a constant flow from the hot tap (even if cold) if not the cylinder could not be filling up.

there could be air in the pipe work that heats the cylinder. Try looking for a bleed tap at the pipe work on the side of the cylinder and bleed to see if any air is there.

Is there a slilver disk on the top of your cylinder? this is an immersion heater and can be turned on by a fused spur located near the cylinder.

It is difficult to comment without seeing the job. if you can post some pictures online and then tell me where they are i could look at it and explain better.

As for flushing your system that could help but to be honest your system sounded clear and these guys could be taking the mickey by saying it needs flushing. if it is a combi boiler and the boiler usually fires up when you turn your hot water on then it could be a sensor or the diverter valve.

Try to get me a picture of your cylinder and i can help you better.

To htg engineer:
Thank you for your reply. I am still without hot water or CH. and I welcome any advice you can provide. My plumbing knowledge is very limited, and I am afraid this is another of BG strategies to force me to incur in unnecessary expenses. The system was installed in 1979: it is old but it is working perfectly well. Besides, I cannot afford to change the boiler now for a new more efficient model.
These are the Boiler specifications:
Type: freestanding/ Open Flue/ Open system.
Total input in (Btu/h) 90,000 to 108,000
Total Output in (Btu/h) 65,000 to 80,000
Measurements w: 483mm; d: 533mm; h: 900mm
Positioned in outside small utility/storage room
From boiler run 28 mm and 22 mm copper tubing reducing to 15 mm to feed radiators, etc.
Feed, expansion and controls; 10 Gallon vent tank, insulated, ball valve and overflow to outside area. From tank run a 22 mm vent to system, and a 15 mm cold feed to system.

Domestic hot water provided by pumped circulation.
Circulation pump:
Model:S.M.C or Grunfoss
Position on boiler
Valving: On pump

I would like to point out that the first diagnosis I got from BG was that there was a blockage in or from the expansion tank. However, water continues running from the hot water taps in kitchen and bathroom, although it is now cold.
The Central Heating system has been working perfectly all right all winter: all radiators were hot: at times there was air trapped in the radiators, which was easily released. During that first visit, the heating was put at 20 degrees and all radiators were hot in one hour. I had even hot water then.
The first quotation given by BG was for: Reconfiguration of pipes in airing cupboard and drain down and inhibit system. I was not explained what did the engineer meant by "reconfiguration". I thought some of the work quoted had to be covered by my contract with them. That is why I requested the visit of the supervisor, who said the valve (actuator) in front of the cylinder was faulty and needed replacement. This was carried out by a second engineer a few days later: He emptied the system and put a Valve Actuator code BGMUSP-9. A year ago or so I had similar problem and the actuator valve was replaced without emptying the system. Now I have been told that the fact that the system does not replenish automatically is proof that the system is full of sludge and totally obstructed, which seems hard to believe.
I would appreciate your opinion.

C.Varela

do you have a magnet?
try putting the magnet on and around the valve area,if you feel a resistance on copper then you are blocking up with magnetite as copper is not magnetic then this will prove you have a problem .
the reason for the system not filling up is the same,if you find the cold feed to the system you will feel a resistance this will confirm that the pipe which refills the system is blocked!
the reconfiguration means that the feed and vent position maybe incorrect and will need to be altered to prevent recurrance of this blockage

To
toneyt
htgengineer
wishiwascorgi
Thank you very much for your comments and advice.
I finally contacted a central heating engineer not related to BG who made the system work again in half an hour. In his opinion, there was no blockage whatsoever nowhere in the system: Before his visit I used a magnet to check and could not find any resistance on copper. And also
- to answer one of your questions- I had a continuous flow of cold water from the hot water taps, so what the BG men told me - that the immersion heater was not filling up - was a blatant lie to charge me £600 for power flushing the system. Four different engineers and supervisors from BG confirm each other's opinion on what was wrong and said the repairs could not be guaranteed.
If this is BG policy regarding service, I am not surprised they managed to make the extraordinary profits they declared a few days ago. Also, it seems their only aim is to force you to change your boiler no matter what: I wonder if it is wise to entrust the service of your central heating to BG.
Thanks again,
C. Varela