Hot water taking priority

Recently have had added two extra radiators to a single pipe system. Since then the hot water takes priority over the central heating but if I switch off hot water the central heating gets hot. Both systems work fine independently. I am also getting lots of unusal sounds banging, water hammer etc in system

What are the symptoms of the problem you wish to solve?

Prior to the addition of the extra radiators the central heating always took priority over the hot water system. So basically in the morning the radiators do not get hot until the hot water has reached its temperature from the hot water cylinder stat. As soon as the hot water motorised valve closes, then the central heating kicks in, totally opposite to what was happening before. Consequently we are getting up in the morning to a cold house

My first suggestion is that the problem should be put right by the person/company who appears to have caused it.

In the meantime, do you know whether or not they did any work to either the pipework around the valve/valves or to the wiring for the programmer/valves?

Yes they fitted TRVs to all but one radiator and moved the room stat to a new location. The electrician has rechecked the wiring connection s for me and all are correct. My gut feeling is that it may be caused by an airlock as there are some strange noises coming from the sysem for eg bubbling noise, banging and water hammer on system shut down.

Don't take this the wrong way, but to save some time please would you list all the recent changes that were made?

Also, what boiler do you have?

OK They fitted TRVs to all radiators except one.
They relocated the room stat.
They fiitted two new radiators.
They increased the pipework by approximately 30 feet with a plastic type.
They did not touch the programmer.

The guy who did most of the job has been back and tried to find out what is causing the problem but cannot rectify it. He is not a qualified plumber by the way. He fitted it as part of an extension to my regret!!!!!!

Forgot to tell you the boiler type.

Baxi solo.

The boiler banging (etc.) is most often caused by poor circulation and hence failure to move water out of the heat exchanger quickly enough. This can be caused by blockages, or a weak/failed pump, or both.

Can you identify the pump and verify at least that it's running?

The apparent change in priority could also be a symptom of the above situation. How many motorised valves does your system have - two two-port valves or one three-port?

Also, assuming that the system was drained, was there any mention of flushing it out, and adding a chemical corrosion inhibitor? If the work wasn't done by a plumber then it seems at least possible that they didn't know what they were doing.

Oh, and is your system sealed or open-vented?

Many thanks for your reply SOFTUS it is much appreciated.

Can I get back to you tommorrow evening as I have to get up for work at 5-30 am and must really be getting off to bed.

Thanks again and Goodnight

Best regards
CHRISWAG

Not sure of pump type but definitely running on both programmes

Two two port motorised valves

The builder added a new drain off valve but when emptying the system did not drain off the old existing drain off valve. He did not flush the system and did not add an inhibitor

Do not know what you mean by system sealed or open vented?

By the way the system is a single pipe system which I know is old hat but it has worked perfectly prior to this work being carried out.

CHRISWAG said:

Not sure of pump type but definitely running on both programmes

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A common mistake with circulating pumps is to make as assumption that they're running when the only external indication is that it's vibrating.

You need to check that the spindle is turning - remove the end cap (with a bowl or an old towel underneath) and check with the end of a screwdriver that it's turning.

Even if it is, the pump might still be ineffective - the impeller could be worn, broken, or loose.

I'm still curious to know whether the system is sealed or open-vented - do you have a feed & expansion cistern (aka header tank) in the loft?

If so, take a good look inside it and assess the quality of the water. Scummy and dark is ok, but rusty and/or sludgy is not. Also, note whether any water is dribbling or pouring from the vent pipe (over the F&E cistern).

Two two port motorised valves

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A failure mode that can case boiler noises is for both valves to be shut with no system bypass. A picture of your pipework around the cylinder would reveal whether or not you have a bypass there. Although MZVs are intended that the boiler should light (and pump run) only when they're open, I don't know whether or not your system is correctly wired.

The builder added a new drain off valve but when emptying the system did not drain off the old existing drain off valve. He did not flush the system and did not add an inhibitor

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This is a good indication that he wasn't thorough. I would never add a radiator to a system and not drain it unless I checked the state of the water, i.e. degree of sludge and concentration of inhibitor - did he do that?

By the way the system is a single pipe system which I know is old hat but it has worked perfectly prior to this work being carried out.

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Try not to be misled by the fact that the fault is sudden - all components fail in time, so it's commonplace for things to be working perfectly right up until the moment that the fault occurs.