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Plumberpro, Plumber
Category: Plumbing
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Experience:  Heating and plumbing answers. 20 years experience
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I am having problems with my central heating system and I want

Resolved Question:

I am having problems with my central heating system and I want to double check that my engineer is competent and doing the right things. I have no real understanding of CH systems but consider myself a reasonably practical person and would appreciate some help here.
Story so far…
I have owned the house for about a year. The two large radiators in the ground floor kitchen extension (a bit like a conservatory) have been particularly slow to heat up but the whole system is not very fast. The pipes feeding these two radiators quickly got hot but hot water seemed to be very slow to fill the radiators. The previous owner said they were always slow and kept the heating on permanently as a result but I wanted to see if we could fix the problem as I don’t like the heating being on at night.
I got the engineer round (the same guy who fitted the boiler in 2011) and in February this year he flushed the system and fitted an expansion vessel (the red tank which is now in the cylinder cupboard) and a pressure gauge, thus apparently switching from the previously ‘vented system’ to a ‘pressurised system’. He said this would help the hot water flow better round the radiators. It didn’t seem to make much difference to the speed of the ground floor radiators but then the spring came and the problem was less urgent.
Now the cold weather is back and we still have slow radiators. I also have a new problem in the last week or so in that the CH system keeps losing all pressure. Last night I re-charged the system from 0 to 1 bar (the engineer told me to do this) but by this morning it is now at zero again. The engineer is hopefully coming back later today but I want to ensure he is doing the right things.
The pressure dropped to zero for the first time about a week ago. Prior to this I was noticing over the last few weeks/months that air kept getting into one of the radiators and I would periodically have to bleed them. I am also aware that when I switch on my CH the boiler (Vailant Ecotec boiler - not a combi-boiler) seems to stop working (ie no whooshing/fan sound) well before the radiators are even lukewarm. Indeed, the boiler fan often only seems to run for about 30 seconds before stopping. The return pipe into the boiler doesn’t seem to be very hot either. Eventually after about 1.5 hours all the radiators are hot and the house gets warm but this isn’t very satisfactory.
Other detail which may be relevant…
- The engineer re-charged the system last week to c. 2 bar when it first dropped to zero and it fluctuated up and down seemingly depending on whether the CH was hot. It stayed at over 1 bar until sometime yesterday or the day before. This is despite me bleeding the radiators slightly after the engineer visited (on his recommendation) to get rid of any air.
- The engineer said there were a couple of fault codes on the boiler suggesting it had ‘tripped out.’ I am not sure if there are new codes but expect to find out later.
- The thing on the pipe which I understand is called a ‘tundish’ appeared quite wet last night and was a bit wet when the thing first hit zero. I haven’t checked at other times so I have no idea if this is relevant. The pressure gage and valve appeared to be connected to the tundish as well as the pipes from the mega-flow.
- We have not heard any booming of banging from the boiler or system. The only noises we heard were a flushing noise in the cupboard last night. This sounded like a pump unable to get enough water onto it and the sound disappeared when I re-filled the system. We also heard what sounded like air a water trickling through the radiator in our bathroom when it came on this morning.
- There are no obvious leaks from any of the radiators although all the pipework is buried in the walls and floors.
Lastly, it isn’t really a problem but I just want to disclose in case it is symptomatic of something else….when we run our shower, the water initially gushes for a couple of seconds, then the pressure goes quite weak, and then it seem to jump up in pressure to a standard level. I’ve not had a mega-flow system so this could be entirely normal and, as I say, it isn’t really a problem and the extent of the pressure changes and times between low and high water pressure does seem to vary.
My questions are therefore:
- What could be causing the pressure to drop and allow air into the radiators?
- Is this likely to be a problem with the boiler or the pipework/radiators/expansion system, or both?
- What should the engineer be checking to diagnose and fix the pressure problem?
- Is there anything we can do to improve how fast the radiators heat up? Again, does this sound like a boiler or a system issue?
Submitted: 1 year ago.
Category: Plumbing
Expert:  Plumberpro replied 1 year ago.
Hi , the radiators being slow to heat is often a pipework installation issue in which the wrong size pipework may have been used. Usually the main branches are 22mm and run in 15 mm to the radiators. Too long runs can slow the flow down.the pressure issue is most likely that the pressure vessel has gone flat. There is a balloon inside that takes up the hot expanded water. If this goes flat the pressure will rise above 3 bar and dump out of the safety valve, ie water running from the tundish . The vessel needs to be repressurised if so upto around 1.5 bar whilst the system is at zerp oressure, ie drained slightly. This can be checked y unscrewing the
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Customer: replied 1 year ago.
I have just checked and all the radiators seem to be connected up with 15mm pipework.If the pipe run is too long, is there anything you can do to get over the problem? what about a larger pump?Are you planning to give me any more advice on my note? I was hoping for a bit more information and consideration than two sentences. What about the pressure problem?!?
Customer: replied 1 year ago.
Apologies...I have just seen you have typed some more. let me look at that.
Expert:  Plumberpro replied 1 year ago.
hi , toby ***********

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