Baxi Advice

leevis · 7 Jun 2020

Hi
i have a Baxi Combi boiler (130E i think) but i have a problem i need advice on how to handle. Basically, i have a loft extension and the boiler is on floor 1. Recently i have not been able to get hot water up to the loft and called the boiler people out number of times because of this. Most of them say that there is something wrong with the boiler, fix it and then go. But still the problem remains.

The last chap i had here said that it was the piping or taps and was NOT the boiler and suggested i change the shower because it was probably faulty (a thermostatic one). I did change this but still not working.

I can get it working IF i turn on a hot tap downstairs, wait for it to get hot. Turn it off and then the boiler recognises the tap being turned on in the loft.

If i turn the shower on in the loft without putting on a hot tap i will get no hot water up there.

Is this the boiler or something else? The boiler is 10 years old so theoretically at the end of its life but I would say that its the boiler and nothing else in the house. Pressure from cold was around 0.75 and when the tap was running it went to about 1 bar.

Any ideas?

Thanks

Lee

alan999 · 7 Jun 2020

How many hot water outlets do you have in the loft?

leevis · 8 Jun 2020

Just two, one shower and a sink.

CBW · 8 Jun 2020

Any work done recently where the connections could be crossed?

DP · 8 Jun 2020

Boiler does not seem to recognise hot water demand from tap in the loft. Also, boiler older than 10 years you say it is.

If you have a stop cock on cold water supply, replace with full bore lever valve. That might make a difference. You might also find boiler may work when demand on cold supply is reduced.

alan999 · 8 Jun 2020

I solved a similar problem once simply by changing the hot tap. If the hot tap is supplied by a flexi pipe and an isolator - and you are confident - you could isolate the tap; unscrew the flexi; hold it over a bucket; turn the isolator on; see if any hot water comes out. Of course you may need 3 hands and it may not solve the problem with the shower.

leevis · 8 Jun 2020

Thanks for the advice

What i need a steer on here is whether to bother calling the boiler man again as i pay for a plan to keep it going. If it is a boiler issue then they need to fix.

Obviously the answer will be YES to this question but should i just get a new boiler? I just don't like repair people who i pay for giving me wrong advice where they cannot be bothered to fix.

alan999 · 8 Jun 2020

I doubt it is just a boiler issue or you wouldn't have any hot water at all. It could be a combination of a boiler issue together with a pipework/tap issue in which case you might be best suited to sort that out with the old boiler. I would try what I suggested above if you can and also compare the flow rate of the hot taps that do work with the hot tap that doesn't.
Another thing to consider is your shower. I assume its a mixer shower. Sometimes the cold supply (which doesn't flow through the combi) has a greater pressure than the hot supply (which does). Depending on your shower the cold water could be back flowing through the shower (whether its being used or not) and into the hot supply pipes. This could act as a partial buffer to the hot water getting up to the loft. I need a non return valve on my shower hot supply for this very reason. If your loft shower has isolators you could shut them off temporarily and see if it makes any difference.

leevis · 9 Jun 2020

The shower that I have is a Mira Thermostatic shower with seperate feeds for hot and cold, both of these have isolators. on the tap side, cold is at a higher pressure than cold

picasso · 9 Jun 2020

Could you post the exact boiler model.

alan999 · 9 Jun 2020

So you could isolate the shower and see if it makes any difference to the loft hot tap. If not you could time how long say a litre of water takes to flow through the loft hot tap compared to a litre through the hot taps that do work. Perhaps there's a significant difference there.

leevis · 9 Jun 2020

Exact Model of boiler is Baxi Combi Instant 105HE

picasso · 9 Jun 2020

Then you need to have the venturi changed, its a small part inside the boiler that affects the hot water delivery, picture of the part below.

leevis · 10 Jun 2020

I'm getting a bit confused here (as always)

If i isolate the shower (hot and cold feeds) then i will be able to test the tap in the loft to see if it is working i.e. being seen as open by the boiler on the hot side. This, i guess, would mean that there is an issue on the shower side.

The boiler pressure, when cold is somewhere between 0.75 and 1 bar (probably closer to 0.75). Should increase this pressure to, say 1.5 bar or 2 bar and see what happens?

Is that venturi change something i can do? Is it as easy as it looks?

picasso · 10 Jun 2020

The boiler pressure has no affect on the hot water delivery, increasing the pressure will do nothing, the symptoms you describe are typical of a broken venturi as its normally the shower not providing hot water is the first sign, its not a difficult job changing the venturi if you have some mechanical experience.

Go to 2.20 for the venturi...

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