Baxi Bermuda Inset 50/3 back boiler not heating radiators

[xWeen82x]

Hi there.

This is my first post and am hoping to get some advice. We have an old style baxi back boiler installed and until a couple of days ago it was working ok (has been temperamental since we moved in) we will look to overhaul the system but with a baby on the way and garage conversion imminent we can't afford it just yet. When I flip the switch for hot water the boiler fires up as it should and is still giving us hot water, but when I do the same for the central heating it doesn't fire up the boiler.

Am I right in thinking it is a valve or pump or something as it's still working for hot water? We really can't afford a costly boiler replacement for quite a while. I have just taken out insurance but have to wait 14 days before making a claim, just looking for ideas or reassurance while we're waiting.

Thank you in advance

 

[stem]

First of all, the boiler is working if it is heating the hot water OK. These old back boilers are very reliable, much more so than the newer ones, but unfortunately size for size they consume gas at a much higher rate. Anyway, I digress.

Where the fault lies will depend upon the type of plumbing the boiler is connected to. With many older systems, the water travels between the hot water cylinder and boiler by natural convection, sometimes referred to as 'gravity'. Then when the heating is required the pump is turned on and circulates water around the radiator circuit. If this describes your system, the problem will be the distribution of the water from the boiler to the radiators, which most likely will be down to the failure of the pump as you suspect.

Is the pump running when the heating is on? usually it is audible and a slight vibration can be felt. If it's not running, the shaft cover can be removed with a screwdriver, (some water will come out) and then the shaft turned manually. If it is just stuck, that may be sufficient to free it and start it running. If it doesn't run either the pump or the wiring to it are likely at fault. If you have a multimeter and can use it safely, then a quick check of the wiring entering the pump will confirm whether it's getting power or not.

Having said the above, some of these older systems have been upgraded and fitted with motorised valves, if you have one or more of these, post back and there are other things you can try.

 

[xWeen82x]

Hi thank you for your reply. I've taken pics of our back boiler, control panel thingy and of the cylinder set up if it's any help. To be fair I think there's been a series of bodge jobs done before we bought the place as it took several plumbers to get to the point where we actually had hot water and heating hence I'd love to have the whole system including pipework redone.

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• xWeen82x
• 18 Feb 2015
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• xWeen82x
• 18 Feb 2015
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• xWeen82x
• 18 Feb 2015
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[stem]

OK, I can see you do have a three port motorised valve. Then the pump will be used for hot water and central heating, so is probably OK. In this case, the first check is the operation of the three port valve. This bit.

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• stem
• 1 Apr 2010
• 8

Turn the heating 'on' and the hot water 'off' then slide the lever on the valve. Is it loose and floppy? It should be. If there is resistance, then the valve is not opening properly, and it is most likely faulty. Wiring faults can cause the same problem, but are less likely. If the valve is faulty, the actuator can be changed without having to interfere with the plumbing,or draining the system.

Don't be too hard on your existing set up. The pipework actually doesn't look too bad at all, I've seen a lot worse. I suspect the boiler maybe from a previous age though.

 

[xWeen82x]

Ok so I tried that and there was some resistance but then went loose and floppy again. Would this cause the boiler not to fire up? Eventhough it's now floppy I doubt a bit of wiggling fixed the issue as the boiler still didn't kick in when I tried it after that. Any thoughts?

 

[stem]

OK, the valve should be fully open when only central heating is required. If it is, the lever should be loose and floppy. But that's only half the story. When the valve is fully open it should also operate a small internal switch that starts up the boiler. The valve may be opening, but the switch not working. There are two things you may want to try, but only if you can do them safely.

1. Set the hot water and central heating to 'off' and remove just the cover from the powerhead. Be careful there will still be live connections going to the valve. Whilst watching the valve internals, have an assistant turn 'on' just the central heating (make sure the room thermostat is turned up enough to be 'on') and watch the valve mechanism. Do you see it operate? At the far end of its travel you should hear a 'click' this is the switch operating that starts the boiler. Did you hear it? There will be other clicks in the mid position, ignore these. It's the one right at the end you are interested in.

2. This is the best test, but you will need to be able to use a multimeter safely. With only the central heating set 'on' (& room thermostat up) check the motorised valve's white and orange wires. Both should be live. A live on the white shows that it is getting the central heating 'on' signal from the controls, and a live on the orange is the one from the switch that starts the boiler.

 

[xWeen82x]

Ooooo that's a little bit too technical for me I really wouldn't feel comfortable messing with electrics especially being nearly 38 weeks pregnant lol. Is it worth trying the manual overide on the switch as a stopgap and see if that works until we can make a claim in our insurance?

 

[xWeen82x]

I did just try the valve in the manual position but didn't seem to do anything... Did you say that the red pump thingy should be humming or vibrating because it isn't... so does that potentially mean that the pump isn't pumping the water for the heating to the valve so therefore isn't telling the boiler to fire up and work the central heating?

 

[stem]

Ignore that original post about the pump, that was before I knew you had a motorised valve.

The manual lever is there to fix the valve open when first filling the system with water, but it often doesn't quite go far enough to operate the switch to start anything electrical going. It can be used to see if the valve is open though, loose and floppy means the valve is open, resistance and a whirring sound when its moved means it's not open.

With your installation, the boiler and pump will most likely be connected together, so if the valve doesn't open fully, or it does open but the internal switch doesn't work, then neither the pump or boiler will start.

The hot water controls the boiler via another method so that can still be OK.

There is one last test you can make. Switch the central heating 'on' and the hot water 'on' then turn the room thermostat and hot water cylinder thermostats up full. Does the pump run now? and do the radiators start to warm up?

 

[Agile]

Even if the pump is not working then the boiler would still eventually heat the hot water by gravity circulation but would take longer and the boiler would cycle much more being on for perhaps 30 seconds and off for 3-4 minutes.

See the FAQ on this site for information on checking pumps!

Tony

 

[xWeen82x]

I'll give that a go tomorrow stem and keep you updated

 

[stem]

Even if the pump is not working then the boiler would still eventually heat the hot water by gravity circulation but would take longer and the boiler would cycle much more being on for perhaps 30 seconds and off for 3-4 minutes.

Agreed! that was my thinking behind.

There is one last test you can make. Switch the central heating 'on' and the hot water 'on' then turn the room thermostat and hot water cylinder thermostats up full. Does the pump run now? and do the radiators start to warm up?

We'll see what happens tomorrow.

 

[xWeen82x]

Hi guys

Just a quick update I whacked the room thermostat to maximum before going to be last night and this morning the radiators came on. I can't quite understand why it suddenly needed to be on max but at least we have heating, hopefully it comes in again this afternoon too. Either way I think the system needs looking at as something's not quite right with it.