Boiler / heating problems following Nest install

ionapaul

Cross posting this from a Nest thread, just in case anyone had any ideas of the best way to proceed:

I've recently jumped on the Nest train and have been having some problems.

1) Turns out we have a 3 zone system that's only wired for one zone; this is according to the first EI installer we had out. So what he did was firstly install a single Nest, with the hub unit replacing our old manual boiler control panel (in our kitchen) and replace the downstairs thermostat with the Nest thermostat. He took a few pictures of our unusual set up, then called a day or two later to ask me if our boiler was running constantly, whether or not we had the heat turned up using the thermostat. Yep, he was right, it was on constantly! So he came back out and determined that we needed another hub and thermostat to replace the boiler control, with this solution meaning we used the 'Boiler' thermostat to turn the boiler on, then the 'Downstairs' thermostat to control the temperature (named it Downstairs despite controlling all of the rads, as we knew we'd add to the new system, see below).

2) A week later a different EI electrician came and installed the 2nd Nest we had previously ordered, which split the upstairs zone from the 'Downstairs' thermostat, so we now have three in the app; 'Boiler' (turns the actual boiler on and off), 'Downstairs' (controls downstairs temps) and 'Upstairs (controls upstairs temps). Synced the schedules so all three and the hot water would come on when we wanted each day; an overly complicated set up many would say (we didn't think we'd need the Boiler one, for example, when originally planning this!) but if it worked perfectly we'd be happy.... BUT

3) Within a few days the boiler itself started to shut off very regularly showing a 'flame failure' warning light, and then not turn on again without multiple resets. Most resets would result in a pump 'clicking' but the flame not audibly starting, and the flame failure or fan failure lights would flash after 30 seconds or so. Got a RGI registered plumber out, who said that a) the boiler mechanically looked fine b) he thought it was probably an electrical issue and c) the heating system was full of air and that could also be a problem. Our automatic air vent in the hot press seems broken, so I can't even try to solve c) myself

I've been trying various things trying to isolate the flame failure, which seems to occur within 15-45 minutes of the boiler starting to run correctly. For one, far fewer resets are needed if I turn 'off' the other Nest thermostats, and only try to turn the boiler on with the 'Boiler' thermostat turned up. It seems the more thermostats that are active and making a request, the sooner the system shows a flame failure.

Gonna contact the original EI electrician later and see if he can come by for a visit. Currently genuinely unsure of how to proceed further though.

DGOBS

A flame failure on a boiler (which boiler do you have) would be unrelated to external controls calling for heat (or not)

I would suggest you have developed a boiler fault, as the particular fault is caused by the boiler sensing electrode being unable to detect a flame, this could have multiple causes, including PCB faults, gas valve faults (or possibly loose connection in the appliance)

ionapaul

It is a Baxi 35 60 boiler.

Plumber seemed adamant that it was not a mechanical issue with the boiler anyhow and really pushed getting the electrician who installed the Nest to come out to solve the issue. Didn't help that I couldn't recreate the flame failure issue for him while taking a look. It definitely is much harder to reset if multiple Nests are making requests for heat, once only one is doing so (the 'Boiler' nest), I can reset easily enough... still get a failure after 15-30 minutes or so though.

Electrician coming out tonight and think we'll remove the Nests that replaced the manual thermostats and just leave the one that replaced the heating control panel, see if that makes a difference; if not I guess I'm a bit stuck if the plumber still maintains it isn't a boiler issue!

DGOBS

very easy for the plumber to loop out the nest on the boiler to test.

ionapaul

Update:

Electrician removed two of the Nests last night, so now we just have the one that replaced the heating control panel, which simply will be used to turn the boiler on and off - this is the biggest benefit we are after, the ability to turn it on and off remotely! It seemed to solve one problem - the boiler shutting itself down with a flame failure within 30 minutes - but the problem of the boiler starting on via the Nest instruction remains; we turn up the temperature with the Nest, the boiler powers up but immediately gets a flame failure It ONLY operates after a manual reset, sometimes multiple, using the dial on the boiler itself.

Is it possible that faulty wiring of the Nest to the control panel wires could be the culprit? Otherwise plan to get a plumber out again to take a look.

DGOBS

When you say, goes to flame failure straight away? Does it attempt to fire at all? If not, is flame failure the only flashing lights?

ionapaul

DGOBS wrote: »

When you say, goes to flame failure straight away? Does it attempt to fire at all? If not, is flame failure the only flashing lights?

Sorry, it does try to fire for 20 seconds or so, then either gives a flame failure or fan failure flashing light. Needs multiple manual resets to get going, then it is fine for at least 30 minutes (this evening gave another flame failure after about 30 minutes, was very very hot at that point I think, if that makes a difference).

DGOBS

Again, I can't see this having anything to do with your Nest install.

There is a boiler issue, could be anything from PCB, damaged rectification probes, or even gas valve failure (as they can be prone to issues that works when cold,, and fail when heats up)

The fact you boiler attempt to ignite, or does ignite and later goes out on flame failure, means Nest is giving the signal (call for heat to boiler swl) and thats all Nest does.

If you are also getting fan failures (multiple faults), it could possibly indicate the PCB

DGOBS

Thought he just did :cool: