Hot water coming on at random, thermostat not working?

After a few days of trying different things I have isolated it some more. Ultimately a plumber will be called, but I want to try and see if I can get a good idea of it first.

BOTH bathroom (ensuite & family) rads, unless they are totally *off* on the TRV valve, cause the boiler to come on (bypassing the new thermostat) and heat up to scorching hot.

No other rads in the house have this, so I can only assume these bathroom rads have some sort of design/feature to warm up the bathrooms for showers/towel drying etc etc.

Has anyone heard of a feature where the bathroom radiator/towel rail warms up x hours after the hot water to dry any towels left in the room? Could there be a hidden timer somewhere that is set up for this?
 
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Another attempt at getting to the bottom of this problem!

Not had a chance to call a plumber out because of the fact the system still works perfectly heating/hot water on demand/timed, and I can't replicate the problem. They also won't return my fking calls! frown

[I am ignoring the two bathroom rads scorching themselves when everything should be off for now. I turn them off, they stay off, and my sanity can handle that for now.]

What I cant understand/get to the bottom of is why the boiler/grundfos pump operate at random - one directly below the bedroom, one directly next to it!! Initially I thought they may be operating correctly and the pump is turning itself on to recirculate the hot water in the cylinder?/circulating water to cool itself off?/circulating hot water to ruin my life? but the fact is that it always seems to occur a few *hours* after an 'intensive session' - ie heating on for a few hours, or heating & hot water on for a few hours and the boiler fires up and heats up makes me think it isn't correct. Why would the boiler *ever* fire up when thermostat is off? Most (all?) of the time it does it it only comes on for a few mins at a time. The Grundfos pump on the other hand seems to stay on for much longer periods of time, but I havn't been able to get an accurate idea of how long.

If I turn the boiler off at the mains/reset it (grundfos pump etc goes off with it) it seems to stop it mucking around for a day/two (until heating system is all required again).

Before I start running out of checkatrade/recommended plumbers and start calling them out at random trying to get hold of one, could anyone shed a tentative light on this? Sadly, ill be here all night...waiting for the damn thing to spark up and make me wish I was living in a cold damp cave in Afghanistan!
 
It is a 2 port Honeywell valve, as you show there! The issue is definitely hot water related, due to the rads all staying cold when the boiler is coming on at random. The grundfos pump runs for much longer then the boiler does, and associated pipework is very hot - hot enough that if the rads were effected I would feel the heat through them!

When the system is running, moving the lever on the top of the Honeywell valve offers little resistance, then the lever moves itself back into place. When the system is all off, the lever doesn't budge.

Thanks for the response mate! :)
 
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Presumably that is the heating valve. There should be two valves, one attached to the cylinder, the other in the heating circuit.
 
This is the wiring diagram of a Megaflo with two 2-port valves. I have added the Heatmiser RC1-WTS receiver.

Can you check that all the wiring is correct.

Untitled

Untitled



(Sorry if the pic was missing when you opened this)
 
Thanks very much for posting that. very grateful! :)

I will have a look when I get home as best I can, but I fear that beyond the basics of electrics/plumbing logic I am in unknown territory.

The fact that the thermostat works perfectly, on demand, for both hot water & heating AND shuts it off afterwards, leads me to believe it is all wired correctly? or could a wiring problem still allow this to be the case?
 
There's no point delving any deeper until you have checked the wiring. Particularly when you have a plumber and an electrician who are not familiar with the components.
 
Ok then, took the wall plate/receiver off the wall and had a look at the wiring and it looks to be wired correctly, as per thermostat instructions anyway. I also spoke at great length to the electrician who fitted it and he said it is a very typical job for him and he had no doubt over the wiring being done correctly.

To confirm it when the boiler fired at random this evening I turned the 'master switch' for the thermostat off at the wall plate and it shut the whole thermostat down - and didn't make any difference to the boiler coming on at random & staying on for the typical 3-5 minutes. This gives me total confidence that the thermostat is not to blame.

I also spoke to the electrician about how I can check the wiring for the Honeywell valve and he strongly recommended not dismantling it until I was certain which one was at fault?


He still strongly feels that the bathroom rads heating up is directly connected to the hot water heating up. This means int he summer with the heating turned off, your bathrooms are still warm for showering & drying towels. A feature I love the sound off if I can get the damn system to work!
 
Andehh said:
I also spoke to the electrician about how I can check the wiring for the Honeywell valve and he strongly recommended not dismantling it until I was certain which one was at fault?
Click to expand...
Do you have a multimeter and know how to use it? If so, there's an easy way to check the valves.

When the fault occurs:

All checks done at the valve connections in the junction box

1. Measure the voltage between the brown and blue wire.
Should be 0Vac if the valve should be closed, 240Vac if valve should be open

2. Measure between grey and blue
Should be 240Vac with valve open and closed

3.Measure between orange and blue
Should be 0Vac with valve closed and 240Vac with valve open.

NB sometimes the grey and orange wires get swapped round.
 
No Multi-meter i'm afraid. I have the electrician coming out on Friday out of curiosity and has offered to talk me through the wiring if I am still concerned about it. The colour matches up with the above layout from what I can tell^


However, after some more hours tinkerng with it I have found the following....

1) Hot water OFF all evening, Central heating ON....issue occurs. Boiler fires at random.

2) Boiler fire up every 10-15mins for 30-40 seconds before turning off. Cycle repeats.

3) Resetting the boiler/turning it off at mains stopped the above happening^

In my mind that rules out the hot water and FRONT Honeywell 2 way valve, as this valve stayed luke warm the entire time (heating on for few hours), so clearly wasn't in use, thereby not triggering.

When i dismantled above Valve I also found the motor turns freely, actuator handle moves freely and switch move freely - all seemed normal. Cycling the hot water on/off also revealed motor turning, actuator moving and switching being switched as I sat nex to it and listened. When hot water turned off....all moved & operated fine.

Following the above I turned my attention to the REAR 2 way valve - the one neigh on impossible to replace! This one is a lot bigger, has a white case compared to steel of Honeywell and I found the following:

The motor was A LOT more sluggish then honeywell, sounded like it was struggling. When I actuated it by hand it felt much more loose, as if not connected to anything. I only noticed resistance to my pushing it during the last 5-10% of it sweep zone. It did not move itself back across the sweep when I moved my hand a way, I had to move it back there. Following this moving it, the boiler now fires 100% of the time, with me turning it on/off at mains. Thermostat has no control over it.

I am now sat here nervously waiting for it to cool down to see if I have now buggered it! frown

Pic of said valve below. Can anyone comment on the above analysis? frown Thanks in advance.

https://dl.dropboxusercontent.com/u/72120595/IMG_20131119_194129.jpg
 
D

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