Bathroom rads hot but thermostat is off and hot water is off

[feebeebos]

Great post by Softus, as he says, some of us do care and aren't just about screwing peeps for their money. No one knows it all and can always learn from these forums.

This happens even when the hot water is off on the main controller. The bathroom rads are hot and I can hear a pump running. If I turn the central heating off on the main controller the pump stops running after about 30 seconds

I would think that as your hearing the pump running, that stops 30 secs after you turn the controller off, zone valve closing and cutting supply to pump, that you still have a demand for heat even though thermostat is turned down. Have you checked that the thermostat is serviceable and contacts making and breaking? The fact why bathroom rad doesn't have a TRV and is only one heating up when pump running to me indicates that those with TRVs are satisfied by the high ambient temp.

So check your thermostat is working, they can be had real cheap on Ebay.

Regards

 

[PEDANTICVINDICTIVEMAN]

EBAY,JEEEEEEEEEEEZZZZZZZZ this post gets worse !!!!!!!!!

 

[Softus]

Valid point by feebeebos - the roomstat could indeed be the culprit, and it's so easy to check and replace.

By the way, if you do replace it, ensure that there are three wires to the stat if it's an analogue/electromechanical one; only two are needed for a digital/electronic one.

As PVM implies, eBay, as a source of plumbing/heating parts leaves a lot to be desired (IMO), but bargains are there for sure. My personal preference is to get parts from a local stockist who will replace any faulty parts really quickly.

 

[MilindPuri]

thanks all for posting - only just caught up with the latest.

To try to answer some of the questions / respond to suggestions (ignoring PEDANTICVINDICTIVEMAN!):

a) looking for clues on the piping near the cylinder - gulp - so many pipes just going down to the floor and up into the loft - I think I have to go in the attic to see what they are. I have been told that the bathroom rads are on separate circuits - whether do

b) checking thermostat - it is less than a year old as the last one didn't appear to be working. Anyway - I can 'click' it on and 'click it off' and the boiler / rads respond appropriately. When the thermostat is set to have the heating 'off' and the bathroom rads get got then other rads don't get hot as the main one downstairs near the thermostat doesn't have a TRV, on others the TRVs not working anyway and they don't get hot. So there are definitely separate circuits for normal heating and the bathroom rads. BTW the bathroom rads do not always appear to be pumped - there are times when the pump does not run.

c) a different problem - but why do I have to have the central heating on for the hot water to come on - is the controller wired incorrectly?

 

[Softus]

thanks all for posting - only just caught up with the latest.

c) a different problem - but why do I have to have the central heating on for the hot water to come on - is the controller wired incorrectly?

I would say so, yes. Or the motorised valve. Or both.

Either way, this is hard to diagnose over the Internet. The only certain method is to yourself get a wiring diagram and work through your connections until you find the error.

However, you could play a hunch - for example, if the CH comes on when you select DHW, and vice versa, then it's kinda obvious what's happened.

As a minimum you should be able to trace back the DHW MZV connections and confirm that the valve is connected to the 'HW ON' output from the programmer.

 

[MilindPuri]

yes you are right it is the domestic hot water and the boiler overrun - sorry about the long time for the reply I only had it confirmed when the boiler was changed!

 

[Softus]

Er, sorry - what? Who is right?

Are you saying that you no longer have a problem?!

 

[Vic Spanner]

Thank god you got it sorted. I`ve been having sleepless nights over the last two years worrying about this one.