Central heating query

[Sergeant Pluck]

The heating system (gas, clapped out) is heating the upstairs radiators despite the central heating being switched off so that it should only be heating water.

The obvious thing to do is to switch the radiators off, but I am reluctant to switch the one closest to the boiler off because of childhood memories of The Radiator That Must Never Be Switched Off.

How do I know if my system has this feature? And is the Never Switching Off because all the hot water for the other radiators has to go via this radiator, or is it because - as my dad informed me - the house will blow up?

[Kim]

Dodgy motorised valve would seem likely.  They usually have a manual lever on them that can be prodded.  Might be near the boiler, or near the hot water cylinder, depending on the system topography.

[Canardly]

What Kim says. Motorised valve heads can be changed.

[Sergeant Pluck]

I should have explained that I am a tenant. This boiler has given grief before and to cut a long story short the only economic way (even without considering the latest idiosyncrasy) to sort it out is replacement of the whole lot. That’s not going to happen until after our tenancy comes to an end in a few months and as it works ok-ish I am fine with that.

So I don’t think I am going to bother a plumber with this - I’d be content to not have the upstairs get hot when the central heating is not in fact on.

Hence, my query - how can I tell if this system has one of these stupid radiators that cannot be closed off? And what would happen if I did it anyway?

[Sergeant Pluck]

Dodgy motorised valve would seem likely.  They usually have a manual lever on them that can be prodded. 

Thanks Kim. I’ll google images of same and see if there are any likely looking and prod-able valves present.

[Canardly]

Try moving the lever on the motorised valve (if it exists) to manual. ( You may have two). I would not mess about with a rad that is not fitted with rad valves as it provides a heat sync for the boiler, often being located in the bathroom. If the boiler gets too hot you will be faced with a boiler stat lock out which will probably require the services of a plumber in any event, depending on the model of boiler and the position of the stat reset switch.

[Sergeant Pluck]

Think of the one radiator as the emergency heat sink for the boiler. When a boiler is opertaing correctly all is well but if something went wrong inside the boiler, as they are prone to do on occasions, then at least it has a chance to push scolding hot water round a short piece of pipework and one radiator so that scolding hot may be kept below the point of the boiler packing up or blowing up.

Interesting. I have noted that the boiler and environs does seem to get remarkably hot of late. Maybe I need a rethink on that plumber.

[Jurek]

Another vote for dodgy diverter valve.
They can (usually) be thwarted manually.

[Graham the gorilla]

Hi

Your heat system will have either 2 x 2 port valves (one for heating one for hot water ) or 3 port valve (diverts the flow of water to heating/ hot water or both )
Inside this valve is a ball which can distortion or get blocked with debris, then even when  the the heating is not turned on water bypasses the valve, causing your radiatorsearch nearest  the valve to get warm.
Temp sloution , you might be lucky if your run the system in heating mode for10 mins  and it might  move the debris from the seat, or if the valve head is removable  remove head  to test if the valve spindle has  stuck, twist lclockwise and anti clockwise  to free off.
Permanent  solotion,  drain system fit new valve, test quality of water and add inhibertor / cleaner to bring system water upto BS standards

Cheers

[Sergeant Pluck]

I was surprised today to receive an email from the landlord, who was not yet aware of the above, asking me when would be a good time to have some plumbers in to quote for new heating system!

When it is cooler and I’m about to leave the premises for a while, I’ll blast the heating on as per your suggestion, Graham the gorilla.Thanks.

Anyhoo, I’m switching the radiator in question off.

I am not switching the radiator in question off as it is fucking stuck. I note that it is the only rad in the house that does not have a thermostatic valve on it - is that of significance regarding the Must Never Be Switched Off question? It’s moot now, I suppose,

[Canardly]

System should have one rad without a trv for the reasons quoted above.

[Sergeant Pluck]

System should have one rad without a trv for the reasons quoted above.

Noted, thanks. I had not realised, until I moved a piece of furniture out of the way this evening, that the rad in question differed from all the others by not having a TRV.

[Quisling]

+ 1 for keeping a "heat sink" radiator uncontrolled by TRVs.  That's standard good practice and the bathroom rad is normally selected as it beneficially dries your towels and is normally the room you want warmest.

+1 for dodgy zone valve.  Note, the mode of failure here could be (a) knackered solenoid in the head - i.e. the bit that tries to turn the valve is knackered, in which case this can be replaced without getting into the wet side of the plumbing, or (b) the valve underneath the metal zone valve box is borked; blocked or jammed, or scaled up and "letting by".  If it's that, then spanners are required.  You may be lucky and have isolating valves either side which should prevent the need to drain down the whole CH system.

Depending on how the valves are configured, switching to the "manual mode" might switch it into heating only (i.e. force the central heating on, rather than just the domestic hot water).  Either way, not fixing it is ramping up your gas bill so if the landlord can't be arsed to fix it then ask for a rent discount to offset the additional wasted energy input in the summer months.

[Kim]

+ 1 for keeping a "heat sink" radiator uncontrolled by TRVs.  That's standard good practice and the bathroom rad is normally selected as it beneficially dries your towels and is normally the room you want warmest.

IME the bathroom rad is often on the hot water circuit, so you still get dry towels in summer.

Common sense (from the days before clever/wireless thermostats) dictates that the radiator in the room with the room thermostat be one without TRVs.

[rafletcher]

+ 1 for keeping a "heat sink" radiator uncontrolled by TRVs.  That's standard good practice and the bathroom rad is normally selected as it beneficially dries your towels and is normally the room you want warmest.

IME the bathroom rad is often on the hot water circuit, so you still get dry towels in summer.

Dunno about that - though some towel rails are.  Having said that, our house in Coventry had a radiator plumbed into the hot water circuit, and fitted as a bath panel. You had to be careful getting in and out!

[Quisling]

+ 1 for keeping a "heat sink" radiator uncontrolled by TRVs.  That's standard good practice and the bathroom rad is normally selected as it beneficially dries your towels and is normally the room you want warmest.

IME the bathroom rad is often on the hot water circuit, so you still get dry towels in summer.

Common sense (from the days before clever/wireless thermostats) dictates that the radiator in the room with the room thermostat be one without TRVs.

Yes, you don't want TRVs trying to control the temperature in the same room as the room 'stat!

I've not seen bathroom rads on the hot water circuit before. There is some logic in it, and I can imagine plenty have been installed, but I'm pretty sure it wouldn't meet Part L of the building regs these days, and would be a particular problem in modern, highly insulated and air tight properties where summer overheating is becoming a serious issue.  You get round the problem now with dual fuel towel rails that use eleccy in the summer (possibly controlled by timer) and the central heating in the winter.

[Kim]

My parents' house when I was a kid had one on the hot water circuit (well, it was more towel rail than radiator).  I think it had a TRV on it, but that was probably a retrofit.  The Radiator That Should Not Be Switched Off was in the hallway, with the room stat.

Best thing they did (in a different house) was separate heating zones upstairs and downstairs (with associated motorised valves and thermostats, and corresponding plumbers-doing-electrics spaghetti).  Meant the upstairs rooms didn't get cold if the fire was lit.

[Sergeant Pluck]

Our set-up is a bit unconventional and probably not legal. The rad with no trv is the one closest to the boiler, so in the case of our little house that means unfortunately that it is a the back bedroom as the boiler is in a closet off the bedroom. The bathroom is downstairs and the towel rad in there has never worked. That has never bothered us as there is underfloor heating in it for the winter and towels aren't really a problem.

Summat's not right as that rad closest to the boiler now gets really hot, rather than just a bit warm, when the boiler is on to heat water. Another clue in the diagnosis, however, is that other upstairs rads would get a bit warm too if they had not been closed off at the trv.

It's all moot as the landlord is going to replace the boiler and whatever else needs to be done. I suspect that this is a prelude to a large rent increase.