Hot radiators in summer

[Gary WoodingParticipant @garywooding25363]

I have an Intergas CH boiler in the garage, and a Honeywell wireless room thermostat in the living room. The room thermostat is switched to manual with the target temperature set to 7 degrees C. Last night, in the heatwave (we had the fan on in the bedroom), the bathroom radiator was hot (not burning hot but much hotter than warm).

Any ideas why?

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Gary, I’ve had a similar situation, but not to that amount of difference in temperature, none the the less though, the room temperature was hotter than the much lower temperature the room stat was set too, and even though I turned the room stat down a little more, the boiler was still heating the radiators, so I just set the room stat to off altogether, this doesn’t stop the hot water side from working, but I don’t know why the radiators were getting hot when they shouldn’t have, maybe I’ve a faulty room stat, but it’s been working okay all through the cold weather.

Regards Nick.

[Dave HalfordParticipant @davehalford22513]

There’s a restrictive link between go and return, sometimes plumbers use the bathroom rad. There will have been an instruction never to close the valves on that rad.

[David JuppParticipant @davidjupp51506]

One possibility of probably many.  Had the boiler been heating the domestic water?  a sticky or passing diverter valve could allow radiator(s) to heat up.

Our own CH even dumps hot water into the radiator circuit after achieving HW target, rather than just shut down whilst still hot.

[Peter Cook 6Participant @petercook6]

Assuming, as David J suggests, you are using the boiler to heat the domestic hot water it may not even be a leaking diverter. Depending on the pipe routing, the return flow from the water heater may use the same return pipe as the  the bathroom radiator.

What you are seeing is possibly convection flow from the shared return pipe back up into the  bathroom radiator.

I have a landing radiator – next to the cupboard containing the hot water tank – which suffers from the same problem.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I have a small radiator in the hall, which is the only one that doesn’t have a thermostatic control valve on it. I wouldn’t think my diverter valve is faulty, as it is relatively new, changed on the annual service before the last one, next service is due soon.

Regards Nick.

[Colin HeseltineParticipant @colinheseltine48622]

All my central heating boilers over the years have had a direct connection to the bathroom radiator. This usually a direct or ‘unvalved’ connection to the bathroom radiator (or a heated towel rail) primarily to act as a boiler bypass. It ensures the boiler always has a safe path to dissipate heat and safely release pressure when the rest of the house is turned off.  As a by product your towels are dried.

[JasonBModerator @jasonb]

Very common to have bathroom radiators or towel rails on the HW loop to the boiler. This means your towels get dried all year as the rad comes on when hot water is being made.

Mine are plumbed that way as are many of my clients systems that I have worked on. These days the bathroom rads should have individual RTVs so you can shut them off if you don’t want your towels to dry in summer.

[Gary WoodingParticipant @garywooding25363]

Many thanks for all the comments.

The boiler is for radiator heating only, the totally separate HW system uses an electric immersion heater, and the room thermostat was new in April this year. Do you think the boiler frost-stat could be the problem?

The annual service is due next month.

[BazyleParticipant @bazyle]

A friend recently had their heating come on unexpectedly at times. Traced to loose wire.

[Gary WoodingParticipant @garywooding25363]

That’s a thought Bazyle, I’ll get that checked at the service.

[JasonBModerator @jasonb]

Is it just the bathroom rad that you mention or more as the title says radiatorS?

If the boiler were to have come on then I would expect you to have felt a similar level of heat in all unless they have their own thermostatic valves.

[Neil WyattModerator @neilwyatt]

With a combi boiler you have to have one unvalved radiator on the circuit for safety reasons.

[JAParticipant @ja]

I notice this with my bathroom towel rail, the unvalved radiator, in the spring and autumn. I have no worries about this.

However, air conditioning is back in the news. If they become the norm the local outside ambient air temperature is bound to rise particular on near windless days (like today). Is this really a comfortable life?

JA

[howardbParticipant @howardb]

“However, air conditioning is back in the news. If they become the norm the local outside ambient air temperature is bound to rise particular on near windless days (like today).

Is this really a comfortable life?”

Air conditioning systems contribute to rising ambient temperatures, particularly in urban areas. The waste heat released from these systems can significantly affect outdoor temperatures, especially at night. Research indicates that this excess heat can raise nighttime temperatures by nearly 2 degrees Fahrenheit (1 degree Celsius).

We’ve been running a 7000 btu portable aircon unit in our main bedroom during our heatwave here in nw france, which has been going for longer and hotter than in the uk and the south facing metre thick stone house walls are now behaving like a storage heater, so we have just ordered a 12000 btu unit which we hopefully won’t have to run continuously to keep the bedroom at a reasonably comfortable temperature.

Adapt and survive.

 

 

[Adrian R2Participant @adrianr2]

The ideal is to have solar panels to run your AC, and position the outdoor units so as not just transfer the heat into the street or your neighbours property. Painting or limewashing external walls can also help a bit and being in France I suspect you already have louvres or shutters on your windows.

[Gary WoodingParticipant @garywooding25363]

The bathroom radiator wasn’t the only one that got hot.

[Howard LewisParticipant @howardlewis46836]

Id there a diverter valve that can divert to and from the radiators?

If this has stuck, it may be allowing hot water, intended for the coil in the hot water tank to flow through the radiators as well

Howard

[Adrian R2]

On Adrian R2 Said:

The ideal is to have solar panels to run your AC, and position the outdoor units so as not just transfer the heat into the street or your neighbours property. Painting or limewashing external walls can also help a bit and being in France I suspect you already have louvres or shutters on your windows.

Thanks for the advice but………

It’s a small portable aircon unit, cost about €200, so solar panels are totally OTT regarding the cost of them.

Transferring the waste heat to the outside isn’t a problem here, big old stone houses in a small village, houses here are not crammed together a la UK.

Houses of the age of ours – built 1927-  are metre thick rubble stone build walls with lime mortar, so any exterior coating will lead to damp problems as the walls would not be able to breathe, the local stone is a light colour with a lot of quartz in it, so is naturally reflective.

The house was renovated in the early 2000’s by the previous owners, the interior walls are insulated and plasterboarded as is the custom here.

We don’t have shutters, and there are no signs of them having being fitted in the past, shutters are a southern french thing, we just close the windows and the curtains when it’s V hot during the day, and open them when the sun goes down.

We do have modern good quality wood framed double glazed windows, which strangely are totally ineffective in keeping heat out !!

There has been local media advice about covering your windows externally with aluminium foil to reflect the heat, apparently it can drop the internal temperature by about 5 deg C.

I don’t fancy living in a pitch black house though !!

[Gary Wooding]

On Gary Wooding Said:

The bathroom radiator wasn’t the only one that got hot.

So that would suggest the boiler got a wrong signal and came on. Firstly check the battery in the wireless thermostat otherwise get the wiring from the reciever to boiler checked when you have the service done.

Won’t be a sticky motorised valve as you say the boiler only does CH.

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