Strange Heating Problem

Southern Comfort

I have oil central heating in the house. It works fine, except for one big problem.

The main timer switch operates the overall system. The thermostat switch is in the sitting room. When the heat is on, and I turn the stat down below the "click," the boiler goes off, as does the pump. All fine, so far.

But, after a while, the boiler will come on by itself (the stat is still below the click so the heat shouldn't come on), without the pump starting up, and the upstairs rads become hot, etc.

Effectively, what I'm saying is that the heat comes on upstairs when I don't want it to.

Has anyone any idea what the problem might be? Thanks in advance.

Dony

Does the heating only come on upstairs when this happens?
Is there a stat upstairs also?
Is the house zoned upstairs/downstairs?

Southern Comfort

Dony wrote: »

Does the heating only come on upstairs when this happens?
Is there a stat upstairs also?
Is the house zoned upstairs/downstairs?

Hi Dony. Thanks for replying.

Yes, the heating only comes on upstairs when it happens. The pump doesn't kick in.

No, there isn't any stst upstairs.

And there isn't any zoning either. It was built in the late 70's. We're living here for the past 15 years and I wouldn't be surprised if the boiler is the original one that the builder put in!

Dony

Thats strange. I suspect that the reason its heating the rads upstairs without the pump coming on is because hot water rises etc.
I'll admit I'm not a plumber but maybe the stat you have is faulty.
There is also a thermostat out where the boiler burner is too.
I'm sure you'll get a better answer than this.

Southern Comfort

Thanks, Dony. I figure that the upstairs rads come on because hot water rises also.

Hopefully someone here will be able to explain fully, as you said.

heinbloed

Your boiler gets electricity from an independant source, not from the room thermostat.
That is the reason why it kicks-in without the room thermostat actually asking to do so.As soon as the set flow or return temperature signals a demand (here: the flow and return to or from the boiler) the boiler will fire-up or stops firering.

This is an installation fault.

The correct installation will allow the room thermostat to be the only signal sender. As soon as the room thermostat is "clicking" 'on' or 'off' the boiler should react.
So rewire the boiler's electricity supply.

Compare the situation with a standard light supply sutuation:
a lightbulb connected to a manual switch AND to to a light sensor will do what it wants, it will switch on the light as soon as the natural light intensity drops, no matter at what position the manual switch is set.

Ask the heating system installer or an electrician to wire the system correctly. The existing room thermostat might not be able to run the boiler and pump on it's own due to it's differing electric current. It maybe only 12 Volt or 240 Volt but not fused to enough Ampere. If so you still wouldn't have to rip-out the existing thermostat, an 'intermediator', a relais, could simply be set between the thermostat and the rest of the electric supply system. At costs of € 5-10 plus work hours.
There are more sophisticated control stations/-centers available for around €100-200 which would allow more thermostats, timers, weather compensation, anti-freeze cycling and an intelligent pump controll to be joined together. And then automatically fine-tuning the system's components.
But with the simple installation described by the OP the solution described above is propably the cheapest and most straight forward.

Check the boiler's manual, modern boilers have these features already build-in and the existing room thermostat might be wrong wired.

I'm not a plumber as well.

Sparkpea

it sounds like a common zone valve problem. you're saying there's no motorised valve though so is the stat just wired back to the boiler and pump? are you sure theres not a zone valve that you just dont know about? as I said this is something you would normally find with a faulty motorised valve head which needs replaced. either way you're problem is electrical (might be worthwhile posting in the electrical forum because those guys fault find problems like this all the time). I'm no electrician but I'm guessing it could be the room stat, boiler thermostat or wiring between the 2 and pump.

Is it possible the boiler has a frost stat fitted and this is why its coming on all of a sudden or is it doing it even in the summer time?

yoshytoshy

Hold on a second ,I wouldn't go messing with the wiring yet.

A lot of old systems have gravity fed hot water and pumped heating. So your thermostat controls the pump.
It's possible there is an upstairs motorized valve coming off the hot water circuit and it's openor. Or someone could have changed the pipework slightly etc.

It's better to have a plumber check it out for you ,before you start messing with it yourself.

Sparkpea

^^^ if the hot water is gravity fed then there shouldn't be a zone valve on it and like you said the stat would control the pump on/off, either way tho the boiler shouldn't be firing if the timeclock says off.. but I agree its likely a zone valve.

yoshytoshy

Sparkpea wrote: »

^^^ if the hot water is gravity fed then there shouldn't be a zone valve on it and like you said the stat would control the pump on/off, either way tho the boiler shouldn't be firing if the timeclock says off.. but I agree its likely a zone valve.

If you read the op ,you'll see southern comfort turns the stat down and the boiler boiler and pump goes off.
If the boiler goes off it could be on temperature ,because the pump has turned off.
The boiler then comes back on when the boiler temperature drops.
This is all pretty academic ,to be honest.

heinbloed

On a DIY base I would connect the boiler to the pump, the boiler getting electricity only when the pump is turned on (via the room thermostat).This is how my central heating system operates since 8 years without any problem.

But this is a DIY aproach, the professional's opinion should be sought.

yoshytoshy

I'll just post this link about what I'm talking about ,the op still hasn't commented on what happens when he just turns his timeclock off.
Which is normally what people do when they don't want their boiler on.

Pumped heating ,gravity water

Southern Comfort

yoshytoshy wrote: »

I'll just post this link about what I'm talking about ,the op still hasn't commented on what happens when he just turns his timeclock off.
Which is normally what people do when they don't want their boiler on.

Pumped heating ,gravity water

Hi yoshy. When I turn the time clock off, the heat goes off completely. (The switch is out in the playroom so I just turn down the stat below the click in the evening but I always turn off the timeclock before going to bed).

Thanks, everyone, for taking the time to reply. I phoned a plumber earlier and he's going to call out during the week to take a look. I'll post again as soon as it's sorted out.

meercat

sorry to jump in but i think an electrician may be better man as its more likely a control problem

Sparkpea

nah yoshytoshy is right, if the timeclock isn't turned off (which is what the OP has just stated) then its likely firing because of temperature or gravity hot water