Trickle heat in unoccupied house

[oldbutnotdead]

Drain it all down, get a plumber to do it if you can't. Turn the external stop tap off, put antifreeze in any traps on Sinks baths and in the wc pan.

If you leave it filled and the heating breaks down after a few days and then the house freezes big problems.

Completely drained down you won't need to worry about it or Check it and inform the house insurers of your plans.

Is exactly what we were told to do with mother's house in similar circumstances. Weren't asked to do the anitfreeze in the pans but did draiin the heatiing and hot water and all header tanks and turned off water at the supplier stop tap. Emotionally felt a bit wrong (the home we'd grown up in going cold over the winter) but practically was the sensible thing to do (sister living abroad, me living 300 miles north, what's to do)

EDIT We were minority owners, our clever mother had done an equity release thing and done very well out of it. If you/family are sole inheritors and the place is as old and draughty as you say then to keep the house appearing habitable you might be better off running the heating on a normal schedule (so the damp that occurs in older houses when they're unheated and unoccupied doesn't appear). Someone would need to check on the place ideally weekly, in the scheme of things a normal winter gas bill will be far less than the price penalty you'll pay when you come to sell and people walk in the front door and smell and see damp. Ultimately it is up to the executors of the estate- do hope your parents didn't appoint their bank!

 

[telnet]

Hi, thanks again for the replies. I see the wisdom of draining down completely, and also of the alternative, which is to keep the heating on to to keep the damp at bay. On the upside, the drafts and chimneys tend to reduce the damp problem. I am also very attached to the house and would hate for it to become uninhabitable. My job makes me a bit of a nomad and I have never settled permanently. It is therefore at the back of my mind to hold on to it and retire there in 5 or 6 years time.

Anyway, I was over on another thread and this quote got me to thinking.

To get the best from your heating, you need to understand how the thermostats work in relation to each other.

If your boiler isn't a combi, and it also heats stored hot water, the boiler thermostat setting should be at least 10 degrees above the hot water temperature setting on the cylinder thermostat, otherwise it will never reach the set temperature and the boiler will cycle continually.

I already said that the hot water out the taps is extremely hot and that I suspected a thermostat failure, which is supported by the regular cycling of the boiler. I got to thinking that if I tinkered with the thermostat connections so that the boiler received a continuous signal telling it that the cylinder water was at or above the set temperature, it would then deliver all its heat to the rads. This is what I had in mind when I asked my first question about the diverter valve.

The next question is what kind of sensor is in the cylinder? Is it a resistor or a thermocouple? I would have thought the latter. At this point I ran out of ideas.

Comments please.

 

[oldbutnotdead]

First job is test the cylinder thermostat (they're usually external and again usually an SPDT switch activated by a bimetal strip and adjusted by a knob calibrated in degrees C). Usually when cylinder temperature is below the set level a circuit is made which sets the 3 port valve (or zone valve) to the appropriate position and fires the boiler (and pump). If there's an immersion heater in the cylinder as well that will have its own thermostat (usually a long brass rod with an SPST switch activated by a bimetal switch). Switch the immersion heater off for definite.

Cylinder stat- with the cylinder cool, adjust the dial on the stat. Somewhere near the actual water temperature you will hear a click as the switch operates. WITH POWER OFF, use your multimeter to determine that the circuit is being made/broken. If it isn't then put a new stat on (£10), make sure you wire it correctly (so that the circuit from the boiler is made when the set temperature on the thermostat is higher than the cylinder temperature). You may find all 3 terminals are in use- note which way round the old one is wired, wire the new one in the same way.

 

[telnet]

Hi, Thanks for the info. I wonder if you can answer some more questions for me. The system dates from about 1970. The cylinder is encased in a hard shell jacket, which I thought was asbestos but somebody above suggested it is more likely fibre glass. Following your post I looked at stats on the web and see the setting dial in degrees C. I have never seen such a thing on our old system, although it could be hidden round the back of the tank.

The only water temperature control I know about is a knob on the front of the boiler, which is not calibrated in degrees. I will try to upload a diagram with this post.

At this point I'm having difficulty formulating a precise question for you. My aim is to safely stop the boiler from delivering any heat to the tank and just sending it round the rads. So rather than repairing the tank sensor, I would rather set the system so that the boiler thinks that the water is up to temperature and it just feeds its energy to the radiators.

From what you wrote above, it seems that the boiler will send heat to the cylinder when the thermostat completes the circuit: ie. when the temperature is above that required the circuit from the stat to the boiler is broken and the boiler will send its energy to the radiators. My question is therefore whether I could achieve my aim simply by breaking the circuit from the defective cylinder stat so that the boiler thinks that the water is up to the set temperature?

 

[oldbutnotdead]

If the system is from the 70s it might be gravity feed on the hot water side (ie whenever the boiler runs the hot water cylinder gets heat). Might be seen as a nuisance but it has some benefits (no pump noise cos thermionic syphon, no need for expensive complex bypass valves to maintain flow rate in the system).
If you haven't found a cylinder stat (and there is no sign of any wiring for one) then that would explain why the tapwater is spanking hot- whenever the timeswitch is set to hot water the boiler runs until it hits its internal thermostat limit (prob 80 or 85 degrees C)

That diagram isn't very useful- what would be more helpful are pictures of the timeclock and of any plumbing arrangements near the boiler and hot water cylinder (3 port valves, zone valves, any sort of stuff like that)
The thermostat on the front of the boiler sets the maximum temperature that the boiler achieves- an elderly oilburner like that won't be modulating the burn so if the heat demand is small (ie only a couple of radiators) it will achieve its internal temperature quite quickly and shut down (despite the timeclock/room stat being active) until circulation through the system cools it to below that setpoint when it will fire up again.
If that thermostat is set too low then the boiler will be prone to cycling on and off while it brings the house up to temperature- this is inefficient, you may get a better result from setting that thermostat higher. There are internal thermal fuses to prevent dangerous temperatures being achieved

 

[MeldrewsMate]

My aim is to safely stop the boiler from delivering any heat to the tank and just sending it round the rads. So rather than repairing the tank sensor, I would rather set the system so that the boiler thinks that the water is up to temperature and it just feeds its energy to the radiators.

My question is therefore whether I could achieve my aim simply by breaking the circuit from the defective cylinder stat so that the boiler thinks that the water is up to the set temperature?

Understood, but there are two systems commonly in use, and which you have determines which solution you take. This is why many have already asked for details, or even photos, of the system. I assume you cannot simply turn off the HW at the timer?
If you have two 2-port zone valves, one for HW and one for CH, then your suggestion of breaking the cylinder thermostat circuit would work. For a single 3-port valve system you must supply a 'temperature reached' signal to the valve to drive it to the CH only position.

You can also fix the 3-port valve into the CH only position manually by wedging a piece of soft dry wood between the pinion of the valve's motor, and the quadrant arm, in the position where both microswitches are actuated. A matchstick will suffice. Do this with the power off!

 

[telnet]

Great info. I'll get back to you in a couple of weeks when I am back at the house. I'll bring my camera!

There is a pump but I have no idea if it serves the rads or the rads plus hot water.

The timer is an electric clock that turns round and little pins you can move round the face throw a heavy duty switch as it passes, one toggles on and the other toggles off. Basically it provides the system with mains power or turns it off again.

More info when I'm actually standing in front of it.

Thanks a million.

 

[gasbanni]

The house will get cold sure but not necessarily damp especially as you have chimneys, unless there's some king of fault it shouldn't get damp ....no cooking or showers means there no water vapour to condense on cold walls. If the gutters, roof and downpipes are all in good order I wouldn't worry about damp. The heating left on after a period of been empty with no one living there to produce vapour that could cause condensation on the cold will warm the fabrich of the house up in two to three days. Turn everything off drain it down and rest easy !!!!

 

[telnet]

Gasbanni, I think you are exactly right. But I've got the bit between my teeth now and I want to understand this old system better. I have photos: a real feast for those that like a puzzle. Please don't comment on the exposed wiring, I know all about it. Anyway, the original question was how do I set the system to heat the rads without heating the tank. The system is a mystery to me. For example I don't see a motorised valve anywhere and the pump runs constantly, even when the room thermostat for the heating has cut out and the boiler is not firing (ie the hot water must be up to temp.). Also, the cylinder has 2 pipes on the bottom and 3 on the top. If anyone can talk me through the functionality of all the pipes I would be most grateful.