central heating not working


Postby delboybully » Sat Sep 04, 2010 8:52 pm

As part of my pre winter check on my home i tried the central heating and it didnt work!

My apologiss if i havent used the correct terminology when describing things. I have a reasonable DIY knowledge of how my system works and have repaired it before.

I have a non pressurised system (have a header tank) and a back boiler (behind fire) that was fitted approx 6 years ago with thermostatic valves on the rads, there is no thermostat. This system has a 3 way valve (one box direct water to heating or water or both). The hot water works fine, the header tank is at the level it should be, i bled some rads (including the highest) and they were full (no air)

When i tested the central heating i turned 2 rads, one of which is the nearest to the boiler to max.

The controler for heating and hot water has 4 positions for each- timed, 24hrs, on and off. When i put both to off and then put the hot water to on i can hear the 3 way valve moving and the pump starting, but when i turn the hot water off and turn the CH to on, nothing happens (no movement on 3way valve or pump starting)

My thoughts are that the 3way valve isnt working. However when the new boiler was fitted the plumber also fitted a new 3way valve. After 2+ years this failed and now the one i replaced it with has failed. This may be a coincident but i doubt it. The only other problem i have had since the new boiler was fitted was that the down pipe coming from the header tank to fill the system blocked where it hits a horizontal pipe.

My apologises for this long post but i wanted to include as much information as possible to make a diagnosis as easy as possible

thanks
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Postby plumbbob » Sun Sep 05, 2010 12:15 pm

Have you checked to ensure the room thermostat is in the "on" position??

The TPV has a lever on the side which allows it to be moved manually. When the heating is in the "on" condition, the lever should be loose and floppy which indicates the flow is directed to the radiators.

If the lever is at its rest position, try moving it over the length of the slot and see if it moves smoothly.
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Postby htg engineer » Sun Sep 05, 2010 2:26 pm

Have you checked that the room thermostat is tuned up, and hasn't accidentally been turned down ?

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Postby delboybully » Sun Sep 05, 2010 8:10 pm

There is no room thermostat

I have been told about the manual override on the 3way valve. When i turn the manual override lever to manual the heating system works. To me this means the 3way valve is either faulty or it is not getting a signal to send water to rads. How do i check/confirm the valve is faulty or if it is something else
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Postby delboybully » Sun Sep 05, 2010 8:11 pm

There is no room thermostat

I have been told about the manual override on the 3way valve. When i turn the manual override lever to manual the heating system works. To me this means the 3way valve is either faulty or it is not getting a signal to send water to rads. How do i check/confirm the valve is faulty or if it is something else
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Postby plumbbob » Mon Sep 06, 2010 10:17 pm

A room stat is normally required to provide the signal to operate the 3PV so if you don't have one we are really in a bit of unknown territory as your system is not a standard wired.

The only way to test to see if the timer or 3PV is faulty is with an electrical tester and the wiring diagram.
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Postby delboybully » Tue Sep 07, 2010 9:13 pm

I dont have a room stat but all rads have thermostatic valves. The system was updated about 6 years ago with a new electronic ignition boiler and various bits to the plumbing.

i think i have solved the problem, the programmer is sending a signal to the 3way valve but it isnt responding. Now how do i tell if it is the motor (is it called the actuator) or the actual valve. I had a new valve with the new boiler which lasted about 2 years, and then i had to replace the whole thing. so thats 3 valves gone in 6 years. Does this point to a problem causing the valves to fail or have i been unlucky
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Postby plumbbob » Wed Sep 08, 2010 12:04 am

delboybully wrote:Now how do i tell if it is the motor (is it called the actuator) or the actual valve.



Now that's a good question!

IF the manual lever moves smoothly without significant resistance, it could be the motor has failed.

If the lever is stiff, remove the actuator (gearbox and motor) assy (no draining required) and try turning the valve stem with pliers.

Consider installing a room thermostat. Accurate control cannot be achieved with thermostatic valves alone. Doing so may place undue strain on the system pump. It's absence might even be an explanation of the premature failure of the 3PV as it is could be held in the neutral position unnecessarily for extended periods of time.
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Postby delboybully » Sun Sep 12, 2010 12:46 pm

The system has a bypass fitted so a room thermostat isnt needed. This also stops the strain on the pump

I took the actuator off and when i set the CH to on the actuator doesnt move so its the actuator that is faulty. The bit on the vavle body that the actuator turns moves freely
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Postby plumbbob » Mon Sep 13, 2010 2:25 pm

delboybully wrote:The system has a bypass fitted so a room thermostat isnt needed. This also stops the strain on the pump


I beg to disagree. All systems need a room thermostat. In fact regulation insists they are fitted.

What I was suggesting is without a thermostat the system would be running continuously without any "rest" periods. This is likely to result in unnecessary wear to the systems components due to the length of time they are running and not whether a bypass is fitted or not.
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Postby delboybully » Mon Sep 13, 2010 5:14 pm

I see what you are saying now. What you are saying is that in my system, the pump and 3way valve are always on when CH is called for whereas if i had a room thermostat, the pump and valve would turn off when the room temperature is hot enough.

Ok I guess putting a room thermostat in can't be difficult. How would i wire one into my system?

Location of thermostat, bearing in mind all rads have thermo valves, in the living room would be a bad idea because if i put the fire on, then the heating would go off all over the house. I figure it has to be in a room that is one of the warmer rooms, like the dining room. The thermo valve there would be set on 6(max) and the cooler rooms reduced to 'taste'. Your thoughts
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Postby plumbbob » Tue Sep 14, 2010 1:13 pm

I think you are on the right track to work out the best place for the thermostat. Usually, the traditional place is in a hallway, but of course, not all houses have one.

It would be normal for the room with the thermostat not to have a TRV fitted for the reason you suggest. Not having a TRV has the advantage of allowing that radiator to act as a system bypass which removes the need for one elsewhere. Separate bypasses can be a pain too as they will often cause a reduced flow to some radiators.

The stat should be easy to connect. It goes in series with the timeswitch.

Choosing a wireless model is easier to connect and has the added bonus of allowing it to be situated in any location but of course it is more expensive and therefore the payback time will be longer.

Cheers
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Postby delboybully » Tue Sep 14, 2010 10:02 pm

I am not to fussed about the cost as i will be doing it myself and therefore have no labour cost. Being a blokes bloke, i like the idea of wireless!!!!

I do have a hallway bit i dont want it to be one of the warmest rooms!!

I shall be draining the system down in the next few months as i am having a single story extension built and i will be adding the rads (have checked that the boiler is man enough for the extra rads) so changing a TVR to a normal valve wouldnt be a problem. Given this information do you think i should change the TVR to a normal valve and put the thermostat into the hall, or just put the thermostat in the dining room

If i do change a TVR how do i adjust the temp of the system. I am guessing that i have to set the TVRs is relation to each other and then set the thermostat in hall so that hall doesnt get too warm but that the other rooms get warm enoguh

I have minimal knowledge of the wiring of CH system, how do i put the thermostat in series with the timeswitch? I would guess that i take the grey from the 3way valve (this should be 240v for CH on, along with white for CH, white only for HW)and connect this to one end of the thermostat, the other end of thermostat going to where the grey currently goes? Am i right?

To me i cant see the point of having a thermostat, it seems to me that TVR's in each room sound great. Set the TVR to the right temp and just let the CH system warm the house. With a room stat and the rest of rooms with TVR's you have to set the stat very carefully, set it too cold and all rads go off, set it too warm and the room with the stat gets too hot. can you see what i mean about the stat being quite pointless!!!! I may be wrong though
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Postby plumbbob » Sun Sep 19, 2010 8:31 pm

delboybully wrote:
I do have a hallway bit i dont want it to be one of the warmest rooms!!


It won't, the thermostat will turn the heat off first!

delboybully wrote: Given this information do you think i should change the TVR to a normal valve


Probably, but you could simply remove the TRV head so allowing it to be converted back in the future.

delboybully wrote:If i do change a TVR how do i adjust the temp of the system. I am guessing that i have to set the TVRs is relation to each other and then set the thermostat in hall so that hall doesnt get too warm but that the other rooms get warm enoguh


You don't. The room thermostat will control the average temperature then you just alter individual TRV's to fine tune each area. This allows a lower temperature in a spare bedroom for example or cut the heat input in the lounge when the gas fire is on etc.

delboybully wrote:I have minimal knowledge of the wiring of CH system, how do i put the thermostat in series with the timeswitch? I would guess that i take the grey from the 3way valve (this should be 240v for CH on, along with white for CH, white only for HW)and connect this to one end of the thermostat, the other end of thermostat going to where the grey currently goes? Am i right?


You haven't mentioned which system you have, but in a "Y" plan, the grey controls the hot water and is connected to the cylinder stat. The white is linked to the CH side of the timer so the room stat fits in this wire. You will of course need a permanent live and neutral to power the wireless circuitry.

delboybully wrote:To me i cant see the point of having a thermostat, it seems to me that TVR's in each room sound great. Set the TVR to the right temp and just let the CH system warm the house. With a room stat and the rest of rooms with TVR's you have to set the stat very carefully, set it too cold and all rads go off, set it too warm and the room with the stat gets too hot. can you see what i mean about the stat being quite pointless!!!! I may be wrong though


TRV's are fitted in addition to and not instead of a thermostat and are only there to offer greater flexibility in system control. Thermostat's were a standard long before TRV's were available. In fact there is no requirement to fit TRV's in downstairs rooms. Only bedrooms.
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Postby hamish72 » Wed Sep 22, 2010 6:34 pm

You don't. The room thermostat will control the average temperature then you just alter individual TRV's to fine tune each area. This allows a lower temperature in a spare bedroom for example or [b]cut the heat input in the lounge when the gas fire is on etc. [/b]


Not after he removed the valve head
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