TRV Default Position

[FullHouse]

I've just moved into a new house and am having real problems getting my head around the Central Heating and Hot Water systems. This looks a brilliant forum and site, its already been great for my education! However i'm really struggling and I think I'm going to have a lot of questions if you dont mind me troubling you.

I'm starting off by trying to understand how the TRV work. I have Boss TRVs installed. This picture looks like what I have.



Am I right in thinking that the flow of hot water into the rad is by default open, and that as whatever is in the TRV (a pin of sorts?) heats, it expands, moving down and closing the flow? Specifically, if the TRV is removed from the rad, will the radiator be always on or always off?

 

[bengasman]

It's all there in FAQ.

 

[FullHouse]

Ty for your reply Bengasman

I appreciate the frustration of noobs coming on and posting the same inane questions time and again without reading the FAQ. I assure you that I did read the FAQ BEFORE posting (and used the search button to look through previous posts) - I've just looked over the FAQ again, and still cannot see the answer to my question. :$

 

[bengasman]

For answers to Frequently asked questions about Central Heating, you could try the Central Heating FAQ, in particular #12.

For future reference, greater minds than my own decide whether something should be files under FAQ, CH FAQ, or Wiki, and apart from some blatantly obvious items, I couldn't tell where to look if my life depended on it.

Well worth going through the lot; you won't remember all of it, but when needed, you will remember that there is info about it readily available.

 

[mikeyd]

Am I right in thinking that the flow of hot water into the rad is by default open, and that as whatever is in the TRV (a pin of sorts?) heats, it expands, moving down and closing the flow?

Yes that's correct.

Specifically, if the TRV is removed from the rad, will the radiator be always on or always off?

If you remove the head the water will flow. Normally when you buy a TRV you get a decorators cap with it which you can use in place of the TRV head to lock the pin down so you can remove the radiator.

I had a quick look at the central heating FAQ's No. 12 and couldn't see the answer to your question there. It may be in one of the others though.

 

[FullHouse]

Thankyou - and sorry I missed it :$

I did go through the CH FAQ, FAQ and Wiki, but didn't associate the answer 12 heading with what I was looking for, so moved on :$

A Thermostatic Radiator Valve is an automatically opening and shutting radiator-valve that opens when the room gets below the set temperature, and closes itself when the room is warm enough. It does NOT make the radiator hotter or colder, and setting them higher does NOT warm the room up quicker.
A TRV is not a calibrated thermometer, hence the number/setting on it is a mere indication.

I confess I'm still not totally clear on what the defualt position is when the thermostat head is removed.

When it is set to maximum temperature required (5), the pin is at its highest point and doesnt push (close?) the valve.
When it is set low (1), the pin is at it's lowest point and the valve is pushed.
If the actual temperature is 3 on the scale, then when the required temperature is 5, the radiator should be on, and the valve is not pushed. Ok - seems to me that the radiator is ON by default. Is my reasoning sound?

I have one TRV where the valve is stuck in the down position (off). I have seen the wiki (and similar in the FAQ) - //www.diynot.com/wiki/plumbing:thermostatic_radiator_valves_-_trvs
I have got as far as tapping with a hammer (how hard a tap can I go? Hard enough that if I was doing it on my finger instead, it would hurt?), but it wont spring back into place. Anything else I should try?

 

[FullHouse]

Thanks for the clarification mikey

 

[doitall]

The head does the controlling, if you remove it from the valve it won't matter what number it's on, as the valve will always be fully open.

When replacing the head, turn it to the highest setting to make it easier to get on.

 

[bengasman]

...When it is set to maximum temperature required (5), the pin is at its highest point and doesnt push (close?) the valve.
When it is set low (1), the pin is at it's lowest point and the valve is pushed.
If the actual temperature is 3 on the scale, then when the required temperature is 5, the radiator should be on, and the valve is not pushed. Ok - seems to me that the radiator is ON by default. Is my reasoning sound?

That is correct.

I have one TRV where the valve is stuck in the down position (off). I have seen the wiki (and similar in the FAQ) - //www.diynot.com/wiki/plumbing:thermostatic_radiator_valves_-_trvs
I have got as far as tapping with a hammer (how hard a tap can I go? Hard enough that if I was doing it on my finger instead, it would hurt?), but it wont spring back into place. Anything else I should try?

It's hard to indicate how hard you can tap (no pun intended), but I'd say about as hard as it takes to drive a small nail with a small hammer into normal wood.

The problems is invariably caused by either corrosion or poor quality of the trv; the model showed in the picture is reasonably good.
Make sure you have a spare valve that will fit, just in case, and gradually increase the force of the tapping. You many even very carefully try to pull the pin out.
Once all the rads are getting hot, add cleaner to the system and leave it in for a few weeks, than keep draining and filling the system til it is clean, and add inhibitor.

 

[D_Hailsham]

Am I right in thinking that the flow of hot water into the rad is by default open, and that as whatever is in the TRV (a pin of sorts?) heats, it expands, moving down and closing the flow? Specifically, if the TRV is removed from the rad, will the radiator be always on or always off?

If you remove the head of a TRV you will see a pin sticking up from the part left attached to the pipes. At the other end of this pin is a conical valve which, when the pin is pushed down, stops the flow of water. The TRV head contains some bellows filled with either gas, liquid or wax. As the temperature of the contents rises the bellows expand. This operates on the pin in the main body, so slowly closing the valve. The TRV head also contains a spring or two. When you adjust the valve setting, you are changing the tension on the spring, which means that the temperature has to be higher before the bellows start to close the valve.

It's important to realise that TRVs are not like a switch, on or off. They adjust the flow through the radiator so it is giving of just enough heat to maintain the set room temperature. Those who are not aware will feel the radiator, find it is cooler than they expect, so they will turn the TRV up until the rad feels hot. The result is the occupants of the room will feel to hot, so they will turn the TRV down again. A vicious circle.

At the moment the temperature outside my house is about 7°C. Inside it is about 20°C and the radiators are about 21°C, i.e "cold". That's because the house is fully insulated.

 

[bengasman]

At the moment the temperature outside my house is about 7°C. Inside it is about 20°C and the radiators are about 21°C, i.e "cold". That's because the house is fully insulated.

Wrong.They are cold because the trv has shut the flow off, and the rad has nearly cooled down to the ambient temperature.

 

[FullHouse]

The problems is invariably caused by either corrosion or poor quality of the trv; the model showed in the picture is reasonably good.
Make sure you have a spare valve that will fit, just in case, and gradually increase the force of the tapping. You many even very carefully try to pull the pin out.
Once all the rads are getting hot, add cleaner to the system and leave it in for a few weeks, than keep draining and filling the system til it is clean, and add inhibitor.

The system is a closed water supply - would I still want to add cleaner and drain? The house was standing empty for about a year before I moved in if that is of any significance

As I said in my original post, I'm really struggling to get my head around the system - so I hope to start a new thread - with photos for clarity (I dont trust myself to explain properly what I see!). However a quick summary of the issues I have identified so far:
- The control unit seems set up wrong - when I activate the CH, nothing happens. When I activate HW the CH comes on (but no HW)
- The thermostat in the hallway seems to have no impact (though presumably unnecessary with TRV)
- The TRVs dont seem to shut down any of the radiators when they get to temperature. I set to 0 (before I read on here that low is better than zero) and the room just continued getting hotter and hotter until I had to manually shut it down.
- 7 radiators in the house - 4 seem to work, 1 I've mentioned - the valve is stuck shut - the other two, the valve seems to work but they dont get hot (they both did once, but not since) - the pipes feeding them are cold (one of the pipes is warm approaching it, but cold by the time it reaches the rad)
- The hot water only seems controllable by an electric plug into the "copper cylinder" - I turn it on and I have hot water, I turn it off and I dont! I have plugged into a timer switch so it is not on all the time. The brand is Albion and the model number is A9045I (I think - written in pen on the cylinder)

The central heating is an amptec C1200 (as here I think - http://www.plumbnation.co.uk/site/amptec-c1200-12kw-electric-flow-boiler/)

 

[bengasman]

The problems is invariably caused by either corrosion or poor quality of the trv; the model showed in the picture is reasonably good.
Make sure you have a spare valve that will fit, just in case, and gradually increase the force of the tapping. You many even very carefully try to pull the pin out.
Once all the rads are getting hot, add cleaner to the system and leave it in for a few weeks, than keep draining and filling the system til it is clean, and add inhibitor.

The system is a closed water supply - would I still want to add cleaner and drain?

Yes, flush needed as in faq

 

[FullHouse]

I haven't looked to "flush" the system yet - to be honest, it's a bit daunting so i'm putting it off whilst I try and sort out the other issues.

I've made a quick sketch of how I see the pipework running to/from each rad. My ladder isn't accessible, so I havent got into the loft yet to check how they connect once the pipes disappear through the ceiling.



I have 3 of the 7 radiators seemingly working well with the TRV (Hallway, Living Room Rad 2, Bedroom 1
2 of the radiators (Living Room 1 and Conservatory) are constantly on - the vales seem seized in the On position - I've been applying pressure to them and tapping them, but have been unable to release them. Any thoughts on anything to try? Or should I look to replace these two? (again, sounds daunting, but probably a good project to do alongside the flushing)

The final "loop" is the one that has me wondering most though - I presume the pipework works as a loop, and the water within only flows in one direction? The pipe is hot up to the "out" on the Bedroom 2 rad. A little hot water gets into the rad through this. The pipe goes cold shortly after the rad and fails to reach the Rad in Bedroom 3. Flushing might solve that? However the immediate question - Are the in and out of the Bedroom 2 rad the wrong way round? If the Bedroom 3 rad were off, then the hot water could never reach the Bedroom 2 rad? Am I misunderstanding the way it works, or is there an issue with the pipework?

 

[D_Hailsham]

At the moment the temperature outside my house is about 7°C. Inside it is about 20°C and the radiators are about 21°C, i.e "cold". That's because the house is fully insulated.

Wrong.They are cold because the trv has shut the flow off, and the rad has nearly cooled down to the ambient temperature.

Wrong. If that was the case the flow pipe to the radiator would have been hot. But it wasn't because the boiler was off although the CH was on.

To the OP
Do you live in a bungalow?
Which end is the boiler in your diagram?
You only show one pipe in the loft. There should be two connected to the flow and return connections on the boiler.
The IN and OUT connections on bed 2 are the opposite way round to bed 3. How did you decide which was the IN side and which the OUT?