Airlocked radiator

indie armada

what is the best way of dealing with a radiator that is cold at the bottom and warm at the top. ive come across this a few times, once recently in my own house. how i dealt with it here was i felt which valve was the hottest and turned the other off, with the hot valve still open i loosened the other from the rad and let it bleed into a basin till the water comming out got up to the same temp as the rad, then tightened everything up and opened the other valve slowly bleeding the rad as i went.
is this the right thing to do? it worked here for me.
what if you dont have an autofill valve on the supply to the system, or an open system. to replace what the water you have bled do you introduce water into the system while you do this or after?

Buford T Justice

In Short No.

Air rises to the top of the rad, so if its hot at the top and not at the bottom, then the lockshield valve is probably open too far, and letting the heat out too quickly.

Firstly, check that is it the three edges of the rad that are hot and the middle stone cold? If it is, then the chances are, its an issue with sludge in the system and you will need to have it powerflushed with an inhibitor added.

On the other hand, you can firstly try the following.

Close the lockshield valve all the way and count the number of turns that it took to close (Useful if you want to put it back) The lockshield is the one with a cap on it that you will need a wrench to turn. Once closed, whack on the heating and let it get good and hot. Open the lockshield valve half a turn to one full turn and see how it goes and if it all heats. Repeat this until you get about half way open or until you get the whole rad hot. If this doesn't work then you it could be sludge

P.S. An open system will top itself up automatically as will a closed system with an auto filling loop. If you have a filling valve on a closed system, you will need to manually top this one up.

indie armada

i prob should have mentioned that when i was flushing it from the feed side that a lot of crap came out, mostly black silty stuff.
so at any given time the lock sheild valve should only be open as much as it needs to heat the rad fully?

Buford T Justice

Lockshields are set to balance the system in order that the heating doesn't heat just one or two rads.

If you are having problems with silt, then you have sludge in you're system. If I was you, I'd add a sludge remove to it for two weeks something like fernox, then get a powerflush done and have an inhibitor added.

Should sort the problem once and for all.

indie armada

nice one thanks for the advice. do you know of any decent straight forward manuals that deal with heating systems and procedures like balancing the system and fault finding. i have the confience to muck about with my own system and would like to know more about how they work.

Buford T Justice

This one is reasonably good. Covers all the basics.

afaik it doesn't cover balancing the rads, but that is a trial and error sort of thing.

The logic behind the balancing is as follows, from the first rad on the system you want to have the lockshield open very little and the last one would need to be open more. Reason being that you need to force the water all the way around the circuit as it will otherwise just take the easiest path available, which would be through the first rad if it was open fully. That sort of thing. Again thats the basic principle of it, but there is more to it than that.

Would highly recommend a desludging though, it'll cripple the system otherwise.

indie armada

think i have an easons voucher here somewhere.
i need to know a few things like how to fill a system after its been drained and from the point of view of my own system i need to know why its set up the way it is and could it be better. the way the heating was installed in this house was a joke and most of it down to pure laziness.
just this evening i noticed the 2 upstairs rads are void of water and i think the water, trough gravity has escaped because fingal have turned off the water and i hadnt closed the pressure reg valve that fills the system.
anyway thanks for the info.

Buford T Justice

indie armada wrote: »

think i have an easons voucher here somewhere.
i need to know a few things like how to fill a system after its been drained and from the point of view of my own system i need to know why its set up the way it is and could it be better. the way the heating was installed in this house was a joke and most of it down to pure laziness.
just this evening i noticed the 2 upstairs rads are void of water and i think the water, trough gravity has escaped because fingal have turned off the water and i hadnt closed the pressure reg valve that fills the system.
anyway thanks for the info.

Do you mean the filling loop, or the pressure relief valve?

That book covers the basics, but it might lack some of the specifics you are looking for. If you post questions, we can help.

indie armada

i have neither, i have a feed directly off the mains with a pressure reg valve feeding the system. i may have been mistaken but i thought that the level of the rads upstairs had dropped when i turned off the heating.
and i thought it had backflowed trough the pressure reg valve when the mains was sitched off by fingal.

Buford T Justice

You're heating system is dangerous if you don't have a pressure relief valve on it.

indie armada

there is a pressure relief valve just above the gas burner, the outlet runs parralel with the flue to the exterior. i only replaced it a few months back as the old one was faulty, stuck in the open position.
should there not be a non return valve fitted where the mains water supply is introduced to the heating system or should the pressure reg valve be closed fully on a sealed system once its at the required pressure.

Buford T Justice

indie armada wrote: »

there is a pressure relief valve just above the gas burner, the outlet runs parralel with the flue to the exterior. i only replaced it a few months back as the old one was faulty, stuck in the open position.
should there not be a non return valve fitted where the mains water supply is introduced to the heating system or should the pressure reg valve be closed fully on a sealed system once its at the required pressure.

The Heating system needs to be fully isolated from the mains supply except for topping up. If I was you, i'd fit an NRV and use a lever valve instead of a gate valve. Gate valves ain't so good on mains.

Anyhow, its against regs to have the mains permanantly connected, as if the mains pressure drops below the pressure of the heating, it will flow from the heating into the mains and contaminate the water supply.

indie armada

yeah that makes perfect sense to me, if i remove the pressure reg valve, which has the gauge, and replace it with a lever valve and a non return valve will this be acceptable. also my gas burner has no built in pressure gauge, so how would i go about fitting a pressure gauge and where is the best place to fit one to get a true reading. there is a gauge on the pressure relief valve so would that suffice.
thanks for the info

Buford T Justice

For starters, you would be bonkers to remove the pressure relief valve.

Post a pic of the current prv, and where you fill the system from

I would recommend removing whatever is there currently, and fitting the following from the mains in the following order.

NRV, Lever Valve, Filling Loop to the heating system.

You have a closed system right? Can you see you're expansion vessel?

indie armada

i dont think i was clear enough in my last post, im not suggesting i remove the pressure relief valve, i was suggesting removing the pressure regulating valve which is where water is introduced to the system.
there is a 1/2 inch tee off the mains,short piece of qualpex, then the pressure regulating valve then a further 4 foot of 1/2 inch into a tee onto one of the 3/4 flow or return, not sure which.
all of the above is in the attic above the burner. the red vessel is up there too close to the hotpress. the house is a bungelow with an attic conversion, with two rads in the attic. im aware of the filling loop method, but its not practical because the flow and return come into the top of my burner which is in a press in the kitchen. the hot press is in the kitchen too.

Buford T Justice

Can you post a pic of the pressure regulating valve?

No reason why you can't remove this valve and add what I have suggested in its place. It can be in the attic just as easily as anywhere else. Plus, it makes sense as there is already a mains supply there.

indie armada

i think ill get those few bits together and change out that pressure reg valve. i have to drain the system soon to replace a faulty trv on a rad so prob do it then. what is my best option for fitting a pressure gauge, will the gauge on the pressure relief valve give me a true reading of the overall pressure on the system. the pressure relief valve it tee'd off one of the 3/4 pipes going into the burner, the pump is inline on the other 3/4 that runs parralel to this one.
ill take a few pics and try post them up but im away up to your neck of the woods 2morrow and the house im goin to has cold spots in two of the rads so ill prob be onto ye from there too

Buford T Justice

Cold spots on a rad are generally a sign of sludge present in the system. I would replace the current setup with a filling loop as the posts above. They come with a pressure gauge that you just screw in, so that will fix that problem for you.

You don't necessarily need to drain the system to replace the TRV.

Kudos to Sparkpea for this.

Drop the pressure out of the system using a PRV. Once the pressure is down, and the system is sealed there will be a partial vacuum within. Then close the rad valves on both sides of the rad that you're going to change the valve. what I do is disconnect the side with the trv on it and use a compression stopend to screw onto the tail of the rad to stop the water in the rad escaping. then break the seal slightly on the pipe coming into the valve just enough to let you turn the valve so that its facing you, tighten it up again. open the valve into a bucket which should drain about 2-3litres of water off before the water will stop completely. then change your valve over quickly and reconnect everything, then uncap expansion, open cold feed, bleed rad, put head on and test.

indie armada

that seems like much better way then i was goin to do, ill upload a few pics of where my mains is introduced when i get back from the sligo and ye might talk me trough the best way of fitting the filling loop.
thanks again.