luke warm rad

km79

hi i just noticed that rad in master bedroom is only warm when heating is on. the "leg" with the + - cap on it feels very hot but the "leg" on the opposite side with the cap that cant be adjusted is only luke warm . the rad is the same temperature all over and dont think it is airlocked. also the system is sealed if that makes any difference. any suggestions?

km79

i turned off all the rads except the luke warm one and it heated up fully! so any help greatly appreciated its going to be a cold one tonight

ART6

km79 wrote: »

hi i just noticed that rad in master bedroom is only warm when heating is on. the "leg" with the + - cap on it feels very hot but the "leg" on the opposite side with the cap that cant be adjusted is only luke warm . the rad is the same temperature all over and dont think it is airlocked. also the system is sealed if that makes any difference. any suggestions?

Probably the valve that you refer to as the one that can't be adjusted is simply not open enough. If you pull off the plastic cap you will be able to open it further using the cap from the other end. The valves are identical -- it's only the caps that are different.

If you have a thermostatic vale on the other end you can still open the valve using a pair of pliers.

km79

dont have trv . so both valves should be twisted fully anticlockwise?

km79

checked all again the downstairs ones are roasting most of the upstairs pretty hot except the one in our room and the one before it . seems like the one in our room is the last one to heat up?

ART6

km79 wrote: »

checked all again the downstairs ones are roasting most of the upstairs pretty hot except the one in our room and the one before it . seems like the one in our room is the last one to heat up?

Sorry for the delayed response--family demands at this time of year!

Anyway, it may be that your system needs balancing, and the way you do that (it takes time) is as follows:

First, check your hot water cylinder valves. The one you want is the bypass valve on the heating coil in the cylinder. Generally the coil is fed by two pipes in the side of the cylinder with a pipe and valve connecting them. That is the coil bypass valve and it should be partly open to prevent the coil taking all of the heat from the boiler.

Then you need to go to the radiators. At one end is the valve with a turnable knob that allows you to turn the rads off. That is the flow valve. At the other end is a valve with a knob that doesn't turn. That is the return valve. The knob on the flow valve can be taken off easily -- generally there is a central screw holding it, but taking out the screw will release the knob. If you then pull off the knob on the return valve you will find that the flow valve knob fits the valve stem and allows you to turn it.

Now, the rads that are running very hot need their return valves closed in while the cold rad needs its return valve opened further. This is where patience is required. You have to keep closing the hot rad return valves a bit at a time until they still get hot but the cold rad now starts to heat up properly.

Once they are all heating equally you need to check that you are still getting hot water in the cylinder. If you aren't then you need to close in the bypass valve a little until you get both hot water and hot rads. And hopefully I am not being insulting, but open is anticlockwise, closed is clockwise.

Expect to take two or three hours at least;)

JamesM

Also make sure that the circulating pump is on the "fast" speed.
Jim.

items

Here's how I balance rads,

First, let heating system go completely cold, set circulation pump at middle setting.

Turn on heating and go to where cylinder is located, check flow and return to cylinder are piped correctly, first pipe at cylinder to heat up should have no valve. Coldest pipe should have a valve located very close cylinder. Make sure the valve is only slightly open. This will restrict the heat flow through cylinder which allows heat to dissipate efficiently.

After that, turn off boiler and allow to cool.

When boiler is cool, turn it back on. With a pencil go to each and every rad and mark which side heats up first. Some times the wrong caps are fitted, flows are adjustable, returns should not be. Change caps to suit.

All sides that heat up first are your flows, the rest are returns.

Open all flows fully, returns should not be opened more than two turns from cold.

Two story houses, open downstairs returns one turn from closed, open upstairs returns one and a half turns from closed.

Bungalows, closest return to boiler barely open from closed, furthest return maximum two turns open from closed. From closest to furthest return open all the others gradually each increasing the further you are from boiler until you reach the furthest return.

The above can give you a good base setting which allows you more to tweak around with should you have troublesome rads. Before adjusting returns, bleed all rads. If some rads are still giving trouble, go to ones that are working good and restrict the return a little more. Failing that, adjust circulation pump to maximum setting.

Never have returns open fully, having them open fully will allow hot water to race through which is not efficient. Returns should always restrict the flow to allow heat to dissipate.

If you want to get best out of heating system, pick up a temp sensor to give a reading of heat at boiler return. Check boiler manual for recommended return temp, standard is around 10 degree temp difference from flow to return. If your temp difference is above recommended, heat is not being dissipated efficiently, you'll have to restrict returns more. If your temp is lower, boiler is working harder than it should be, you've over restricted rads, you'll have to open returns a bit more.

Thermo rad valves can be a nightmare while balancing a system, to difficult to describe how to balance a heating system with thermo valves correctly on this.

Heat loss is another factor, balancing depends on how well house is insulated and how well pipe work is insulated, sometimes its impossible to achieve temp difference as stated in boiler manual.

km79

thanks for all the help

Pete67

To balance a system with TRVs the process is exactly the same as described above, just remove the thermostatic heads from each valve first so all flow valves are fully open.