balancing radiators, thermometer shows changing values

Kencollins

Hi all,

I am trying to balance my system. I have a thermocouple thermometer with the probes taped to the lockshield and on/off valves.

I can set the temperature drop to about 12 degrees easily enough, but then it starts changing. Over 5 minutes the value creeps down to 3, then up to 15, then down to 3 again and so on.

I presume this is caused by the radiator taking time to pass on the changing temperature of the water due to the boiler cycling.

What value should I use, or can i stop the variation?

Pete67

You can minimise boiler cycling by increasing the load on it, in other words, make sure all the radiators are on full. If you have any thermostatic rad valves, remove the heads so that they do not start to close down when the room warms up. Turn all room stats up to maximum to keep the boiler enabled.

You want the boiler to be running close to maximum load, so that it is firing continuously. Then go around each radiator one at a time and adjust the lockshields for a 10 degree drop or 15 degrees if you have a condensing boiler. It's a slow process if you do it properly, and you will probably have to repeat it a couple of times to get them all right, as each adjustment effects the other radiators slightly.

Kencollins

Its an old house so there are no thermostats, trvs, or anything fancy!

I had the boiler turned up to full and it was still cycling, not very often though. I was having a big problem with one of the rads, I couldnt get more than a 5 degree drop on it. I know I have some of the radiators upstairs set very low though. Could this have a knock on effect on the radiator that I cant get the drop on?

I think I will try again tomorrow and follow the proper instructions. I didn't open all the lock shields fully before I started, just went around and adjusted from what they were at.

Pete67

It can be very difficult to get a decent temp drop on a small radiator, as the flowrate through the radiator has to be very low to allow the water to cool sufficiently. The lockshield valves are not very precise in regulating very low flows.

Kencollins

The bathroom radiators upstairs are all but turned off and still get very very hot. The lockshield valves are open less than a quarter turn on both of them and I can hear the hiss of water through them, so they must be just about shut. Heating is a pain in the arse!

whowantstwoknow

Hi

Having a new condensing boiler installed in the house and need to re-balance the system. Is there any difference between these approaches?:

diynot - balancing
diyfaq - balancing (used this method in the past)

With the boiler at the max and everything open, should the difference between the flow/return be the 15 degrees mentioned here. In the guides it mentions adjusting the pump rate. The pump is an integral part of the boiler. As I dont want to be messing with a boiler component, should I get the installer to check the rate (ie is that part of the commissioning process?)

The diynot method talks about closing all the rads and then restarting the boiler; what would happen if there is no bypass installed? Is that required, or again another question for the installer?

Finally as the HW is closed during this process, how would it adversely affect the balancing when both circuits are open at the same time completing for hot water? Should it be treated as another rad in the CH balancing process?

Thanks in advance

W.

whowantstwoknow

Well,

I got the CH balanced, with the 15 degree differential between flow & return as its a condensing boiler (well as close as possible). Happy enough, with even heat to all rads.

Just one question, on 1 rad there is a sort of whistling noise. I know it can be removed by opening the LSV, but in doing so the flow across the rad will be increased and thus reduce the temp drop. I guess there is no harm in doing the above?

Thanks
W.

Wearb

whowantstwoknow wrote: »

Well,

I got the CH balanced, with the 15 degree differential between flow & return as its a condensing boiler (well as close as possible). Happy enough, with even heat to all rads.

Just one question, on 1 rad there is a sort of whistling noise. I know it can be removed by opening the LSV, but in doing so the flow across the rad will be increased and thus reduce the temp drop. I guess there is no harm in doing the above?

Thanks
W.

I think that will be fine. After all what you are really aiming for by doing this is a low enough temperature return to your boiler to have it running in condensing mode as much as possible.