Heating Problem - last radiator is cold...

murphyp2

Hey all,

This is my first post here, so I'm hoping for loads of replies!!

I have an oil-fired central heating system, which is quite old. I had new radiators installed downstairs and in my bedroom. When I run the heating, downstairs is very warm, but upstairs is cold. More specifically, the later the rad is on the system, the colder it is. The master bedroom is ice cold as it's last. I'm trying to figure out why.

If I shut off the thermostats on the downstairs radiators, the master bedroom jumps to life and is at full heat. I have bled all the radiators of trapped air. It seems there is not enough pressure to reach the master bedroom when the downstairs rads are on. Does anyone know if any of the below solutions will help, and if not, what will??

1: Service the boiler. Is it just knackered?
2: "Balance" the radiators by adjusting the output valves (trying this tonight)
3: Add water to the system somehow? (How??)
4: Something else...

Any and all help appreciated.

Cheers,

Cold Pete.

willah

Balancing should sort the problem. Do you have thermostats on the rads? If so you will have a lockshield on one side and a stat on the other. Close all the lockshields then open one full turn each. Turn the heating on and feel the rads the ones closest to the boiler should heat quickest and hottest. These may need to be turned down. Keep checking the rads and adjust as needed.

murphyp2

Thanks Willah,

I'm going home now to test this and I'll report back tomorrow. Watch this space!

Cheers,

Peter.

Lex Luthor

Murph, willahs advice would be what I'd suggest. You just need to balance the system. Here's the 100% method to do it
http://www.diydata.com/projects/centralheating/balancing/balancing.htm

I did this once using a thermocouple and it took the full weekend. Rule of thumb for balancing is as follows:

Close all rad lockshield valves.

Lets say for example you have 12 rads in your house and your lockshield valves take 3 full revolutions from open to close.

Rad closest to boiler, open lockshield 1/4 turn. Next rad closest open 1/2 turn and so on to the furtherst away rad which will be open fully. That way you have roughly opened each of them the same amount difference. However with distances between some rads being different to others, its a rough guide and they might need tweaking but its a good place to start

When you say you had new rads installed, are these additions to the existing system or just replacements? If extra rads, you might need to turn up the o/p of your burner a notch to cope with the extra load. This would involve increasing the burner pressure and/or increasing the nozzle size. Try the balancing first and see how you get on

crosstownk

I had a similar problem when I moved in last year. Not quite as bad as your problem as the last rad was only warm despite balancing. I then found a switch on the water pump that stepped up the speed of the pump. It was turned to speed 1 (of 3). I turned it up to 2 and all was well.

JamesM

crosstownk wrote:

I had a similar problem when I moved in last year. Not quite as bad as your problem as the last rad was only warm despite balancing. I then found a switch on the water pump that stepped up the speed of the pump. It was turned to speed 1 (of 3). I turned it up to 2 and all was well.

Yes, normally the pump should be at the highest speed. Sometimes with an open system this can cause pitching into the header tank, but not usually.
Jim.

crosstownk

JamesM wrote:

Yes, normally the pump should be at the highest speed. Sometimes with an open system this can cause pitching into the header tank, but not usually.
Jim.

Interesting. I was thinking of setting my pump up to 3. But, what do you mean by 'pitching'? I have a sealed system - what are the relevant implications of 'pitching' in a sealed system?

murphyp2

Hey folks,

Thanks for all the replies!! I tried balancing last night and got a fair bit of hit into the last rad. Thanks Willah!

But now that I've seen Lex's reply, I'm sure I can improve the situation. I opened all lockshield valves 1 full turn. This evening I'll reduce this on rads closer to the boiler. Then I will hopefully get full heat on all rads! Thanks again for the help.

Crosstown - I have an oil burner in the shed - would this have a pump speed setting somewhere? Can you give me some pointers on how to find it?

Thanks,

Warm Peter.

JamesM

crosstownk wrote:

Interesting. I was thinking of setting my pump up to 3. But, what do you mean by 'pitching'? I have a sealed system - what are the relevant implications of 'pitching' in a sealed system?

You should not have a problem with a sealed system if your pump is at the fastest setting.
With an open system, sometimes if you do not have many radiators on, the pump pressure will push water up the expansion pipe into the expansion tank.

I would think that the faster the water circulates in the system and the quicker the cool water get back to the boiler, the more balanced the heat around the house.
Jim.

Moanin

I have the same problem as the OP, but I have a gas system.I balanced the rads as advised by many people and the rad was working ok for about 2 days.Now it's back to square one again, i.e. luke warm to cold.I also have to regularly bleed one rad that has alot of air in it.I mean at least once a week.Any ideas how to cure this much appreciated.Thanks

crosstownk

murphyp2 wrote:

Crosstown - I have an oil burner in the shed - would this have a pump speed setting somewhere? Can you give me some pointers on how to find it?

The switch is on the pump body. At least thats the case on my pump. It is possible that not all pumps have a speed selector.

@JamesM. Thanks. I've a sealed system and I turned the pump to 3 (fastest). Seems that the rads heat a lot quicker now. Only thing is, I can hear the water through the system. But I think this is due to the thermostatic valves restricting the faster flow. I don't reckon the noise is curable.......................or is it?

JamesM

Moanin wrote:

I have the same problem as the OP, but I have a gas system.I balanced the rads as advised by many people and the rad was working ok for about 2 days.Now it's back to square one again, i.e. luke warm to cold.I also have to regularly bleed one rad that has alot of air in it.I mean at least once a week.Any ideas how to cure this much appreciated.Thanks

Probably a sealed system with insufficient water. You may need to find a valve for filling the system - probably in the hot press. Search for previous posts on the subject.
Jim.

JamesM

crosstownk wrote:

@JamesM. Thanks. I've a sealed system and I turned the pump to 3 (fastest). Seems that the rads heat a lot quicker now. Only thing is, I can hear the water through the system. But I think this is due to the thermostatic valves restricting the faster flow. I don't reckon the noise is curable.......................or is it?

Yea, It's probably the sound of fast flowing water. I don't think that you can do much about it - apart from going back to the slower speed. It also could be air in the water ?
Sometimes the faster flow can cause the thermostatic valves to vibrate :eek:
Jim.