oil fired central heating system problem

redmv · 19-10-2010 05:13PM #1

rads upstairs get very hot, while downstairs hot at top of each but cold at bottom!!!!
no special thermo valves on system.
have tried bleeding downstairs rads but no air seems to come out just water immediately.
any advice would be much appreciated

Avns1s · 19-10-2010 07:02PM

Is your system zoned? Sounds like the circulation pump for the downstairs zone is either not working or is pumping at too low a speed. They are generally 3 speed. You could try and turn it up a bit.

Another posibility is that the motorised valve is sticking somewhat.

If the system is not zoned, you could look at balancing the rads so that the flow through them is more even.

JohnnieK · 19-10-2010 08:10PM

First of all. Turn the rads up stairs off. If they start to heat then it might very well be a pump problem.
Has this problem just happened?

redmv · 20-10-2010 10:55AM

Avns1s wrote: »

Is your system zoned? Sounds like the circulation pump for the downstairs zone is either not working or is pumping at too low a speed. They are generally 3 speed. You could try and turn it up a bit.

Another posibility is that the motorised valve is sticking somewhat.

If the system is not zoned, you could look at balancing the rads so that the flow through them is more even.

Thanks
Sorry but not sure what or where motorised valve is.
I dont think system is zoned. ..1 water pump beside boiler.
To balance rads do i need to close in valves at both sides of each and then open both the same amount?

redmv · 20-10-2010 10:57AM

wrote: »

First of all. Turn the rads up stairs off. If they start to heat then it might very well be a pump problem.
Has this problem just happened?

Thanks JohnnieK,
Will try that today and let you know

CBYR1983 · 20-10-2010 12:55PM

I get the same problem, but I get it upstairs, not downstairs. My boiler is downstairs. I assume your boiler is upstairs?

My rads upstairs don't heat fully at the bottom. The pump has been replaced and is set to the highest speed. They're big double rads, and they produce ample heat anyway, but I was surprised they don't heat all the way through.

Some of the guys suggested sludge previously but they're new rads, and upstairs.

I notice that any of my rads heat first at the top, regardless of location. I figure therefore that the pump is just having difficulty getting enough water to the upstairs rads.

This seems to be because the upstairs rads are fed from downstairs by 1/2 inch pipes. Plumber suggested to me that this was reason why they are slow to heat.

I would have thought that they should be fed by 3/4 inch piping, which only branches off to the rads using 1/2 inch, thereby ensuring adequate flow.

Any thoughts? Could this be cause of my and OP's issues?

JohnnieK · 20-10-2010 08:57PM

CBYR1983 wrote: »

I get the same problem, but I get it upstairs, not downstairs. My boiler is downstairs. I assume your boiler is upstairs?

My rads upstairs don't heat fully at the bottom. The pump has been replaced and is set to the highest speed. They're big double rads, and they produce ample heat anyway, but I was surprised they don't heat all the way through.

Some of the guys suggested sludge previously but they're new rads, and upstairs.

I notice that any of my rads heat first at the top, regardless of location. I figure therefore that the pump is just having difficulty getting enough water to the upstairs rads.

This seems to be because the upstairs rads are fed from downstairs by 1/2 inch pipes. Plumber suggested to me that this was reason why they are slow to heat.

I would have thought that they should be fed by 3/4 inch piping, which only branches off to the rads using 1/2 inch, thereby ensuring adequate flow.

Any thoughts? Could this be cause of my and OP's issues?

Was the system cleaned before the new rads were fitted? If not it still can be sludge. How many rads are fed from the half inch pipes?

CBYR1983 · 25-10-2010 08:28PM

JohnnieK wrote: »

Was the system cleaned before the new rads were fitted? If not it still can be sludge. How many rads are fed from the half inch pipes?

The system was drained, not flushed/descaled.

There are 4 radiators fed by the 1/2 inch pipe. All double panel convector.

2 are 1600x500
1 is 1400x500
1 is 700x600

What would surprise me is how the sludge would not have drained out from the upstairs.

In fairness the upstairs rooms heat fine now but it seems a bit weird that the bottom third doesn't heat fully except on the rad that is fully open (which is also the smallest rad).

oil fired central heating system problem

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