Pressurised system problem

[larch731]

I have a pressurised system run off an oil fired boiler. The pump is on the return. The system appears to run from the bolier straight into the immersion tank and then onto the radiators. There is a thermostat at the bottom of the tank which appears to control the pump. I have a problem where the radiators upstairs work (excluding the bathroom) but none of the down stairs work unless you turn off the upstairs rads.
My plumber has tried putting a valve in to shut off the flow to the tank , this appeared to make very little difference, he then tried putting a larger pump into the flow side , this made little difference , in fact the pump burnt out ( we don't know if it was a faulty pump as it was cheap or some blockage). We have now power blasted the whole system and put a pump back into the return (not wishing to risk another burnt out pump), but we are back to square one.
I think the system may have been originally a gravity fed system as there used to be a Franco Belge in the kitchen which used to feed the system and I think the present system was cobbled from this. Is it possible there is a 'gravity' valve in the system which has clogged ?.
Anyone reading this will probably become aware I know nothing about central heating systems. Help would be greatly appreciated.
PS Both my plumber and boiler service engineer say that they have never seen a system like this !

 

[SimonJohns]

I would say you just need to balance the system

But the flow should not go through the cylinder before going to heating circuit

If this is the case. Have a re pipe of controls

But try balancing rads first

 

[larch731]

Thanks Simon. How do I do this , I don't want to keep calling the plumber As Xmas is near and cash short. As I have said I have had a motorised valve put into isolate the tank which is not at present wired this I am isolating manually.

 

[SimonJohns]

Turn all rads off on one valve. I reccomened the left (providing you have not got a trv on this side)

Fire boiler

Go to closest rad to boiler

Open closed valve 1/2 turn

Wait 2min. See if either pipe gets warm going to rad

If not open valve 1/4 of turn extra

Repeat working away from boiler

Go back to first rad. Waiting about 10 min atleast. If rad is not hot enough.

Open valve 1/4 turn more. Repeat on other rads

 

[SimonJohns]

Repeat process till satisfied

Shild of said that further away from boiler you will notice you are opening the valves alot more

 

[larch731]

Thanks Simon. I shall give this a try tomorrow. Any thoughts on why the other pump burned out when put into the flow ?. As I said it was a cheap pump off Flea bay. Thanks again

 

[SimonJohns]

Says it all

Spend the £££
Buy a Grundfos

 

[larch731]

Still having problems, I have balanced the system as best as I can , it is a bit better but I still have 4 radiators which don't work however one is a slight bit of warmth.
Before ballancing the system I bled each rad and I had air in the bathroom rad ( I had it in the same rad before).
Also my pump runs all the time and seems to be controlled from a stat which is at the bottom of the hot water tank. The pump runs when I turn this stat up, however should this happen as I have had a valve put in to bypass the tank.

 

[larch731]

System seems to have got worse again, I have noticed that on two occasions I have had air in one of the radiators , I think this is third in line (hard to tell as system has been added to at least three times by previous owners). On the last occasion there was a significant ammount of air.
One thing I forgot to mention was that the pressure vesel filled up with water about a year ago, however it has not done this since and I had the vesel repressurised.
Upon innitial start up there is a gushing sound , could this be air ?. I have tried ballancing the system but to no success , does it have to be done in a different way when TRV valves?.