CH hot water not reaching top floor

[johnnyfavorite]

My house has a gravity fed pumped CH newish gas boiler with motorised valve in cellar with 3 floors above, HW tank on 1st floor. CH header tank is only slightly higher than top of the highest radiator on 2nd (top) floor.

House has 13 radiators across the three floors, and all get nice and hot except those on the top floor which only get slightly warm after prolonged period on... have balanced radiators, they are bled...
Boiler is Worcester Greenstar Ri, can be used in pressurised system. Pump is Grundfos super selectric 15-60.

I hope someone can advise me - to get hot at the top am I best to

1. Fit a more powerful pump or
2. Fit a pressurising kit and get rid of the header tank or
3. Do something I have not thought of.

Here's hoping for help!

 

[D_Hailsham]

have balanced radiators

What is the maximum and minimum any lockshield valves is open?

Boiler is Worcester Greenstar Ri

Which size - kW output?

What is the total output of all your rads? Use Stelrad Elite Catalogue page 31 (50 Δt) to find out.

Pump is Grundfos super selectric 15-60.

That should be OK.

 

[johnnyfavorite]

Thanks for the reply.

The boiler is 20 KW output and turned almost fully on, and the rads total is 20021W using the Stelrad table you referred to.

The hall rad (biggest in the house) valves are fully open and is the only one with no thermostatic valve (to satisfy the rule that there must be one rad always open) and there is a small rad in the loo whose valves are barely open a crack. All the rest are in between.

Hope this is enough info...

 

[johnnyfavorite]

oops the boiler is 24KW

 

[D_Hailsham]

The hall rad (biggest in the house) valves are fully open and is the only one with no thermostatic valve (to satisfy the rule that there must be one rad always open) and there is a small rad in the loo whose valves are barely open a crack. All the rest are in between.

None of the valves need to be fully open - one turn from closed is probably the most any rad will need. You need to balance the system properly.

Read How to balance a CH system

If you don't want to bother with thermometers etc, start with all valves open half a turn and feel the flow/return pipes to estimate the temperature drop. Make sure you remove the TRV heads while balancing. Close the lockshield valve to increase temperature drop and vice versa.

 

[johnnyfavorite]

OK will have a go at rebalancing many thanks for your help

 

[Agile]

Why was it installed as an open vented system?

Tony

 

[johnnyfavorite]

When the boiler was replaced a couple of years ago the fitter, who now works for Gas Safe as an inspector I understand, did not think it necessary to change from the existing open vented system. Maybe he thought the old pipe work joints could not cope with the additional pressure.
I see that I could buy a kit to pressurise it on eBay for £60 or so and have been thinking this might be a good idea...

 

[Agile]

Close the lockshield on your hall rad and then open it just ONE turn.

It is probably stealing most of the flow!

Balancing is very important for good performance.

You dont need a sealed system, you need balancing!

Tony

 

[johnnyfavorite]

OK many thanks will give it a go.