weak flow in the system

[shopwherever]

We have a conventional system with 10 radiators (30+ years old, the boiler is 4 years old). The radiators are not getting hot water, although they are all bled.

When all radiators are open, it takes couple of hours for the first couple get hot, next two get worm, then next two luke worm and the rest stay cold. If I close the first two, everything moves on. If I close all the radiators and leave the last couple on the ground floor open only then they get worm / hot.

My unprofessional conclusion is that the pump is not crating enough preassure or the pipes are clogged up and the flow is restricted. I checked with the magnet and the pipes around the pump do attract it.

My questions are:

1. Can the pump impellers be dirty and not be push the water properly?
2. If the pipes are clogged, can a magnetic system filter with Sentinel X400 clear it?
3. Any other suggestion?

Many thanks

 

[Armo74]

Wouldn't hurt to give it a chemical clean but I would have a read up on here first about system balancing and give that a go.

 

[oilhead]

Is it fully pumped or gravity DHW?

 

[shopwherever]

It is gravity DHW, but the problem is with CH

 

[shopwherever]

Wouldn't hurt to give it a chemical clean but I would have a read up on here first about system balancing and give that a go.

The system has not been changed and not sure why would balancing help? Also, it takes couple of hous for hot water to get to the last radiator even if all others are closed.

 

[oilhead]

It is gravity DHW, but the problem is with CH

If the system is clogged, then the additional resistance will not be moved by the pump. If your pump is fitted on the return before the boiler, then any circulating pressure can get lost in the primary circulators.

 

[oldbuffer]

1. Pump impellers can clog. You can isolate the pump via the valves either side of it, remove the head by undoing the four allen headed bolts, clean and re-install. However, typically the valves don't work at all or they let a fair bit of water through. Safer to drain down, but refilling can be a problem.

2. It sounds as if the pipes are not completely blocked, as every radiator will get hot eventually. In this case using something like Sentinel X400 is quite likely to work. Better to flush the system out thoroughly first (to get rid of as much debris as possible), install the filter (if you don't, all the loosened debris will flush through the boiler's heat exchanger) and then run as normal for 2 to 4 weeks. Flush all out again, and keep flushing until the water is clear. Add inhibitor and heopefully bask in the heat.

3. Get the system power flushed (£300 to £500, takes a full working day), replace the pump if its worn.

 

[shopwherever]

1. Pump impellers can clog. You can isolate the pump via the valves either side of it, remove the head by undoing the four allen headed bolts, clean and re-install. However, typically the valves don't work at all or they let a fair bit of water through. Safer to drain down, but refilling can be a problem.

2. It sounds as if the pipes are not completely blocked, as every radiator will get hot eventually. In this case using something like Sentinel X400 is quite likely to work. Better to flush the system out thoroughly first (to get rid of as much debris as possible), install the filter (if you don't, all the loosened debris will flush through the boiler's heat exchanger) and then run as normal for 2 to 4 weeks. Flush all out again, and keep flushing until the water is clear. Add inhibitor and heopefully bask in the heat.

3. Get the system power flushed (£300 to £500, takes a full working day), replace the pump if its worn.

Many thanks for your reply oldbuffer!

1. I have not done this, but will check and see. First close the valves, then unscrew the release screw to see if there are any leaks and only then proceed with opening the pump.

2. Filter installed with x400 and is trapping dirt, however it is too slow to unblock it all and the radiators are the same as before - no noticable improvement

3. I was told to stay away from power flush as it can create unwanted problems. How true is this? I wouldn't like the pipes start leaking under the boards afterwards.

 

[chantelle]

Change the pump.

 

[shopwherever]

Problem resolved. The pump impellers were full of gunk, plus the pipes around clogged. All cleaned and the CH works beautifuly, rads too hot to hold!

Thanks for all your replies and suggestions.