Central heating - possible blockage

[Wurlitzerwilly]

Hi.

I have a central heating system that I installed over 10 years ago. It consist of an Alpha Ocean Combi Boiler 4 double radiators, 1 towel radiator, 1 plinth heater and I later added HEP2O underfloor heating to the conservatory, all on the ground floor.

The main flow and return are 22mm copper and the radiators are teed off in 15mm copper.

The boiler pressure vessel failed a few years back and was replaced with a separate under-floor vessel at the manufacturer's recommendation.

This year on turning the central heating on for the Winter, one of the radiators and the underfloor heating are not getting hot. The underfloor heating is on the end of the line but the radiator is not and has one radiator in the line (which is working) between it and the underfloor supply.

I can bleed both the non-working components and there seems to be plenty of pressure. If I feel the flow and return to the underfloor, just before the shutoff valves, I can feel heat in the flow but not in the return. With the radiator there's no heat apparent in either the flow or return.

I checked the TRVs and they appear to be OK, so I'm begining to suspect a blockage. A few years back the system was losing pressure and as I couldn't locate the leak, I applied Fernox leak sealant and I wonder if that could have caused a blockage?

Also, If I drain down the faulty section and apply high pressure air from my workshop compressor, is this likely to cause any damage?

Any other suggestions?

Regards,

Alan.

 

[Groovejet]

Have you tried turning every radiator off apart from the radiator that is not heating? Keep this one fully open on both sides and give it a chance to pull heat through.
Also make sure your pressure gauge reads over 1bar when system is cold.

This boiler has settings on the pump it should be on maximum setting or this will reduce hot water flow rate and reduce c/heating ability.

If heat does come through, open the under floor heating and let this do its work also.
Open 1 by one then you'll get them all working eventually

Fingers crossed

Also if you dont use Thermostatic valves they can seize up. Remove the head of the valve get a screwdriver and use the handle end to push the center pin in and out 4-5 times to free them up , put heads back on when your happy there not causing a problem.

 

[Wurlitzerwilly]

Have you tried turning every radiator off apart from the radiator that is not heating? Keep this one fully open on both sides and give it a chance to pull heat through.
Also make sure your pressure gauge reads over 1bar when system is cold.

This boiler has settings on the pump it should be on maximum setting or this will reduce hot water flow rate and reduce c/heating ability.

If heat does come through, open the under floor heating and let this do its work also.
Open 1 by one then you'll get them all working eventually

Fingers crossed

Also if you don't use Thermostatic valves they can seize up. Remove the head of the valve get a screwdriver and use the handle end to push the center pin in and out 4-5 times to free them up , put heads back on when your happy there not causing a problem.

I did try turning the other rads off but I can't get to the plinth heater without dismantling half the kitchen!

I wasn't aware of a pump setting on the boiler, or do you mean the user heat control on the front lower panel? I'll look into that.

I will have another go at the radiator TRV but I don't think I can get at the underfloor heating stat because it's part buried in the wall. Even bleeding it is a pain.

The pressure gauge reads 1 bar when cold and more when hot or calling for heat.

 

[Groovejet]

No!!........The pump inside the boiler has speed settings 1,2,3 make sure its on 3.
Turn power off at wall switch / fuse spur and remove four screws on front panel, 2 top , 2 bottom.
Locate pump and turn switch on top of pump to 3
Dont worry about the plinth, just turn all rads off to push the water through the u.f heating seen as though your having access problems.

But remember to sort them trv pins out , simple to do.

ok

 

[Wurlitzerwilly]

No!!........The pump inside the boiler has speed settings 1,2,3 make sure its on 3.
Turn power off at wall switch / fuse spur and remove four screws on front panel, 2 top , 2 bottom.
Locate pump and turn switch on top of pump to 3
Dont worry about the plinth, just turn all rads off to push the water through the u.f heating seen as though your having access problems.

But remember to sort them trv pins out , simple to do.

ok

In all the years of owning the boiler I had not realised there was a pump speed control and I don't ever remember seeing it in the installation manual.
However it's on the side of the pump and is set to "3".

I'll try to tackle the TRVs today.

 

[Wurlitzerwilly]

.........................But remember to sort them trv pins out , simple to do.

ok

I sorted out the TRVs and all's working now.
The radiator TRV was stuck shut and I freed it by twisting with pliers and it's been working ever since.

The under floor heating was a different matter. The TRV is a Danfos type and works differently to the radiator ones. Instead of pushing the pin in to close the valve, the pin needs to be held in to open the valve. There are also adjustment rings inside the head and they were set incorrectly. Either something has worn so the pin was not depressed ever, or it has been out of adjustment since installation. I checked the original installation instructions and there is nothing about calibration. Anyway, its fine now and three pussy cats are loving it!!!