Hi there, looking for some guidance here please.
Running a Baxi Solo boiler, which is located on the 1st floor of 3 storey property. There 17 rads in total 9 of which are on the ground floorbut 3 have never heated up at all. the pump is a SMC gold GP63. The 5 rads on the 1st floor and 2 rads on the top floor all heat up adequately.
Could the pump size be the problem here ?? if so what model/size pump should be installed ?? thanks in advance for your advice Cheers Ted
Hi, before you go to the expense of buying another pump which may not improve anything, have a go at balancing the system. It really isn't difficult.
To see if it is a balancing problem, shut off all your other rads and see if the cold rads get hot. If they don't then you either have a blockage or the pump isn't man enough to overcome the resistance of the pipework. I would doubt that this is the case.
To balance the system, if you have TRV's take heads off. Start off by shutting all the rads that do get hot to half a turn open on the lockshield valve. The lockshield valves can go through about 4 to 5 turns fully open to closed but you get no regulation (valve authority) until the last turn. If you have any rads that you know heat up very quickly, you can probably set these to a quarter turn open.
You should now have something that resembles a rough balance.
After that it is just a matter of tweaking and rechecking to see what rads are hotter or cooler. Shut the system off and on a few times to see what rads heat up first. Its a bit of running around but and trial and error but like I said its not some great art.
If you have a temperture probe you can check the on and off temps across each radiator. You can get IR non contact guns with laser pointers for under a tenner if you can be bothered to do this. You need to have the same differential across each rad. So if you had one rad with 78c on and 73c off (5c degrees diff) and another that has 80c on and 60c off (20c degrees diff) the rad with the low 5c differential is getting too much flow. The water is traveling too fast to allow the transfer of heat. A 20c degree differential is ideal. This is the differential your boiler is design to work at.
Remember, the radiator that is in the same room as your thermostat wants to be the last one to be able to satisfy the room temp. If this rad is blasting out heat it will activate the stat and shut off the boiler before the other rooms are heated. This rad should never have a TRV fitted for the same reason but to the opposite effect. The rad will shut off and not let the stat operate and the boiler will run on and on until it shuts down through over heating.
If you get your system balanced you can probably turn your boiler down and save some money. Lots of people try to fix a poorly performing system by turning their boiler up.
You might want to check your water quality too. If your system is becoming sludged up the sludge will naturally collect where the water is at its slowest velocity. This will be in your radiators (check if any rads are cold across the bottom) or even in any pipework where the flow is struggling. If this is the case you may need to get you system flushed. I would recommend that you get a company that uses a thermal imaging camera to check that any blocked rads are cleared properly cleared. I've seen the jobs some companies do and it isn't adequate.
