Heating wows

[Scott Mills]

My mum's heating system is playing up again. It is a standard open vent pumped system.

Yesterday, when she put the hot water on, the rads got hot which it has never done in the past. What causes this? Persumably a blocked valve somewhere but where, is it boiler side, near the hot water tank? I just don't know.

Also, why would it block anyway? I'm told the water in her header tank is full of red sludge, and she has just had to replace a pump that is a year old as it was rusted, but she tells me she has been using inhibitor. But it doesn't seem to do much. Could it be possible, she has a leak somewhere and the system is slowly flushing out the inhibitor? She has to bleed the bathroom rad a lot too so a lot of air is getting in somewhere I guess - would this go along with the leak theory?

She has had no end of grief with this system, and I would say that after

18years it is probably time it is put to bed. What kind of figure would be looking at for a new system - boiler, pipes, rads, valves, (10 in total 4 new - the other 6 are already new) to be fitted in a 3 bed end of terrace with concrete floors on the ground level? Does she need a piping, or would a flush do?

Cheers Scott

[geoff]

In message , Scott Mills writes

Knacked diverter valve?

[N. Thornton]

So, see if I'm right here... the rads dont leak, the pipes dont leak, the boiler works ok, but youre gonna replace it all anyway. I dont understand that approach at all. Seems quite popular though!

Regards, NT

[Scott Mills]

Rads do leak, evidence suggests pipes might somewhere. Boiler is very old and inefficient. Is replacing it such a bad idea?

[N. Thornton]

Ah, that would explain more, if it leaks all over the place. From what your initial posts said I got the impression that leaking was a guess rather than a fact. I cant possibly know unless you can tell us.

If leaks are found in the piping it would make more sense to rejoin the leaky joints than to replace all the piping, which wouldnt really gain anything. New copper piping is no better than 18 y/o piping.

If theres a rad leak the sensible thing is to replace the leaky rad, no reason to replace sound rads after 18 years.

Regarding your talk of a leak, which Im fairly unclear about, if there is one there will be a wet patch somewhere. Basically, no wet patch, no leak. If there is a leak then fresh water would be drawn into the CH which would outgas into the radiators, thus requiring bleeding.

Much more commonly air enters the system via one of the pipes in the header tank. This is a relatively common problem with unpressurised systems, and is very simple to fix. There are 2 pipes in the average CH header tank: one at the bottom of the tank, and one return pipe above the water line. Extending the upper pipe so it goes below the water level will eliminate air intake: if anything is sucked in through that pipe it will be header tank water, not air.

If you have a lot of sludge you might want to flush the system, and then replace the inhibitor.

Hot water demand causing the rads to come on is probably a diverter valve fault, or possibly the wiring to it come adrift.

Re replacing the boiler, although modern boilers are very much more efficient, it is still not financially worth replacing old ones until they actually keel over. Old boilers may run for decades before so doing.

In short it seems you have 2 problems to repair, neither of which are major, and that proposing to replace the whole system would be a considerable expense that might well not be warranted. I say that without seeing the setup, it might be anything for all I know. If its a 1910 backboiler range with gravity feed that has been extended with garden hose then I'm sure its due for an upgrade. :)

Maybe you can fill us in a bit more on the leak situation. And also how you know the pump needed replacing after 1 year, since that is not normal.

Regards, NT

[Ian Tracey]

Hi

Is that "good practice" or experiance/ thought put into a traditional setup. My system had the other problem of pumping over, but an 8 pound gadget ( Air seperator) from B&Q sorted that one out. Not sure how it really works, but it works.

cheers

ian

[MIKE THORNE]

No it's not good practice, it can make the header tank act like a rad, not good! most of the other advice is good, sounds like the system has sludged up causing pump-over which introduces oxygen into the system causing more sludge. My advice is to power flush then check pump speed.

[N. Thornton]

If I understand it correctly, a) that would only occur in the occasional situations where at present air would be introduced, so is an improvement b) the amount of water occasionally reaching the header tank this way would be way less than would reach a rad c) the header tank is normally very well insulated, making the potential admittance of a very small amount of hot water an issue dwindling to very small proportions.

Am I wrong on this?

Regards, NT

[MIKE THORNE]

a) You don't want it to happen at all so the air break at the vent pipe ( the 22mm going over the top) stops any syphonage either way if you have pump-over something is wrong. On a new system it could be that the head is too low or a number of other reasons. The installer should know what he/she has done wrong. On an old/existing system its usually a blockage (sticking neck out ) or the pump setting is too high.

b) Not necessarily with 22mm feeding one way on the vent and when I started plumbing 22mm cold feeds where standard you could have more, not usual now I grant you.

c) I would not advocate 80 odd degrees of water passing through a plastic tank/cistern even though they are designed to withstand more heat than the cold storage tank/cistern. I hope that answers your question NT without coming across as bulshy, I am new at this.

[Scott Mills]

Thanks for all your advice guys.

It turns out that the pipes (return side I guess) to the boiler where blocked with crap. The header tank was filling up with hot water and draining to the overflow. This has probably gone on a while which expalins all the inhibtor she has lost and the excessive rusting of rads, and pumps.

She has had that section of piping replaced now and all seems ok. The boiler is 18years old, but does work and the rads (& valves ) are slowly being replaced as each one finally leaks...!

Scott