Heating problems...

[emjaybee]

Anyone on here got experience of household heating systems?

We're having problems.

We have an oil-fired boiler, about 10 years old. We have a cold water tank and a header/expansion tank with a hot water tank.

Recently we've had the system banging and blowing hot air back into the expansion tank.

Plumber has been and changed the three way valve, and actuator and the pressure relief valve.

The system is still doing exactly the same.

Anybody got any ideas?

[jims-terrano]

Wasn't it Paff that fixes these but I bet Rick will have some good ideas too.

Good luck

[rayf3262]

Originally Posted by emjaybee

Recently we've had the system banging and blowing hot air back into the expansion tank.

My guess is that the water is boiling in the heat exchanger. This could be caused by a low rate of circulation. Maybe poor pump performance, the vanes in the circulator pump can over time become clogged up with debris.
Pop the pump out and give it a 10 year birthday clean up....

[emjaybee]

Ok...

...what pump?

...and where is it likely to be?

[macabethiel]

Originally Posted by emjaybee

Ok...

...what pump?

...and where is it likely to be?

I had a similar problem with my old central heating system a few years before I replaced it.

In my case the gas boiler was bumping and as soon as the water got hot it just switched off again. At first I thought it was the thermostat. I knew it was not the pump as I had replaced it about 5 years previous with a Grundfoss, also I could hear the pump running.

In the end I got a Plumber out and he said it must be the pump but did not have time that day to replace the pump as he was so busy. I bought a pump off him from his van but felt it was not the problem.My pump was under the floorboards in the back bedroom big job to drain the system as there was only an isolation valve on one side of the pump pipework.!

I isolated the pump and disconnected it then ran it dry whilst I had it in my hand. Sure enough the pump buzzed away as it rotated. On dismantling the pump I found the impellor that was made of plastic had worn away !

New pump fitted and it was fine even on low speed setting !

[jims-terrano]

I've come across pumps that were sticking because it hadn't been used for a few months and there was no inhibitor in the system. A good couple of sharp taps on side of pump freed them up.

[solarman216]

let me expand on this a little, if hot air is being delivered to the expansion tank then the boiler is doing just that "boiling" cos it is getting no water from the cold feed, if it was the pump not circulating then the boiler will be shutting down on its stat, Rick

[Mobieus_uk]

after checking the pump I would then start looking at the cold feed as stated above, cold feed is often ignored and people spend shitloads before they bother checking, a giveaway is if the header tank is full of hot waters the blockage occure between the open vent and the cold feed, when blocked the system find it easier to pump water up to the headertank thought the open vent(pumping over) then back down the cold feed using the tank like a radiator - as also stated above many so called heating engineers still don't understand and dance around the problem
I get this a lot at work so this is what I check
1..pump remove and check, this is the heart of the system and can tell you alot about whats going on
2.. check for system filters, some boilers have them on the return and will cause circulation problems as they start to block up
3.. once happy with the pump and filters then start look at the cold feed, this will require some knowledge about central heating design as you may have a close coupled setup, combined or the system maybe sealed, technically the cold feed is done away with but should have been checked for blocked when system converted

4..if the pump is good and the cold feed is clear and filters are clear then its either sludge in the system causing poor flow or you have a buildup in the heat exchanger may be able to flush but you may end up replacing

on the plus side most circulation problems end up being a faulty pump which is the easiest fix, its common with grundfos pumps for the impellor to shear so you cannot go by checking the shaft rotation, you need to remove the head from the body, dont know what make pump you have but grundfos are very common

[solarman216]

Originally Posted by emjaybee

Anyone on here got experience of household heating systems?

We're having problems.

We have an oil-fired boiler, about 10 years old. We have a cold water tank and a header/expansion tank with a hot water tank.

Recently we've had the system banging and blowing hot air back into the expansion tank.

Plumber has been and changed the three way valve, and actuator and the pressure relief valve.

The system is still doing exactly the same.

Anybody got any ideas?

OK three port valve tells me you have a hot water cylinder, three port valves have their own problems related to system design, your problem is most likely the cold feed/vent configuration from the header tank, if not correctly made then they grow magnetite till they block, basically the cold feed from the header should be as close as possible to the vent pipe, so imagine the flow pipe from the boiler which has to rise all the way to the vent then teed into this is the feed from the tank then it carries on to feed heat to your rads/hot water, this crucial junction if not correct will get blocked a lot depends on the position of the pump in relation to this tee, is it on the flow or the return? sorry to be complicated but it is just that and most plumbers do not fully comprehend the implications of not getting it right, and for you a householder, not easy to near impossible to describe your layout enough to offer a cure other than this junction will almost certainly need cutting out and renewing, Rick