Problems with Oil Fired Central Heating

bjdodo

Hi All,

I and my wife have bought a second hand house that is a bit old, but we could not afford a new house. It is fine except for the heating. I have never lived in a house that had central heating, also in one that had oil fueled heating, so this is something totally new to me.

After reading a lot and climbing up to the attic I have a good picture how it should work. It has two circuits, one is for hot water, and it has a corresponding tank in the attic, and there is a circuit for the radiators that has a much bigger tank in the attic. Our heater unit is a Firebird super-Q 50/90, the circulating pump is "Terrier circulating pump Model tc5 class H 10 bar max", our cylinder has an electrical part, but there is also a pipe in it so that hot water circulating in this pipe heats up the water in the cylinder.

The heating works fine, when turned on all radiators are hot and it provides hot water. There is a pipe from the roof that can lead excess water from the tanks out to the yard. The problem is that when we turn on the heating, the pipe from the roof starts dripping after a while (~10 minutes), then after some more time it starts a heavy flow.

I went to the attic to see what's happening, there is an "emergency pipe" that is used I think to limit the pressure in case something wrong happens in the system. This "emergency pipe" is drilled into the pipe that brings the hot water to heat up the cylinder and it goes up to the small tank in the attic. So there is a "junction" of pipes at the cylinder: there is the hot water pipe that's coming from the Firebird heater, this will split into a pipe that goes into the hotpress and into the "emergency pipe" that goes up to the attic; this emergency pipe is open ended and flows into the smaller tank in the attic. If the pressure in the pipe that goes into cylinder is bigger than the pressure of the height of water in the "emergency pipe" (it goes from the cylinder up to the attic) then the water will flow up in this "emergency pipe" into the tank.

Ok so we know that the pressure will suddenly increase a lot after a while. My guess is that the water is overheated and it starts to boil and this is what's causing the trouble. I checked the pipe that is supposed to deliver the cooled water into our Firebird heating unit, and it is almost as hot as the water that leaves the heating unit and goes to heat the house. Also, there is an "emergency valve" next to the Firebird heating unit that starts to whistle when the water flows from the roof.

So my questions:

- Is it possible that the water really starts to boil? If not, what is happening here?
- Should the heater regulate itself not to overheat the water? Does it regulate itself, or an external unit should do this job?

Thank you very much for all answers!!

Joe

Avns1s

Try....

1. Check that the little tank in the attic isnt overfilling because the ballcock is continually filling. The ballcock may also need adjusting so it's not overfilling the tank even if it isn't dripping.

2. Turn down the thermostat on the actual boiler itself to 60 degrees or so.

3. Turn your circulation down a setting or two if it is at the highest.

JamesM

As Avns1s says.
But you have a few facts wrong. The return pipe at the bottom of the boiler should be almost as hot as the flow from the top. Most likely only one of the tanks in the attic is for the heating system.
As well as turning down the boiler thermostat, make sure that it is working, it should shut the burner off once it reaches the required temperature. Make sure that it doesn't run continuously. If it does, then the boiler is certainly overheating - and the water is boiling.
Jim.

bjdodo

Hello Guys

Thank you very much for the answers!

The ballcock in the small tank is ok.

> Most likely only one of the tanks in the attic is for the heating system.
Yes, I think the big one is for the circuit that heats the radiators, and the small one is for heating the water in the hotpress.

Can I ask what you refer to as boiler? Is it the hotpress or the heater?

The heater has a thing that can be rotated, the scale says min to max, and it says temperature. This also has an off position. I have turned this to min, and the flow still happens, and the heater seems to work continuously.

Ok, so if boiler means the heater then most probably the thermostat in the heater is broken. Do you think the thermostat can be replaced, or we have to buy a completely new heater?

Again, thank you for your great help!!

Joe

JamesM

Hi Joe, The Firebird is the boiler. If you set it's thermostat to min, and it still runs continuously, then the thermostat is faulty and can be replaced.
Most likely the large tank in the attic supplies the taps, toilets etc. in the house. The smaller tank supplies the whole heating system, the pipes that heat the radiators and the pipes that heat the hot water.
Jim.

JamesM

Read this, http://www.sei.ie/Schools/Secondary_Schools/Subjects/Architectural_Technology/Domestic_Heating/
It will give you an idea of a heating circuit.
Jim.

bjdodo

Hi Jim,

Thank you again, that article is very useful!

Joe