Hot water in expansion tank + other heating questions

[dazjstuart]

Hello Everyone,

I have a tendency to waffle so please bare with me!!

I have recently moved house (flat), I detected a small puddle water in the loft which I assumed was a small leak in the roof, closer inspection revealed that the expansion tank was heating up and steam was condensing on the roof and running down the inside.

I have observed the tank while the heating is on and a constant trickle of hot water returns are taken to the header tank all the time the heating is on, the speed seems to reduce as the heating heats up (which I presume is due to the water initially expanding as it heats up?). The water level in the tank never changes much, it doesn't go anywhere near the overflow and doesn't trigger the ball cock.

All the radiatiors heat up properly, very hot as the boiler was set to max, I have since turned it down a bit but it doesn't seem to have made much difference, the boiler incidentally is quite new, the seller informed me he replaced it in 2011. The expansion tank is probably about 15ft above the boiler, possibly more, the tank is right at the peak of the loft (large loft) and the boiler is in a cupboard halfway up the stairs between the ground and first floor (its a first floor flat with private stairs).

The other thing is that, the hot water cylinder is also in the attic, it is on the same system as the heating, i.e. you cant have heating or hot water, only both or neither, which I thought was a little strange?

In time I will probably look to get a combi boiler as I can't stand hot water tanks and the cold showers / large gas bills that they bring! I know every system is different (I'll try and get a picture) but does anyone know how easy / difficult it would be to put the heating and water on seperate systems in the mean time, I believe you can install zone valves to split areas of pipe work up?

My thinking on the hot water in the header tank is that if the boiler is pumping water up to the hot water cylinder in the loft then it only has another 6ft or so to overcome to pump it into the header tank?

Any opinions / advice gladly received

Thanks

 

[dazjstuart]

Bump

 

[D_Hailsham]

Pics please.

 

[dazjstuart]

As you can see, the larger diameter pipe going to the loft is the one that flows into the header tank, the smaller diameter one comes from it. Both are on the outlet of the boiler but before the pump. The pump is on the correct way. From what I can see the hot water and heating are all on one loop but I am not sure, is this likely? There is a thermostatic valve on the pipes on the outside of the hot water tank before it goes into the coil.

Thanks

 

[D_Hailsham]

I know this doesn't solve your problem, but ...

I assume the pic is the correct way round, i.e the top is up and bottom down. If so the pump is not correctly installed; it must not be pointing downwards.

Grundfos Instructions
Where pumps can only be installed in horizontal pipework, it is imperative that the pump shaft is horizontal, or slightly higher at the vent plug end.
The shaft must not fall below the horizontal plane, even by a few degrees, as this causes premature wear of the top bearing and shaft.

Back to the problem ...

Do you have any motorized valves? (see pics)

View media item 11762 View media item 5946
Can you post a more general pic, showing the whole boiler and what happens to the right of the current pic?

How many tanks are there in the loft (not counting the HW cylinder)?

What make/model timer do you have? (pic if unsure)

What speed is the pump set to? (black switch on top)

 

[dazjstuart]

Thanks,











There's some pictures. The clock is a Danfos SET1E. There are 3 tanks in the loft, the expansion tank, hot water tank and the cold water tank for the hot water. No motorised valves that I can see, only valves are the radiator ones and the aforementioned one on the hot water tank, can just about see it in the photo. You can see the expansion and cold water feed pipes in 2 of the photos, expansion one jut curls in over the top of the tank, theres not really any more room to extend it, its already pretty much in the peak of the roof.

Pump was set to 3, I turned it down to 2 today and the problem seems to have stopped. Would still be interested to hear your thoughts on the system though as I am guessing I have just cured the symptoms rather than the actual problem?

Thanks again

 

[picasso]

Look for a blockage here using a magnet.

View media item 89652

 

[D_Hailsham]

If you don't have any motorized valves:

1. How do you control the HW temperature?

2. How do you turn the CH off in the summer?

Provided all rads get hot, there's no harm turning the pump down to 2.

There are two reasons why the system is pumping over:

1. The connection of the vent pipe near the boiler
The water will always prefer to take the path of least resistance, i.e straight up the vent pipe, and not go round the bend towards the pump. The solution is to replace the T joint with an elbow and move the vent connection to the right, so it comes off the horizontal pipe.

2. The length of vent pipe at the expansion tank
There needs to be a least 450mm of pipe, measured from the water line to the top of the bend. This is to provide sufficient room for the water to expand without overspilling into the tank.

 

[dazjstuart]

Only way of controlling the water temperature that I can see is the valve on the pipes outside the cylinder, it's the same as a radiator valve, goes from 1 - 7 and has a max. You can't have only hot water other than turning the radiators off.

All the radiators still seem to get just as hot so I'll keep it on 2 just now.

That makes sense, I haven't measured the vent pipe but there's no way it's 450mm, I'll have to have a looks to see if any water at all goes into the tank while the systems heating up, but it's not circulating through the tank anymore.

Now that the problems gone should I drop some fresh inhibitor into the system? I'm guessing circulating through the expansion tank can oxygenate the water?