Hot water going up the vent pipe

[sotal]

I recently upgraded my central heating system.

The old system was a very basic time switch which when activated supplied power to the pump and the boiler. When the timer ended power was cut. When heating was on hot water was on and vice versa.

I purchased a Danfoss Y plan kit and a Grundfoss pump (the old pump was on it's way out)

In terms of pipework I basically just replace the T peice which went between water and heating with the Y valve, and replaced the pump.

I wired it all up and it all functions perfectly everything switched on and off as required.

What I did notice was that when the timer switched everything off, the vent pipe got hot very quickly and when I checked the header tank in the loft the water was warm.

I asked about that on here and was advised to add a pipe stat to the flow pipe from the boiler to overrun the pump after everything is switched off. I did this and that cured the hot vent pipe.

All was fine and it's run like that for a week but now I have found another problem.

If the hot water comes on, on it's own without heating the Vent pipe becomes hot again even though the pump is pumping and it drips into the header tank. The pipe coming out of the bottom of the cylinder goes to a T peice which is a verticle pipe, I think this possibly joins to the vent higher up?? Anyway that pipe gets hot as well all the way up.

Is there any usual cause for this - should I worry? (I don't think it's right)

The only obvious thing I can see is that the output from the bottom of the cylinder comes out as a large pipe (seems a couple of mm bigger than 22mm - migth be wrong) but then instantly goes down to a 15mm pipe with a gate valve in it, this then goes to the verticle pipe I mentioned before which again is 15mm.

Is the 15mm pipe restricting the flow?


Another problem I have had since this happened is quite a bit of air in the system, one rad keeps getting a bit of air in it (the bathroom rad) and you can hear it going round the system. It takes about 20 seconds of nice silent running then you get 10 seconds of air type noise going through the pump. I can open the bleed bit on the pump and it expells some air but seems to take ages to bleed.

Is this related? Maybe the water was boiling?

 

[Ricky_M]

Which pipe are you reffering to, the one coming from the bottom of the cylinder should be the Cold Feed to the cylinder, not an outlet. Its normal for this to be warm, but ussually loses temperature the higher it rises.

The reduction is size shouldn't be a huge problem, it would just restrict how quick the cylinder will fill up.

 

[heatingman]

draw a picture or post photo

 

[leakydave]

from boiler, first pipe should be vent, then cold feed from tank, then the pump and then zone valve... are you sure you have these in the right order... vent, feed, pump, zone valve... if not you could be pumping over, causing the intake of air and continuous pumping through vent pipe...

 

[sotal]

I can see three pipes on the cylinder, so I presume ther is a 4th somewhere?

There is a 22m pipe coming out at the top which I figured was the hot water out for the taps etc.

There is a 22mm pipe about 2/3rds of the way up which I figured was the boiler flow in.

There is then a 22mm pipe a few inches up at the front which I though was the return out of the boiler, this is the one which drops to 15mm straight away.

I presumed there was another pipe at the back or something for the cold water feed in?

 

[sotal]

leakydave.

The flow pipe from teh boiler comes in from the bottom of the airing cupboard (22mm pipe) This goes straight up as the Vent, there is a T off this at 6" up. This goes to the pump, above this there is a 22mm pipe which goes up to the Y valve (it also has a bleed pipe on it with a thumb screw on the top - before the Y valve)

So I'm just confused about where the cold feed is?!

 

[Softus]

WTF is all this presuming and assuming?

Just look at the pipes with your eyes and describe them with your keyboard - if you don't know their function then don't guess, just ask.

 

[sotal]

sorry - just about to post a photo

 

[sotal]

 

[Softus]

Well I can't see a cold feed there, but who put that PTFE over all the threads!

 

[sotal]

So is pipe 2 causing a problem being restriced to 15mm?

Is there anything wrong with PTFE tape?

 

[sotal]

Having had a closer look, where you can see the drain off valve next to the pipe stat (3) that drain off valve comes off a T off another pipe which connects to the back of the cylinder - Is that the cold water feed?

 

[heatingman]

looks to me like the system cold feed is connected at the domestic return, wrong place! Pipe No 5

 

[heatingman]

Remove pump from pipe 4 and cap, Rotate pump 180 degree upwards and cut tee into pipe 4 about 300mm above pump, cut pipe 5 at the 5 (on photo) and cap upright leg, then link down leg into pipe between pipe 4 and pump, it will sort of look like an H with pump on r/h lower leg

 

[sotal]

I'm pretty sure that pipe 5 is the return.

The pipe at the back is at about the same height and seems warm to the touch but not hot, that pipe at the front gets too hot to hold on to so I wouldn't have thought that was the cold feed, it gets too hot to hold on to all the way up to th ceiling