central heating only comes on with h water, stumped engineer

[doitall]

So how accurate is the new drawing.

You need to expose the pipes and produce an as fitted drawing, including the boiler connections.

My/our drawing is indicative, and nearly shows the pipes in the possible fault connections, which incidentally is a good theory.

 

[UpgradeME]

OP, can you confirm if there are physically TWO pipes entering the top of the boiler or one? (It's not clear from your drawing)

Looking at the manual, the top connection(s) are 1" BSP FLOW and the bottom is 1" BSP RETURN. The smaller 1/2" pipe is gas.

DIA, I'm guessing that one of the FLOW pipes is connected to the CH circuit and one is connected to the pump. The return from the CH is then coming through the 3PV as per my original drawing below:

Untitled

• UpgradeME
• 28 Feb 2012
• 1

(Assume the bottom feed on the boiler image is the flow and my arrows ARE correct)

 

[doitall]

You can't have two htg flows, it has to come from port B in the MV

The drawing is nothing like the first which is worrying.

The first was wrong and I questioned it.

The 2nd makes no sense whatsoever.

I'll jig it with what we know after food and see whether it makes sense then.

 

[UpgradeME]

You can't have two htg flows, it has to come from port B in the MV

The drawing is nothing like the first which is worrying.

The first was wrong and I questioned it.

The 2nd makes no sense whatsoever.

I'll jig it with what we know after food and see whether it makes sense then.

Looking at the manual, it looks like there are physical connections:

If there are four physical pipe connections to the boiler (2x flow, 1x return, 1x gas), I'm guessing someone may have (incorrectly) just plumbed in the pump/valve to the HW flow pipe near the cylinder (perhaps not realising there are two!?) and 3pv to the CH when attempting to convert from gravity to pumped system.

 

[bonkersbill]

I cut a hole in the conduit, there are 2 28mm pipes reduced at the bends to 22mm, these then go through the chimney breast as 2 pipes side by side touching each other towards the top of the boiler, one of the 15mm pipes tees and goes through chimney breast with a 22mm which comes from below the ground floor floor boards touching and side by side towards the bottom of the boiler, i can not see the pipes entering the boiler roughly 2 feet away, the other 15mm just goes down below ground floor and i can move this from side to side quite easily. if i can veiw these by removing the front of the fire i will do so but i cant figgure out how the front comes off and i dont want to break it.
if need be i will test the pipes for which heats 1st in this hole and upstairs to figgure out which is which if possible.
i am waiting for the system to cool down to test at the 3pv which gets hot 1st

 

[bonkersbill]

My original drawing does have a circle on it which says this is the only pipe work i could see, the rest was guess work after looking at boiler & rad diagrams, as you know i have only just opened up the conduit to view, so i hope this has not caused problems.

 

[doitall]

My original drawing does have a circle on it which says this is the only pipe work i could see, the rest was guess work after looking at boiler & rad diagrams, as you know i have only just opened up the conduit to view, so i hope this has not caused problems.

No problem at all, quite the opposite as it was very productive because it was wrong.

You could try running the boiler on low as per my earlier test to see which pipe gets hot first, but you need to transfer the information to the cupb.

 

[bonkersbill]

The AB port in the middle of the 3pv gets hot 1st with valve set to mid, the 15mm pipe teed into boiler gets hot way before the other if this helps, i will be able to find out when its cooled down which of the 15mm upstairs this is, and just to be clear, i managed this with out disconecting the pump.

 

[doitall]

Did you have the pump turned off electrically

Did you test the return pipe on the bottom of the cylinder.

 

[bonkersbill]

No, there are now that many test its hard to keep track, it was port AB and the bottom port, i think B which goes to rads, i will do yours next and turn the pump off which i have now found the switch

 

[doitall]

There's only one test you need to do at the moment.

Turn the boiler on low, isolate the pump electrically, then tell us which pipe gets hot first

The return connected to the bottom of the cylinder or the flow going to the pump

Picking up on that comment you just made.

Port B should go to the cylinder, it's important you confirm it does.

 

[Agile]

OP mentions a 15 mm pipe which gets hot.

It was quite common to take a 15 mm feed direct to the boiler from the F&E tank in the olden days.

If its the same OP then it would have been far quicker with a pro.

He should NOT be removing the fire as that has a live gas connection.

Tony

 

[stardanny]

Try do what doitall say. that's a good test.

That will tell which 28mm is the flow make sure you disconnect pump flex and make safe, and leave 3pv open to hot water, keep boiler on low. Switch on hot water only on timer. It will start it gravity run. Check which get hot, the pipe toward the pump or the pipe coming from bottom of cylinder, also before you go upstairs, check which of 28mm coming out of chimney breast wall get hot first.

Don't worry about the heating for now.

Let us know how you get on.

Oh, any chance of a picture of pipes inside duct?

Other thing, you say you moved the cylinder, what was it for?

Dan.

 

[bonkersbill]

The 28mm to 22mm pipes after opening up the hole more for a better view are on top of each other going through the chimney breast, 3 test done, with programmer set to HW only, 3pv to HW the bottom 28mm pipe through the chimney and the pipe to pump gets hot before pipe out of bottom of tank, same result with prog HW&CH, 3pv HW or Mid

 

[bonkersbill]

The pipe that comes out of the top of 3pv that goes up towards the pump does not connect upto the pump, it is blanked off, it just looks like its attached, the pipe out of the pump does connect the 3pv at port ab in the middle and the bottom port is b though after looking at the old 3pv it does not appear to make any difference which way up it is as long as the actuator is on the right way to operate the spindle.

I moved the tank because it was in the middle of a wall which made the room triangular, i knocked down a dividing stud wall into the old bathroom to make a larger bedroom with a smaller shower room where the old bath was and moved the tank 3m to the middle of the house to where the old bathroom door was to make this into an airing cupboard at the top of the stairs, i moved the bathroom next door into what was the box room and knocked down a stud wall which had a seperate wc to make one large bathroom.
i labeled all pipes before removal, extended them and reconected them.