central heating only comes on with h water, stumped engineer

[UpgradeME]

Give the guy a break. He doesn't know.

I wasn't directing the question at the OP, just chucking my hat into the ring hoping another contributor would come pick it up and suggest possible causes.

I wondered if the OP's pump was wired directly to mains but looking at a standard Y-Plan wiring diagram and the OP's wiring, if OP confirm's the pump is the cable labeled below, it looks to be wired correctly.

Untitled

• UpgradeME
• 4 Mar 2012
• 1

Untitled

• UpgradeME
• 4 Mar 2012
• 1

Either way, I don't think this has anything to do with the OP's initial issue of the boiler switching off when the 3pv is set to CH only. I think we have already confirmed (in my mind at least) the OP's main issue is a plumbing one with crossed pipes (as per DIA's tests) and not electrical.

 

[Mikefromlondon]

Mike ! I'm intrigued by your suggested test on the motor.
The motor must be OK if you get CH and HW on at the same time.
Not only that, it has been confirmed the valve moves to CH only.
Also it needs more than just the motor moving the valve to fire the boiler. A micro switch also has to be triggered.
My understanding is that the valve is operating as it should and therefore the problem is elsewhere.

Sorry mandate, you are right, I was only going by what the man in the video said about 3 way valves are different to the two way valves, in that motor and boiler have seperate switched lives,, hence why I suggested that, but yes I can see that may not be right, as the schematic clearly shows the pump and boiler connected to terminal 8, as well as Op's wiring picture, so if one works the other should as well, since if the boiler fires, then the motor must run as well. Secondly, I am not deviating from the fact it has already been established that the flow & return pipes are wrong way., as per Doitall's dignostics. That has already been now confirmed.

because it is still proving to be quite a puzzle for some of the other issues on plumbing, and tests contardict some of Doitall's expectations, I would have personally reactified what we know already that is wrong and then go from there, first correct that mistake, i.e. reverse the connections on flow and return, and then see what new senario greets us, surely its not going to make things any worst, if anything it might actually help us figure out exactly any other outstanding issues or figure out other errors in the installation.

so by just reversing the flow & return it might resolve the whole issue,
there may not be any other after that, but if we are left with any new issues then this would surface and we would be able to work on that more easily, it would give us a better picture and then we can plan our next move, one step at a time.



One question I would like to ask Bonkersbill is that as I understand he had been having this problem for 2 years, but was this problem there before or after he moved his cylinder, in other words, how long ago did he move his cylinder?

 

[matt1e]

21 pages now!

Just noticed this from last November

the grundfos pump always keeps going when boiler shuts down and this pumps cold water round the CH quickly

The OP has a Baxi Bermuda back boiler, which as far as I know, does not have pump overrun on any models. So why is the pump continuing after the boiler shuts down?

because the boiler is shuting down via its control stat dave, it still has demand on it as does the pump, but the boiler shuts down due to the poor flowrate through it when it is only hydraulically connected to the rad circuit

I wondered if the OP's pump was wired directly to mains but looking at a standard Y-Plan wiring diagram and the OP's wiring, if OP confirm's the pump is the cable labeled below, it looks to be wired correctly.

Untitled

• UpgradeME
• 4 Mar 2012
• 1

Untitled

• UpgradeME
• 4 Mar 2012
• 1

Either way, I don't think this has anything to do with the OP's initial issue of the boiler switching off when the 3pv is set to CH only. I think we have already confirmed (in my mind at least) the OP's main issue is a plumbing one with crossed pipes (as per DIA's tests) and not electrical.

the pump could be the one labelled "boiler" but either way upgrademe go with your instinct mate
I agree the problem is plumbing not electrical

so by just reversing the flow & return it might resolve the whole issue,
there may not be any other after that, but if we are left with any new issues then this would surface and we would be able to work on that more easily, it would give us a better picture and then we can plan our next move, one step at a time.

doubtful, but for testing purposes I would reverse the pump as it is as I think it has already been established that the valve and pump are fitted on the return as per a primatic cylinder y-plan

I'm going to bow out of this thread now as it's getting rediculously long

Bonkersbill as stated earlier (about 15 pages ago), you need to get someone in to sort out your pipework

Matt

 

[Mikefromlondon]

Oh my God! no up dates! so how would we ever know what was the real problem?

Come on Bill, get your wrench out!

 

[bonkersbill]

Hi all, back again, i called out an engineer to service my boiler, he took one look and said erm i think i will call my boss and get him to ring you, that was the last i heard from that company which i got from yellow pages. After doing this for over 4 months i was ****ed off so ive had a break, back now and have been over a load of tests and have done a proper diagram to the best of my knowledge of what ive got and what i think it should be. What i need to know is will what i think i have cause the boiler to shut down when CH only is selected.

Actual

• bonkersbill
• 15 Mar 2012
• 1

Correct

• bonkersbill
• 15 Mar 2012
• 1

If changing the 2 15mm pipes over upstairs will probably fix the problem then its time to do something. There are still unknowns like any extra Tees but unlikely, any old pumps etc left over from when it was originally put in or if there are any extra pipes on the other side of the boiler. The main question that has been asked is where is the return, if the 15mm pipes are swaped then there is the return. i have based most of the diagram on which pipes get hot 1st with pump running, so how far off am i or am i right?

 

[Norcon]

Another on site head scratcher. Typical.

 

[doitall]

Until you change the primary pipes over so the return goes to the bottom of the cylinder, and the flow goes to AB in the mv there's no point playing.

The flow and return is how it should be in the drawing, except the heating return should be common with the cylinder return
.

 

[UpgradeME]

What i need to know is will what i think i have cause the boiler to shut down when CH only is selected.

Yes, IF that's what you have!?

If changing the 2 15mm pipes over upstairs will probably fix the problem then its time to do something.

Time to do something I agree with, however, as DIA says above and your earlier tests proved, the flow and return at the boiler side are incorrect! (the boiler's 'flow' is connected to the return when pumped).

The main question that has been asked is where is the return, if the 15mm pipes are swaped then there is the return. i have based most of the diagram on which pipes get hot 1st with pump running, so how far off am i or am i right?

Hmm, this thread is now 21+ pages yet it seems we are starting again here, you say you have done many tests but not told us what you tested or the results, then provided a very different diagram of what you think is your system

I'm now bowing out of this one too. The one bit of advice I will say is if you want this resolved, you need to be clear, consise and provide answers to the questions being asked.

I wish you good luck in solving this puzzle!

 

[doitall]

UpgradeME

It concerns me when a so called engineer turns up to do a service, takes one look and legs it.

What we actually need is an engineer to strip the boiler down and identify the pipes.

 

[Mikefromlondon]

Bonkersbill, your first layout on the left appears to be wrong even if you traced it as best as you could, as it is, you are not going to get heating on with your hot water, which infact you said that you get your heating on when you run both Ch+HW. Secondly , if you said you have drawn it as best as you thought it was, by feeling where the hot water gets to first, then again it is wrong as we had already determined that your flow and return were cross wired/plumbed, whereas you have drawn them as if they are now what it should be. (all in yout left layout)

I am willing to help you further, but I rather discuss this over a phone, I have left you my phone number on your message box, so if you like, you can give me a call, its a land line number and you wouldn't have to pay an arm and leg to give me a call.

 

[bonkersbill]

Hi, i have managed to get the fore off the boiler and as some of you have been wanting to know, the pipes arnt connected as i thought, but they appear to be connected like the baxi bermuda inset 2 manual shows.

Actual 2

• bonkersbill
• 16 Mar 2012
• 1

The only part i cant confirm at the moment is what the 3 pipes are conected to under the grounfd floor, ive had 2 carpets up but brick walls have prevented me from getting to the underside of the boiler.

 

[bonkersbill]

As for the tests, i have just retraced my steps to make sure which pipes are getting hot 1st, the pipe to port ab definatly gets hot before any other pipe including the pipe from the cylinder, so unless it can be explained how this is happening as a return, this must be the flow.
I have also tried my best to answer as many questions as i was able to in the best possible way i could, i have never thought that the 28mm pipes were the wrong way round though i have not discounted it.

 

[doitall]

As for the tests, i have just retraced my steps to make sure which pipes are getting hot 1st, the pipe to port ab definatly gets hot before any other pipe including the pipe from the cylinder, so unless it can be explained how this is happening as a return, this must be the flow.
I have also tried my best to answer as many questions as i was able to in the best possible way i could, i have never thought that the 28mm pipes were the wrong way round though i have not discounted it.

And was this test done with the pump on or off.

How about some actual pics instead of assuming.

 

[Mikefromlondon]

Bill has a lot of patient, he has gone for months trying to sort this problem for once and all, whereas many have left him stranded and he had to pay them as well, we can all do our best to help him, like we all are doing. Thats the whole idea of these forums, don't give up now, and go easy on him, there is only so much he can do, bit at a time.

He is almost there and the latest layout he posted on here reveals that a possible problem could be under the floor boards which he had circled, the 22mm pumped return should be connected to the return from the GF rads, and thi9s is where his problem may be, now all he needs to do is to lift his floor boards and get underneath to see what may lie there waiting for him.

until he can do this, we can all speculate, so its now better for him to first get some fresh air, take a little rest, start with a fresh clean head and remove all that is in the way, and check what is underneath as circled in his drawing.

Another thing is (this is just my mind speaking, or thinking and is not a question against anyone on here)

If as Doitall is asking Bill whether he traced the pipes with the pump running or without the pump running, I am of the opinion, that he should check with the pump running since that is how the water will be forced to flow, whereas, just relying on gravity it may run or flow in the opposite direction and give us confused results, so I really don't know what would be expected if the pump was not running, but its just my opinion, not an attack on anyone's suggestion otherwise. you guys are more expert but it would be nice to know the resaon why the pipes should be checked without the pump running.

 

[matt1e]

If as Doitall is asking Bill whether he traced the pipes with the pump running or without the pump running, it would be nice to know the resaon why the pipes should be checked without the pump running.

Because it will tell you which pipe is connected to the boilers designated flow outlet as that will always get hot first on gravity circulation

Matt