No hot water to taps from Megaflo - outlet pipes are hot.

[GF]

Thanks

Found it and checked - it had not tripped.

back to square one!

NB: in my earlier post I stated that the pipe above the 2 port valve was hot and the one below was cold. When I latched the 2 port valve the pipe below it became hot and the water from the hot taps was also hot. Can anybody tell me what is happening here?

thanks
G

 

[mickyg]

when you have a demand for hot water from your programmer, check if you have 240v going to the motor inside the 2 port valve closest to the cylinder.

 

[GF]

Sorry for not getting back on this one - took the opportunity to get in that bath I ran.

Checked the valve and am getting 33.7v at the microswitch terminals on t5hat valve.

Boiler ignites for a few seconds, thinks that temp is up to 70 degrees and shuts down. Result - no hot water at the taps!

cheers
Graham

 

[DP]

The pipe directly above the 2 port valve is hot and the pipe below it (into the cylinder) is cold.

I would be looking at the valve above. HW demand at the programmer opens this valve. If no power at the motor, meter backwards to the programmer.

If valve does not open, water will not get hot. Boiler is firing (know not why), reaching operational temperature and shutting down. Fires again when it cools sufficiently.

Correct operation would be, programmer comes on for HW, motorised valve motor opens the valve, microswitch operates and boiler NOW gets a signal to run.

I would be looking at the control wiring as well.

 

[GF]

If anyone is still looking;

I have established that if I turn off the hot water command at the programmer, then latch the 2 port valve onto the 'manual/open' position and then ask for hot water via the programmer the boiler starts up and continues to run, heating up the water.

If I unlatch the valve so that it goes into the auto position the boiler goes straight to 70 degrees and shuts down.

Is this a valve fault (seem to be only getting 33 volts at terminals) or a programmer fault?

Is there any issues associated with latching the valve to manual/open for an hour or so at a time until I sort out the problem?

Graham

 

[Llan1observer]

how long has the system been installed?

 

[Agile]

What would be the effect of placing the 2 port valve into the Manual position?

graham

Latching the two port into the manual on position is bypassing a safety device and is potentially very dangerous as cylinders and explode and destroy a house!

Tony

It seems that the problem is bacause the two port is not opening. That may be a failed control circuit, a tripped overstat or a stuck or open circuit valve motor.

Tony

 

[DP]

It seems that the problem is bacause the two port is not opening. That may be a failed control circuit, a tripped overstat or a stuck or open circuit valve motor.

In that case why is the boiler firing?

 

[gas4you]

Perhaps it has been wired so that the 2 port valve is on the megaflo stat/overheat stat and the boiler is getting the 240 V demand from the 3 port valve when on for HW.

I would be looking at the wiring and the megaflo stat now.

 

[Agile]

I find very few ( if any ) ever wired with the boiler HW "on" going through the two port when the original system is a three port.

Do any of the instructions for installing unventeds give any suggestions for wiring them in conjunction with a three port or is it left to the installer to do what he chooses?

How would most RGIs connect them when the three port is to be retained?

Tony

 

[gas4you]

Megaflo instructions give a wiring diagram for this Tony.

CLICK HERE

 

[DP]

Dave control wiring is alien to a lot of heating people. I regularly see MVs wired but auxiliary switches not connected.

Above megaflow would seem to be one such example.

 

[Agile]

A quick look with my head on one side makes me think that the two aux switches are in effect connected in parallel.

That will still enable the boiler to work if the aux switch in the two port has failed.

I suppose wiring them in series gives no more protection but more failure points.

Tony

 

[GF]

The system was installed into a new house 7 years ago. It is fair to say that there were several problems with it in the first 2 years and we had a sucession of Heatrae Sadia appointed guys trying to sort it out. The last one changes the PCB and the 3 port valve.

They all had a go at doing different things so i am sure it is no longer to the original design.

I have more than a hunch that it is the Honeywell V4043H1056 valve which is failing to open, so I have ordered another.

I will let you all know if it solves the problem.

Graham

 

[Agile]

All you really needed to do is to order the valve head!

However, measuring the motor resistance would identify if that has gone open circuit and just replacing the motor would be a lot cheaper and easier!

Tony