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Morco heater leak


blackrose

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I fitted my new Morco instant water heater this evening after work but it appears to have a water leak somewhere at the top left. I can't see where it's coming from but was there anything up there I was supposed to tighten before putting it on the wall or is it likely to be a leak in the heat exchanger? I had enough tonight so it'll have to stay up there until tomorrow night. 

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Thanks. Don't Morco pressure test these things before sending them out? I resent paying good money in order to get used as a manufacturer's QC dept. I'm too busy for this and have my own job to do, so I don't want to be sending it back and fitting it twice. What a ball ache. 

Edited by blackrose
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It seems most odd.

 

When I last installed a Morco it had clearly had water in it during manufacture - it seems unlikely they would not test.

 

If the leak is from the heat exchanger AFAIK it's only a piece of continuous copper pipe wrapped around the outside - if they have managed to supply one with a hole in that pipe it seems most careless.

 

3504.jpg

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I called morco today and they suggested I send it back to them rather than going through the retailer as it would be quicker, so I sent it to them today. When I took it off the wall I still couldn't see when the leak was. Anyway I'll let them repair and test it. 

 

They say they're pressure tested to 10 bar so yes it is odd. 

Edited by blackrose
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1 hour ago, alan_fincher said:

 

10 bar?  That could be enough to have caused it!

Yes it's high but that's what he said. 

10 hours ago, alan_fincher said:

It seems most odd.

 

When I last installed a Morco it had clearly had water in it during manufacture - it seems unlikely they would not test.

 

If the leak is from the heat exchanger AFAIK it's only a piece of continuous copper pipe wrapped around the outside - if they have managed to supply one with a hole in that pipe it seems most careless.

 

3504.jpg

That copper pipe must be joined to something surely? 

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11 hours ago, alan_fincher said:

If the leak is from the heat exchanger AFAIK it's only a piece of continuous copper pipe wrapped around the outside -

 

No, it wraps around the outside for pre-heating on the way up to the real heat exchanger at the top (which is a horizontal grid looking rather like an old style car radiator), where the pipe then zig-zags back and forth about six times directly over the gas flames. 

 

The zig-zag bit with the fins is usually brazed into the two pipes that go up to it and down to the water section etc. These joints re usually visible so my guess is the grid itself has frost damage from residual water used for the pressure test.

 

And 10 bar is a perfectly reasonable pressure to test to. Some water pumps alone go up to 3 bar and mains pressure has no upper limit. Used to rise at night occasionally to 6 or 7 bar in certain areas prior to them winding the pressure down as a cheap win to meet leak reduction targets. 

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30 minutes ago, blackrose said:

That copper pipe must be joined to something surely? 

Yes, I am wrong.

There are different bores of pipe in its lemgth, and presumably onr of the joints is the source of the leak

1 minute ago, Mike the Boilerman said:

And 10 bar is a perfectly reasonable pressure to test to.

Yes, accepted.

A failed attempt at humour, it seems!

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9 minutes ago, alan_fincher said:

There are different bores of pipe in its lemgth, and presumably onr of the joints is the source of the leak

 

Highly unlikely, all the joints are visible for inspection at the ends of the grid.

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13 hours ago, alan_fincher said:

It seems most odd.

 

When I last installed a Morco it had clearly had water in it during manufacture - it seems unlikely they would not test.

 

If the leak is from the heat exchanger AFAIK it's only a piece of continuous copper pipe wrapped around the outside - if they have managed to supply one with a hole in that pipe it seems most careless.

 

3504.jpg

That copper pipe must be joined to something surely? 

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Interestingly, when I mentioned on the phone that I'd chosen this model because it was almost exactly the same in dimensions as my old Vaillant, he said they were made in the same factory. He also explained to me that these heaters struggled to work well in boats because the operating water pressure (as opposed to static pressure) was often insufficient to open the gas valve in the heater. Anything below 1 bar is problematic. 

 

My pump cut out pressure is 25psi (1.8 bar) and the cut in pressure is 15psi (just over 1 bar). The operating pressure will depend on a variety of factors including pipe lengths, diameters, number of elbows,  etc, but how does an accumulator set to a few psi below the pump's cut in pressure affect the operating pressure? 

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9 hours ago, blackrose said:

 

 

My pump cut out pressure is 25psi (1.8 bar) and the cut in pressure is 15psi (just over 1 bar). The operating pressure will depend on a variety of factors including pipe lengths, diameters, number of elbows,  etc, but how does an accumulator set to a few psi below the pump's cut in pressure affect the operating pressure? 

Not a jot.

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9 hours ago, blackrose said:

Interestingly, when I mentioned on the phone that I'd chosen this model because it was almost exactly the same in dimensions as my old Vaillant, he said they were made in the same factory. He also explained to me that these heaters struggled to work well in boats because the operating water pressure (as opposed to static pressure) was often insufficient to open the gas valve in the heater. Anything below 1 bar is problematic. 

 

My pump cut out pressure is 25psi (1.8 bar) and the cut in pressure is 15psi (just over 1 bar). The operating pressure will depend on a variety of factors including pipe lengths, diameters, number of elbows,  etc, but how does an accumulator set to a few psi below the pump's cut in pressure affect the operating pressure? 

I can't see how the water pressure at the inlet can be the critical parameter. If you dismantle the water control of one of these things, you'll find that there's no port sampling atmospheric pressure. The water flows through a restricted orifice and the diaphragm reacts the the pressure difference across that orifice. In other words, what's critical is not the pressure but the flow rate. The flow rate is somewhat related to the delivery pressure of the pump, but it's also affected by the hydraulic resistance of the entire pipe run, pre and post the Morco, and it's affected by the volumetric properties of the pump. Water pumps don't deliver more and more output as the delivery pressure decreases: if you run them with the outlet disconnected, they deliver a defined flow rate determined by the speed of the motor and the volumetric characteristics of the pump mechanism.

 

To add to the fun, the metering orifice is not fixed, it's changed by the temperature control knob on the heater, If you turn that to a very cold setting.  on our installation, the heater cycles the flame as the pump cycles on and off. At the temperature setting we use, it's fine. 

 

MP.

 

 

 

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40 minutes ago, MoominPapa said:

I can't see how the water pressure at the inlet can be the critical parameter. If you dismantle the water control of one of these things, you'll find that there's no port sampling atmospheric pressure. The water flows through a restricted orifice and the diaphragm reacts the the pressure difference across that orifice. In other words, what's critical is not the pressure but the flow rate.

 

Atmospheric pressure IS sampled, at the nozzle of the hot tap when fully opened!

 

I suspect Morco were clumsily explaining that to cause sufficient water flow through the venturi to generate the pressure difference necessary to move the diaphragm, an inlet pressure of 1.0 bar or higher is necessary. But I agree flow rate through venturi is what counts, Morco are just saying when a high enough flow rate through their particular venturi is present, the inlet press always happens to be above 1 bar. This translates for the non technical user into 'you need at least one bar of pressure'. 

 

46 minutes ago, MoominPapa said:

To add to the fun, the metering orifice is not fixed, it's changed by the temperature control knob on the heater, If you turn that to a very cold setting.  on our installation, the heater cycles the flame as the pump cycles on and off. At the temperature setting we use, it's fine. 

 

Ah now this is interesting. Are you SURE about that? I've never investigated a Morco specifically but on other water heaters, the temperature dial is a needle valve in a bypass circuit. The bypass takes some cold water from the inlet and mixes more or less cold water into the hot water from the heat exchanger, depending on where you set the control. For reasons I can't quite remember, I have the impression the Morco does this too.

 

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11 minutes ago, Mike the Boilerman said:

 

Atmospheric pressure IS sampled, at the nozzle of the hot tap when fully opened!

 

I suspect Morco were clumsily explaining that to cause sufficient water flow through the venturi to generate the pressure difference necessary to move the diaphragm, an inlet pressure of 1.0 bar or higher is necessary. But I agree flow rate through venturi is what counts, Morco are just saying when a high enough flow rate through their particular venturi is present, the inlet press always happens to be above 1 bar. This translates for the non technical user into 'you need at least one bar of pressure'. 

 

 

Ah now this is interesting. Are you SURE about that? I've never investigated a Morco specifically but on other water heaters, the temperature dial is a needle valve in a bypass circuit. The bypass takes some cold water from the inlet and mixes more or less cold water into the hot water from the heat exchanger, depending on where you set the control. For reasons I can't quite remember, I have the impression the Morco does this too.

 

 

Yes, but if atmospheric pressure is sampled at the hot tap, it's also sampled on the other side of the pump (therefore cancelling the first sample) at the water tank vent :)

 

2nd para: you're undoubtedly right.

 

3rd para: Yes, I'm sure. Look up underneath a Morco and you'll see that the "out" external connection pipe is simply the outlet side of the heat exchanger. It goes nowhere near the water control valve, so there's no way the valve can be injecting cold bypass water into it.

 

MP.

 

 

 

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7 minutes ago, MoominPapa said:

3rd para: Yes, I'm sure. Look up underneath a Morco and you'll see that the "out" external connection pipe is simply the outlet side of the heat exchanger. It goes nowhere near the water control valve, so there's no way the valve can be injecting cold bypass water into it.

 

 

 

 

Oh yeah, I've just had a look and you're right!

 

I'm still not convinced the cross section of the venturi orifice is changed by the temperature control. I bought a whole new water to keep as a spare part a few years ago. If I can find it, I'll dismantle it and have a proper look.

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1 hour ago, Mike the Boilerman said:

I'm still not convinced the cross section of the venturi orifice is changed by the temperature control. I bought a whole new water to keep as a spare part a few years ago. If I can find it, I'll dismantle it and have a proper look.

I'd be interested in  the results.

 

MP.

 

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