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Morco Instantaneous Water Heater


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OK.

 

I fully appreciate a device that's virtually three times as powerful will heat the water, errm, nearly three times as fast.

 

That information doesn't really move me forward though.

 

I realise you are now joking about descaling, but on a more serious note, if it doesn't appear to have scaled up much in 13 years, it's hard to see that 4 weeks of total disuse could cause it.

 

If anything has so far produced an improvement, (and the jury is out on that), then it was a minuscule amount of silicone grease on the "spindle" attached to the pressure plate actuated by the diaphragm.

 

I also wonder if gas starvation is a small problem. Despite being fed by a (new) very adequately size regulator, and 1/2" pipe for all but the final few inches to the heater, I am measuring a drop in inlet pressure as it runs (14" WG instead of 14.8" WG). As the end of the feed pipe is the lowest part of the gas system, if any sludge had got in there, that is where it might gather. (I'm thinking of that black goo that sometimes gathers in LPG systems - although if undisturbed it doesn't usually make it out of the cylinders.....)

 

EDIT:

 

Sorry, also cross posted with Dave.

 

I can't easily measure pressure at the "cylinder" end of the boat - no manometer point there, as I tried to minimise joints.

 

The hob and oven sit half way along - I don't think either has a test point, but worth a look, I suppose. What I do know is that the flames on these don't visibly get smaller if the boiler is fired up.

 

However I haven't tried measuring the input pressure to the boiler with everything running. If that were less than 14" WG, it would further point to restricted flow. If I suspect anything it is the fact that the final bit of pipe before it rises to the heater is the low point. Any crap restricting that would not affect other appliances on board.

 

A lot of people seem to only use 3/8" pipe to a Morco, so I'm hoping our 1/2" feed is more than adequate.

Another point is do you control the flow before or after the heater, it can make a diffence to the heater operating pressure. I should have asked if you live in a hard water area, scaling is a very common problem where I live. I take it that the flames are ok now. You did check the gas filter? I've got a bucket with holes in it if it's of any help! Only joking, it hasn't got holes. :lol:

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  • 5 weeks later...

Trying one more time, if everybody is not totally bored by my Morco yet.

 

After managing to convince myself it was managing to get somewhere near the manufacturer's quoted performance, it is once again heating the water very little.

 

What I'm confident of includes....

 

1) No scaling in the heat exchanger.

2) Heat exchanger fins are clear

3) Flue clear.

4) Inlet water pressure way above quoted requirement of 1 bar.

5) Burner airways are completely clear, and spider free.

6) It's possible to pass water through it at more than the 5 litres per minute it is supposed to be capable of.

7) There is a small fall in input gas pressure, (to about 14" WG) when it fires up.

8) The diaphragm on the water control side looks unholed and in good condition - but I can't say if it might be stretched.

9) The thing fires up with a full "roar" just as it always did before current problems, (or so it seems).

 

What I'm less confident of....

 

1) The flames are still not completely blue - there is some orange tipping. However because of it's location, it's very hard to see in, and I don't know if they are any worse than they used to be.

 

What I've still failed to check.

 

1) Mike Bryant asked whether I can see evidence that it's modulating, and if it's possible that it's "stuck "on a low heat output. From the "roar" it doesn't sound like it is, but I will investigate further.

 

Other than complete replacement by a new unit, I'm then more or less out of ideas.

 

Morco have indicated that from it's build date (1995) it's a very old unit, with many spares no longer available, (there appear to be around 5 different D-51 variants, unfortunately). If I can get one, is it worth punting a tenner or so on replacing that diaphragm, please ?

 

Also I now have access to a spare propane regulator, and some LPG hose, so could consider temporarily feeding it from a cylinder stood right by it. That would rule out any problems with the gas locker regulator (new in May) or the pipework run on the boat. Is it worth trying, as I know I'm seeing 14" WG at the input when it's running anyway?

 

Any other ideas, please, (that don't involve descaling, acetylene, dynamite, nitro glycerine, etc., etc.).

 

Alan

Edited by alan_fincher
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Alan,

Is it possible to set the flow rate to Morco's spec and then measure the temp rise, so that you will know just how far off the spec you are???

 

Having been out last week the thing that we noticed was how much colder the cold water was than what comes from the tap at home. Could it be just very cold inlet temp thats causing the problem??

 

Dave

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Alan,

Is it possible to set the flow rate to Morco's spec and then measure the temp rise, so that you will know just how far off the spec you are???

 

Having been out last week the thing that we noticed was how much colder the cold water was than what comes from the tap at home. Could it be just very cold inlet temp thats causing the problem??

 

Dave

I did do this before and was about 15% off their spec, I think.

 

A little tricky, as I'm not really sure of the accuracy of the infra red thermometer we were using to measure. It's the most basic Maplin one, and doesn't give me the level of confidence of the much better one my son has. (Unfortunately he's living away, so I don't have access to his until Christmas).

 

However it feels a lot cooler now than when I took those measurements, and instinctively more than I'd expect to be the case with a lower input temperature.

 

Several people previously reported that theirs gives a good hot shower in all weathers, although I do note they probably have a later D61 model, which claims a somewhat higher hear output than my elderly D51.

 

I'll try some more measurements, if I can, but is there any mileage in this diaphragm replacement, do you think, please ?

 

I also need to capture as much info as I can, and try and work out if it's so old that spares just are not a goer.

 

Alan

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Is it possible to set the flow rate to Morco's spec and then measure the temp rise, so that you will know just how far off the spec you are???

 

I'll try some more measurements, if I can, but is there any mileage in this diaphragm replacement, do you think, please ?

 

It's hard to match Morco's quoted flow rates, but eventually got it delivering just over 5 litres per minute.

 

At 5 litres per minute, Morco say the temperature of the water should be increased by 25 degrees Celsius.

 

The water coming from the tank is only about 6 degrees today, and it came out of the heater at 24 degrees. So I'm seeing an 18 degree temperature rise, not a 25 degree one.

 

That seems to be 18% short of what it should be.

 

24 degrees feels little more than lukewarm, although I acknowledge that even if working to spec, the water would only be coming out at 31 degrees - not exactly suitable for showering.

 

I'm still interested if changing the diaphragm can make a difference, even though it appears undamaged. Some have suggested it might, but I don't really understand why.

 

Alan

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The water coming from the tank is only about 6 degrees today, and it came out of the heater at 24 degrees. So I'm seeing an 18 degree temperature rise, not a 25 degree one.

 

That seems to be 18% short of what it should be.

Might be worth finding out the heat output with minimal pressure drop from gas supply pipework.

 

 

24 degrees feels little more than lukewarm, although I acknowledge that even if working to spec, the water would only be coming out at 31 degrees - not exactly suitable for showering.

I'd consider feeding the gas heater from the calorifier via a thermostatic valve set to 25°c.

 

Then even if the water in the calorifier is too tepid for a shower, it can still be used to boost the output of the heater.

 

cheers,

Pete.

Edited by smileypete
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I'd consider feeding the gas heater from the calorifier via a thermostatic valve set to 25°c.

 

Then even if the water in the calorifier is too tepid for a shower, it can still be used to boost the output of the heater.

Yes that does sound a possibility, but I'm sure I've previously seen a suggestion you absolutely should not do this. I suppose when all is going well it could get very seriously hot.

 

Anyway, I've decided to punt a tenner on a replacement diaphragm for Morco. I'm not optimistic, but it appears to be one of the few parts still available at reasonable cost in the bits I feel confident to get dismantled.

 

I've also worked out that the current model (D61) has a 90mm flue, whereas mine (D51) is only 83mm, so it seems obvious one can't do a completely straight replacement, leaving everything else "as is" (unfortunately).

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Alan,

 

Having reread some posts you gave an input pressure of 14" as against 14.8", are you able to measure the actual burner pressure and compare with the manufacturer's spec??. If this is down by the 0.8" or very close then changing the diaphragm probably wont help as the gas valve must be fully open.

 

If you have a regulator and can pipe so you have the full 14.8" at the inlet and try rating the appliance again to see how much difference the 0.8" will make.

 

The actual burner pressure is the governing factor in the heat output of the appliance and is the one thing to get right before looking for other faults. On these type of appliances the inlet pressure can directly affect the burner pressure at the full gas rate. If you get the inlet pressure right then if the burner pressure is low then look to the diaphragm or gas valve. If the burner pressure is ok then you will need to look at the heat exchanger.

 

If doing the above is a pain, then a tenner on the diaphragm wont break the bank, and may save some work with the above and do the trick. If it doesn't the do the above.

 

Feeding the Morco directly from a calorifier would be a no no, as if the engine had been running all day the calorifier could be around the 80deg mark and another 25deg would give you a steam shower-ouch!!!

 

However as suggested feeding from a thermostatic blending valve set to 25deg would give you around 50deg. Although why use gas to heat the water thats already heated freebies????

It would I suppose make the calorifier hot water last longer, if there are a few aboard for showers.

 

 

Good luck

 

Dave

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Dave,

 

Very helpful, once again - thank you!.

 

I've now ordered up a diaphragm from Morco, so will change that before I do anything else.

 

I did lubricate the sliding pin on the disc it presses on last time, with Silicone grease, but I'll check again that that is still moving freely.

 

If still down on spec, it should be fairly easy to feed it direct from a bottle close by, (and with an alternate regulator).

 

I hadn't until recently seen that the manual says what the burner pressure should be - 36.3 mbar if running on propane.

 

I make that 14.6" WG, but when I tried to measure it back in October, down in London, only got about 13.6" WG, (so only about 33.9 mbar).

 

That sounds like nearly 7% short of what's expected.

 

Once I see where we are with the replaced diaphragm, I'll take some more measurements, and see what needs to happen next.

 

Alan

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Yet more on this....

 

I changed the diaphragm. Sort of as I expected, it certainly hasn't improved things. In fact without taking detailed measurements, if anything, it seems worse. :lol:

 

I ran a manometer over it again, and it's much as before....

 

Input pressure, before it fires up 37.36 mbar (book says 37 mbar)

Input pressure once it fires up 35.37 mbar (again I assume it should ideally be 37 mbar)

Burner pressure when running as hard as I can get it 34.13 mbar (book says 36.3 mbar)

 

So to answer Dave's question, at 34.13 mbar rather than the 'book' figure of 36.3 mbar, I am I estimate about 6% short of where I should be. Previously I came up with a deficit of just under 7%, so given my Micky Mouse home brew manometer, (it's mounted on a bit of pallet!) the results are as consistent as I would expect.

 

I failed to measure any more temperatures, as the water on board ran out, and the marina taps were frozen up!

 

The only thing I can still try is direct feeding it with a cylinder and bottle close by, and eliminating the 1/2" pipe run through the boat.

 

The frustrating thing is it was working fine, so it's hard to see what has failed.

 

I sense I'm going to have to replace it. :lol:

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If you read back, I have already tried to use descaler on the heat exchanger, (Fernox DS3), and there is every evidence there was bugger all scale in there.

 

Even if the theory stood up, I can't for the life of me see how scaling could cause the sudden and dramatic fall in performance that we suffered. Surely scale would build up slowly over time.

 

I can't make up my mind if the flame quality is good enough or not - it's certainly less than a perfect blue, but I think it always has been.

 

I don't think the economics stack up to get an expert out to this, so reluctantly I think I'll have to replace it. I still think the likely cause is probably something quite small, that ought to be fixable.

 

One thing I do realise is that even if performing to spec, it's not going to produce bundles of hot water in this weather. With the cold water in my tank at only 5 degrees, then at 5 litres per minute I should only be getting 30 degrees out - still not hot. As I'm only getting an 18 degree rise , that's only 23 degrees out - only luke warm. Obviously if you throttle it back it gets hotter, but I'd struggle to get a hot shower.

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I can't make up my mind if the flame quality is good enough or not - it's certainly less than a perfect blue, but I think it always has been.

Is the flue the recommended length and diameter?

 

 

As I'm only getting an 18 degree rise , that's only 23 degrees out - only luke warm. Obviously if you throttle it back it gets hotter, but I'd struggle to get a hot shower.

What sort of shower head is on there, a normal one?

 

cheers,

Pete.

Edited by smileypete
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sorry but limescale will...

 

1) reduce the amount of heat exchanged in the exchanger

2) encourage the water to flow through less fins at a higher rate

 

both reducing the heat exchanged.

 

Next i would ask if there is a 'thermostatically controlled' mixer involved in the shower assembly.

(these are very common)

 

if so its also likely to be the safety stat not functioning correctly and mixing it with cold even at the temperatures you mention. (these also fail to work properly due to limescale and is very sudden as you describe)

Edited by Pretty Funked Up
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Is the flue the recommended length and diameter?

 

No absolutely not. THe usually recommended length is 600mm, and few narrowboats have anything like that length on an instantaneous heater. But it has always been that way, and passed a BSS spillage test with no issues.

 

What sort of shower head is on there, a normal one?

 

Very basic B&Q (or similar). My challenge is not how much water actually gets pumped through the shower head, as I can alter than anyway my the manual water control valve on the Morco. The issue is that if you select one of Morco's quoted flow rates, (5 Lpm for "high flow" 2.5 Lpm for "low flow", then I cannot achieve anything like the quoted temperature increases (25 degrees for "high" 50 degrees for low).

 

sorry but limescale will...

 

1) reduce the amount of heat exchanged in the exchanger

2) encourage the water to flow through less fins at a higher rate

 

both reducing the heat exchanged.

 

Next i would ask if there is a 'thermostatically controlled' mixer involved in the shower assembly.

(these are very common)

 

if so its also likely to be the safety stat not functioning correctly and mixing it with cold even at the temperatures you mention. (these also fail to work properly due to limescale and is very sudden as you describe)

 

I have left the heat exchanger sitting with hot Fernox DS3 descaler in it for several flushings. This is supposed to change colour if it dissolves scale, but did so only for the first pass.

 

It's not possible for the water to flow through "less fins", as the water passes through one single tube of around 1/2" bore, and can't take any other route, (this bends bacwards and forwards through the finning).

 

I still can't see how limescale can suddenly appear overnight, when it's been working fine for years, but having used a heavyweight descaler on it, I still rule this one out.

 

There is no thermostatic valve of any find on shower or taps - what I'm measuring is exactly what the Morco is delivering without passing through anything clever.

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No absolutely not. THe usually recommended length is 600mm, and few narrowboats have anything like that length on an instantaneous heater. But it has always been that way, and passed a BSS spillage test with no issues.

I'd try a temporary flue extension just to see if it cures the yellow flame tips and possibly improve hot water output. (But I'd first try an improved gas supply as previously mentioned)

 

 

Very basic B&Q (or similar). My challenge is not how much water actually gets pumped through the shower head, as I can alter than anyway my the manual water control valve on the Morco. The issue is that if you select one of Morco's quoted flow rates, (5 Lpm for "high flow" 2.5 Lpm for "low flow", then I cannot achieve anything like the quoted temperature increases (25 degrees for "high" 50 degrees for low).

Low flow setting should be enough, even if the heater is underperforming a little.

 

Won't create a decent spray from a normal shower head, a low flow shower head should be better, somtimes available for electric showers, or caravan accessories places may do them.

 

cheers,

Pete.

Edited by smileypete
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OK, i have a mate in the trade I'll ask him on Sunday. :lol:

 

Is it possible for you to post a pic of the burner flames while on main burn?

 

its a morco DH51? 13yrs old? did the temp drop coincide with any other jobs being done on the boat?

any info that maybe of use for him to try an work it out??

Edited by Pretty Funked Up
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Is it possible for you to post a pic of the burner flames while on main burn?

 

I can try, but it's a challenge - it's in a very badly located space.

 

its a morco DH51?

 

Yes - DH51B to be precise.

 

13yrs old?

 

Assumed to have been same age as boat, so yes.

 

did the temp drop coincide with any other jobs being done on the boat?

 

No - it just happened when we were cruising.

 

any info that maybe of use for him to try an work it out??

 

Nothing I can think of, I'm afraid

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he said tricky without even a pic to see how its burning but theres only a few things it can be...

 

too high water pressure

too low burner pressure (sometimes a 13kg bottle cant keep the pressure up in the winter)

scaled heat exchanger

knackered gas valve

 

Test with a good 19kg bottle. Also make sure main burner jet/s is/are totally clear with a clear and perfectly round hole in it. (hold up to a strong light to see size n shape using a strand of copper wire to poke through the hole).

 

If ya post a pic i'll make sure he gets it. Sorry cant be much more help otherwise. :lol:

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  • 4 weeks later...

Hi - not sure if you still have problems with youre water heater. Had you considered contacting a qualified gas installer. Would you pull your own teeth. Your local boat yard should I would have thought been able to point in the right direction. Regards Chris.

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Hi Chris,

 

Welcome to Canal World Forums.

 

I think that even if I can find a suitably qualified and registered LPG engineer who is prepared to work on an open flued heater it is still likely that the cost would exceed what is reasonable to try and revive a 13 year old heater.

 

There is no guarantee of success, and it's highly likely that it is old enough that such an exercise might turn up a requirement for parts that Morco can no longer supply.

 

It is frustrating though, because it was working fine, and suddenly stopped.

 

I've not given up hope of fixing it, but with an integral tank surrounded by ice, the water is coming through at close to freezing, so it's hard to assess how far off spec it is.

 

I don't live aboard, so hot water on visits to the boat is currently by saucepans placed on the solid fuel stove. Not a problem at the moment, but we will need to sort it before we next cruise.

 

I think I'll probably invest around £170 in a modern model, but suspect it's going to cost more, as the flue almost certainly needs changing, and I'm not yet sure what else.

 

If any friendly person who understands the internals of these things is in the Tring summiut area, I'd welcome a second opinion, even if they don't want to get involved in actually trying to fix.

 

Alan

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I've not given up hope of fixing it, but with an integral tank surrounded by ice, the water is coming through at close to freezing, so it's hard to assess how far off spec it is.

 

I've only just read through this thread and the fact that we have the same water heater and have experienced (and solved) the same problem may be of interest.

 

The cause, in our case, was rapid fluctuations (pulses) in the water pressure due to an insufficient volume of air in the water accumulator which is fitted on the pressure side of the water pump. The pulsations were barely discernable but they were sufficient to prevent an efficient flame in the Morco burner. That problem had, in turn, been caused by running the tap with the pump/electricity turned off.

 

To correct the accumulator pressure; pump it up to the correct pressure (30 psi in our case) with a high pressure tyre pump fitted with a gauge, keep one of the water taps partially open so that the pump is running - when there is sufficient air pressure and volume the pump starts cycling slowly without any change or pulsation in the water flow rate.

 

When we had done that, the Morco worked fine . . .

 

Of course, none of this helps if you haven't got an accumulator in your water system :lol:

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I've only just read through this thread and the fact that we have the same water heater and have experienced (and solved) the same problem may be of interest.

 

The cause, in our case, was rapid fluctuations (pulses) in the water pressure due to an insufficient volume of air in the water accumulator which is fitted on the pressure side of the water pump. The pulsations were barely discernable but they were sufficient to prevent an efficient flame in the Morco burner. That problem had, in turn, been caused by running the tap with the pump/electricity turned off.

 

To correct the accumulator pressure; pump it up to the correct pressure (30 psi in our case) with a high pressure tyre pump fitted with a gauge, keep one of the water taps partially open so that the pump is running - when there is sufficient air pressure and volume the pump starts cycling slowly without any change or pulsation in the water flow rate.

 

When we had done that, the Morco worked fine . . .

 

Of course, none of this helps if you haven't got an accumulator in your water system :lol:

Graham,

 

Thanks for this......

 

I don't think it's the problem I have, but I'll certainly keep an open mind.

 

Our accumulator is very elderly, (the same age as the boat), and when I did all the work fitting a calorifier recently, I was suspicious that it may not be holding it's pressure charge properly.

 

I haven't got used yet to also having an expansion vessel in the hot water circuit, and am often thrown by how long the pump can now run with all taps turned off, (have lifted a few panels and looked under floors, just in case, but it's not my plumbing!)

 

I'll certainly give the accumulator another once over, but I'll wait until the weather has stayed a bit warmer, as the water in the tank is currently so cold that I think the Morco would struggle, even if it were not misbehaving.

 

To clarify one thing, it's possibly worth mentioning that the newer Morcos have a higher heat output, so it's not reasonable to expect our old one to produce as many degrees rise in temp, for a given flow rate, as a new D61 model could manage.

 

Are you ice free where you are yet ?

 

Alan

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