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Hot water not getting hot enough from morco


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Morning folks, thanks to your great tips I’ve fixed the thermocouple issue I had and now to another problem. 

My heater is a morco D16, pump is jabsco par max 2.9

The hot water seems to get less and less hot, first winter was fine- this is 3rd winter. 

If feels like something is stopping the gas from firing at full capacity. Occasionally though the water will go back to being nice and hot, sometimes after running for a little while or other times intermittently without reason. 

I know the outside temperature is a factor but it used to get hot enough, even mid -winter. 

 

I’d be grateful for any suggestions. 

 

Many thanks 

 

Ed

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Could be a few things but if you think the gas flame is not at full strength, that narrows it down a bit. People tend to think that gas regulators are “fit and forget” but in fact they really should be changed every 10 years or so. Amongst other problems they tend to fill up with “gloop” (technical word - not!) otherwise known as condensate. This is an oily kind of liquid that condenses out of the gas and clogs things up. So might be worth taking the regulator off and checking if any liquid comes out when it is held in different orientations.

 

I had this problem in my caravan and it was amazing how much gloop came out! A contributory factor in gloop build up is not having a steady rise in the pipes between cylinder and regulator. Any low points trap it.

 

But it might be easier to just check the gas pressure at the inlet to the Morso using a manometer (aka U bend of clear pipe with water in it.) when the burner is on. If it is generally low, perhaps a blockage in the pipes. If it is fluctuating, that is a sure sign of gloop.

 

Correct gas pressure but low flame = burner jet blockage.

 

If the burner is in fact full strength, could be a build up of limescale inside the heat exchanger, especially if you are in a hard water area.

Edited by nicknorman
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2 minutes ago, nicknorman said:

Could be a few things but if you think the gas flame is not at full strength, that narrows it down a bit. People tend to think that gas regulators are “fit and forget” but in fact they really should be changed every 10 years or so. Amongst other problems they tend to fill up with “gloop” (technical word - not!) otherwise known as condensate. This is an oily kind of liquid that condenses out of the gas and clogs things up. So might be worth taking the regulator off and checking if any liquid comes out when it is held in different orientations.

 

I had this problem in my caravan and it was amazing how much gloop came out! A contributory factor in gloop build up is not having a steady rise in the pipes between cylinder and regulator. Any low points trap it.

 

But it might be easier to just check the gas pressure at the inlet to the Morso using a manometer (aka U bend of clear pipe with water in it.) when the burner is on. If it is generally low, perhaps a blockage in the pipes. If it is fluctuating, that is a sure sign of gloop.

 

Correct gas pressure but low flame = burner jet blockage.

 

If the burner is in fact full strength, could be a build up of limescale inside the heat exchanger, especially if you are in a hard water area.

Thanks.  If it was a gas issue, would it be effected when I use hobs etc at same time?  I’ve tried turning on cooker at full whack and hobs and these don’t seem to have any effect on gas strength for heater although this may not be an appropriate test. 

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30 minutes ago, nicknorman said:

If the burner is in fact full strength, could be a build up of limescale inside the heat exchanger, especially if you are in a hard water area.

I would have expected that to mean it could never produce hot water.

OP suggest that once in a while it still will for a bit, which to me points to a gas supply or burner problem rather than obstruction or scaling of the water circuit.

As Mike suggests, I think the OP has got the heater description wrong, so it is worth them clarifying what they actually have.

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Just now, Polishicebreaker said:

I was close :)    Yes that’s the one, thankyou

 

Ok. In which case, the flame control has "high' and 'low' settings and the flame size is substantially different on each. If yours is the same then deffly summink wrong. Probably water scale contamination restricting the water flow which the gas valve recognises and keeps the flame size to low. Especially likely given the gradual onset of the problem you describe. The heat exchanger needs chemically descaling. A subject worthy of a whole forum by itself!

 

 

 

 

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2 hours ago, Mike the Boilerman said:

 

Ok. In which case, the flame control has "high' and 'low' settings and the flame size is substantially different on each. If yours is the same then deffly summink wrong. Probably water scale contamination restricting the water flow which the gas valve recognises and keeps the flame size to low. Especially likely given the gradual onset of the problem you describe. The heat exchanger needs chemically descaling. A subject worthy of a whole forum by itself!

 

 

 

 

Ok I’m ready ?

 

maybe already covered in another thread?  I’ll take a search 

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2 hours ago, alan_fincher said:

I would have expected that to mean it could never produce hot water.
 

No when there is a build up of limescale inside the heat exchanger, water can still flow but the limescale acts as insulation between the burner and the water. So the water gains less heat and more heat goes up the flue. Obviously in an extreme case, the water might be blocked altogether by limescale but I don’t think that is a normal “failure mode” and certainly not in this case.

2 hours ago, Polishicebreaker said:

Thanks.  If it was a gas issue, would it be effected when I use hobs etc at same time?  I’ve tried turning on cooker at full whack and hobs and these don’t seem to have any effect on gas strength for heater although this may not be an appropriate test. 

Yes, I think this demonstrates that it isn’t a fundamental gas supply /regulator problem.

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6 minutes ago, nicknorman said:

No when there is a build up of limescale inside the heat exchanger, water can still flow but the limescale acts as insulation between the burner and the water. So the water gains less heat and more heat goes up the flue. Obviously in an extreme case, the water might be blocked altogether by limescale but I don’t think that is a normal “failure mode” and certainly not in this case.

I've obviously not explained myself very well.

What I meant is that I would not expect the "works properly sometimes" element of the original post.

Yes if it is scaled reduced heat will still get through, but I wouldn't expect periods of it performing as if it were not scaled.

And for clarity I'm talking about the eat exchanger bit only.  Scale in other bits of it, like Mike suggests, could obviously also affect behaviour.

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On 03/01/2020 at 13:39, alan_fincher said:

I've obviously not explained myself very well.

What I meant is that I would not expect the "works properly sometimes" element of the original post.

Yes if it is scaled reduced heat will still get through, but I wouldn't expect periods of it performing as if it were not scaled.

And for clarity I'm talking about the eat exchanger bit only.  Scale in other bits of it, like Mike suggests, could obviously also affect behaviour.

So a de-scale may be needed!   Any tips or links?

 

sounds like a fun Sunday ?

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