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Morco D61B Instant Water Heater Query


system 4-50

Morco Usage  

11 members have voted

  1. 1. I use my Morco D61B for showers, varying the temperature by

    • Using a thermostatic mixer only
      3
    • Using a manual mixer only
      1
    • Using the temperature setting on the Morco only
      3
    • Using the temperature setting on the Morco And one of the other two
      3
    • None of the above because I have not got a Morco D61B
      2
    • An alternative mechanism because I like to be different
      0


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This question is for those Morco users who control their shower water temperature by the setting on the Morco itself and not by using a mixer.

Do you need to adjust the setting on the Morco for different input water temperatures? For example, if you've just filled your water tank and the water is much colder than that which has been in the tank in the boat for some time and has got warmer.

I'm finding it necessary to get out of the shower to adjust the Morco setting more often than I would like, I wondered whether this was just me, a fault on the Morco, or the norm. The Morco is quite new.

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12 minutes ago, system 4-50 said:

I wondered whether this was just me, a fault on the Morco, or the norm.

I'd say the norm. Any instant heater such as the Morco will raise the incoming temp by x degrees. Turning up the temp reduces the flow, allowing the water more time to heat and therefore heating it by x+y degrees. The colder the incoming the cooler the outgoing at any specific setting. 

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3 minutes ago, WotEver said:

I'd say the norm. Any instant heater such as the Morco will raise the incoming temp by x degrees. Turning up the temp reduces the flow, allowing the water more time to heat and therefore heating it by x+y degrees. The colder the incoming the cooler the outgoing at any specific setting. 

but I understand that the device claims to maintain the set temperature despite variations in water pressure/flow, as in the following extract from the manual:

"To adjust the hot water temperature, turn the selector control to the right for hotter water and to the left for cooler water.

  • Whatever the water temperature selected, it remains constant even if there are

    fluctuations in the mains water pressure, (within the minimum and maximum

    range), due to the action of the automatic water flow regulator. "

 

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On 13/07/2017 at 10:08, system 4-50 said:

This question is for those Morco users who control their shower water temperature by the setting on the Morco itself and not by using a mixer.

Do you need to adjust the setting on the Morco for different input water temperatures? For example, if you've just filled your water tank and the water is much colder than that which has been in the tank in the boat for some time and has got warmer.

I'm finding it necessary to get out of the shower to adjust the Morco setting more often than I would like, I wondered whether this was just me, a fault on the Morco, or the norm. The Morco is quite new.

 

I finally gave up trying to use my D61 with a manual shower mixer as the temperature rise of the water flowing through the Morco fluctuates with inlet water pressure as well as temperature, as the pump cuts in and out. I fitted a cheapo thermostatic bar type mixer from ebay which worked well for a few weeks then it seized and I was back to square one.

So I replaced it with a decent brand (Triton) and it has been a brilliant shower ever since. 

Something else my Morcos do is cycle the flames ON and OFF in summer if I have the flame size set to 'HIGH'. LOW flame setting is necessary when the inlet water temperature is about about 14C.

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Yep, but none of that disagrees with what I wrote. 

1 minute ago, system 4-50 said:

"To adjust the hot water temperature, turn the selector control to the right for hotter water and to the left for cooler water.

  • Whatever the water temperature selected, it remains constant even if there are

    fluctuations in the mains water pressure, (within the minimum and maximum

    range), due to the action of the automatic water flow regulator. "

 

It claims to maintain a constant temp regardless of incoming pressure. It doesn't claim the same for incoming temp. 

(Or incoming flow rate)

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On 13/07/2017 at 10:33, system 4-50 said:

but I understand that the device claims to maintain the set temperature despite variations in water pressure/flow, as in the following extract from the manual:

"To adjust the hot water temperature, turn the selector control to the right for hotter water and to the left for cooler water.

  • Whatever the water temperature selected, it remains constant even if there are

    fluctuations in the mains water pressure, (within the minimum and maximum

    range), due to the action of the automatic water flow regulator. "

 

 

Which of course doesn't happen in real life. Or not on any of the several Morcos I've ever owned.

I suspect if you send it back they will say there is nothing wrong with it. You could, I suppose, ask them to confirm in writing the tolerances of their statement "it remains constant". I bet they say something like +/- 3C, a range very noticable in a shower. Your could then test yours for compliance but I'd say you are wasting your time as the quicker and simpler solution is fit a thermostatic mixer.

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Thank you all. I'll add the thermostatic mixer back into the planned work, probably in a configuration where I can use a manual mixer, or the thermostatic, or just the Morco setting, and play with it until I find a favourite. 

I think it is a fantastic device that works very well. All I am doing here is fine-tuning it.

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Using a manual mixer can upset the flow through the heater, and if it is on high flame with warmish water coming in the heater will cycle as the flow rate is too low to operate the diaphragm. You can get a similar effect if the pressure switch on the pump becomes unstable.

At this time of year, I find a mid setting on the low flame can be finely tuned by the manual mixer. I've steered clear of thermostatic mixers as they lose performance over time with scalling.

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On 13/07/2017 at 20:32, Ex Brummie said:

Using a manual mixer can upset the flow through the heater, and if it is on high flame with warmish water coming in the heater will cycle as the flow rate is too low to operate the diaphragm. You can get a similar effect if the pressure switch on the pump becomes unstable.

At this time of year, I find a mid setting on the low flame can be finely tuned by the manual mixer. I've steered clear of thermostatic mixers as they lose performance over time with scalling.

 

Cheap crappy ones do. Decent ones don't (in my experience).

I've removed three cheap, 'no name' thermostatic mixers recently (from two houses and one one boat) an replaced them with Triton mixers, which seem not to do it.

If you've money to burn, AquaLisa and Mira thermostatic mixers definitely don't yield to water scale, but they are three times the price.

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One other (I.M.H.O.) important point I should have made is that balancing the cold supply to the mixer with the hot supply is necessary. The multipoint is quite restrictive at 6 litres per minute, and the introduction of cold water to the mixer will give the water an easier path, so the cold wins and flow to the heater is reduced. I overcame this by throttling back the cold supply with an isolating valve that is turned down to about 1/4 of the bore. You can experiment to achieve the best result.

When multipoint water heaters were popular in normal domestic situations, all the manual mixing valves had specific versions for them with a smaller cold water orifice.

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A lot of thermostatic mixers are intended for high pressure systems ie several bar like from a Megaflo. The cheapest ones are typically high pressure, so people looking to spend the least are likely to end up with one of these.

Possibly a thermostatic mixer for a low pressure system, ie loft tank, has a better chance of playing nicely with a Morco. Maybe less vulnerable to scale too.

It's one of these issues where it's hard to get specific answers from those having problems or not, as most won't know the min bar rating of their mixer, so it's difficult to give a recommendation...

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34 minutes ago, smileypete said:

A lot of thermostatic mixers are intended for high pressure systems ie several bar like from a Megaflo. The cheapest ones are typically high pressure, so people looking to spend the least are likely to end up with one of these.

Possibly a thermostatic mixer for a low pressure system, ie loft tank, has a better chance of playing nicely with a Morco. Maybe less vulnerable to scale too.

It's one of these issues where it's hard to get specific answers from those having problems or not, as most won't know the min bar rating of their mixer, so it's difficult to give a recommendation...

I've been researching this for home where we have gravity hot feed and mains cold. It appears from the specs that a TMV3 valve (as opposed to the more common and cheaper TMV2) have a far wider pressure tolerance. Many of the valves claim to work from as low as 0.1bar and state that they can cope with a 10 bar differential between hot and cold. The ones that are intended to be hidden away all tend to be less than £50 too, it's only the fancy chrome external shower mixer TMV3 valves that can run to hundreds. 

Edited by WotEver
Added a bit more
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53 minutes ago, Arthur Marshall said:

I always assumed that there just wasn't enough pump pressure for it to work efficiently and turning on the cold feed lowers the pressure to my water heater so it just cuts out. 

It can be figured out reasonably easily by doing temperature and flow measurements, but IME many people are seemly highly resistant to Actually Measuring Something. :)

Seems to me the Morco needs at least 1 bar across the inlet and outlet of the heater to keep the gas valve open OK. If the mixer downstream is too restrictive and so creating higher 'back pressure' at the heater outlet, it lowers the pressure drop across the heater and the heater cuts out.

So you want a mixer that creates as little pressure drop as possible.

Edited by smileypete
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ETA OK here's an easy-ish way to do it.

Set the Morco to max temp and open the hot tap in the galley fully.

Open the cold galley tap until the Morco just starts to cut out then back it off.

Run both taps into a large bowl for a few minutes.

Stir the water in the bowl up a bit, and if the temperature of the water in the bowl is some way less than 40C ('elbow temperature') then theoretically a thermostatic mixer can work***

ie. a mixer can introduce enough cold water to get a proper shower temperature without making the Morco cut out. After all a mixer is just doing the tap twiddling by itself, to get a comfortably low enough shower temperature, is it not? :)

BTW - If it's high summer it may be necessary to set the Morco to half power to get a low enough resulting temperature.

*** But if a mixer is tooo restrictive, ie designed for high pressure systems, then all bets are off... :wacko:

Edited by smileypete
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