Bother with new gas fired water heater - help sought

[Graham Bowers]

I’m having a bit of bother getting a new Morco Primo 6 water heater commissioned and am hoping for some pointers please. It’s brand new and is a replacement for a Rinnai 58e. The problem is it trips out after about 20 seconds. Both the main burner and the pilot light are extinguished, however water continues to flow. This has happened consistently over several days with varying wind conditions. See video of a tripout event.

 

Gas pressure seems OK. It has a dedicated 10mm feed from the propane cylinder and the pressure at the inlet with the burner off is 15.5 inches of water (38 millibar) and with the burner firing is 14 inches of water (35 millibar). Stated nominal inlet gas pressure is 37 mb and allowable pressure drop when the burner is on is 2.5 mb. The commissioning instructions also require the gas pressure to be measured at the burner. I measured 9.5 inches of water (24 mb) and the requirement is 28 mb. A little low, however the instructions indicate that required pressure is needed for full performance. All pressures measured using a U tube water manometer.

 

Water pressure seems OK. Minimum pressure is 0.2 Bar, which is 6.7 feet of water. I put a 5mm tube from the heater water inlet up to the top of the TV mast which is 9 feet above the heater inlet and water came out the tube with gusto when the burner was on.

 

The flue is just over the 600mm height requirement. It’s the same flue the Rinnai used. The Morco (Innovita) has a flue gas spill transducer that from my reading seems to be a temperature “stat” however I don’t think the Rinnai had this functionality. I did a smoke match test and don’t really know how to interpret it, although I did video it, also attached. Finally, and don’t hate me for this, for test purposes I unscrewed the spill transducer from it’s location on the diffuser and placed it in a small jamjar out of the fluegas flow, although it is still connected electrically. The thinking is that if I took the spill sensor out of the equation and it stopped tripping, then the tripouts were probably due to a spill problem. Putting the spill sensor in the jamjar made no difference at all.

 

Other than making the flue longer, I think I’ve done all I can. I’m not to confident that would help based on the experiment of taking the spill sensor out of the diffuser.

 

Thoughts please……………………..

[mrsmelly]

Is it anything to do with the " Stella " effect?

[Graham Bowers]

Knew I should have edited that out ? In mitigation, I'd point out there was only the one, on this occasion!

 

[Richard10002]

Not a plumber, but have f'**ed about with my Rinnai from time to time, and I'm sure someone with more knowledge will be along soon.

 

Have you tried increasing the water pressure. My guess is that it's overheating after the 20 seconds, so it shuts down. More pressure should mean more water flows, so things don't get quite as hot.

 

Presumably all that smokey stuff is steam from the hot water, and not actual smoke from the heater?

[Graham Bowers]

1 hour ago, Richard10002 said:

Not a plumber, but have f'**ed about with my Rinnai from time to time, and I'm sure someone with more knowledge will be along soon.

 

Have you tried increasing the water pressure. My guess is that it's overheating after the 20 seconds, so it shuts down. More pressure should mean more water flows, so things don't get quite as hot.

 

Presumably all that smokey stuff is steam from the hot water, and not actual smoke from the heater?

The test condition is with the sink hot water tap fully open and I've tested the water pressure in that condition and it's over the low limit of 0.2 Bar. Since the system is operating at full flow, I'm not sure how I'd increase the water pressure. I have, however, operated the system by opening the hot tap in 10 second bursts and then allowing the pump to re-pressurise the accumulator. It still cuts out. Also, I forgot to say before, but I measured the volume pumped in the 20 seconds it took to trip out, and it was just over 2 litres, so the average flow rate is over 6 litres a minute, which is within spec.

 

All that smokey stuff in the second video is indeed smoke, from a smoke match, as I did a flue spill test. Trouble is I'm not sure how to interpret the result.

 

Thanks for commenting.

[Tony Brooks]

It maybe an illusion caused by camera angle but is the pilot light playing on the flame failure probe enough? The pilot light burner looks to be bent over to the right.

 

I too think an overheat is possible, have you tried with the water temperature control set to minimum temperature rise?

[MtB]

1 hour ago, Tony Brooks said:

It maybe an illusion caused by camera angle but is the pilot light playing on the flame failure probe enough?

 

Nail on the head.

 

That pilot flame is WAY too small.  It ought to be completely enveloping the thermocouple tip but it doesn't reach it by about 1/4". Despite this it just about warms the thermocouple tip enough to generate enough leccy current to hold the electromagnetic valve open. 

 

Once the main burner lights the increased airflow cools the thermocouple tip (as the pilot flame does not envelop it) so after a few seconds the electromagnetic valve ceases to be energised so it shuts and isolates the gas.

 

The pilot flame gas jet is prolly partially blocked, or the pilot gas feed is adjustable on the gas valve and needs turning UP. The flame looks far too small to me. 

[Graham Bowers]

Thanks gents. The pilot flame does not play on the flame failure probe (thermocouple) and MtB is on the money with the distance of about 1/4 inch.

 

To the right of the pilot burner there is damage to the sheet metal shroud that was there as received. This is a brand new unit so I wonder if the unit has had a knock in transit that's resulted in that visible damage and also displaced those pilot parts. If so it must have been quite a knock as the adjacent parts that could have hit it are quite a way from the sheet metal, so I'd concluded that part was damaged during the manufacturing process and allowed to flow through the system. I'd have expected it to have been tested during manufacture and the thermocouple tip was blued, indicating it has felt heat.

 

I'll let you know how I get on.

 

 

 

[MtB]

5 hours ago, Graham Bowers said:

Thanks gents. The pilot flame does not play on the flame failure probe (thermocouple) and MtB is on the money with the distance of about 1/4 inch.

 

To the right of the pilot burner there is damage to the sheet metal shroud that was there as received. This is a brand new unit so I wonder if the unit has had a knock in transit that's resulted in that visible damage and also displaced those pilot parts. If so it must have been quite a knock as the adjacent parts that could have hit it are quite a way from the sheet metal, so I'd concluded that part was damaged during the manufacturing process and allowed to flow through the system. I'd have expected it to have been tested during manufacture and the thermocouple tip was blued, indicating it has felt heat.

 

I'll let you know how I get on.

 

 

 

 

There is no visible damage to the pilot assembly as whole. The bar holding the pilot burner, the thermocouple and the ignition electrode is tilted ever so slightly but remains straight and undamaged itself and the relative positions of the three components appears unaffected. The flame is simply smaller than it ought to be. The superficial damage to the thin sheet metalwork around it is a red herring in my opinion.

 

Two things to check in correcting flame size. 

 

1) The pilot assembly and pilot jet are both clear of lint, fluff, soot or any other blocking debris. Being a brand new appliance this is unlikely but dismantle it completely all the same to rule possibility this out. The blueing of the thermocouple suggests a brief running test at the factory took place and at that point, the flame was big enough to reach it. There is a hole about 2.5mm diameter just above the nut connecting the aluminium gas pipe to the pilot assembly proper, clearly visible in your first picture. Check this hole in particular. It is an air induction port and very prone to blocking with fluff. Try a good hard blow though it to clear any concealed debris.  

 

2) The gas valve probably has a needle valve for adjusting pilot flame size. Try finding and adjusting it. 

 

 

 

Edited August 19, 2019 by Mike the Boilerman
Add a bit

[Graham Bowers]

Thanks Mike. Interestingly the unit came with a small plastic bag containing a brass part and fibre washer, labelled "Spare pilot injector part code MP0110". It looks like the part at the base of the pilot assembly. Not sure if this is usual for Morco - it seemed to be a sort of "expect trouble" statement.

 

[MtB]

7 minutes ago, Graham Bowers said:

Thanks Mike. Interestingly the unit came with a small plastic bag containing a brass part and fibre washer, labelled "Spare pilot injector part code MP0110". It looks like the part at the base of the pilot assembly. Not sure if this is usual for Morco - it seemed to be a sort of "expect trouble" statement.

 

 

I think you're right,t is unheard of for a 'spare' pilot jet to be supplied with a gas appliance! Pilot jets don't wear out. So there must be something specific making them supply this. I bet fitting it solves the problem. 

 

 

 

P.S.

 

Read the manual first to check this is not intended for converting to natural gas. Also, to check it is not supplied jetted for NG in the first place! 

 

 

 

Edited August 19, 2019 by Mike the Boilerman
Add a bit

[Graham Bowers]

OK. Thanks for your input.

 

[Graham Bowers]

I put in the spare jet and the pilot flame now bathes the thermocouple. It fires up and operates perfectly. Thanks for all assistance received.

Graham

[Tony Brooks]

That give some concern. As Mike advised, did you check to see if the whole thing was jetted for domestic gas? If not then what about the jet(s) for the main burner. I do not know enough about the things  but I would have thought a phone call to the UK distributor would be an idea.

[MtB]

I checked the manual earlier, this appliance ships ready for LPG. 

[Richard10002]

8 minutes ago, Mike the Boilerman said:

I checked the manual earlier, this appliance ships ready for LPG. 

Except when it doesn't?

 

It certainly looks like the pilot jet fitted on delivery was for domestic gas, and the additional jet is the LPG jet.

 

Would you expect a domestic gas pilot jet to show the short flame symptoms in the video?

Edited August 19, 2019 by Richard10002

[Graham Bowers]

The appliance is also marked up that it is specified for propane at 37 mb. I re-read the manual and the spare jet label and there was nothing to suggest it was for conversion to methane. The pilot flame became progressively worse so I’m satisfied a blockage was the cause. However for completeness I will check with Morco why a spare jet was supplied. The jets do have markings however I need a magnifying glass to read them. 

[MtB]

4 hours ago, Richard10002 said:

Except when it doesn't?

 

It certainly looks like the pilot jet fitted on delivery was for domestic gas, and the additional jet is the LPG jet.

 

 

No it doesn't! The manual and data label show this appliance is suitable only for LPG.

 

 

 

 

[Graham Bowers]

I phoned Morco today and they stated the spare jet is the same as the installed jet. And the reason was simply that they had an over-supply of that part. It seems a bit of an odd thing to do, but I'm going to accept it at face value.

[Simo]

On 19/08/2019 at 11:29, Graham Bowers said:

I put in the spare jet and the pilot flame now bathes the thermocouple. It fires up and operates perfectly. Thanks for all assistance received.

Graham

Hi Graham, I wonder whether you’re still here. we have the same problem with our Primo! I’ve bought a new injector as unfortunately we didn’t  a spare. I’ve taken all apart now but I cannot manage to separate the old injector from the top mushroom shaped part in order to put the new injector in. How did you do it? 

[Tony Brooks]

If you mean you can't grip the brass tube to unscrew the injector rather than trying to grip the tube so it might get squashed I would use the air holes (there is usually one on the other side) to put a decent fitting rod through, possibly a long drill bit, and use that to stop the tube rotating as you try toundo the hexagon.

[Simo]

Thanks Tony! That was another top suggestion. 
All changed now and indeed the new part is working, the heater is no longer cutting off as the flame coming out of the injector assembly is bigger. I’m so thankful to you all! Going to have a shower!!! This has gone on for months...thanks!!!

[matty40s]

6 minutes ago, Simo said:

Thanks Tony! That was another top suggestion. 
All changed now and indeed the new part is working, the heater is no longer cutting off as the flame coming out of the injector assembly is bigger. I’m so thankful to you all! Going to have a shower!!! This has gone on for months...thanks!!!

phoooeeeee?

[Simo]

17 minutes ago, matty40s said:

phoooeeeee?

? 

[Graham Bowers]

21 hours ago, Simo said:

Hi Graham, I wonder whether you’re still here. we have the same problem with our Primo! I’ve bought a new injector as unfortunately we didn’t  a spare. I’ve taken all apart now but I cannot manage to separate the old injector from the top mushroom shaped part in order to put the new injector in. How did you do it? 

Pleased you got sorted. I'm not a "regular" however followed up as I got an email. alert.