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As a next step, bleed any air from the system starting at the outlet from the heater and the square bleed screw at the top of the heat exchanger just by the outlet, then all the rads all the while making sure the header tank is topped up. Personally I prefer presure systems with a relief valve and auto bleeder as it helps so much with this kind of issue as you can bleed without even running the heater or even the circulation pump.

Edited by NMEA
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As a next step, bleed any air from the system starting at the outlet from the heater and the square bleed screw at the top of the heat exchanger just by the outlet, then all the rads all the while making sure the header tank is topped up. Personally I prefer presure systems with a relief valve and auto bleeder as it helps so much with this kind of issue as you can bleed without even running the heater or even the circulation pump.

Thanks, first job for the morning. Will let you know how we get on..

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Thanks, first job for the morning. Will let you know how we get on..

At the risk of teaching "Granny to suck eggs" you know you need to hve the heater (or at least the pump) running to bleed the system?

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Question: - the fuel pump has 2 speeds corresponding to hi and low heat settings. You can hear it clicking to judge the speed, on startup it clicks slowly, then once light-up is detected it goes to the faster speed (roughly twice as fast). So does the fuel pump remain on fast-click right until it shuts down, or does it go to slow click for a while before shutting down?

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At the risk of teaching "Granny to suck eggs" you know you need to hve the heater (or at least the pump) running to bleed the system?

 

I did realise that but please treat me as if I am still learning! Any info is welcomed.

 

[quote name="nicknorman" post="1175098" timestamp="1383941871"

Question: - the fuel pump has 2 speeds corresponding to hi and low heat settings. You can hear it clicking to judge the speed, on startup it clicks slowly, then once light-up is detected it goes to the faster speed (roughly twice as fast). So does the fuel pump remain on fast-click right until it shuts down, or does it go to slow click for a while before shutting down?

 

Hi nick,

 

The pump has varied in speed, last time it slowed down after quite a while, the if went up a gear before it cut out.

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If you have a cold calorifier and a good few radiators (say 3 or more) I would expect it to run at full power for more than an hour, maybe 2, before going to 1/2 power. If its going to 1/2 power after less than 30 mins that is abnormal. Yes it could be air in the system, and bleeding is definitely a good idea. But I do wonder where this air suddenly came from (assuming it hadn't been worked on just before you bought it). So if that is not the issue, there could be something restricting the coolant flow. I would check for any kinked rubber hoses (though Steve normally uses plastic plumbing, with copper adjacent to the Mikuni) and in particular check any gate valves. Our system has a gate valve for each of the radiator circuit and the calorifier circuit. I would make sure they are both fully turned on, and also that the radiators are turned fully on.

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At the risk of teaching "Granny to suck eggs" you know you need to hve the heater (or at least the pump) running to bleed the system?

 

Without wishing to engineer the usual fall-out on this section of the forum, I can't really agree with that statement.

 

Providing that your header tank is mounted at a suitable height you can bleed your system of air without having to run the heater. Simply ensure that it is filled to the maximum level and if it's a sealed system, remove the header tank cap to avoid creating a vacuum when you open any bleed valves. Have a pre-mix of suitable antifreeze/water available to top the header tank up and if possible, have another crew member situated there to top up for you. Then, from the boiler outwards, proceed to bleed the system methodically, ensuring that all rad valves including any thermostatically controlled valves are set fully open. Providing that as previously mentioned, you have no constrictions in the system, you should now have a fully filled circuit, other than any trapped air in the system.

 

In order to free any trapped air, run the heater for as long as possible, this should then purge the circuit of air from any air locks due to poor circuit design. Bleeding and purging of air are two different techniques.

 

Be sure to check the coolant level in the header tank once this process has been completed, then once again after the heater has been run for an hour or so.

 

From reading your previous posts where you say that the rads were running hot, did you check them right up to the highest point? Unbled rads will heat up part way and remain cool at their uppermost point. Also, have you been in touch with the previous owner to enquire whether he or she had similar problems? It is possible that prior to selling, they may have serviced the boiler and replenished the coolant without bleeding and purging the system fully. On our boat, Steve's plumber had built in several connections where air locks were prevalent and upon changing the coolant, I had to purge the system repeatedly to clear any air locks. I have since redesigned the circuit to eradicate these problems.

 

Next, if after ensuring that the coolant system is bled, purged and free from any restrictions, you still have the overheat problem, check that the stainless steel flexible exhaust pipe has not been crimped by anything pressing against it, creating excessive back pressure. Our Mikuni runs relatively quietly compared to other makes, but if you have a partial restriction in the exhaust circuit, the noise level may be higher as the exhaust gases increase in velocity whilst passing through the restriction.

 

There is also the possibility that your heater is overdue to be serviced or overhauled, given the age of your boat. There could be excessive carbon build up in the combustion chamber, causing the overheat problem. If you send the heater off to be serviced or overhauled, I would expect the engineer to test the overheat sensor is functioning correctly if he's worth his salt, failing that, the electronic control unit could possibly be the source of your woes as a last resort.

 

If you wish, I can email a copy of the service manual which although quite comprehensive in its content, is a little dated with some redundant information.

 

Hopefully, the advice given so far will help you in correcting any niggles that exist on your heater. In return, if you, or any other contributor to this thread, has any tips on kitten behavioural problems, I would be obliged if you could forward them without delay, otherwise I'll be compelled to have this little sod sectioned under the Mental Health Act!

 

Mike

 

P.S. Apologies if this post has repeated previously offered advice.

Edited by Doorman
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Hi -

Trying to deal with a sequence of events similar to that experienced by 'Chilligibbon'. Mikuni MX40 started heating rads but cut out abruptly without going through post-purge sequence. 'Overheat' indicated on Control Box flashing LED code, but once system re-set (by turning off main power supply) on turning power on again new fault code indicated 'water pump failure'. This turned out to be a blown fuse ( 3 amp). Rplaced fuse, bled rads and checked header tank. The same fault occured at least twice more, each time resulting in an 'overheat' warning as a result of the water pump fuse blowing and bringing the heater to a sudden stop without it having had chance to cool down as it would normally do. Touch wood the last repacement fuse seems to be holding, although I did experience 'ignition failure' which may have been something to do with the glow plug leads being loose. It fired up O.K. once this had been sorted, initially with great clouds of white smoke but then cleanly and powerfully for about thirty minutes, the rads got very hot, but it seemed to trigger the overheat thermostat causing the heater to enter the post-purge sequence and then shut down, rather than going into a low / hi phase of operation, i.e., with the circulating pump continuing to operate and the heater re-starting after the water temperature has fallen below a certain level.

 

'NMEA' can you confirm that the plug, part no. 36 on the MX40 parts drawing is definitely a bleed screw, and that it is O.K. to open this to bleed air from the system ? When I asked someone at Mikuni if this was so, they said no, don't touch it !

I am frustrated by the lack of technical information available although I have picked up some valuable stuff from this forum. If anyone has a copy of the service manual available I should appreciate a copy - I only have the operation manual for it's original function as an engine preheater, which is short on illustrations and troubleshooting advice.

As the service engineer has said it will be at least ten days before he can come out, I need some good advice now! Regards, Les

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Hi and thanks to all of you who have offered valuable information. I have now bled the system and released quite a lot of air through the small rad in the bathroom.

So far so good, all is running well and I have hot water!

 

Again many thanks, onwards and upwards to the next issue that will need sorting, I'm sure I will be back picking your brains very soon!

 

Chris

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Without wishing to engineer the usual fall-out on this section of the forum, I can't really agree with that statement.

 

Providing that your header tank is mounted at a suitable height you can bleed your system of air without having to run the heater. Simply ensure that it is filled to the maximum level and if it's a sealed system, remove the header tank cap to avoid creating a vacuum when you open any bleed valves. Have a pre-mix of suitable antifreeze/water available to top the header tank up and if possible, have another crew member situated there to top up for you. Then, from the boiler outwards, proceed to bleed the system methodically, ensuring that all rad valves including any thermostatically controlled valves are set fully open. Providing that as previously mentioned, you have no constrictions in the system, you should now have a fully filled circuit, other than any trapped air in the system.

 

In order to free any trapped air, run the heater for as long as possible, this should then purge the circuit of air from any air locks due to poor circuit design. Bleeding and purging of air are two different techniques.

 

 

Your comments regarding bleeding make good sense Mike.

 

I have always understood that radiators are best bled without the circulating pump running since otherwise air bubbles are being pushed around the system rather than settling adjacent to the bleed point.

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Hi -

If anyone has a copy of the service manual available I should appreciate a copy - I only have the operation manual for it's original function as an engine preheater, which is short on illustrations and troubleshooting advice.

As the service engineer has said it will be at least ten days before he can come out, I need some good advice now! Regards, Les

I believe that NMEA has offered to email a copy of the service manual to anyone and maybe he has a modern version of the older one that I can gladly email if you wish.

 

You made an excellent point regarding the blown fuse, something that none of us has touched on until now and should be the first port of call with any piece of equipment involving electricity. With regard to the bleed plug part No. 36, I can't speak for NMEA's opinion on this but personally, I would concur with the guys at Mikuni. The coolant outlet next to the bleed plug should be piped with a gradual rise towards the feed to the header tank. This way, any potentially trapped air in the heater will naturally be dispelled without the need to vent the unit with the plug.

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Thanks 'Doorman' for the advice on the Mikuni MX40 coolant preheater/ diesel boiler. " Bleed and Purge " is now my Mantra.
Tried again yesterday, but quickly got an 'overheat shutdown'. The heating system on the boat is a simple layout with a feed to the calorifier and pipes to two small radiators in the saloon and forecabin/bedroom.
You mention that the coolant outlet from the heater should have a gradual rise towards the header tank - I take it from this that you are referring to the return pipe part of the circuit as on our boat the header tank is teeded-in at a point just before the water intake to the heater.
The hot water from the outlet on top of the heater has to be pumped down (or falls?) to near floor level in the saloon through a couple of right-angle bends (elbows) - would this be likely to cause resistance and / or an air lock ?
There is a pressure relief valve in the hot water outlet pipe on top of the heater - when this is backed-off water seeps out - i havn't tried it with the pump on !

As a point of general interest, I can confirm that the sequence of flashes given by the LED in the on/off switch is not the same as those given by the self-diagnosis lamp visible when looking in the control box window / viewing aperture. The differences between them are indicated in diagrammatic form in the original operation manual, my interpretation is as follows :

 

(1) When first switched on the operation LED (on the on/off switch) pulses with a slow, steady flash (initiating combustion).

(2) When the heater enters steady combustion, the LED stays on constantly.

(3) When the switch is returned to off, the heater enters the post-purge phase and the LED pulses with a slow, steady flash again and then goes out.

 

(4) Should an 'Overheat shutdown' occur then the switch LED will give three long pulses followed by six short pulses (as observed by 'Chilligibbon') but the self-diagnosis lamp in the control box gives a fault code of nine equal flashes, = 'Overheating failure'.

If the fault is cleared by switching off and then switching on again the power supply, (remembering to reset the operational switch to off) the control box might then indicate a specific fault,e.g., four equal flashes = 'Water pump failure'. This could be something as simple as a blown fuse, so don't automatically assume that the component itself is dead.

(5) 'Ignition failure' is indicated by rapid pulsing of the switch LED after three automatic attempts have been made to initiate combustion, and the same occurs if combustion is interrupted. The self diagnosis lamp on the control box gives just one flash at regular intervals.

(6) If 'Inadequate voltage' is detected whist the heater is operating, the switch LED pulses rapidly and the self-diagnosis lamp gives eight equal flashes indicating 'High or low voltage'.

(7) When operating normally under low-load conditions, the heater can cycle down, going through the post-purge phase, stopping and then re-starting, during which the switch LED will pulse slowly and evenly, presumably until steady combustion is established again and the LED then remains constantly on as per example (2).

When I have achieved this happy state of affairs, I will let you know !

I must stress this is my own interpretation of the information in the manufacturer's handbook and is subject to amendment in the light of experience.

Regards, Les

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Not necessarily Redeye.

 

If you fit a 'T' connection to the fuel line close to the pump on the suction side and have a short length of fuel pipe extending from the spare leg with a female connection and compression olive, you can attach a bleed device via a 6mm ID section of fuel hose fitted over the olive. With this set-up you can bleed fuel from the tank via the new filter right up to the pump.

 

Once this has been achieved, simply screw a male blanking connection to the spare leg on the 'T' connection to seal it up and away you go. Simples. If I ever get chance to return to the boat from our house I'll post a photo of this arrangement that I have on our Mikuni, all will be clear then.

 

Mike

 

Interesting,

 

I now have a PJ Harworth pressure jet boiler in my new (old) boat. Its the best think I ever fitted absolutely reliable, quiet and works on a fuel circulation setup so is completely self bleeding.

 

Different sport to a Mikuni.

 

Cheers

 

Redeye

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Thanks 'Doorman' for the advice on the Mikuni MX40 coolant preheater/ diesel boiler. " Bleed and Purge " is now my Mantra.

Tried again yesterday, but quickly got an 'overheat shutdown'. The heating system on the boat is a simple layout with a feed to the calorifier and pipes to two small radiators in the saloon and forecabin/bedroom.

You mention that the coolant outlet from the heater should have a gradual rise towards the header tank - I take it from this that you are referring to the return pipe part of the circuit as on our boat the header tank is teeded-in at a point just before the water intake to the heater.

The hot water from the outlet on top of the heater has to be pumped down (or falls?) to near floor level in the saloon through a couple of right-angle bends (elbows) - would this be likely to cause resistance and / or an air lock ?

There is a pressure relief valve in the hot water outlet pipe on top of the heater - when this is backed-off water seeps out - i havn't tried it with the pump on !

 

Regards, Les

Hello Les,

 

Your description of the heating circuit is typical of a standard system where the header tank is on the return circuit rather than the flow. This design with a single pipe feed to the tank from the return, is to avoid the pump forcing the coolant level over the top of an open header tank and to be fair, with this system, the bleed plug on the heater would be the normal outlet for any trapped air in the boiler, or, as in your case, the pressure relief valve. Interestingly, is there a cap on your header tank? As this should also incorporate a pressure relief valve. The caps on our (Eberspacher) tanks are sourced from Ford Transit vans as standard.

 

I would try bleeding the heater again at the pressure relief valve and then purge any further trapped air with the pump running, obviously taking care once the coolant begins to warm up! Presuming that the rest of the system is thoroughly cleared of any trapped air, your overheat problem should then be solved. Failing that, please refer to previous posts on this thread suggesting other causes of this problem. The elbows, although not perfect in terms of smooth flowing of the coolant, are normal connections in a system and would not cause a problem. Presumably, the flow and return pipes are 22mm in diameter?

 

I prefer to situate a sealed header tank on the flow side of the boiler and in parallel to the system. In other words, it is piped like a rad or calorifier. This way, the system bleeds naturally once any trapped air is bled and purged from the rads etc., and avoids air locks at the boiler. Hence my description of a gradual rise from the heater outlet to the tank is really only applicable to a circuit of similar design. In order to avoid the heated water finding it's easiest route back and forth to the header tank, I position a service valve in the feed pipe and slightly close it in a similar way to a flow control valve.

 

An advantage with this layout is that I can see the coolant flowing through the transparent tank and confirm that the circulation pump is working. The other advantage is that if ever I need to top up the antifreeze level, I can simply pour neat antifreeze into the tank and it will mix readily with the existing coolant. If I were to do this with a single feed header tank this wouldn't be the case.

 

Our system also incorporates a three way valve taken from a domestic central heating system. This electrically operated device allows me to either pre-heat the engine directly from the heater, pre-heat the engine and warm the rads simultaneously, or best of all, heat the rads whilst out cruising from the engine. So really speaking, it's not your average heating system.

 

Another modification is that I have incorporated electrically operated isolation valves in the feeds and returns to the calorifier from both the boiler and the engine. These are normally closed until a thermostatically operated switch, via a relay, energises them to their open position. This design allows both the engine and the heater to reach their optimum operating temperatures quicker, before allowing coolant through the heat absorbing calorifier.

 

Once the engine or boiler are turned off, the relay then reverses the valves to their closed position, thus containing the heated water in the calorifier and avoiding it dissipating through either the keel tank, or the cooling rads respectively.

 

With regard to the switch LED light, I must confess that I only view it as an indicator that something is wrong then look to the control box display. In future, I shall take more notice of it and refer to the manual, or your interpretation for guidance. Thanks for the enlightenment.

 

Mike

Edited by Doorman
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Interesting,

 

I now have a PJ Harworth pressure jet boiler in my new (old) boat. Its the best think I ever fitted absolutely reliable, quiet and works on a fuel circulation setup so is completely self bleeding.

 

Different sport to a Mikuni.

 

Cheers

 

Redeye

Hello Redeye,

 

How big is the PJ Harworth boiler? From what information I could find on the web it appears to be quite large and bulky. I note that it is designed to run on red diesel and is not just a engine pre-heater with a different title.

 

Mike

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Hello Redeye,

 

How big is the PJ Harworth boiler? From what information I could find on the web it appears to be quite large and bulky. I note that it is designed to run on red diesel and is not just a engine pre-heater with a different title.

 

Mike

 

Hi Mike,

 

It is quite big, I installed ours in an airing cupboard next to the shower with a horizontal flue. While it takes a bit of space up it is so much more refined that the unreliable 12v heaters installed in boats i've previously owned. All the components are industry standard 240V and it uses about 6A @24v while running (the heater cycles on and off) which I think is pretty good. I installed it as a bog standard y plan installation using a domestic wilo circulating pump which are super efficient. Its also really quiet in the boat although does have a low roar outside, it's nothing like the noise made by a mikuni or webasto.

 

Hope this helps.

 

Cheers

 

Andrew

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Hi Mike,

 

It is quite big, I installed ours in an airing cupboard next to the shower with a horizontal flue. While it takes a bit of space up it is so much more refined that the unreliable 12v heaters installed in boats i've previously owned. All the components are industry standard 240V and it uses about 6A @24v while running (the heater cycles on and off) which I think is pretty good. I installed it as a bog standard y plan installation using a domestic wilo circulating pump which are super efficient. Its also really quiet in the boat although does have a low roar outside, it's nothing like the noise made by a mikuni or webasto.

 

Hope this helps.

 

Cheers

 

Andrew

Thanks Andrew,

 

The boiler sounds like a proper job and not a dressed up pre-heater, although I don't know where I'd accommodate such a unit on our narrowboat given all of the pots and pans that Mrs Doorman has on here following her dedicated viewing of Masterchef on TV! :-(

 

Mike

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It never ceases to surprise me to learn that so few people know that Mikuni, Webasto etc also make pressure jet boilers and have done for many years, it's probably their fault for not marketing them well enough, they should really as all evaporator heaters have the same drawback. Even more surprising, I fitted a 30,000w Webasto to a barge this week and it cost less than a thermo top 5,000w kit at under £1300 including VAT.

Edited by NMEA
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However presumably they are significantly larger than the equivalent evaporative heater? One of the advantages of the latter is their small size, a major factor in a narrowboat.

Not really, there are no equivelant evaporator heaters of the output provided by most PJs to compare size for size, certainly (for instance) the 35kw is not more than 3.8 times the size of a Thermo 90 (9kw) or seven times the size of a Thermo Top C (5kw). Still a bit biig for narrowboats though and would probably melt the occupants, barges and widebeams is really the place for them.

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OK - and 35kw sounds more suited to an ocean liner than even a widebeam!

laugh.png I have to confess that the boat I installed the 30 kw was 35m, it didn't half get the rads and demisters up to temp quickly,

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It never ceases to surprise me to learn that so few people know that Mikuni, Webasto etc also make pressure jet boilers and have done for many years, it's probably their fault for not marketing them well enough, they should really as all evaporator heaters have the same drawback. Even more surprising, I fitted a 30,000w Webasto to a barge this week and it cost less than a thermo top 5,000w kit at under £1300 including VAT.

I think the answer to your amazement is in the output of the pressure jet boilers. Why, when as a narrowboat or even a wide beam owner, who is in the market for a boiler rated at approximately 5kw, would anyone seek advice about one capable of creating a Scandinavian sauna inside of their vessel?

 

When sourcing a 7 tonne flat bed truck for my business, I discounted all of the available paraphernalia relating to multiple wheel juggernauts.

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I think the answer to your amazement is in the output of the pressure jet boilers. Why, when as a narrowboat or even a wide beam owner, who is in the market for a boiler rated at approximately 5kw, would anyone seek advice about one capable of creating a Scandinavian sauna inside of their vessel?

 

When sourcing a 7 tonne flat bed truck for my business, I discounted all of the available paraphernalia relating to multiple wheel juggernauts.

I was referring to all boat users not just a narrow band, even 60 foot seagoing boat builders where they are really suited seem unaware, the lowest power is 16kw which would be fine even for a large wide beam or small barge whose owners generally also seem unaware. Most wide beams need around 10 to 12 kw for a live aboard comfort when the calculations are done properly which means a thermo 90 or equivalent Eber evaporator at the low end with all the attendant drawbacks, a pressure jet will maintain a heat level and cycle without problems, with greater reliability, lower cost and longer life span, it will also heat a large calorifier quickly for the morning shower. So,yes there is a place for them but they need to be correctly specified.

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