Mikuni MX60 with Danfoss BTS5 / Danfoss TP5

[jhodgski]

I am just installing a Mikuni MX60 (heater, pumps, control unit, on/off switch). Everything is just about wired up, but I have a couple of Danfoss timer/thermostat units and I'm not sure how they should be wired into the existing circuitry. Can anyone advise? (I have the MX60 operation manual, which contains the wiring diagrams - but it doesn't seem to mention where to put the thermostat/timer.)

Also, would I be better to use the timer unit (Danfoss BTS5) rather than the thermostat unit (Danfoss TP5)? (I ask as I see a few people have had issues with the TP5 causing the Mikuni to cut out.)

Many thanks,
James

PS - Lastly, the thick red and black cables - am I better of wiring these directly to the battery (i.e., for less voltage drop) or should I just connect them to my boat's switch panel wiring? (And would doing the latter be OK for the boat safety examination?)

[NMEA]

Under no circumstances use the thermostat. Wire direct to battery with a fuse. Thermostats and TRV cause excess cycling and increase service costs. Wiring direct to the battery is the way to do it correctly, though wiring to the permenant live side of the isolator is also acceptable if it is easier, this has nothing to do with voltage drop though, if the heater accidentally has the power to it cut whilst still in full burn it can cause damage as it will just stop dead and the latent heat in the exhanger will not be removed by the coolant. The heater should always go through its controlled shut down cycle where the chamber is purged and the circulation pump continues to run for some time untill the heat exchanger cools to a safe level. Heaters are one of the componenst listed by BSS as acceptable for wiring with no isolator.

 

Edited June 3, 2017 by NMEA

[NMEA]

This should be the type of switch you Have?

 

[jhodgski]

OK, thanks, I'll just use the timer.

My switch is a bit different - see attached photos.

[jhodgski]

...the heater says it was made in 1999, so I presume the switch is from around that time, too.

[NMEA]

OK, you will need to do a bit of tracing with a meter, the control switching uses pins 1, 6 & 20 on the control box (ecu) Get it installed and working using the manual switch before you start making any mods, then you will know if you have a correctly wotking unit or not before continuing with installing the timer, you should keep the switch in the circuit along with the timer anyway.

Edited June 3, 2017 by NMEA

[jhodgski]

OK, thanks. Have just checked with my multimeter. It's pin 1 (common) and pin 6 that are used for the ON position. (Pins 1 and 20 for the PUMP ONLY position.)

Would it be best to wire the timer in series with the Mikuni switch (cutting into the yellow wire that comes from pin 6 - so OFF on the Mikuni switch always means OFF) or in parallel (across pins 1 and 6 - so ON on the Mikuni switch always means ON)?

Presumably, the in series would be best (as I think that's how a thermostat would be wired into a house's central heating system), but I don't see any evidence of the yellow (pin 6) wire having been cut before. And the Danfoss came with batteries and screws in it, so I presume it has been integrated at some point...

Edited June 3, 2017 by jhodgski

[jhodgski]

Just discovered that my Danfoss BTS5 timer has packed up and I can't find that model anywhere on the web. Can anyone recommend another battery-powered programmable timer?

[WotEver]

2 hours ago, jhodgski said:

Would it be best to wire the timer in series with the Mikuni switch (cutting into the yellow wire that comes from pin 6 - so OFF on the Mikuni switch always means OFF) or in parallel (across pins 1 and 6 - so ON on the Mikuni switch always means ON)?

I'm only guessing as to what's 'normal' but I'd wire it in parallel. That way the timer controls it normally but if you just want to override it and switch it on then you can do so without messing with the timer. 

[NMEA]

I normally wire in series, timers have an overide switch anyway, its useful to be able to just turn the whole thing off without affecting the timer settings. Not a fan of battery powered timers but a good 12v one is the Heatmiser TM1-N, they take very little power.

 

[WotEver]

6 hours ago, NMEA said:

I normally wire in series, timers have an overide switch anyway, its useful to be able to just turn the whole thing off without affecting the timer settings.

Fair enough

[jhodgski]

On 03/06/2017 at 15:19, NMEA said:

Not a fan of battery powered timers but a good 12v one is the Heatmiser TM1-N, they take very little power.

 

Thanks, NMEA, so can the thermostat be disabled on this and it just be used as a basic timer? I think I would prefer a battery powered unit - do you think the Heatmiser PRT-B would be a safe bet?

[jhodgski]

Re the wiring configuration, I think it's more important that OFF always means off (on the Mikuni switch) rather than ON always meaning on - esp. as there is a bulb lit up when it's in the ON position - and I'm trying to make coming back to a flat battery a thing of the past... So I'll wire up the timer in series.

By the way, I got my MX60 fired up. Started up first time! Very smokey (as I think there must have been a lot of diesel sloshed around the heater during transit, etc.) but once that cleared it ran like a dream.

Does anyone know how much current the MX60 typically draws and how much diesel they use?

Incidentally, I asked Danfoss if they have a replacement for the BTS5 and they said the closest they have is the Danfoss TP5000 Si. Does anyone know if this would be a good option in terms of compatability with the MX60?

Edited June 7, 2017 by jhodgski

[NMEA]

10 hours ago, jhodgski said:

Re the wiring configuration, I think it's more important that OFF always means off (on the Mikuni switch) rather than ON always meaning on - esp. as there is a bulb lit up when it's in the ON position - and I'm trying to make coming back to a flat battery a thing of the past... So I'll wire up the timer in series.

By the way, I got my MX60 fired up. Started up first time! Very smokey (as I think there must have been a lot of diesel sloshed around the heater during transit, etc.) but once that cleared it ran like a dream.

Does anyone know how much current the MX60 typically draws and how much diesel they use?

Incidentally, I asked Danfoss if they have a replacement for the BTS5 and they said the closest they have is the Danfoss TP5000 Si. Does anyone know if this would be a good option in terms of compatability with the MX60?

Absolutely agree on the wiring and one of the reasons I do it that way. Full chat consumption is published as .86l assuming the heater is properly tuned (which it is unlikely to be) and .43l at low setting. Electrical consumption is not published apart from the max of 16.5a at start up but my observations on my calibrated power supply during testing is typically up to 18a during start up and a normal running consumption on high of around 8a. It should be remembered that these things are very old technology (a double edged sword) and therefore not even close to the efficiency of modern heaters. By the way any control timer with volt free switching will work with these heaters.

 

10 hours ago, jhodgski said:

Thanks, NMEA, so can the thermostat be disabled on this and it just be used as a basic timer? I think I would prefer a battery powered unit - do you think the Heatmiser PRT-B would be a safe bet?

It is a simple timer with no thermostatic control and therefore best suited, the PRT-B is a good unit and I use them on PJ heaters which are happy with cycling, I guess you could use one and crank up the temperature.

Edited June 8, 2017 by NMEA

[GUMPY]

Ran my mikunl for years on a timer/stat with the temp set as high as it will go 30C. Only time it was a problem was hot summer days when I wanted hot water but then having it come on to heat the water at 0430 cured that.

[jhodgski]

OK, thank you, both.

Just found a Heatmiser TM1-N (12 volt timer) on ebay for £15, so I've gone for that.

One final question re the MX60, does anyone know how many radiators (i.e., total surface area) it can power? Presumably, it could power two or three square meters of radiators and a calorifier comfortably?

[NMEA]

Best use the kw rating for the radiators, look up the same size and type on screwfix site and get the kw that way ic needs be. The MX60 should be loaded with about 7kw. Ignore the calorifier.

 

[jhodgski]

OK, thanks. Am I right in thinking that if I keep the load below 3.5KW then the MX60 will run in low mode (i.e., 0.43 litres per hour)?

[NMEA]

only after the coolant return temperatures reach the required level. Actually anything below what I wrote earlier is not good for them as it causes excessive cycling so be aware that it will require more frequent decking.

[WotEver]

26 minutes ago, NMEA said:

... be aware that it will require more frequent decking.

Hmmm... checking? Servicing? Ahhh... decoking

[NMEA]

Bloody predictive text

 

[jhodgski]

So I should aim for 7KW of radiators?

[NMEA]

To do it correctly yes, otherwise you may just have well used an MX40 or Webasto TTE, when I'm planning an install the heater is the last thing I specify, 1) How many kw to heat the boat properly? 2) can I get those rads or matrix in and if so where? then choose the heater to power the rads.