Lincar Wood Pellet Stove advice needed.

[paul8f]

Hi all,

this is my 1st post, so hope I'm asking this in the right place...
Just wondering if anybody has any experience with Lincar stoves (made in Italy).

Need some advice on fitting a pressure switch.
Thanks!

 

[johneh]

Welcome to the forum
Nice looking stoves but never heard of them
Maybe someone on the forum can help
good luck

 

[paul8f]

Yeah, hopefully
I know that I need to connect the normally-closed switch contacts to the stove, but I just can't remember which of the two air-tubes I need to connect to the flue (see photo attached).

Should positive or negative pressure signify a blockage in the flue? On my Perla system, when switch continuity is broken, the stove automatically shuts down.

Any ideas?

 

[johneh]

Should positive or negative pressure signify a blockage in the flue

Depends
Is the combustion fan before or after the vac switch
If it goes fire-vac.switch- fan it would be positive pressure blockage
which means you have a negative pressure stove .
If the vacuum switch is after the fan (in the exhaust ) you have a positive pressure stove
now that's about as clear as mud

 

[paul8f]

Is the combustion fan before or after the vac switch

So, I have the 514S model where the order is as follows:
Combustion Chamber --> Exhaust Fan --> Temperature Sensor --> Pressure Switch --> Flue.

That must mean I have a positive pressure stove, but I'm still not sure what is considered a safety shut-down event.
. . . . If a blockage occurs near the Temperature Sensor due to ash build-up, negative pressure would result at the vac switch (due to the natural draw from the flue). On the other hand, if a blockage occurs up near the cowl due to a birds nest etc, then positive pressure would result.

Please see my (very crude!) sketch attached. Something tells me it should be the P2 option that I connect the air-hose to.
What do you think?

 

[johneh]

being an Italian stove which I have never seen let alone worked on
your guess is as good as mine!!

 

[paul8f]

your guess is as good as mine!!

Not the answer I was hoping for johneh!!

I'm just trying to reason the whole thing out, so here's my thinking:

The ash build-up blockage scenario is probably much more likely than a birds nest.
The general stove layout is surely repeated by many other manufacturers. So, if the stove is a positive pressure design, then negative pressure should be the fault condition. (And even if a birds nest did block up the flue, it would take a long time for the pressure to activate the vac switch due to the long length of exhaust pipe. At that stage a vac switch would probably be pointless as the flame would be starved of oxygen by that stage..??? - No air out means no air in.)

The word 'probably' was used a lot in my last paragraph. My head hurts, I'm going to bed! Hopefully a fresh brain will be able to figure it out! Thanks for the advice.

 

[johneh]

I know of no company that makes a positive pressure stove !!
Within the last 25 years.
Too many places to leak smoke eg door hopper and others
So I can not follow your reasoning
The switch may be a pos pressure switch, not a vac switch
if it says there is a blockage it can be from anywhere intake to the outlet
or the switch is toast.

 

[SidecarFlip]

I know of no company that makes a positive pressure stove !!
Within the last 25 years.
Too many places to leak smoke eg door hopper and others
So I can not follow your reasoning
The switch may be a pos pressure switch, not a vac switch
if it says there is a blockage it can be from anywhere intake to the outlet
or the switch is toast.

100% correct. All negative pressure today. Positive pressure stoves are prone to hopper fires among other issues.

My very first Englander was, that was 30 years ago and yes, I set the hopper on fire too.

 

[paul8f]

The switch may be a pos pressure switch, not a vac switch

I thought a vacuum switch was the same as a pressure switch, but with the little air-hose swapped over to the port on the opposite side of the diaphragm?

If the vacuum switch is after the fan (in the exhaust ) you have a positive pressure stove

... now I'm really confused (as this is the exact order of the parts in my Lincar stove.)

 

[johneh]

It may be a pos pressure switch and if the fan is not working no pressure no pellets
But your stove is still a neg pressure stove fan after fire

 

[SidecarFlip]

Easy way to ascertain if it's a positive or negative pressure stove....

Lift the pellet hopper and look at the lip that surrounds the hopper itself. If it has a sealing gasket on the lip that engages the lid and the lid has a positive latching mechanism, it's positive pressure. If there is a thin gasket and the latching mechanism is not substantial (as in a positive lockdown), it's a negative pressure.

Reason why I say that is because with a positive pressure stove the pellet hopper must be tightly sealed when the stove is operating r you will get burn back into the hopper.

 

[paul8f]

If there is a thin gasket and the latching mechanism is not substantial

Yeah, I checked it out, and it's a very basic seal. Adding this info to the fact that the fan is after the burner-basket all means it's a negative-pressure stove. The stove was bought brand-new in 2013, so it all makes sense now! Thanks for the tip.

 

[paul8f]

So, I've finally figured it out.... (apologies for the ultra-long post, but there's no point in doing a half-explanation in this case...!)

Ok, so the pressure switch (vacuum switch in my case) is not used to detect a blockage, but instead it's actually used to detect the build-up of ash.

The initial error-code on my stove's display showing 'ALAr deP FAil' should have been a warning for me to get the flue and exhaust cleaned. But in my case, it was actually a false-alarm, as it was the damaged pressure switch itself that had an intermittent fault.

How the system works....: The build-up of ash is detected by very clever use of Bernoulli's principle. See the attached picture (taken from from tec-science.com website) showing a demo of the Venturi-Tube in action. Ash build-up in the exhaust-pipe will cause a reduction in the effective internal diameter of the pipe. In this region, airflow will speed up due to the restriction. In turn, this will cause a drop in pressure at this point (yes.. a DROP in pressure... read up on Bernoulli...!) And, if you happen to have a vacuum-switch connection-port at this exact point, then the low pressure will pull on the diaphragm, open the switch contacts, and the stove will correctly go into safe-mode.

To verify this, I did a little experiment. I simulated the build-up of ash in my exhaust-pipe using a custom made insert, which simply consisted of corrugated cardboard and play-dough modelling clay. (Yes... I remembered to remove these flammable materials before re-installing my stove...!) I paid attention to getting a good seal between my bespoke insert and the leading-edge of the exhaust pipe, and also a good seal around the small connection-port protrusion for the flexible switch-pipe. I wanted all the airflow to be directed through the centre of the insert (not bypassing it by going around the outside). Next, I directly wired the exhaust fan to mains power. This forced the fan to run at max RPM, which would be the case during the 'Foyer Cleaning' operation. (This cleaning action happens regularly during normal use of the stove.) Sure enough, when the fan came up close to max RPM, the pressure switch contact opened, and correspondingly, soon after turning off the exhaust fan the contacts closed again. I repeated this operation several times for confirmation. After removing my homemade insert, normal operation was again resumed. This design is ingenious, as you get lots of pre-warning ever before a complete blockage occurs. The only downside is that there are certain conditions where 'fail-safe' operation could be missed.

It was interesting to inspect the design of the exhaust pipe in the Perla. Tracing along from the fan end to the flue end, it transitioned from a rectangular 4536.5mm squared cross-sectional area shape, down to a circular 4185.5mm squared area shape. At the welded junction there was an abrupt change in shape making it more likely for ash to be deposited in the round pipe section where the port connection pipe attaches.

Just to point out a few more details:
(1) In the pressure switch datasheet, pay attention to the mounting instructions. In my case, for reliable operation it was best for me to mount the switch in a secure vertical position, and not at some odd angle.

(2) Some stoves will have their pressure-switch connected to the exhaust with two pipes/hoses rather than just one. Two pipes just means the differential system is used.

(3) Some systems use NO rather than NC switch contacts, so it's worth labelling all wires before disconnecting them.

(4) Ensure that your replacement pressure-switch has the same pressure trip-point rating, max-pressure rating, and the same electrical ratings as the one it's replacing. (Regarding electrical specs, be aware that some are rated for high mains voltage, while others are only rated for e.g. 30Vac).


For further reading it's worth checking out the following blog pages:
https://wowman.altervista.org/how-to-solve-pellet-stove-pressure-switch-alarm-depr-sic-fail/
and
https://wowman.altervista.org/how-to-test-pellet-stove-pressure-switch/

. . . . . . however, in this blog, I would recommend skipping the part advising you to blow compressed air into the pressure-switch ports to clean them out. The delicate internal diaphragm will be damaged, and this is how I ended up in this predicament in the first place...!

Anyway, I hope this helps out anybody having pressure/vacuum switch issues. The world needs more well maintained wood-burning appliances rather than oil/gas/coal ones which are far from carbon-neutral.

Paul.

 

[johneh]

In other words, the stove and chimney were dirty

 

[Mt Bob]

You are overthinking the whole issue. It is a simple on/off vacuum switch. Almost all stoves have them. As a safety device,and to prevent poor combustion.It opens the contacts when the flow is low--
restricted flue,dirty flue, bad,weak or dirty combustion blower, dirty stove, door open,or bad gasket. bad control board,not running combustion motor fast enough.
The switch rarely fails, but air pressure can ruin it, along with vacuum cleaning, leaf blower trick with door closed. Or dropping it.

 

[SidecarFlip]

In other words, the stove and chimney were dirty

That covers it nicely and again for the umteenth time, the stove and the exhaust tract has to be kept clean. Regular maintenance is absolutely necessary, no matter where you live, ash is ash.

Neve blow into the vacuum port as you will rupture the very thin disc that senses the vacuum. Not all that fond of the vacuum port location on the pictured stove but that is only my opinion.

 

[paul8f]

In other words, the stove and chimney were dirty

Well no, you got it wrong. I admit my last post was a bit long-winded, but in a nutshell the issue was the intermittent operation of the pressure-switch.... which was caused by me cleaning it with an air-compressor... which I did as I can't afford to have a professional to come service my stove for me...

You are overthinking the whole issue. It is a simple on/off vacuum switch

Maybe so, but I'd prefer to be as thorough as I can when it comes to a safety device, or anything to do with a unit that could potentially produce carbon-monoxide etc.
In an ideal world, everyone would specialize in a certain role, and weekend-warriors/jack-of-all-trades like me wouldn't be trying to maintain something I don't understand or even have an interest in.
Thanks again for the help.