Lochinvar KBN 285

Steve Whitbeck

Found something I don't like.

The install manual says that the manual reset limit can be set to 210* but mine will only go to 200*.

the other problem is with the outside tamps at 0* here the boiler is running at 100% and when it shifts over to heat the indirect water heater it wants to hit the auto reset high limit set at 190* ( can't go any higher or it trips the manual reset limit at 200*) ( I have the boiler limited to 40% firing rate in indirect mode)

This wouldn't be a problem if when it shut down on auto reset it also stops the boiler pump. since the water piping all comes off the bottom of the boiler it will sit there for quite a while before it turns back on.

Is there a update program to fix these problems?

furnacefigher15

flow

"The install manual says that the manual reset limit can be set to 210* but mine will only go to 200*.

the other problem is with the outside tamps at 0* here the boiler is running at 100% and when it shifts over to heat the indirect water heater it wants to hit the auto reset high limit set at 190* ( can't go any higher or it trips the manual reset limit at 200*) ( I have the boiler limited to 40% firing rate in indirect mode)"



Sounds like a flow issue through the indirect, or maybe a heat transfer issue.

BoilerGuy

Moving the Heat

Is it safe to assume you have the boiler set point for dhw at 180 or less, There is no reason to set a condensing boiler higher.

If so I would suspect low flow through the DHW coil, most dhw tanks with a coil need a high head pump to get the required flow, If the coil is scaled up from poor water conditions that will reduce heat transfer also.

BoilerGuy

Moving the Heat

Is it safe to assume you have the boiler set point for dhw at 180 or less, There is no reason to set a condensing boiler higher.

If so I would suspect low flow through the DHW coil, most dhw tanks with a coil need a high head pump to get the required flow, If the coil is scaled up from poor water conditions that will reduce heat transfer also.

Steve Whitbeck

Flow

Flow is not the problem - The indirect can't flow 29 GPM - That is why I have the boiler limited to 40% firing rate in indirect mode. The problem is when the boiler at 100% space heating mode shifts to indirect mode and the burner drops to 40% firing rate.

The heat in the combustion chamber raises the boiler temp faster than the indirect can absorb it. It then hits the auto reset limit and shuts down. AND then the pumps stop ( WHY ).  It then sits there untill the heat exchanger cools enough to come back on.

Landry Mechanical

ahl

ahl

I ran into this issue on a smaller whn85, I turned the curve down so it

would only go up to 170 at 0, there definetley seems to be an issue with

pump changeover on these sometimes. I don't like how the pump shuts

when the AHL is hit either it seems kind of pointless and makes the

problem worse

meplumber

It is flow.

Those boilers are extremely flow critical.



What size circulator do you have on the DHW? This is a 285,000 btuh boiler, if you drop it to a 40% firing rate for DHW, you are still putting out 114,000 btu's. Check your pump curve to make sure that you have the right circ on it.



The second question is why on earth are you banging this boiler off that high of a temperature. You will kill it prematurely. If you were gonna run the thing at 190, then you should have chosen different equipment. This is a mod/con. With out condensation to wash the Giannoni Exchanger, it will plug quickly and exchanger distortion is the result.



I had an engineer spec one for similar temps. Problems started showing up after year 4. He wouldn't listen when we tried to tell him. Now the facility is pissed that they are having to replace one boiler and will most likely have to replace the other 3 soon.

Steve Whitbeck

Meplumber

I put the wrong m# in the tittle. But I did say that it is the wall hung model. It is the new fire tube heat exchanger.

I Install Mod/Con's for a living. I have the right size circs. UPS26-99's ( what the manufacturer suggests) You can't flow 29 GPM through an SSU 60.

This house has 4 air handlers, some in floor and and the indirect. I have the air handlers set to reset with a max temp at 5* of 180*, The in floor is also reset to have 120* at 5* ODT. There is a mixing valve.  The indirect is set for 180* boiler temp at 40% max firing rate.

Steve Whitbeck

pump shutting down

Is there a fix for this. I have never seen a boiler shut the pump down when it hit limit.

Is there a fix from Lochinvar?

---

I can fix this by installing a time delay relay to keep the pump running for 30 seconds after switch over.

It just seems I shouldn't have to - this is there mistake not mine.

Steve Whitbeck

Lochinvar program

Smart system program.    Is anyone else having lock up problems?

It wants to glitch constantly.  Running Windows 7.

meplumber

Missed the wall hung part.

Sorry Steve I missed the wall hung part. I was looking at the model number only. The larger btu floor model Knights are extremely picky on flow. That is what I was basing my response off of.



I apologize for my tone. I had just gotten off the phone with a sub that is dragging his feet and driving me nuts.

Steve Whitbeck

No offence taken

Meplumber - No offence taken.  ---   I used to install LOTS of Munchkins. The local rep gives out my name as the guy to fix Munchkin problems.   --- Munchkin has gotten a bad rap due to bad installs. I have to repair systems installed by others all of the time.

tim smith

Re WHN boiler and bumping limit

I was just pouring over the service manual on the WHN boiler last night. Having a little problem with reset curve and not getting change in temps when parameters set. Any way, while looking over  the service manual, I think there is a setting to allow both pumps to run for so many seconds before full switch over to dhw or c/h. Look over the service manual closely. I am not 100 % on this but my mind thinks pretty sure. This would cure the residual heat issue if this is correct. Good luck.  Ps, I have 4 of the whn 285 installed.  1 399, couple 199s and don't remember what others off hand. Pretty good little boiler but I am getting a fair amount of noise off comb air pipes which usually go out different location than the flue which I normally chase up the chimney. 

 See attached page from manual, see lower right paragraph highlighted. This should fix your problem. Tim

Steve Whitbeck

Tim

That setting is so that you can run the domestic hot water heating at the same time as space heating. In the normal setting they run seperate with domestic water heating as priority. In the zone setting they can both run at the same time.

I just changed it to run at the same time untill I can get an answer from Lochinvar..

Why would a boiler manufacturer design a boiler control program to shut down the pumps if the boiler gets too hot.    ---    That would be like having the furnace shut the blower off if the furnace overheated.

Mark Eatherton

Sensor or thermostat on the tank?

If you use a sensor (10K) on the storage tank, the boiler control can "see" how close it is to meeting the set point, and if properly programmed, the boiler will modulate down to MAINTAIN the maximum set point.



It seems that we, as an industry believe that all conventional indirects REQUIRE 180 degrees F to get any hot water out of it. I'm rarely seeing more than 160 degrees F on my own systems during a call for DHW.....



THe trick to programming is to give it some "room" (AKA offset in the manual) If you give it a 20 degree offset, then it has 20 degrees F to slow down and modulate to the load and not hit the high limit. Hitting the high limit isn't a good thing to do. With a conventional bang bang tank stat, the boiler cant see rate of rise, and approach temperature so it keeps the pedal to the metal until it runs into the brick wall. All of my boilers use a sensor for controlling the DHW, and they always modulate to the load.



Mine also have a time delay in their programming, which unless there is a simultaneous call for CH and DHW, the pump runs for X minutes after burner cessation. Maybe my boilers never hit their high limits...



ME

Steve Whitbeck

Using the sensor

The problem is not when the boiler is space heating or water heating BUT when it is space heating AND shifts to water heating. In cold weather the boiler is running at 100% and max temp ( 180* ) Yes it is ODR. The boiler doesn't slow the burner fast enough and it overheats. Cleaning the indirect may solve 90% of the problem. It is 18 years old. Thought I might try cleaning it but the customer can't have the hot water down all day if I use vinegar. If I use calcisolve it WILL clean it in a few hours BUT may cause leaks in the stainless steel tank.

tim smith

Lochinvar whn

I swear when I was reading through service manual that they had a delay on off for pumps when switching from heat to hw and vise a versa. But I may have been dreaming. That would cure to overheat problem if burner shut down and then delay pumps for 30 sec or so to switch.

Steve Whitbeck

Tim Smith

The setting you are talking about is the amount of time either of the pumps runs on after a call for heat or hot water. The problem is when both modes are on. and it shifts from one to the other. There is NO pump run on from the previous mode. The boiler just shifts over to the new mode and shuts off the other mode's pump.

Gordan

So... I hesitate to suggest this... but.

I'll put it out there anyway. If you were to wire the boiler pump to the system pump terminals on the Knight, it would give you more control over its behavior. If I'm not mistaken, it's the boiler pump that cuts out when DHW call comes on (unless you've got "DHW locks out system" setting set to on.) You could control the system pump through other means (or control both pumps from the same Knight contacts via a relay, or even wiring them in parallel if total amps don't exceed the rating on those contacts.)

Steve Whitbeck

Temporary fix

UNtill I get a means to fix this problem I set the Knight to just treat the indirect as another zone. The boiler will run the space heating and indirect pumps at the same time if both modes are calling.

Mark Eatherton

Something's not right...

If it were me, I'd grab a cell phone and call the factory help line and have them walk me though the programming sequence to make certain that all parameters are where they are supposed to be before I replaced the board. It just takes one parameter being turned to 0 or off to throw a whole bunch of curves into mayhem.



I've been working with their controls since they came out, and I know a LOT, but I don't claim to know EVERYTHING. They keep adding features :-)



ME

Steve Whitbeck

Mark

I havn't changed any of the pump settings. The pumps and boiler run perfect untill it hits either limit. I also called MY rep last monday. He called me back on Wednesday. he is going to call the Factory.