Lochinvar mod/con boiler question

kalex1114

@keyote oh I agree. For now i'm in a decent mood. But it won't last for long

kalex1114

Leon82 said:

> @keyote said:

> isnt PVC bad for HX



They do want 7 feet of cpvc initially if I recall correctly

hmm i don't know if i have that much. Do elbows count as more?

keyote

He means at least 7 feet of cpvc before any PVC because it is alleged to be not ideal PVC runoff into boiler.I dont think its really really bad but thats why boiler used the grey CPVC on the flue that condensates runs back into boiler.
Theres another requirement that both intake and exhaust are at least 12' equivalent feet" which means yes elbows count as i think five feet and 45 count as three, plus straight,check your manual. Is it 2"" or 3'' pvc.

plumbbob

temp probe is usually installed when 2 units are cascaded together

mikeg2015

The best system has both comfort AND efficiency. But it takes getting flow and temperature to work together. The best reset curves adapt to demand. But that takes a lot more logic.

What I haven't seen mentioned that return water temp dramatically impacts temperature. If your return temp isn't below 140F, you wasted your money on the Mod Con and might as well have gotten a cheaper, longer lifecycle (last 2x as long with fewer issues) high mass cast iron boiler. This is largely misunderstood by my HVAC professionals and sadly, I think some engineers that design these system don't understand this.

For reference...roughly (Lochinvar publishes inefficiency curves for the knight) 130F is about 88% efficiency, 120F is 90%, 110F = 92%, 100F = 94%, 90F = 95%, 80F = 97%.

This is just a ballpark. efficiency is better at lower firing rates because approach temp of the heat exchanger (difference between the flue temp and return water temp) is lower. It varies from about 1-5F. Flue temp are limited to 160F, so is return water gets over that, it will increase secondary air to cool the flue gases (dilutes it with more air and efficiency drops even further. Could drop down to around 85% when your running 180F water temps. Again, same as a cast iron unit.

Personally, on new construction I would have used a combination of hydro air (hot water coil in the air handler) on a very low airflow and radiant (fin tube is a great choice as a cost compromise over radiant floors) You need air movement for an HRV on tight modern construction anyway. Most new construction lacks lack adequate ventilation for the first 15 years until door and window seals start to wear out.

keyote

I get all that in fact I started by saying you want your modcon oversized in the sense that its most efficient at low mods. That said where would you put the sweet spot in DT vs RWT in a radiant system? would you widen the DT more than 15 to lower the RWT?
while Im at it would you aim for constant run or say 18 hrs runs and off at night in a radiant like you might in finn tube or euro cast panels?

kalex1114

Monitoring station has been setup
Not idea position but it will do for now


Version 2.0

kalex1114

Hello All. Here is an update. Hvac company managed to get explosion and rumbling issues fixed. They brought a lochinvar rep in and they replaced gas valve with new one. With new gas valve in place explosion happened only once next day and hasn't happened again. Its also running smoother at least to me.

I ended up attaching few weather strips to the metal covers and that got rid of the transformer buzzing sounds

2nd issue of execisve cycling - hvac company can't figure out. Lead tech and lochinvar rep spent about 3 hours here trying to solve it. They came up with an idea of using 0 offset and enabling ramp delay and that made it worth. I had to go back to my previous settings. I have to say I love the usb port on the lochinvar. Save/Load settings file in few seconds. Reboot and poof its done.

While they were troubleshooting I hired a hvac designer to do proper heat/cool loads for my house.
According to his findings this is what i have:
Heating Load = 31,124 BTU/HR at 15’F and 70’F inside.
Sensible Cooling Load = 28,767 BTU/HR at 90’F and 74’F inside.

He recommended new curve and I applied it. it is now 7f @ 145f and 68f @ 105f. He thinks that 135f at 15f should be sufficient for longer boiler burns.

I want to thank Boone for helping me out behind the scenes. I learned a lot from him and others here as well.

Now I just have to solve the annoying way lochinvar behaves. So far what I noticed is that when there is SH call and it cold starts it shoots up over the system temp then blocks itself for 1 minute. Refires again and sometimes on 2nd or 3rd refire it works perfectly. From what I noticed if it ignites during specific range of temps where system, inlet and outlet are close together it modules and runs for a while. If outlet, inlet and system have a big difference it tends to overshoot and then gets blocked. I'm thinking that programming code of how its suppose to behave is not that great. Antoher thing i noticed is that when there is dhw call and SH call is waiting, right after switching to SH call it still fires to 100% and gets very quickly blocked even though the outlet temp is at around 187f which is what i use for DHW side

Will update with more info as it gets colder.

Alex

Leon82

So your boiler is 3x oversize. Enable the ramp delay and in the 6th slot put 50% .in1-5 you can rise gradually to 45%

This will let the water rise at a slower rate.

keyote

Thanks for update Kalex. Im having both your noise problem and the not being able to maintain a modulation you describe at the end.
I was sure i had solved the rumbling when i discovered a rubber washer meant to seal a ball float in condensate trap had come unglued and might be preventing the ball from re sealing against the cond drain outlet when there was not sufficient condensate to flood it sealed. However I since found the noise continues since repair. since i siliconed the rubber gasket washer in place.

Im stumped I have had the entire flue apart twice from the bottom and the top nothing is blocking the exhaust yet its coming out this condensate trap during the noise.I am now thinking theres is this short window where there's just enough condensate to raise the ball enough to let some flue gas escape, but not flow freely so it sort of rumbles as the ball struggles to either float up and get flooded or drop down and seal up. the fluctuating back pressure in the flue reverberates back up into the combustion chamber and the flame can dance a bit as this happens. since the HX and burner was cleaned I have only witnessed it once, but heard it several times and the flame still vibrated but remained nice and blue. However my theory would suggest that all units would do this, but you are the only one who seems to positively have a similar problem.

I finally recorded it but noticed it doesn't sound the same as it does in real life, on the recording, and then remembered thinking your recording of it didn't sound the same as my noise so assumed maybe you had a different problem. Maybe a description instead of recording.
Mine lasts sometimes only a second usually several seconds occasionally maybe 8-10 seconds. Its deep and hollow sounding, pulsing. Maybe others don't notice because a condensate neutralizer kit might muffle it. i haven't installed one yet.

I just cant understand how the flue gas would not prefer the 2" flue over trying to work out through the condensate line. especially since theirs the two rubber hoses cond hoses into trap it could release its pressure back up the flue. On the other hand, this idea of simply having a free floating plastic ball over the hole while a fan is blowing flue gas does seem a bit like asking for trouble. It work in theory when i had it apart i held my finger over the small hose tap and blew into the intake and the ball does seal when there insufficient cond to float the ball up off the discharge opening. But what about when their just a trickle if condensate coming in and the fans blowing?

Leon82

The ball it for a dry trap. The water in the trap makes the seal as far as I know

keyote

Thanks leon I edited because figured i wasnt being quite clear. Yes when the condensate is below the bottom of ball it seal fine and of course when theres enough condensate to lift the ball up a bit it must be self sealing with the condensate. i just think it must be the transition period where its making the ball dance. Because i am absolutely certain that air/ flue gas is coming out the condensate when this happens. what i can figure out is why it wouldnt be happening to every boiler with this set up

keyote

Lochinvars retarded response was i probably needed to prime the condensate trap

Boon

@keyote said >>> i am absolutely certain that air/ flue gas is coming out the condensate when this happens.

If that is happening then you are going to kill or poison someone. You need to stop running that thing and get a pro out there.

keyote

Yes Boon Im well aware of the danger

Leon82

> @keyote said:
> Lochinvars retarded response was i probably needed to prime the condensate trap

Filling it is step two in the manual

kalex1114

Leon82 said:

So your boiler is 3x oversize. Enable the ramp delay and in the 6th slot put 50% .in1-5 you can rise gradually to 45%



This will let the water rise at a slower rate.

Yep that is what I'm thinking of doing next. They setup it up from 25% to 100% but what i noticed weird is that in first ramp delay it never fired over 14% never got to 25% then in 2nd ramp delay it went to about 27%.

It still doesn't explain the screwed up logic of the code. It seems that its not reading outlet, inlet and system temps correctly or doesn't know what to do with them. very strange. Also seems that there are no software updates available for it either since 2015

Gordy

Have you read the I/O manual? Did the installers leave them?

keyote

leon
The boilers been running for a year, it can fill a 5 gal bucket with condensate in a day during heating season, so its always topped off (dhw indirect year round),
But yes to be clear at commissioning it was "primed" its got a properly sloped drain with a vent tee, Just not a neutralizer yet.

But if you think about it its not a pump it self primes, and continues to "prime" as it operates. But yes when i opened it up each time to see what's going on it had condensate up to the rim of the discharge opening, and its clean no sludge at all.

I think a better question is what prevents it from discharging flue gas along with condensate when the ball is raised. If you think about it the level only has to rise very slightly to raise the ball. That wont be enough fluid above the rim to flood the 3/4" opening if its simultaneously got positive air pressure. and why wouldn't it have positive pressure its a continuation of the flue/HX having a fan pump air through it. The answer of course because they sized the fan and vent so the path of least resistance is up and out. But that aint happening.

Of course we are going to assume all the things like the static pressure and the weight of the ball and flue pipe friction, fan speed, gas pressure, was all taken into consideration when float was designed. and yet someone explain to me how if it is a good design it could possibly push air out the condensate line?

At first I thought well maybe if the flue were blocked it could build excess pressure, But besides the fact that its been taken apart three times and the flue and HX are not blocked, and when its running it discharges flue gas out the flue perfectly fine and strong no matter at low modulation or high mod, that blocked flue theory doesn't really make sense.
first because, why after a few seconds it operates fine at all modulations, and why doesn't it happen every time, and It only happens when its starts a call.

Imagine for a second the cond water. it finished its last call and the last of the condensate has drained out to the level of the rim and the ball has resealed.then it gets a new call and starts to condensate again just a bit at first, it barely raises the ball and all around the opening the cond pours over the edges of the rim, but theres a big whole in the center not flooded and the air pressure also pours through there. the air and condensate mix as the ball bounces as the new condensate ramps up, and it makes the sound and i can feel air out the cond vent.

Also when I had it apart i tested could just air dislodge the ball it cant you can blow hard into into it and the ball keeps it sealed. It needs to be raised just a tad with water and i think the air rushes through with the water. But why only at start up? I dont think even once into the cycle it has enough condensate to flood the opening. It must be designed to seek the vent even if the balls floating a centimeter.

If its not an inherent problem with the design of the condensate float seal, then one of the parameters they used to design it is off. My flue is the correct size and length. Its actually just long enough meaning it has the least possible friction and back pressure. Its clear all the way from the combustion chamber through the trap. assuming no one else is having this problem then its not the design and that leaves the fan and maybe the gas valve. I suppose its possible they are somehow exceeding predicted values for the float system. Lochinvar claims they dont have a problem with their gas valve I think they are in denial. But i gave them the benefit of the doubt and have first cleaned the HX, burner, ignitor, flame sensor, and pulled the venting and condensation tubes apart several times. Im now going to insist they get a rep down here monday on their dime.

Leon82

When the water reaches the top of the outlet it exits as new water comes in. 4drops in 4drops out the discharge

keyote

Yeah 4 drops doesn't fill a 3/4" pipe so what must be supposed to happen is a tiny little circular waterfall all around the opening and a big empty hole in the center of the round waterfall, but the waterfall is floating the ball so sealing 360 degrees a couple molecules over the rim. But now for some reason obviously this tiny film of a 360 waterfall doesnt hold back the air pressure. My guess is there shouldn't be any positive air pressure strong enough to push past even 4 drops- and yet it does and yet the flue is clear.

kalex1114

Gordy said:

Have you read the I/O manual? Did the installers leave them?

Me? They did leave them. I read it few times