Short or long elbows for boiler venting

bphillips921

I have a Rheem 199K Combi-boiler for my radiant system. The vent is 3" PVC pipe with ~50ft (give or take 5ft) of straight pipe, the exhaust has 1 elbow and 3 45's. The intake has 4 elbows and 4 45's. They end in a 3" concentric pipe kit where they exit the house. My boiler allows for an equivalent 100' of vent with 3" pipe. They say to add 5' for and elbow and 2.5' for a 45. Given this, I'm within the 100', but close on the intake pipe.

The boiler has run fine for 2 months, but now I'm getting and ER.12 error.


The guy that came to look at it said my combined length on the intake is too long and that the installer should have used long elbows, that would have made the equivalent length within tolerances.

Also, the boiler still throws the error code with the front panel off the boiler, the service tech said that with the front panel off the boiler is pulling room air as well, which kind of contradicts his vent problem theory.

The boiler also threw a ER.38 code (Abnormal Operation; Memory Error on the
Circuit Board) last week, I'm wondering if that's tied to the ER.12 code and I have a bad board.

What do you guys recommend, is it ok to use a short elbow on venting? Is the venting even my issue?

heathead

Did the directions say to use primer on the pipe joints? Did the installer bevel the pvc pipes before gluing? I know this doesn't answer your question. The manual should give very specific directions on venting.

mattmia2

45s for the offset would be better than 90s.

hot_rod

It sounds like you are close enough to lengths that it should not cause the lockout. You can run them with air from the room if it meets the criteria in the installation manual.

Not sure what they mean by intake air filter? A screen on the concentric cap?

Alan (California Radiant) Forbes

Yes, your vent lengths are below the stated maximums and the fittings that you used are fine and don't need to be long sweeps as the instructions do not say anything about having to use long sweeps. The calc's. on the air intake and vent lengths are 80' and 62.5', respectively.

You're going to have to dig a little deeper on the error codes as you may need some testing equipment, i.e. a manometer, combustion analyzer, volt meter, etc. to figure this one out. Call Rheem at (800) 432-8373. Have your model and serial number available for the technician.

EBEBRATT-Ed

Most install manuals prefer long radius elbows, but if your under on footage you should be fine

You also have to glue the pipe joints. Especially the flue pipe needs glue & primer

You also need to check to see if PVC is allowed for the flue. It is not allowed in some states or by some codes. The only PVC that is listed for use as a flue is IPEX that I know of. Charlotte pipe is not listed for venting

Edited: Ipex is the only PVC listed for venting this appliance.


Also, your PVC is DWV pipe (drain waste and vent) which is not allowed for the flue or the intake

I would suggest your installer read the manual that came with the boiler

hot_rod

Looks like schedule 40 PVC to me? If so Rheem allows that. Cell core is not allowed for exhaust side.
But local codes may have a different opinion.

EBEBRATT-Ed

@hot_rod Yes schedule 40 pvc is allowed (subject to any local restriction),

But the only schd 40 LISTED for flue gas is Ipex as stated on pg 22 (I think) of the install manual.

IPEX is the only PVC I know of approved for venting. In addition it says so (approved for venting) on the ipex pipe

bphillips921

hot_rod said:

It sounds like you are close enough to lengths that it should not cause the lockout. You can run them with air from the room if it meets the criteria in the installation manual.

Not sure what they mean by intake air filter? A screen on the concentric cap?

The unit requires 50 cubic feet of room size per 1,000btu's in order to draw air from the inside. I would need 995 sq ft (10 ft ceiling). My mechanical room is only 300 sq ft.

There is an intake screen on the intake side. It has mesh with roughly .25"x.25" squares. It's clear.

hot_rod said:

Looks like schedule 40 PVC to me? If so Rheem allows that. Cell core is not allowed for exhaust side.
But local codes may have a different opinion.

Correct, it's schedule 40 PVC and it's allowed by Rheem and local codes. It's also been glued.


Thanks everyone for the help. It sounds like the intake length is fine, which leads me back to my original assumption, a bad board. Of course, those are all on backorder...

mattmia2

did anyone do a combustion analysis on this?

Alan (California Radiant) Forbes

Before getting a new board, check your gas pressure with a manometer. That's what the error message wants you to look at.

Also, watch the pressure when the boiler lights off. If it drops more than 1"-2", the pipe size may be too small or the gas regulator at the meter needs to be adjusted or replaced.

mattmia2

The gas piping could be too small and the pressure drops too much when it high fires along with other appliances.

Especially since at high fire it is 200,000 btu/hr. Very few natural gas systems are set up for that unless they were specifically designed for it.

bphillips921

Alan (California Radiant) Forbes said:

Before getting a new board, check your gas pressure with a manometer. That's what the error message wants you to look at.

Also, watch the pressure when the boiler lights off. If it drops more than 1"-2", the pipe size may be too small or the gas regulator at the meter needs to be adjusted or replaced.

Yep, the tech that was here today tested the gas pressure and confirmed it is good.

mattmia2 said:

The gas piping could be too small and the pressure drops too much when it high fires along with other appliances.

Especially since at high fire it is 200,000 btu/hr. Very few natural gas systems are set up for that unless they were specifically designed for it.

It has a 3/4" gas line that is about 10 feet long from the gas manifold to the boiler. I have a 1" line coming in to the house. The gas manifold has a 600K BTU regulator (Maxitrol 325-5L). Here is the manifold, it supplies 8 lines (after the regulator) . 2 fireplaces (not being used), a range (not hooked up), a deck grill (not being used), a fire pit (not being used), 2 furnaces (70K btu each) and the boiler (last line on the left). Even if both my furnaces were at full load and the boiler was at full load everytime the boiler threw the error, I'd still only be at 340K btu. Plus, the boiler only supplies 120K btu for radiant heating, so it would be more like 260K btu max.


I'm also having random issues. For some reason "33℉" is always being displayed on the screen where it's supposed to show the water temp. My Outdoor reset setting had changed and the "low average temperature" setting was at "74℉" outside of the allowed range of options (-4℉ - 61℉), and it gave me a "FILL" warning even though I had plenty of glycol/water(25/75) in it (15.5psi). The boiler also thinks the glycol/water pressure is 27psi but I have 3 separate gauges on my primary loop that show 18psi (I added some glycol/water as I was troubleshooting this. All this together makes me suspect the board is bad.

Everything worked great for 2 months, and it was really cold when it worked. The weather is mild now (30℉-50℉ highs) so it shouldn't be working as hard.

mattmia2

Check the power.

bphillips921

mattmia2 said:

Check the power.

The 110V power? It's good. It's on a dedicated 15amp line. The only thing other than the boiler on that line are the 3 circulating pumps, which draw at most 1 amp.

mattmia2

Not if it is theoretically the right size, if it actually is the voltage it should be.

Alan (California Radiant) Forbes

Has the house been under construction for the last two months? Sawdust, construction debris getting sucked into the boiler? Open up the combustion chamber and look for any occlusions.

bphillips921

Alan (California Radiant) Forbes said:

Has the house been under construction for the last two months? Sawdust, construction debris getting sucked into the boiler? Open up the combustion chamber and look for any occlusions.

Actually, yeah. We have been finishing the basement, just got done framing. All the wood cutting was happening about 35 feet from the boiler. 

How hard is it to open the combustion chamber? I'm pretty mechanically inclined, but should I leave that to a pro?

EBEBRATT-Ed

@bphillips921

your pipe says DWV right on it "Drain Waste and Vent"

It's not the right material.

Pvc used for flue pipe has to be listed.

IPEX is the only PVC that is

bphillips921

EBEBRATT-Ed said:

@bphillips921

your pipe says DWV right on it "Drain Waste and Vent"

It's not the right material.

Pvc used for flue pipe has to be listed.

IPEX is the only PVC that is

It's dual marked pipe. Here is a link to where I bought it.

It is also marked ASTM D1785 for venting


I'm glad you brought it up, because I had to double-check that it was correct.

Alan (California Radiant) Forbes said:

Has the house been under construction for the last two months? Sawdust, construction debris getting sucked into the boiler? Open up the combustion chamber and look for any occlusions.

I took a good look in the boiler, and blew some compressed air inside the boiler cabinet to clean it out. It's pretty clean in there, and the boiler was pulling air from the outside. Plus, the dust doesn't explain my other issues. I'll keep this in mind, but I'm going to talk with tech support about a new board.

mattmia2

So who installed this? Who did the combustion analysis?

bphillips921

mattmia2 said:

So who installed this? Who did the combustion analysis?

I installed the boiler but hired someone to run the gad and vent. A different company came out to check the gas pressure. That different company raised concerns about the intake vent length, but I'm starting to think they did that because all their tests checked out.

EBEBRATT-Ed

@bphillips921

This is the last I will say about this.

mattmia2

I don't see it in the instructions, but modulating boilers like this are usually sensitive to exact mix of gas and vent lengths to have the right mixture and need to be adjusted with a combustion analyzer.

hot_rod

EBEBRATT-Ed said:

@bphillips921

This is the last I will say about this.

I don't disagree with using a listed product. That Ipex is all but impossible to find at suppliers in the US. PP is more common, but it is backordered all over the place.

EBEBRATT-Ed

@hot_rod

I agree that IPEX may be hard to get. Around here (MA & CT) Independent Pipe had it in stock. I don't know about other parts of the country.

My understanding is that PVC is basically not allowed anymore unless the boiler MFG specifically names a listed PVC (like Ipex) that can be used. At least in MA on a replacement you are supposed to rip out the exposed PVC and can reconnect to the existing PVC if no signs of overheating.

Everyone is going to PP

hot_rod

EBEBRATT-Ed said:

@hot_rod

I agree that IPEX may be hard to get. Around here (MA & CT) Independent Pipe had it in stock. I don't know about other parts of the country.

My understanding is that PVC is basically not allowed anymore unless the boiler MFG specifically names a listed PVC (like Ipex) that can be used. At least in MA on a replacement you are supposed to rip out the exposed PVC and can reconnect to the existing PVC if no signs of overheating.

Everyone is going to PP

The only bell that IPEX rings around here is Kitec memories:)

There have been issues with some of the PP, gasket leaks, sagging pipe. The 230° rating is cutting it close. Flue gas temperature limit switches are 210°. Makes one wonder how hot the flue can get after a tripped limit?

167F is the typical operating temperature limit on Euro boilers.
Remembering when German mod cons first arrived and they asked why we need 180 operating temperatures.

The first batch of high temperature venting was a lawsuit disaster, stainless never took off for various reasons Hopefully PP can work and last as advertised.

GGross

EBEBRATT-Ed said:

@hot_rod

I agree that IPEX may be hard to get. Around here (MA & CT) Independent Pipe had it in stock. I don't know about other parts of the country.

My understanding is that PVC is basically not allowed anymore unless the boiler MFG specifically names a listed PVC (like Ipex) that can be used. At least in MA on a replacement you are supposed to rip out the exposed PVC and can reconnect to the existing PVC if no signs of overheating.

Everyone is going to PP

@EBEBRATT-Ed
In Michigan you can vent with any material that the equipment manufacturer approves, even if the vent manufacturer does not approve it (solid core sch 40 pvc for example, or in the case of some furnaces even cell core) They are changing it soon to include vent material with the proper UL listing even if the manufacturer does not approve the material. PVC is still widely used even though we all know it doesn't pass the tests. And I certainly wish everyone were going to PP here, I have been banging that drum since I started in the business