maximum horizontal vent length after penetrating outside wall?

Bill751

Finally getting around to installing the HTP UFT I bought a while back. Due to the unconventional building design and location of the boiler, venting is going to be more of a challenge than the last mod con I did. I know at some point over the last few years I read somewhere the maximum horizontal vent length for a mod con once it penetrates the wall and is outside. I cannot remember and cannot find this information stated anywhere now. i'd prefer to sidewall vent but i have an excessive roof overhang in the only location I can side vent. The HTP manual says I need to be one inch below the soffit for every inch of roof overhang. So the question remains how far is too far? definitely don't want the condensate freezing in the vent.

I'm hoping I don't have to vent out the roof but even that has it's own set of problems due to the building design. it would be hard to get above the roof line without running the venting up the underside of the rafter at least some distance to get closer to the roof ridge before penetrating the roof. I found one link on this site for venting a a Buderus mod con though an unconditioned space.

https://www.bosch-climate.us/files/201001220052570.TBG-5_Guidelines_for_venting_through_an_unconditioned_space.pdf

They're saying insulate the venting if ran in an unconditioned space. It's been quite some time since I've done serious research on this, but correct me if I'm wrong. I believe everything I've ever read said to never under any circumstance insulate Polly or PVC. I'm planning to run Polly by the way.


Hopefully I can run exposed horizontally further than I'm thinking and just side vent.

lchmb

http://www.htproducts.com/literature/lp-542.pdf page 32 on discusses the proper venting of the HTP. It does require a 12" stand off minimum from the building so not sure how far your going. You can either use a 45 pointed up or a 90 straight out to help drive it away from the building. Make sure to get your separation for air intake... reference another boiler manual..that's specific to them..I wouldnt do anything without talking with tech support from HTP and wouldnt insulate pvc venting..

Lance

Every mfg requires you follow their instructions. Our code references this also. Including the type material. We have found many that used cell core on exhaust to now be excluded as it overheats and gets soft. The major point is not let the flue gas into the house once you get it out.

Bill751

lchmb said:

http://www.htproducts.com/literature/lp-542.pdf page 32 on discusses the proper venting of the HTP. It does require a 12" stand off minimum from the building so not sure how far your going. You can either use a 45 pointed up or a 90 straight out to help drive it away from the building. Make sure to get your separation for air intake... reference another boiler manual..that's specific to them..I wouldnt do anything without talking with tech support from HTP and wouldnt insulate pvc venting..

Thanks. I did read that in the manual, but nowhere does it state a maximum length after penetration. I've looked at a few other manuals as well. the problem is the soffit is about the same height as the ceiling and the ceiling in this room very low. couple that with the huge overhang and unless the vent is unusually long, there is no way to meet the " 1" below for every 1" of overhang" stated in the HTP manual. I was hoping there was a general rule on this. I'll check with HTP.

NY_Rob

HTP doesn't specify a max outdoor length in the current manual, but they do specify a minimum horizontal separation of 12" between the outboard edge of the intake and the edge of the exhaust pipe.

They also note in bold "DO NOT thermally insulate the exhaust vent or intake pipes."





The "Snorkel" style exhaust seems to work well as the steep pitch stops water from collecting and freezing. We had single digit temps here for days at a time last week and I saw zero freezing in/on my snorkel exhaust.

unclejohn

They may have a separate venting manual in addition to the installation manual. When in doubt call the manufacture.

Bill751

Lance said:

Every mfg requires you follow their instructions. Our code references this also. Including the type material. We have found many that used cell core on exhaust to now be excluded as it overheats and gets soft. The major point is not let the flue gas into the house once you get it out.

Thanks. I'm not sure what the code is for that around here. I do know that the local contractors generally don't seem to care much about code. One look at the local installs or talking to them during estimates make that very obvious. No one in my area from the wall either. we don't have a lot of mod cons around here and the ones I do see vented are not done correctly. I'm going to check with HTP

NY_Rob

The maximum outdoor length spec (that we can't find) is to prevent possible freezups... are you in a cold weather area?

Bill751

NY_Rob said:

The maximum outdoor length spec (that we can't find) is to prevent possible freezups... are you in a cold weather area?

Yes sir I sure do, that's exactly why I was looking for that information. Was below zero here last week! How's your system treating you? I think it's been close to a year since I've been on this site. I bought everything last last Jan/ Feb when we were discussing it and it's been sitting in boxes ever since. Unfortunately I went back to working out of town so life/ projects get put on hold.

I did a snorkel on the Freestyle I put in the basement last year to make sure I was well above the snow. working nicely. Unfortunately the location I have for the HTP has a number of challenges and the updated UFT manual just added another. I did not see anything in my manual about the 14' equivalent minimum vent length. Right now I'm hitting 12' equivalent. I think I'll be able to make it over 14' by adding another 90 elbow ( that I don't need) and changing the routing slightly. That elbow will give me another 5' equivalent. I have a very limited location to mount and limited area to vent. The ceiling is only 74 1/2 inches high and the soffit of the 4' roof overhang is the exact same elevation as the ceiling. So I have to mount low and exit as low as possible. Lucky for me HTP said the exposed horizontal maximum was 3' but if I was venting with 3" I could go another 1 foot, providing I have proper pitch of course. I asked what they would recommend increasing the pitch to but they did not specify. They just said "slightly greater" I am venting with 3" so the 4' maximum will be enough for me.

Bill751

unclejohn said:

They may have a separate venting manual in addition to the installation manual. When in doubt call the manufacture.

I did end up contacting HTP. They have an updated manual which has some additional information on venting. The revised manual did not state what I was looking for, but tech support did answer my question. 3' maximum for 2" vent and 4' for 3" vent with a "slightly greater" pitch. They did not specify if their requirement varies by location but I did provide my zip code in the initial email.

EBEBRATT-Ed

Most codes on Mod Cons refer to the mfg instructions.

hot_rod

I think the support of the horizontal after it leaves the building will be important, Is there a way to hang it to protect from snow loading, for example.

Bill751

EBEBRATT-Ed said:

Most codes on Mod Cons refer to the mfg instructions.

Makes sense it would be that way. I know I'd feel much better following a reputable manufactures guidelines than local codes.

Bill751

hot rod said:

I think the support of the horizontal after it leaves the building will be important, Is there a way to hang it to protect from snow loading, for example.

Good point, however in my case the snow won't be a problem. I haven't had a chance to get back to the venting yet so I don't know the exact termination point. I do expect it to be protected under the roof though. Not under by much, but short enough to avoid problems with the snow/ice. otherwise I could see that being a serious issue with snow or ice coming off the roof onto or over the end of the vent. For stability in excessive wind I plan to use more supports per feet than the minimum required. Better safe than sorry.

NY_Rob

Bill751 said:

EBEBRATT-Ed said:

Most codes on Mod Cons refer to the mfg instructions.

Makes sense it would be that way. I know I'd feel much better following a reputable manufactures guidelines than local codes.

Maybe on old-school products they're knowledgeable, but on current mod-cons HTP "tech support" has proven to be close to clueless on several occasions. Speak with three different support techs... you get three different answers.

When discussing the HTP UFT-80W mod-con, one HTP "tech" told me "it can't keep running all day without hitting setpoint", "we have a proprietary algorithm that will keep raising the SWT till setpoint is met" when I said 'isn't that the point of a mod-con to keep running all day just keeping up with heatloss?' he said, "no, it isn't designed to run all day like that". This was the same HTP tech that didn't use a ODR sensor on his HTP mod-con at home and just ran it at 180F SWT all year long

hot_rod

Why would a horizontal run outside the building be any different that through an attic for example? As long as it is supported and protected from the elements outside??

All plastics break down in sunlight occasionally. We used to put a coat of latest paint on solar insulation to help keep the UV at bay. It also blends it in to the roof color better.

We worked with an architect that insisted all the plumbing vents thru the roof were painted to match the shingles. It really did help hide the bright white PVC.

Bill751

NY_Rob said:

Bill751 said:

EBEBRATT-Ed said:

Most codes on Mod Cons refer to the mfg instructions.

Makes sense it would be that way. I know I'd feel much better following a reputable manufactures guidelines than local codes.

Maybe on old-school products they're knowledgeable, but on current mod-cons HTP "tech support" has proven to be close to clueless on several occasions. Speak with three different support techs... you get three different answers.

When discussing the HTP UFT-80W mod-con, one HTP "tech" told me "it can't keep running all day without hitting setpoint", "we have a proprietary algorithm that will keep raising the SWT till setpoint is met" when I said 'isn't that the point of a mod-con to keep running all day just keeping up with heatloss?' he said, "no, it isn't designed to run all day like that". This was the same HTP tech that didn't use a ODR sensor on his HTP mod-con at home and just ran it at 180F SWT all year long

Well that's good to know and disturbing all at the same time. This seems to be the norm these days with most companies I've dealt with in general ( non heating related) but I was hoping a company that makes products that could potentially kill people would have well trained techs. hopefully they are correct on the 4'. seems reasonable with a good pitch. I'll keep an eye on it. Been so long since I researched this boiler I'm having to re familiarize myself with it. I can't remember off the top of my head if it has a pressure switch for a blocked vent. I'll have to look into that. if it doesn't, it sure wouldn't hurt to have one on it.

Bill751

hot rod said:

Why would a horizontal run outside the building be any different that through an attic for example? As long as it is supported and protected from the elements outside??

I'm not sure why you're asking, wasn't sure if I said something to suggest that. I don't think there would be a major difference, or from the manufacturer standpoint any difference at all. In real world applications though there may be a slight difference due to the wind hitting the outside vent verses a vent in the attic which would be protected from the wind. Excessive wind would steal heat from the vent pipe potentially causing it to build ice easier than a vent in the attic. My prior comment in the previous post about the wind was just a concern of storm damage blowing the vent sideways. I don't believe the minimum requirements per foot suit me with 4' of pipe in 75 mph wind. it would probably be OK, but I'll likely add an extra support to be safe.

In my case if I would have vented through the attic and ran up the underside of the rafter to get to a suitable penetration point, the pipe would not really be horizontal. the pitch would be far greater than say a 4' side vent. Here again the manufacturer may not differentiate between the two in their recommendation ( or maybe they would) but surely the truly horizontal properly pitched side vent would be far more susceptible to ice than say a 5/12 pitched pipe in the attic.

hot_rod

I doubt a manufacturer would have a suggestion or recommendation for this type of application unless they had tested it and confirmed it was workable. But as you mentioned, so many variables to consider with outside venting.

I know there is an engineering company that will design and approve unique venting. They do high rise buildings and buildings that are close to one another and need plume dispersion. Some of the boiler manufacturers refer to them for special application venting.

JUGHNE

There was a recent posting of a frozen ModCon discharge going thru the roof. There was some horizontal piping in the cold attic that had more than enough pitch to drain back under normal circumstances. But as time passed and the ice bank grew it eventually plugged a 3" pipe.

I suppose that horizontal run could have been a 45 or 60 offset, though off-setting can be a PIA versus 90's.

Are you going to make it rain/drip off the bottom of the soffit?
Would coming out lower and then offsetting up so the last horizontal section would project past the end of the soffit give you more slope to get drain back? All of the horizontal parts would look they have quite a bit of slope, but sure beats freeze up.

Bill751

JUGHNE said:

There was a recent posting of a frozen ModCon discharge going thru the roof. There was some horizontal piping in the cold attic that had more than enough pitch to drain back under normal circumstances. But as time passed and the ice bank grew it eventually plugged a 3" pipe.

I suppose that horizontal run could have been a 45 or 60 offset, though off-setting can be a PIA versus 90's.

Are you going to make it rain/drip off the bottom of the soffit?
Would coming out lower and then offsetting up so the last horizontal section would project past the end of the soffit give you more slope to get drain back? All of the horizontal parts would look they have quite a bit of slope, but sure beats freeze up.

How can I find the post with the frozen vent? I tried a few search terms. is it on the wall? I'd just like to see it out of curiosity.

I'm planning to terminate just under the edge of the roof in hopes that I don't get condensation on the soffit. The plan is to come out of the wall as low as possible so that I can get a good slope. Unfortunately The updated revised UFT manual now states there is a 14 foot equivalent minimum vent length. I was not aware of that. it was not in the original manual/paperwork that came with the boiler. to hit 14 feet I will probably have to come out of the boiler 90 over for a horizontal run then 90 vert then 90 to exit. I'll have to use three 90's total ( puts me at 17 feet) instead of two so that I can hit/ get past 14 feet equivalent. The first 90 doesn't count according to the manual. this of course will also add some additional height to my exit. I haven't had a chance to get back at it with the tape measure since I learned of the 14'. I believe I'll have enough room to make it happen with the boiler mounted low.

Also I'll have to look into the fittings. I guess my pitch options would depend on that. The Z dens elbow is 87 degrees. 45 would be too much. I know 2 45's together can be rotated to get what you need but that's probably not very professional. I can't see any reason that would be frowned upon from a technical standpoint, but I'd have to ask.

rick in Alaska

In my area the local gas company tells us that they want to see no more than four feet sticking outside without insulation around it. The reasoning is as others say, just to prevent ice buildup. So, I would see what the gas company will allow before going any further.
Rick

Bill751

rick in Alaska said:

In my area the local gas company tells us that they want to see no more than four feet sticking outside without insulation around it. The reasoning is as others say, just to prevent ice buildup. So, I would see what the gas company will allow before going any further.
Rick

I don't believe they get too involved with that here. When they came to put the meter in for the first floor they said they could go ahead and install the second meter at that time if I wanted. The second line was pipe just in to the basement and capped. Didn't seem to concerned with the boiler install. just looked at the gas line quickly from what I remember and verified it was pressure tested.

Good to hear four feet is acceptable in Alaska.

NY_Rob

You may want to consider going with 2" vs. 3" pipe to add a little velocity to the exhaust which will help keep the inside of the pipe warmer.

At very low fire rates the UFT-80W just gently puts along (you need to actually look at the display for the flame icon to see if it's firing at 8K BTU rate because the exhaust fan is running so slow) with the exhaust basically floating up out of the 2" exhaust pipe- if I had to estimate I'd say it's lower velocity than some normally exhaling.

Using a 3" pipe at 8K fire rate under very cold conditions could encourage freezing because the exhaust would have almost no velocity and linger then condense/freeze to the sides of the 3" exhaust pipe.

Just and idea....

Bill751

NY_Rob said:

You may want to consider going with 2" vs. 3" pipe to add a little velocity to the exhaust which will help keep the inside of the pipe warmer.

At very low fire rates the UFT-80W just gently puts along (you need to actually look at the display for the flame icon to see if it's firing at 8K BTU rate because the exhaust fan is running so slow) with the exhaust basically floating up out of the 2" exhaust pipe- if I had to estimate I'd say it's lower velocity than some normally exhaling.

Using a 3" pipe at 8K fire rate under very cold conditions could encourage freezing because the exhaust would have almost no velocity and linger then condense/freeze to the sides of the 3" exhaust pipe.

Just and idea....

Good point, however then according to HTP my max exposed run could only be 3 feet using 2". I think 3' will cause issues with the roof. damned if I do damned if I don't. I'll probably try 3" , keep an eye on it and I have a few questions to ask HTP about the the sensitivity of the air pressure switch.

My freestyle is about the same on low fire. you can can hardly feel the air moving as it exits the 3" vent.

Bill751

Getting ready to work on the vent plan/ordering venting. I took thorough look at the updated revised manual. I believe in a panic after reading the email from HTP I completely over looked the word "combined" in the revised manual they sent for the combined minimum vent length. Here I was thinking I now needed 14' equivalent on the exhaust and 14' equivalent on the intake. I wasn't combining the two runs. 14' total sure makes things much easier.

NY_Rob

I don't know how much local support there is for HTP in your area Bill, but my supply house literally told me flat out "we carry zero parts for that boiler" when I ordered it.

You may want to make a short list of spare part to purchase now and keep on hand for future use. The good news is, some of the sensors (flame, low water, Burner Overheat, CH Return temp, etc..) are under $10 so it's not a big hit to stockpile them for that 9pm Sat night outage.

Bill751

NY_Rob said:

I don't know how much local support there is for HTP in your area Bill, but my supply house literally told me flat out "we carry zero parts for that boiler" when I ordered it.

You may want to make a short list of spare part to purchase now and keep on hand for future use. The good news is, some of the sensors (flame, low water, Burner Overheat, CH Return temp, etc..) are under $10 so it's not a big hit to stockpile them for that 9pm Sat night outage.

Thanks for the tip Rob. I'll definitely look into doing that at those prices. I just got ripped off last week for two day shipping when I needed an igniter for the freestyle. I was charged $74.20 shipping. The actual shipping charge for that size box at that weight from zip to zip would be $33.99 my cost. (possibly a manufacture gets a better rate as well) Someone made an extra $40 on the shipping, and the igniter was already overpriced. Not sure if it was the supply house markup or the manufacturer. Not exactly ethical considering it was something needed, not just wanted.

As soon as I get it up and running I'll check in to spare parts.

NY_Rob

^ when you're ready, I can print the list I made w/part numbers to save you some time.

For the UFT, you order direct from HTP website, no middleman and you can choose UPS ground to save $$.

FWIW- the "Ignition Rod" for the UFT is $23, Flame Sensor is $6, etc... pretty reasonable. A new mainboard is $238, again pretty reasonable when you see people paying 3X that for replacement boards.

Bill751

NY_Rob said:

^ when you're ready, I can print the list I made w/part numbers to save you some time.

For the UFT, you order direct from HTP website, no middleman and you can choose UPS ground to save $$.

FWIW- the "Ignition Rod" for the UFT is $23, Flame Sensor is $6, etc... pretty reasonable. A new mainboard is $238, again pretty reasonable when you see people paying 3X that for replacement boards.

Wow all great news, thanks. The igniter for the Freestyle was $83!! I couldn't find it anywhere online and no one locally stocked it.