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Does This Look Correct?

mattstuff Member Posts: 5
Hello All,

I have been getting a lot of great information from this site so I wanted to say thank you! When we made an offer on our house in 2016 it had a used 2009 Viessman Vitodens 200 that the prior owner had installed in 2012 along with new pex distribution piping and slant fin baseboard (I think it was replacing an old gravity hot water system). As part of the closing they had the boiler serviced and according to the paper work it had "burner cone damage, coil plugged, extremely noisy fan, condensate trap full and were unable to get a accurate reading on the combustion". The prior home owner went ahead and replaced the boiler with a new HTP Elite Fire Tube Combi 140w with an outdoor temp sensor.

Mostly we heat the home with a wood stove and the boiler serves to keep the the house from ever dropping below 55 which so theoretically it should hardly ever run. I was surprised and concerned when we had the cold spell last January to hear the boiler turn on and run for around 45 second before shutting down over and over again. I would estimate this was occurring 6-12 times an hour and it was happening when there was no call on the thermostat (house temp in the low 70s, t-stat set at 55 and outside temp between 10 and -15f). I also had a giant ice mountain under the exhaust vent for the boiler.

I started looking the the manual and found that the way that they had plumbed it directly from the boiler to the heat distribution manifold was not how the plumbing diagram showed it should be plumbed. It also said in big bold letters to use a minimum 1" pipe and it was all in 3/4". I was having a difficult time trying to get a heating contractor out to the house because of the extremely cold weather they were all booked unless it was a emergency call (understandably) and this problem was driving me mad. My main concern was the wear and tear the cycling was causing on the boiler so I started researching on my own. Thats when I found this great resource and learned all about the advantages of primary/secondary and mod/con boilers. I also contacted HTP support and they advised me that the root of the problem was the direct piping.

I made a trip to the local plumbing supply outfit FW Webb, and working with on of there salesman got everything I might need and did my best to plumb it with how HTP recommended (side note: my experience with FW Webb was amazing, they really took the time to help me figure out what a needed and too fully answer all of my question).

This seems to have solve the short cycling issues but I'm pretty sure the boiler is way oversized for the house (when I used the slant fin heat calculator I came up with 41k on the design day). Also, I know I need to put a real backflow preventer instead of the check valve (right now I have been closing the make up water valve after filling) and I still need to put a new condensate pump in (thats why I have it draining into a mop bucket). But is there any thing else I may have missed?

Thank you all for you help and I appreciate any advise you may have!


  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    edited April 2018
    You really should orient your circulator so the electrical connections are on the top. You simply valve off each side and unbolt the stator (motor part) turn 180 and bolt the stator back on. You cleaned up the original version well, considering what was there!
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • Ironman
    Ironman Member Posts: 7,376
    That appears to be a UFT combi. It has a minimum turndown of 19k btus in space heating. Not much if your load is 41k at design temp. You could install a buffer tank to get longer run cycles and extend the boiler's life.

    It was a mistake to get rid of the original cast iron radiators and install fin tube baseboards. What's done is done.

    Here's the I/O manual:

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • mattstuff
    mattstuff Member Posts: 5
    OK I’ll switch that stator around, is that just to keep it dry?

    I do wish they had left the radiators, it really seems like the mod/con with radiators is a very complimentary set up. I thought about adding a buffer tank but as little as we use the boiler to heat I’m not sure the efficiency gain would be worth it unless we zoned the house. In the future I may still zone to the house (I tried to leave room on the return manifold to incorate valves) in which case I will reevaluate.
  • Gordy
    Gordy Member Posts: 9,546
    edited April 2018
    If that is the UFT 140 you are missing a circulator for the primary loop.........I don't care how small the zone is it should run for more than 45 seconds.

    By repiping from direct piped you need to have a circulator for the primary loop also.

    Is the above pictures before and after repipe?

    If it is the elite combi there would be an on board circulator also for the primary loop. Looks like the elite combi.

  • mattstuff
    mattstuff Member Posts: 5
    The sticker on the boiler showed it as model EFTC-140w and it has a built in circulator for the primary loop. There is a connection on the board is for the thermostat but ididnt see any for a secondary pump, I was confused by this at the time because the manual showed a connection for the secondary circulator. After contacting HTP they said the 199 model has a spot for the secondary but the 140 needs a pump controller which is what I did.

    The last picture in my first post is what it looks like now.
  • Gordy
    Gordy Member Posts: 9,546
    How many zones is the system? One thermostat for the whole house?
  • mattstuff
    mattstuff Member Posts: 5
    Currently just 1 zone, the house is 1340sf 2 story and the single zone seems to control it fairly equity which is why I took a wait and see approach to adding any more zones.
  • Gordy
    Gordy Member Posts: 9,546
    I wouldn't zone that small of a space with a 41 k total load.

    In all actuality the real world loss is 30k maybe less, and you always burn wood.

    I would get intimate with the manual in order to understand how to program that boilers logic. Is outdoor reset installed?
  • mattstuff
    mattstuff Member Posts: 5
    I lean more that way evey day, especially since the wood stove does 80% of the heating. The boiler has a outdoor sensor and is on a reset curve that Im still trying to dial in. I was able to set the maximun fire rate at 50% and that seemed to extend run time as well. Currently in the shoulder season if I turn the t-stat up it runs in about 12-15 minute cycle on 5-8 minutes off when its trying to raise the house temp. The circulator is a 3 speed thats on low would raising the circulator speed hurt or help?
  • hot_rod
    hot_rod Member Posts: 22,121
    If the main goal is to extend the boiler run cycles, a buffer tank would be a good choice. The boiler is oversized even without additional input from the wood stove.

    Many areas are at or below design conditions less than 20% of the heating season, you could calculate tat with past weather data.

    Adjust the boiler settings as much as possible to cut down cycling, but you need a smaller boiler or make that one think it is a large mass boiler.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    I wonder if having a primary source of heating, (wood stove), and the boiler, using outdoor setback, as secondary will act like a temperature setback,causing slow recovery. I would think the temperature in the loop will be cold, and then only as hot as the outdoor setback thinks is necessary, when the wood fire goes out.—NBC
  • GBart
    GBart Member Posts: 746
    Your unit has a variable firing rate with a spread of 28,000-140,000 so it is a wee bit over sized (sarcasm) but it should never ramp up beyond 41,000 but it can only go down to 28,000, a smaller unit would be best but what's done is done, it sure would be nice to see contractors doing load calc's and building inspectors checking them.

    For example the EP-80 has a firing range of 8,000-80,000. Still oversized but it can ramp down farther on warm days.