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mod/con on one pipe

tabaker1960tabaker1960 Member Posts: 4
Hi all. I am looking to replace my 1957ish 87,000 btu net load boiler. My house is 1500 sq ft. with a heat loss of 48,254. I am planning to replace windows soon so that number should improve a bit. It is a 1 1/4" one pipe system with 92 feet of baseboard w/3/4" diameter copper fin same era. I went with a minimum 570/ft and calculated 52,720 btu's. I have only lived here a year but ran the boiler at a max of 140 degrees almost all of last year but bumped it up to 160 when the temps were down to -10 -15 a day or two last year. I usually had a 3 to 4 degree delta T using a infra red temp gun. B&G series 100 106189 pump.
I was thinking of putting in a Lochinvar WHB055N even though the 51,000 DOE it is awfully close to the heat loss. Also I was thinking running this as a full flow, single temp system with no zones. Even tho the price for the Lochinvar is pretty steep and way more bells and whistles than I need, it does come with the variable speed pump/control. And setup for my application should easy peasy. My brother is in plumping and heating but has not installed any mod/cons.

1. Do you think this system will work fine and make it into the condensing temps.
2. Is there any reason to replace any of the existing components in the piping system? It has a taco air scoop with a steal expansion tank off the top in the correct position in the system, a taco flo-check and B&G diverter tees.
3. Do I need to flush the system. I do not see any mention of that in the install manual. Just to install a screen in the return line.
Any comments/advice are appreciated. And thanks in advance.


  • IronmanIronman Member Posts: 5,641
    edited October 2019
    You should be fine with the 055, but you MAY wanna insulate the piping in unheated areas so that you get as many btus to the rad's as possible.

    500 btus per lineal foot is a more realistic number for BB output - if they're clean and in good condition.

    We always do all of the ancillary components with the boiler (pumps, exp. tank, MBR, fill valve, etc.). The circulator should be placed down stream of the exp. tank connection to the system (pumping away).

    I don't think the variable speed pump feature is available on anything smaller that the 199k btu Loch - unless they've changed something.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • DZoroDZoro Member Posts: 1,035
    Sounds like a older system and you will be well served with some upgrades. Post a picture of your system and we can help you better.
  • tabaker1960tabaker1960 Member Posts: 4
    Her she is. I added the vent damper last year. Couldn't really tell if it saved me anything. It keeps the water in the tank at temp all the time.
  • tabaker1960tabaker1960 Member Posts: 4
    Here is a pic out of the Lochinvar install manual. All the components are in the same location as my current boiler with the pump in the inlet side of the boiler. When you all say put the pump downstream from expansion tank, I always thought closely after the tank but a guess in this pic it could be considered downstream. Just way down stream???
  • Gman66Gman66 Member Posts: 34
    You don't say how you got to your heat loss calc but most all the typical models are quite conservative so 48K is likely high. Based on your house size the modeled loss is 32 BTU per ft2 which is really high. If you are able to satisfy design day conditions @ 160 degree supply with 92 ft of fin tube emitter you are likely in the 36K heat loss range (a more reasonable 24 BTU per ft2). So the 055 should be perfectly capable. Having said that, the 055 is not a 10:1 boiler like the rest of the WHB model range. Going to the 085 would cost you an insignificant penalty on the minimum input (8.5K vs 8.3K) while giving you lots of headroom if you are still concerned about size or more horsepower for an indirect water heater. HTP has their UFT model which is similar to the Lochinvar in design (Fire Tube) and measurables but a cheaper price point. There are a handful of guys on this forum w/ the HTP and I think they are pretty happy.
  • tabaker1960tabaker1960 Member Posts: 4
    Thanks for the reply Gman. I used the slant fin app for my heat loss. Are you sure on the 055 not being a 10:1. Looking at the literature it appears all except the 399 are 10:1. But would not be the first time I have seen factory info wrong. The attached files are what I looked at. I will check out the HTPs' again but I do like the idea of the boiler controlling the pump. If the boiler programming is good you would think that would be the way to go. It should keep itself out of all kinds of trouble. But maybe just a delta T pump on a HTP would do about the same thing. That's above my pay grade though.
    From what I have read if a person can run the system without a primary/secondary setup they are better off with better delta T from the system. Do you agree?
  • Gman66Gman66 Member Posts: 34
    Take a careful look at the two documents you attached on the boilers and look in the sections where they detail the dimensions for the various models. You will see the max and min input MBU and you will see that the 055 is not 10:1. Again, he 055 should be just fine for your situation but the 085 having almost the same low fire would work almost as well.

    My intent is not to push you to the HTP, I have no actual experience with either boiler, just noting that the HTP is basically similar (FT design that can be piped direct) at a lower price point.

    I suspect your intuition that the Lochinvar managing the variable speed circulator is indeed a good thing; there was a poster on this forum who is no longer around that installed a HTP UFT with a delta T circulator and was having problems. Should you care you can search for it. With the boiler modulating the fire rate and the circulator modulating flow the system became unstable for him. There was some speculation that perhaps his low supply temps (radiant application) was part of the problem and that higher supply temps of a fin tube application might work better, but I would be hesitant strapping a delta T circ onto the HTP. Could be HTP has tweaked their firing control to fix.

    As for direct piping vs primary/secondary, I am not a professional so take my opinion for what it is worth, but I agree that direct seems like it would optimize the return temps as the lowest possible. You seem to have only one zone so I guess you could easily synch the primary and secondary flows but for multi zone designs I feel like direct piping seems the best way to go.
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