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Bradford-White Combi 2

mark schofield
mark schofield Member Posts: 153
this is just the kind of feedback I was looking for. Thanks. Mark S.

Comments

  • mark schofield
    mark schofield Member Posts: 153
    Bradford-White Combi 2 gas/LP DHW and Heating

    Has anyone had any experiences with this unit (gas/LP)? The specs seem to show a hydronic heating output of 55k BTU. But what might happen if one needed DHW at the same time. And if reset was desired, would it have to be incorporated in the heating loop. thanks for any replies. Mark S.
  • Mad Dog_2
    Mad Dog_2 Member Posts: 6,719
    I learned the hard way..........................................

    We had used them on a few radiant/domestic hot water situations....you know a few jobs where I had around 300 s.f of radiant...worked well. We recently had a job that .....I thought would also work well, but I had THAT feeling that I'd better double check with Bradford White. We were looking to supply dom. water and about 40 feet of baseboard. The room did have a high heatloss. So, I called their tech support(always get a name, time and date, guys)had HIM run all the numbers, assure me that the unit could put out 180 and recover fast enough. Long story short: we were sent the older version(despite the fact that I had given them the make a model for the Combi 2which must have been sitting in a warehouse somewhere which had a smaller coil and tappings, which of course we didn't find out until it was uncrated in the basement. Decided to go for it as it was freezing out. That was our mistake..should have sent it right back. Hey, if it worked out....NOT!!!!!!! It wouldn't put out more than 150 and had very poor recovery - room chilly. Now the fun began: After getting a Bradford White engineer on the phone - who was a decent guy - he broke the news that I was given erroneous info from there tech (did you happen to get his name???) and that yes, their advertsing for the unit SHOULD make it clear that when they claim it can be used for space heating...THEY REALLY ONLY MEAN RADIANT! and, in fact, the newer model with larger HX and output would not help. I was still furious that I had been duped by the wholesaler trying to pass off the older model, and they were going to take back the other and get us the new one, but that wasn't going to solve the lack of output and recovery. So, we wound up having to add a small boiler for the b.b zone and lost our shirts. Dan's article in this month's P & M tells an all too common story about the industry: WE get left holding the bag. What I learned from this is when it seems too good to be true...it is...don't pick a boy (hwh) for a man's (Boiler) job AND that we have to be our own enginneers on much of our work...no one is gonna watch your back like you. Hope this helps. Mad Dog

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  • hot_rod
    hot_rod Member Posts: 21,866
    55,000

    BTU is just that. You can't have it twice if the heating load is 55K and the DHW load needs 55K.

    Calculate how many BTUs you need for dhw, and how often. The balance is available for heating.

    Here is the formula for DHW= 8.33 (gallons required per day) (Th-Tc)
    Tc = temperature of incoming water
    Th = setpoint temperature of hot water

    Consider 20 gallons per person for the first two people, 15 gallons per additional people. So a family of 4 = 70 gallons per day. Rule of thumb of course.

    Then calculate the output of the baseboard at the temperature and flow rate and see how the numbers line up.

    The biggest unknown is how much and how often you need DHW.

    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
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