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Tankless with hydronic heating coil

paule
paule Member Posts: 17
Hi,



I have a Spacepak air handler (5 ton) which uses a hydronic coil for heating.  I'm leaning towards pairing this up with a Rinnai modulating condensing tankless water heater (RC80HPi).  Are there any disadvantages to using a tankless water heater for this purpose?



Thanks,



Paul

Comments

  • Timco
    Timco Member Posts: 3,040
    edited December 2009
    Rinnai

    I took the Rinnai certification class and this tankless is rated to do the job, but regular scheduled maintenance is very important. follow the mfg instructions and pipe in provisions to make cleaning the hx easier. Also, you will need an expansion tank.  As I was told at the time, Rinnai was the only tankless rated as a heat source.  Their customer service will help size the unit if you need help.



    Tim
    Just a guy running some pipes.
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Do Your Homework

    Not being familiar with the model you posted I went to the web site. After reviewing this unit I have a couple of questions. Are you using the MCC-91 control as per the manufacturer for hydronic heating. Also, the flow rate chart listed in the specs is based on a 50PSI system pressure, a heating system runs at 12PSI so the question becomes. Can you deliver the proper flow rate/gpm to overcome the heatloss. I have also attached the specs on SpacePak hydronic coils. My last question is this. You have to weigh this in your mind. What is the cost of the Rinnai Unit with the control compared to the cost of a condensing boiler? Why? The warranty on the unit  you are speaking of is only 5yrs.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • paule
    paule Member Posts: 17
    Tankless with hydronic heating coil

    Thanks for taking the time to respond to my post, I appreciate it!



    I should probably step back and say that I don't plan on installing this unit ... I don't have the knowledge/expertise.  I had gotten an estimate from a boiler guy,  but I don't quite feel comfortable that he had properly evaluated the system and its needs (perhaps he had, but he didn't ask for model # of the air handler, or -- at least from what I could tell -- do a load calc).  Since I was burned on the initial install 6 years ago (long story), I'm trying to make sure that it doesn't happen again.  And I should also mention that I need to do something for DHW, the person suggesting the Rinnai for the hydronic coil was also going to add a second Rinnai for that.



    Yes, the MCC-91 was the control unit that was going to be used.  I looked at the specs that you pointed me to, and I'm afraid I don't quite know how to figure out if the Rinnai will work properly with the hydronic coil (Spacepak AC-WPAK-120).  I also had looked into getting a condensing boiler -- either a Triangle Tube Prestige Solo 110 (http://www.triangletube.com/TriangleTubeProduct.aspx?CatID=1&PID=1) coupled with a Triangle Tube Indirect Water Heater (http://www.triangletube.com/TriangleTubeProduct.aspx?CatID=6&PID=2), or a third option was Heat Transfer's Phoenix Water Heater (http://www.htproducts.com/phoenix.html).  The 2 Rinnai's were the cheapest option by about $1000, but I don't want to be penny wise and pound foolish and end up with an installation that doesn't quite do the job.



    Any thoughts (or other suggestions) are greatly appreciated.



    Thanks.
  • CMadatMe
    CMadatMe Member Posts: 3,086
    edited December 2009
    Get a couple

    Of more estimates. I would start at SpacePak's web site. Check to see who they have in your area that installs and is familiar with their product. A phone call to them wouldn't hurt either. Most of my customers who install this type of high velocity system also specialize in radiant heat, mod/cons and other aspects of high efficiency heating. I'm sure your area has the same type of contractors. You should also do the same by getting in contact with Triangle and find out what contractors in your area have been factory trained. Penny wise starts with good planning and getting yourself the basic knowledge to ask the right questions. An estimate is an interview process and you should treat it as such. Check references.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
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