choosing (1) Integrated Boiler Hydro-Air and baseboard, vs (2) Separate Furnace and Boiler

Tom C._3

I am a homeowner and read this forum for a while. I would appreciate your opinion on choosing between <strong>(1) Integrated System with Boiler for both Hydro Air and baseboard and DHW, and (2) Separate Furnace and Boiler and Water Heater</strong>.



Our house is 5500 sf in Massachusetts, and heating need is much greater than cooling. Currently 80% of the house is heated by un-zoned central forced air with 2 gas furnaces and 2 A/C units, while rest 20% by 2 zones of baseboard with a gas boiler. There is also a 50 Gal gas DHW heater. All of them are natural vent going to same chimney. All units are old and need a total replacement now.



I have talked to several contractors and we are now comparing the following two options:

<strong>(1) 1-to-1 replacement with separate but standard gas furnaces, gas boiler, and gas DHW heater. For this option, we probably do not need to change any structure (ducting size for furnace, chimney etc). The only thing need to change is probably BTU downsizing since we are adding insulation into empty walls and sealing the ductwork.



(2) An integrated system with only one heating plant: a much larger gas boiler, which provides hot water for (i) Indirect DHW, (ii) 2 zones of hydronic baseboard for 1100 sf of space heating, (iii) hydro-air air handlers for forced-air for 4400 sf of space heating.</strong>



The integrated system is quite complicated to us, and thus we have hard time to figure out which option has less total replacement investment cost, or in general a better choice in this situation. It seems the hydro air-handler in the integrated system is simpler than gas furnace (less cost?), there is only one heating plant instead of 3, only one vent, one gas supply, and should be simpler. Also less unit to maintain in the future. But integrated system probably need more components to connect and control in between, and the air-handler may have different dimension so that the ductwork connecting to air-handler need to change shape. So we are not sure which option is better.



From reading, I understand ORC is very good thing to have. Beyond that, we are not sure about the payback time for other advanced features, such as 95% high efficiency units vs standard units. What will you recommend for this kind of 80% forced-air 20% hydronic baseboard house retrofit?

nicholas bonham-carter

Choices choices

I would certainly combine all the heating/hot water units into one system, with one control.

First of all, have any of the contractors calculated the heat-loss of the house? This should be a first step, and you can do it yourself using the SlantFin boiler sizing app available on their website for nothing. This will take into account the new insulation, windows, etc, and point the way towards selecting the right boiler for the whole house. The right boiler will have the capacity to keep up with all the heating/hot water needs, therefore not oversized.

Modern boilers can vary the firing rate, so that the output matches the heat load at any time. However this requires they be chosen carefully. They will also be able to vary the temperature in the hot water loop to suit the outside temperature (outdoor reset), which would be of even greater benefit if you had large cast iron radiators.

Make sure that the contractor has enough hydronic experience. You can use the find a contractor button to see if such an expert is in your area. The benefit of finding someone on this website is the ability to read any postings that person may have written here, and by his writing, know the measure of the man.--NBC

Eric_32

I will

I will 2nd what he said. If that were my own house it would be one boiler heating up an indirect heater, the baseboard heat and go with hydro air instead of the furnaces. You'll have to have heating water lines run to the hydro units as well as thermostat wiring back to the boiler.

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If your furnace is in the attic, most installers won't put in high efficiency due to the condensation that will form from combustion and the possibility of it freezing in the winter, so your stuck with an 80+ furnace with B-vent flue.

icesailor

Attic's

If you have a gas WA furnace in the attic, it can be replaced with an air handler and heating pipes can be run to it. There can be freezing issues but they are resolvable, depending on the circumstances.

Rich_49

Heat loss

Since you have been reading for awhile you should know about the importance of heat loss calculations before designing / installing any system .  Has any of the contractors performed one yet ? If not you should move onto the next guys in line or seek out one that will do this . 

 Now the next concern .  Is the home insulated , what kind of windows are there ? Be very careful of who does the heat loss or you may still end up with an oversized unit . Tell whomever quotes this your priorities also such as hot water usage for your family and how you use the heat .

Pointer :  If you hear anything remotely like " Well I have been doing this for so long I just know " , or South of the Mass Pike gets 25 BTU per ft and North gets 35 get rid of that guy also and move on or buy a house South of the Pike .

Where in Mass are you ?  

  The part of the system supplying the air handlers if in the attic should have a heat exchanger and at least a 30% glycol fluid to avoid freezing as Ice has stated .

icesailor

Insulation:

And if you have a WA furnace and you replace it with a Air Handler in the attic, be sure that you have all the ductwork covered with insulation. If it is flex duct, get it replaced with R-8 and cover over what is left exposed with 9" batts. If the ducting is in an  unconditioned attic space, you have no idea how much heat can be gained or lost in that space. Insulation is the gift that keeps on giving. In savings and possibly smaller equipment.

If you got went to the trouble of getting three prices for the work, one should have stood out above the rest. That would be the one that was more thorough. Like the one who explained how adding insulation could cut the cost of installation down. AND, decrease the long term cost of operation.

Tom C._3

(1) Heat-Loss Cal. (2) turndown ratio vs summer/winter load ratio (3) total replacement

Thanks for all your good suggestions.



I am in Concord MA. None of the contractors have done a heat loss cal for us yet. I did try once myself using www.builditsolar.com/ with estimated numbers, assuming our scheduled wall-insulation work will be done well to increase R value (4200sf wall with R15, 880sf windown/doors R1.8, 3000sf ceiling R26, 70sf skylight R1.8, 3000sf floor R30 b/t 1st floor and basement). The cal gave me a total loss of 150k BTU/Hr. But I probably underestimate loss from un-insulated 3000sf basement with stone-foundation (17k BTU, or 11% of total loss), while probably overestimate infiltration loss (70kBTU, or 47% of total loss). I will definitely try a cal using SlantFin.com.

150k BTU/Hr loss is far smaller than our existing heating plants capacity which is oversized.



One question about integrated system is turndown ratio, which is 5:1 with most mod/con boiler. But our summer DHW heating need is about 25 therm/mon, vs winter heating load of 500 therm/mon, which means the summer/winter load ratio is 20:1, or at least 12:1 even if we add insulation into the wall to reduce winter heating load. So 5:1 turndown ratio is not enough, and 4 to 6 months during a year the boiler will work with less than 10% of max capacity very inefficiently with short cycle. Is this correct?



I don't heat the attic and basement, and basement seems warm in winter as the heating plants are located there.



You have pointed out many good things about integrated system. In term of total replacement/installation investment, will it be more costly than standard 1-1 replacement with separate furnaces/boiler/water heater?

Rich_49

150K ?

Tom,  something is wrong with this heat loss . If you are doing the upgrades you mention I cannot imagine the load being anymore than 110,000 at design . I am in Jersey and design to 0* and take steps to make sure the equipment does not short cycle while ta the same time is able to provide my clients with ample heat on those record cold days . Mass is not much different than what I design to .  This may be a matter of a block load calc like you have done as opposed to a room by room .  The system you are describing will require some kind of thermal mass on the equipment side , this will allow your equipment to run optimally at ALL times . I doubt any of the folks you have had there as of now even considered such things . Before you make an unwise decision that seems wise let us help you for a bit .  

Tom C._3

thermal mass on the equipment side

Hi Rich

Thanks for your kind help and suggestion. Yes I was doing block load calc not room by room . You suggest using some thermal mass on the equipment side, could you explain a little bit what is thermal mass in this situation? Is it something like a mass reservoir to store heat for a late use, like electric thermal storage ceramic bricks?

Rich_49

Tom C

I read the newer discussion you started and must say In my opinion what you are thinking of is gonna be 1 giant pain in the butt . Whoever performs this work will have to charge a large fee for all the repiping and controls to make it work . There is equipment available that offers mass , modulating / condensing technology , outdoor reset and that is versatile and won't short cycle w/o all kinds of extra components . You would save yourself much time and added expense by installing the new stuff now and gathering your data . The time , money and effort you are thinking of would just be throwing money away , but hey , if you can throw money away who am I to deter you . 

Indirects , boilers and furnaces , OH MY !  Have a look at the provided links and watch the videos by the owner of this Mass Company and READ what theses units capabilities are .  My suggestion would be to purchase and install these , not use ANY furnaces but instead just AHUs and be done with it . 

  Boiler component  :  http://www.htproducts.com/pioneer.html  .  This is a 55 gallon mass space heating appliance that will not short cycle and is very efficient .

Heat for the AHUs and DHW  :  http://www.htproducts.com/phoenixwaterheater.html  .  This water heater is modulating / condensing also and we have used it many times for DHW and AHUs  combined without fail , it works great .   

Tom C._3

HTP Pioneer / Phoenix Water Heater vs Boiler for Hydro-Air and baseboard.

Thanks Rich, I have read the websites you suggested and the HTP new products look very attractive by combining water heater and hydro heating. You mentioned both HTP Pioneer and HTP Phoenix w/Air Handler --- which one would you recommend for our application?



HTP website also shows Versa Hydro (55-119Gal DHW module, plus a 160F space heating module) and Versa Flame (180F 50 Gal high mass space heating module, plus a tankless DHW module). For Phoenix, does it contain separate DHW module and space heating module, or just one module for both functions? Most of those HTP products seem to me are essentially a water heater. Do you think water heater is better than boiler in driving Hydronic AH? Besides forced-air, our house also has baseboard zones. Is HTP a good choice for conventional baseboard heating too? I see many of those HTP products’ max temp is 160 degree. For 180F baseboards, does it make sense for us to choose something like Phoenix PH199-55SA which has max temp of 184F ?



For Phonenix, as well Versa Hydro and Versa Flame, I guess there is no need to add a separate Indirect DHW as they have built-in DHW module. For Pioneer, do we need a separate Indirect ? (this is a lot of questions and thanks again)