low mass boiler with hydro air

1973charger

We need to replace our 17 year old oil boiler that recently developed a crack. our heat loss calc is roughly 90,000. Heating with hyro air - 1 air handler in basement next to boiler, the other in the attic, quite a distance away from boiler. Current hot water in tankless coil, but we will replace with an indirect (40-50gallons). Two story house approx 2400sf in New England with typical NE winters. My question - would a low volume boiler like the Utica trifire be a good option given our system? i like the installer, but not sure about low volume and the Utica trifire. I do not know if we would be better off with a buderus given the two air handlers and the fact that one is far away from the boiler. i also have friends who swear by buderus with their same hyrdo air type set up. Would really like to see some fuel savings. Thanks in advance for any comments.

4Johnpipe

Look into HTP Phoenix water heaters. Depending on your hot water demands a PH 100-80 or 130-80 would be a great fit. They are stainless tanks and modulate and condense. I have a system with 5 hydro air coils installed in a large home on the water. Runs beautiful and great on fuel!

1973charger

thanks 4john, will look at HTP tanks. I have to correct heat loss calculation, it is not 90,000, it is closer to 73,000 (inadvertantly calculated a single story part of the house as 2 story). so, my question still is how would a low water volume boiler like the Trifire handle the winter season with 2 air handlers (one in attic) and adding a third zone to handle the indirect. Choice is Utica Trifire vs Buderus. i like the Buderus name and know people who are happy with them, but somehow i think a low volume boiler would be better in the summer months when all I need to do is keep hot water supply heated. There is not a lot of info that i have found on the trifire, but I read on this forum that the Trifie is similar in design to the Biasis B10 (I also learned that trifire castings are imported from Belgium - not sure if that is a plus or not). Thanks for any insight.

RobG

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Aaron_in_Maine

I have done a couple trifire boilers with no issue. Actually they run quite well and if the installer is a good one it will work just fine.

Paul48

The distance away from the boiler is not a concern, as far as the boilers ability to function correctly. Part of the equation when figuring a system for the correct circulator, is GPM, which translates to feet per second in a given pipe size. But that involves proper sizing of the circ, not the boiler.

hot_rod

if the air coils were sized to need higher supply temperatures, maybe above 160F, to meet load conditions or provide adequate output, a condensing style boiler may not be the best match.
I'm not sure you want to run stainless tank style boilers at high temperatures for both efficiencies and thermal stress.

If the system can perform at lower temperatures, allowing the boiler to condense, go for it.

As for cycling, it has to do with the mass of the boiler and the fluid content, and how the lowest but load matches up with that.

I'd think a cast iron boiler, properly sized, with ODR connected to a couple air handlers would perform well.

Kakashi

I like Energy Kinetics. Go with what ever brand your trusted installer/service company likes AND can fix.

4Johnpipe

Low volume boilers have no issue with hydro coils. You need to research design and specify the hydro coil. They have their own BTU capacity tables for output at different average water temps. You will need to have boiler piping and system piping or primary secondary as well. For a little extra cost you could benefit from using a small buffer tank as your hydraulic separation. Also size your system circulator for the flow and head pressure of the hydro coil.
The system we installed with the HTP Phoenix is running with 145 degree supply water temperature.

1973charger

thanks for all the feedback. air handlers are rated at 74,000 and 63,000 at 140 degrees. Does this mean boiler should be around 130-140k btus? also, will have to add a third zone for indirect hot water as current system is tankless. thanks.

Paul48

Look at the rooms each air handler is supplying. Obviously the air handlers are over-sized, based on your 90k heat loss. Are they equally over-sized? I'm not familiar with that boiler, if there is a difference, it would need to run 2 seperate curves. The boiler needs to match the heat loss. The air handlers being over-sized is a good thing. You should be able to get your 90k at well under 140* supply temperature, and keep that boiler condensing.

njtommy

Are you staying with oil or are you looking to go propane?

Paul48

I was thinking the tri fire was a mod/con...it ain't. That poses some problems.

njtommy

@ Paul48 as the numbers sit for there coil size and temps they are prefect for a nice mod con boiler if the go propane.

Paul48

It's a really good match for a mod/con, for sure. I think going propane from oil might be a wash, dollar-wise, with the mod/con.

OuterCapeOilguy

If you're staying with oil, I should think that a good cast-iron boiler properly sized for your heating/hot water needs would be ideal. Out here on the outer Cape, we have a lot of Weil-McLain Golds, which give great service. I've had one in my home since late '09; the Gold with the Carlin EZ-1 with Carlin's pre/postpurge primary is the bomb, as far as I'm concerned. I'm running a combination of baseboard (main & 2nd floor) and fan convectors (basement workshop, laundry and music studio), as well as a 50-gal. SuperStor Ultra indirect. (If I were to do it over, I'd have picked the Crown Mega-Stor indirect).

1973charger

thanks for all the info. had to stick with oil. had the trifire delivered today, i feel very comfortable with the installer, he was happy to answer questions and explain how this boiler would be set up. cant wait for install, the old burnham v7 is leaking a lot more since my first post.

njtommy

Cool let us know how you like it.

1973charger

So far so good. The local bldg inspector commented on the neatness and quality of the install. The tri-fire runs very well, but tough to say how much I am saving since the temps this winter have been warm and oil prices are less than half of what I was paying last year!! 40 gallon Heat-Flo hot water tank working flawlessly, plenty of hot water for family of 4. thanks for the advise.

todd_ecr

Very nice! Enjoy your TriFire. Is there any reason the braided flexible oil line wasn't used? Are they not allowed in certain jurisdictions?

billtwocase

Looks nice, but I would coil that excess oil line under the burner, and out of the path of travel. Nice job

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njtommy

Varying fan speed with supply water generally works pretty nice with hydro air. Lower supply water temp = lower cfms. It keeps the run times longer and the house warmer.

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njtommy

It's was more so aimed to mod con boilers or a oil boiler with more mass/ mid mass. Didn't realize that boiler only holds about 3-4 gallons of water till looking up the specs. Seems like you setting the boiler up for short cycling. Trying to match the load of the units and having a coil design for around a 30 degree delta T along with a properly matched pump or even a delta T pump would help. You could also add additional hot water storage and dump some extra heat into that.

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njtommy

The only down sides to heat pumps and hydroair mix is how fast can you get that hot water to the coil for defrost.

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njtommy

Defrost on a mini split they shut the fan down of the inside unit so it does not blow cold air.
I would assume defrost for a mini split is a bit different do to having EXVs.

In defrost they blow cold air on a traditional heat pump. The back up heat source must be able to over come that cold air.

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njtommy

EXV == Electronic expansion valves.

You could do that but some times it's not about efficiency it's about comfort.

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njtommy

Efficiency is great, but it doesn't mean a rats crap if the customer is comfortable.

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CMadatMe

99.9% of Air Handlers are oversized for the heat loss of the particular zone. Lower water temps and using a buffer tank is the optimum solution. Make sure aquastats are on the return, lower that boiler speed.

John Mills_5

My gas furnace takes a long time to purge, ignitor warmup, etc. so it is of little use for tempering a defrost. So I get blasted by 40° air every time my heat pump goes into defrost. That's why I think any backup should be used during defrost unless you or the HO doesn't mind the cold blast.

As for shutting the blower off altogether, remember that your average split heat pump has a lot more surface area to clean than a mini split and needs to pickup heat from the house to get the condenser (outdoor coil in defrost) to warm up. Our American Standard supplier stopped stocking the 4NXC coils as their tech rep found defrost issues caused by that coil not having enough refrigerant volume to remove enough house heat in defrost in a colder part of the state.

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njtommy

I'm not sure how you would do that. The defrost cycle changes. It's Time or coil temp. Which ever comes first.

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