hydronic furnace

[Big_Hitter]

anyone have a hydronic furnace?

this is essentially a water heater hooked up to run hot water through a an air handler and it also supplies hot water to the house

my tank started leaking and am looking at options, including replacing it with a forced air unit.

thanks

[samclem]

Is your WH gas or electric?

My MIL has an installation like that in a small addition they built on to her home. It produces enough heat. Obviously, the burner in the WH gets used a lot more than it typically would, and using tap water as a heat transfer medium has negative aspects (lime buildup). I'm not sure what the plusses are, aside from maybe saving some space and an additional flue. Water heaters already have a shorter expected service life than a gas furnace, so this looks like it would require more frequent replacement of major stuff, and replacing that WH gets more expensive and complicated with the nearby additional connections. Seems simpler and maybe more fuel efficient to keep the functions srparate.
If I had an installation where the WH heats the house, I'd install a powered anode rod to help the WH live as long as possible. Also, it would be even more important to flush the sediment from it annually.

[Big_Hitter]

the WH is gas, it's similar to this one

HTP - Phoenix Water Heater

only half the house is heated by this unit, the west wing and basement use a forced air furnace

[samclem]

Quote:

Originally Posted by Big_Hitter the WH is gas, it's similar to this one HTP - Phoenix Water Heater

Wow, that is a very expensive water heater (stainless steel tank). They retail for $3500-$4500, which is amazing. I hope yours lasted a very long time. It appears to cost about double the combined cost of a good regular water heater ($700) and a good furnace ($850-$1800), and on a whole system basis it will not heat air as efficiently as a modern condensing gas furnace. Both are about 96-97 pct efficient, but the furnace doesn't need a water pump.

[Big_Hitter]

Quote:

Originally Posted by samclem Wow, that is a very expensive water heater (stainless steel tank). They retail for $3500-$4500, which is amazing. I hope yours lasted a very long time. It appears to cost about double the combined cost of a good regular water heater ($700) and a good furnace ($850-$1800), and on a whole system basis it will not heat air as efficiently as a modern condensing gas furnace. Both are about 96-97 pct efficient, but the furnace doesn't need a water pump.

it lasted about 15 years

I figured this was going to cost about 3 to 4 grand to install. Tech will be out tomorrow afternoon to get me a bid.

[ERD50]

The only time I've seen one of these was in an apartment my DD moved into in central IL. I looked at the furnace, and was scratching my head - where's the gas flame, etc. Then I see the separate coils for heat and A/C and figured it out.

So the building had a central boiler, and all they needed was to pump the hot water around. For an apartment building, that seems pretty smart. One boiler in an area the owner has easy access to for maintenance, versus a gas burner and vents in every unit, which have maintenance and safety concerns. Since the units had A/C and a blower motor, the only addition in each unit is the hydroponic coil. I don't know if each unit had a pump on the boiler or at the unit (I don't recall seeing a pump), but they might even get by with a single pump. If your fan isn't running, it wouldn't draw much heat out away. Maybe a bypass solenoid at each unit, and a single pump that runs on any demand?

Maintaining and replacing a single boiler seems better than maintaining and replacing all those gas furnaces.

-ERD50

[samclem]

Quote:

Originally Posted by Big_Hitter it lasted about 15 years I figured this was going to cost about 3 to 4 grand to install. Tech will be out tomorrow afternoon to get me a bid.

I'm sure your question is the same as mine: why does a $3000 stainless steel water heater have a warranty of just 7 years? It's a special unit with its own internal liquid-to-liquid heat exchanger coil for the hydronic furnace, which (together with the SS tank) drives up the cost a lot.


I sure wouldn't choose a setup like this unless there was a very special reason. A regular gas furnace has a longer warranty, costs much less to buy, and will be more efficient at heating the air. There will be no circulation pump to go bad. A regular high-end water heater has a longer warranty and is less expensive to change out when the time comes.

[Big_Hitter]

Quote:

Originally Posted by samclem I'm sure your question is the same as mine: why does a $3000 stainless steel water heater have a warranty of just 7 years? It's a special unit with its own internal liquid-to-liquid heat exchanger coil for the hydronic furnace, which (together with the SS tank) drives up the cost a lot. I sure wouldn't choose a setup like this unless there was a very special reason. A regular gas furnace has a longer warranty, costs much less to buy, and will be more efficient at heating the air. There will be no circulation pump to go bad. A regular high-end water heater has a longer warranty and is less expensive to change out when the time comes.

I'm going to have them work up a quote to install a regular furnace and water heater

[Big_Hitter]

my house has a lot of high end stuff like this

[samclem]

Quote:

Originally Posted by Big_Hitter I'm going to have them work up a quote to install a regular furnace and water heater

That sounds like a good idea. And you might want to get another quote for the regular furnace/regular WH from a company that doesn't normally sell these hydronic units.


If the air handler has to be in a place where there's no easy way to run a flue/vent or a gas line, then the flexibility of being able to put the WH in a separate, more convenient, place could make some sense. Or, in the situation that ERD50 describes, where it allows one central burner to service a lot of different air handlers. But if the WH is right beside the single air handler (as it is at my MILs house), it would seem to make little sense.

[Big_Hitter]

let me see if I can upload a photo!

[Big_Hitter]

here's the unit

[samclem]

Quote:

Originally Posted by Big_Hitter here's the unit

I see your problem--they are installed upside down.


I can't see any good reason to do things this way, rather than a conventional furnace and WH. The gas line is right there, and apparently running a flue is no trouble. It will be interesting to hear any rationale from the HVAC guy. If he says anything about "improved efficiency" you should throw down the flag.

[Big_Hitter]

Quote:

Originally Posted by samclem I see your problem--they are installed upside down. I can't see any good reason to do things this way, rather than a conventional furnace and WH. The gas line is right there, and apparently running a flue is no trouble. It will be interesting to hear any rationale from the HVAC guy. If he says anything about "improved efficiency" you should throw down the flag.

the WH sits right next to an exterior wall - the big pipe is a flue that runs directly outside

the tank itself is leaking a little so I just need a new WH - not sure if I will have to get another boiler unit or not

[meierlde]

If the house is older and had steam heat originally, you would have to put duct chases in to get to the furnace (take up a bit of floor space if there are multiple stories). Actually today in the north a hydronic furnace backing up mini split systems for AC might make sense. (Have the furnace only kick on to back up the minisplit heat pump when it gets below about 30)

[Big_Hitter]

i rotated it

[ERD50]

Quote:

Originally Posted by meierlde If the house is older and had steam heat originally, you would have to put duct chases in to get to the furnace (take up a bit of floor space if there are multiple stories). ...

If you look at that boiler/WH picture, it has a PVC flue (high efficiency model). If there is no 'old school' existing flue, I don't think you'd have any problem getting a high eff WH and a high eff furnace to share that PVC flue (or run a second PVC flue, they don't take up much space and usually go out the side, not up through other floors).

Quote:

Originally Posted by meierlde ... Actually today in the north a hydronic furnace backing up mini split systems for AC might make sense. (Have the furnace only kick on to back up the minisplit heat pump when it gets below about 30)

Sounds expensive/complex to add even more systems. Would the delta between Nat gas and electric heat pump ever pay back?

Quote:

Originally Posted by Big_Hitter i rotated it

Did that fix the leak?

-ERD50

[meierlde]

Quote:

Originally Posted by ERD50 Sounds expensive/complex to add even more systems. Would the delta between Nat gas and electric heat pump ever pay back? -ERD50

I was thinking of an older house such as the one my grandparents had which was built in the 1920s with steam heat, converterted to hot water in the 1950s. So no duct chases were included. The main idea was to put AC in using the minisplits but since they all are heat pumps one might as well use that function. (Otherwise it is window units only, unless you want to go to a major renovation to put the chases in). So the minisplits would be paid for by the AC, with the cool weather heat pump function coming along for the ride.

[sheehs1]

I have an Apollo gas water system in my new condo for "heat" and "hot water" and a regular air conditioner outside for "cold air". When either needs replacing I am considering switching it all out for an HVAC system for heat and air.

In my condo the pipes leading from the gas hot water Apollo unit go thru the walls to the air handler which is located in a closet at the back of the condo. I hear these pipes or their fittings can bust. So to eliminate that as a possibility I will seriously consider switching it out when either fails. Heck, I may do so before the failure! In the meantime, I have placed "water alert" devices everywhere in the condo where water may leak (toilets, washer, sinks, and this gas water heater).

I have already replaced the fittings I can see with new stainless steel and reinforced fittings but of course I can't get to the ones in the walls!

I will say I was pleasantly surprised at how efficient this unit is. My Gas bill for heat is so low it is ridiculous compared to the HVAC at my primary home.

[pb4uski]

Quote:

Originally Posted by Big_Hitter anyone have a hydronic furnace? this is essentially a water heater hooked up to run hot water through a an air handler and it also supplies hot water to the house my tank started leaking and am looking at options, including replacing it with a forced air unit. thanks

We have a system that is an Takagi on-demand hot water heater that supplies our domestic hot water, heats our downstairs zone by running hot water through tubing in the slab (radiant heat) and heats our upstairs zone by running hot water through baseboard registers.

It is a bit unique, but not unheard of.

There are controls that give domestic hot water priority over heating so when I take my shower I get nice hot water.

Similar to this except ours uses an on-demand HW heater rather than a tank HW heater. https://www.radiantec.com/about-radi...ating-systems/