domestic water heat for radiant heat

777

I have a nice functioning radiant floor heat system and a separate water heater for domestic. I am impressed with how nice the new high efficiency tank type domestic water heaters are and would like to eventually purchase a tank type that can do my radiant floor heat as well.

I have not found any brands that have an internal heat exchanger that would allow me to do my floor heating and while I could install a brazed plate, it would be nice not to have to do that.

Anyone know of any brands that are 1) tank type 2) high efficiency direct vent 3) natural gas?



TIA!

M Lane

Why?

Sounds like you have well-functioning space heating boiler already, but you insist on replacing it with a unit that will provide domestic as well? OK then, check these out:

http://www.htproducts.com/versaseries.html



Why not consider a side-arm water heater with a domestic hot water priority zone controller?

bob eck

Water heater doing radiant

I have a customer that has installed many A O Smith tankless gas water heaters for doing the heating in homes and radiant. He uses the ATI540H model and a Burnham Alliance indirect water heater to get the domestic hot water. www.hotwater.com check out the tankless gas water heater.

jumper

makes sense to me

Why not use a water heater for radiant? Cheap and way over engineered pressure wise. And without raw water being continuously introduced it'll probably last forever.

777

answer to M Lane

I currently have a 92% condensing radiant boiler and the standard direct vent, probably like 70% domestic water heater. I was thinking one day I will have to replace the domestic water heater so why not go with a unit that could do both domestic water and my radiant floors? Plus with an alleged efficiency of 95 to 96%, it would be a big step up from the current domestic water heater. I seriously wonder though if they attain that efficiency with tank temperatures of say 125 degrees F? Or if that's rated at some unrealistically low tank temperature.

The current boiler for the floors needs a fair bit of maintenance with the Giovanni heat exchanger that develops the "coffee grounds" etc. I don't think the heat exchangers in water heaters have that issue, hence less maintenance (I think anyhow).  And while my current system works well, I like the idea of a tank full of hot water year around that could do very small loads like my towel warmers without having to short cycle--the big tank buffer idea.

M Lane

Giannoni HX

That explains a lot. Normally, I don't advocate replacing a unit that functions well unless the client has a specific need to. Check out the HTP units I posted a link to. That's one option. Can you separate the towel warmers from the heat piping? If so, you can run your domestiuc supply at a higher temp, tee off to the warmers with another pump, and heat them with domestic hot water (use a mixing valve to bring down the rest of the hot water distribution). You should sterilize the piping if you do that.

I'm partial to Turbomax indirect heaters, then you can go with a firetube boiler that has a domestic hot function built-in like the Triangle Tube Prestige. I can think of about 4-5 variations to do what you want to do, just a matter of how much you want to spend and not building an insanely complicated system.

I did a 3000 sf. condo in Vail with one of those HTP's, both heat and domestic. my advice would be to find a radiant guy in your area who has at least 10 years with references if you want to proceed with the slightly complicated year-round towell warmer idea; or a good contractor if you just want a new boiler and water heating alone.

Good luck, ML

Derheatmeister

Buffer/DHW Combi Tank..

I'd stay away from integrating Towel warmers into the Domestic side for various reasons..



As for the HX on your current system "Fouling up": Any boiler shall be maintained depending on many factors i.e.

1. Combustion air: Is the boiler subject to contaminants like Pollen from trees,Dusty dirt roads, painting of a house...Wood working shop exhaust near by..Construction?

2. Gas: is it on Propane which may be "Punched" or Nat Gas...What is the Rondex Index of the Gas?

In other words: I have seen 8 year Munchkins/Viessmanns that were clean as on day one...I have also cleaned the same manufactures boilers that were only 2 years old and completely Clogged up... Sometimes it is not the manufactures Fault or design...



If your boiler is pushing the Eff. that you mentioned maybe a reverse indirect fired water heater and a Good boiler cleaning may be your best ticket..

TriangleTube also has a Buffer/Indirect combo that may be integrated with your existing boiler .. Hope this helps..Richard.

777

fouled up exchanger

The boiler does run on natural gas. There is a  lot of pollen in the air, but it mainly runs in the winter so I don't know how much pollen is out there in the winter months.

I do combustion analysis annually and my CO levels are always well below 100 PPM and the oxygen is right within specs. The boiler is in a residential neighborhood, no woodworking shops etc. and no folks painting their houses nearby.

I am surprised that you can open older boilers and have a perfectly clean Giovanni type heat exchanger. I do some routine work on other boilers for my company and find they have to be cleaned out annually. Maybe the air in Madison WI has a  lot of contaminants?

I have read many other posts that say these types of heat exchangers need regular cleaning...If there is a secret to keeping them clean I'd like to learn it....

Derheatmeister

Condensing Mode

How much does your boiler Condense?

System Design and layout can also contribute in keeping your boiler clean.

If you have tons of Heat emitting surface it will allow your boiler to condense more while keeping the house at a comfortable level..Bigger is better in this case...

This condensate will in turn"Rise"/Clean your HX...

Not sure which boiler it is that we are talking about...But i have found that The HTP Munchkin likes to be tilted ever so slightly towards the back to allow for better condensate drainage..

777

response to derheatmeister

This boiler condenses a lot since it runs a max temperature of 110 degrees F and a min of 100 degrees F. It runs a radiant floor system for my house.

So you're saying since it condenses  a lot of moisture it should keep the HX clean? Again, I service quite a few Giovanni (sp?) heat exchangers and it seems the low temperature ones that condense moisture always have to be cleaned out annually for "coffee ground" looking material...some kind of byproduct of combustion and/or condensate. And again, the boilers I service always have combustion analysis and look good so where this stuff comes from I don't know. And again, I'm amazed to hear that you can run these types of HX in a low temp. environment and not need cleaning.

Jean-David Beyer

Condensing and HX cleaning.

I am a homeowner and I have a W-M Ultra 3 that does not use a Giannoni heat exchanger, but a cast aluminum one. I get it serviced annually whether it needs it or not. During the warm part of the heating season it condenses over a bucket (2.5 gallons?) of water a day, and more when it is really cold outside. It condenses all the time when heating the radiant slab zone (the largest): supply temp is 76F to 128F, some of the time when it heats the baseboard zone (very small): supply temp is 110F to 140F, and only a little bit when heating the indirect::175F (I am sure it does not condense when producing 175F, but it does when heating its way up to that temperature..



The first year there was a little of what seemed to be aluminum powder in the condensate trap, which the technician had analyzed and it was only a little bit, and he said it was probably manufacturing residue. It has not done that in the years since. This boiler is powered up all the time because it is providing my domestic hot water all year around. The technician does open the heat exchanger and cleans it every year. At the same time, he puts a new igniter in, checks the condensate trap, and replaces all those gaskets. He then does a combustion analysis, measures the pH and Sentinal X-100 concentration in the system water.



I watch him all the time because I am interested, and I have never seen anything that could be called "coffee grounds" in either the HX or the condensate trap.



Perhaps this is a result of the design of the heat exchangers, or perhaps the air intake is sniffing the exhaust in, but I do not know.