indirect water heater for radiant floor?

waldemar13

I am currently renovating a 1920's bungalow. it's solid brick, plaster and lath, no insulation. In the kitchen I installed 280 ft of 1/2 inch pex tubing embedded in 2 inches of deck mud and porcelain tile. The rest of the house is cast iron radiators. I have a Triangle Tube 110 btu prestige mod-con boiler with their Smart30 indirect water heater that i planned on installing. Apparently Chicago code does not allow for a single wall indirect water heater to be used for domestic hot water.

So I was thinking I could use the indirect water heater for the in floor radiant zone and the mod-con just for the cast iron radiators. Or should I use the mod-con for the whole system and just forget about the indirect tank. I also plan on finishing the basement this spring, so that will be another heating zone to be added in the future. My basic question is which way would be more economical and simpler to install and maintain?

BTW the domestic hot water is currently supplied by an on demand water heater that works just fine. I could keep that set up.

I attached a picture of the floor plan if that helps. Thanks in advance for any input.

JohnNY

Most codes allow the single wall indirect water heater unless you're using chemicals, like propylene glycol (antifreeze) in the system. Are you sure you can't use a standard indirect in Chicago?

waldemar13

Yes. 3 different Hvac contractors said as much and they won’t risk their business license installing it.

waldemar13

Let me clarify. Chicago won’t allow single wall indirect water heater to be used for domestic hot water. Double wall heaters are ok for that purpose. I can use it for a closed loop radiant heat. I’m trying to figure out if I should use it for the kitchen floor and future heating zone in the basement or just use the mod-con for the whole system.

Brewbeer

mod con for entire system, mix down for the radiant floor if you can't run the floor at the same temps as the cast iron radiators. Size your basement radiation to give adequate output at the same water supply temp as the radiators.

hot_rod

Only reason to use the indirect for the radiant is to separate a glycoled loop. No need to add yet another heat exchange to the system, it does cost some efficiencies.

waldemar13

Brewbeer: why do you prefer to use high temperature for the future zone?I was leaning toward using low temperature radiant thinking that would be more efficient.

Hot rod: the reasoning I was using for the indirect water heater was that it is designed for lower temperature operation which the radiant floor needs anyway. I am concerned about short cycling the mod con with the low temperature zones.

Brewbeer

If you already have the radiant installed in the basement floor, you can use the lower temps. But if you were putting in baseboard, you could design it to run at the same temp as the cast iron radiators.

hot_rod

Cann you get enough output from the ads running at the floor temperature? I have 3 cast iron rads running on my slab temperature, even at 120 set they give off some heat.

if the temperature requirements are 15 degrees or more apart you need a mixing assembly. sure the indirect would work for the low temperature buffer, in that case.

GroundUp

I would be very concerned about short cycling if the kitchen is a zone of its own, in which case the indirect would make a pretty neat buffer tank. If it runs along with other zones however, a simple mixing valve would be sufficient IMO

Gordy

Are you sure the “hvac” guys are not confusing a heat exchanger with an indirect per code?

Some one doesn’t understand that the water in the indirect tank is at a higher pressure than the heating system. If there were a breach in the indirect tank the system would get the Potable water not the other way around.

Does anyone know of any double walled indirects ? That’s a huge market the indirect manufacturers are losing out on if true.

Rich_49

http://www.htproducts.com/literature/lp-81.pdf

Gordy

^ yes RIch, the heat transfer goes right down the tubes. 40 gal 1st hour rating for double wall, and 212 gal 1st hour for single wall at 140 degrees for the ssu45..............

Gordy

Someone needs to understand the wording a little better.
From cook county plumbing code heat exchangers. Are you using any boiler treatments, or glycol in your system?

waldemar13

Brewbeer: no I haven’t installed anything yet for the basement. Can you please explain why you would choose the high temperature radiators over the low temperature radiant.

Hot rod: no I don’t think I woul get enough output on the coldest days here. I have seven cast iron radiators. The house is inisulated.

Groundup: I too am concerned about short cycling. That’s why I’m trying to figure out if I should use the indirect boiler for a dedicated radiant loop and if it is worthwhile to do it that way or maybe I’m overly concerned and should just use a mixing valve with the modcon.

All: I am not an hvac contractor. I’m a welder by trade. I thank you all for your patience and taking the time to answer.

waldemar13

Oops I just saw the typo. The house is uninsulated.

hot_rod

If you already have one, an indirect is a nice way to isolate and buffer that small zone,

A small buffer and mixing valve might be less $$? You are wise to consider some buffer for those small zones.

Brewbeer

waldemar13, do you have sufficient height in your basement to install the radiant over the existing presumably uninsulated slab?

And radiators don't need to be run at high temps if you have enough emitter, mine run in the low 100F degree range when it is 32F outside.

Take a look at my system (linked in signature), it is a mod con with buffer and indirect.

waldemar13

Brewbeer: my basement height is 7’ 6”. With a finished floor I think it will be 7’4”. I thought about running radiant tubes along the ceiling but I think it might be to close for comfort. I’m 6’3”. I am thinking about running radiant on the walls. I would have an air gap then 2 inch xps foam board. On this I would attach the pex tubing and hardware cloth and then plaster it all in. It would be about 4 ft high. Much like a wainscot radiant wall. I would do this on the two opposing walls forward of the stairs as that is the only part of the basement I’m finishing. It would take about 350 ft of pex. Doing it this way I would minimize the worry of blocking any heat with furniture.

Hot rod: yes I already have the mod-con and the indirect water heater. I bought them a couple of years ago when hvac convention was in town. I bought it at half the retail price from one of the vendors when they were packing up. . At the time I didn’t realize I would not be able to use the indirect for domestic hot water in Chicago. (The danger of impulse shopping!!! Lol).

I think I will use the indirect for the radiant zones and the mod con for the cast iron radiators. Now the challenge is to find a contractor familiar with something like this. The contractors I spoke with never did anything like this before. One said he did something like this for towel warmers. They all installed radiant floors but only with boilers, not water heaters.

hot_rod

Plenty of good contractors in the Chicago are, let me know I can connect you to some. I visited a few job sites up in Chicago a month ago, buffer tanks are being implemented.

As for double walled Indirects, it comes down to the actual inspector that shows up, my Chicago contractors tell me.
Really how they interpret "boiler fluid' there concern is someone, someday may put non potable chemicals in the system. Still a reach to get the two fluids mixed, but...

I fought the law and ...

waldemar13

...and the law won!!! 😂

Yes please send me the names. I don’t know what the policy is of posting names and numbers on an open forum but you’re more than welcome to message me.

Thank you

hot_rod

Sent a PM, sometimes they get tripped up, let me know you got it.

waldemar13

Nothing in my mail box.

hot_rod

mail me at bob.rohr@caleffi.com

waldemar13

Sent

duffy_4

I have installed plenty of indirects in CHICAGO from TT smart ,lochinvar and Nti ,just depends on the inspector ,most know code is outdated and that potable water pressure higher that boiler pressure and if there is a leak the relief valve will let go on boiler. I asked about code at water Dept city hall they said takes city council to amend CHICAGO plumbing code . I have installed one double wall indirect it was made by peerless and that was bout 8 years ago .