guidance & design help for floor heat please

[rust in the eye]

Greetings to all!
I'm about complete with my workshop and am having trouble getting educated enough in floor heat with hydronics to feel comfortable designing my own system.
Tubing is in the slab with a manifold installed.
Local contractors I inquire with for completion either want staggering sums for rather nebulous descriptions of what will be performed and what equipment used. Also no consensus on heat source type or size.
At this point I'm committed to doing the labor myself but will need help deciding what the heck to use for heat source, boiler vs. tank w/heater vs. on demand WH.

Lots of questions for you guys in the know.
ALSO willing to pay for a local(Chicago) expert to give me a plan.
Who can help?
Thanks!

 

[rust in the eye]

Some useful info;
located in Chicago Il , winter temps can go below zero but seldom do.
fuel is natural gas, want direct vent and closed combustion
This is a workshop/garage of 1100 sq ft, 14' ceiling, attached to my home on the north side. 2 2" insulated O/H doors on west wall comprising ~200 SF, also 200SF of double glazed windows near the ceiling.
insulation consist of 2" foam(R10)beneath and around perimeter of slab, R19 walls & R49 blown above the ceiling.
I've had people tell he I need anywhere from 32k to over 100k BTU to heat this space. My calculations always work out between 40 & 45k.
I need reasonable recovery time when the doors are opened but this isn't Jiffy Lube.

 

[RayBob58]

Did your tubing go in according a planned layout, or, as many do, did you just roll out a bunch of tubing? I worked with Nibco in laying out mine, and they'll also help you plan the rest of the system, except for the heat source. But they will tell you how many BTUs you'll need.

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[rust in the eye]

Tubing is in a correct layout done by me. 4 loops, approx. 225' ea.
Nibco is interested in selling prefab "panels" which I am not interested in.
My intent is to fabricate the "panel" myself using sweat connections and good components.
I just need guidance to design it, building it is no problem.

 

[Dick in Wisconsin]

"Sweat" … as in copper?

Isn't it a matter of getting a manifold, hooking the existing "zones" in the concrete floor to the manifolds and then hooking to the condensing boiler (or condensing water heater like is in my sister and BILs 15 y/o house they just bought) with the appropriate pump(s), expansion chamber, etc? Aren't there a number of websites that will do that for you? Won't they make the heat loss calcs?

I have 1000sf with 10' ceilings. I could show you what my deal looks like. Your cold temp is probably higher than mine.

 

[RayBob58]

If there's a Menards in your area, they have Nibco and Hydro panels on display. Plus most if not all of the parts. I think I'd just walk in there and take a picture.

 

[rust in the eye]

looking to build my own, also need help deciding between boiler v on demand w heater

 

[Firebrick43]

First, you are doing a closed system with oxygen barrier pex right?

I "assume" by boiler you are talking about a modulating and condensing. A cast iron boiler is a completely different animal.

A "boiler" is designed for constant use and high flow and realitively low temp rise. In a radiant floor 80-90 return temp to 120 output temps, maybe higher if doing dhw.

A instant hot water heater is ment for low flow and high rise. The restriction will lead to increased pumping losses, and the tend to overheat since cold 50 water is not coming in. Many can not modulate and tend to short cycle especially in milder temps. This leads to low life span.

The instant water heaters do work but you have to decide if the shorter lifespan and results of equipment failure are worth the savings over a modcon.

Both need regular yearly or every other year cleanings of the heat exchangers. HVAC guys I know hate both due to the tight packaging.

Traditional cast iron boilers are cheaper and need much less maintenance. Some last 40-50 years. However there efficientcy is much lower (except maybe the weil McClain gv90 series) and their stand alone packaging isn't space saving like a modcon/instant water heater. The cast iron boilers need a primary loop to keep the boiler from operating in condensing temps as well(except the gv90) p

 

[tdkkart]

I'm 4hrs west of you, I successfully heat a very similar building on 41,000 btus worth of electric instant water heater.

 

[finn]

Another vote for taking a few minutes to visit the local Menards. The display will let you identify the layout and parts you should be considering.

The component prices are about as good as you are going to find online, as a bonus.

I recommend you consider a primary/secondary loop system.

 

[Verado1250]

I did the Menards suggestion. I took a note-pad with me and diagramed the entire system with their different parts/prices. All added up with me just buying the parts and making it myself, it was about 1/2 price of their already made up board. The sales people at Menards were very helpful during this. Most of the parts were in the immediate area of the radiant heating section.

 

[rust in the eye]

First, you are doing a closed system with oxygen barrier pex right?

I "assume" by boiler you are talking about a modulating and condensing. A cast iron boiler is a completely different animal.

A "boiler" is designed for constant use and high flow and realitively low temp rise. In a radiant floor 80-90 return temp to 120 output temps, maybe higher if doing dhw.

A instant hot water heater is ment for low flow and high rise. The restriction will lead to increased pumping losses, and the tend to overheat since cold 50 water is not coming in. Many can not modulate and tend to short cycle especially in milder temps. This leads to low life span.

The instant water heaters do work but you have to decide if the shorter lifespan and results of equipment failure are worth the savings over a modcon.

Both need regular yearly or every other year cleanings of the heat exchangers. HVAC guys I know hate both due to the tight packaging.

Traditional cast iron boilers are cheaper and need much less maintenance. Some last 40-50 years. However there efficientcy is much lower (except maybe the weil McClain gv90 series) and their stand alone packaging isn't space saving like a modcon/instant water heater. The cast iron boilers need a primary loop to keep the boiler from operating in condensing temps as well(except the gv90) p

Yes, closed system 1/2" oxygen barrier PEX, four loops, ~ 230'each.
Will be using glycol solution and was told by one that tubing should have been larger for the more viscous fluid. I'm stuck with 1/2"
The consensus(among those not peddling DIY on demand water heater systems) seems to be that the mod/con boiler is superior.
Can you tell me if I will need a primary and secondary circulating system? I'm trying to avoid this for simplicity and reliability.

Mixing valves have also been mentioned and I am unclear about this too.

All of the mod/con boilers are well in excess of what I expect will be the load, around 40something k. I am concerned if using one that short cycles will be an issue.

Not interested in the Manards/Nibco panel or replicating it.

Ideally, I would like a heat source, single pump, exp tank, fill valve and controls.
The on demand water heater manufacturers do not warranty their products when used in heating applications which I think speaks volumes about their suitability for this purpose.
I understand Lochinvar is making a smaller mod/con(55k)in response to request from contractors wanting them for this purpose.
Thanks firebrick. Seems you know your stuff. Interested in making up a drawing for me?

 

[rust in the eye]

I did the Menards suggestion. I took a note-pad with me and diagramed the entire system with their different parts/prices. All added up with me just buying the parts and making it myself, it was about 1/2 price of their already made up board. The sales people at Menards were very helpful during this. Most of the parts were in the immediate area of the radiant heating section.

Yep. Those snap connections also left me shaking my head over that set up.
Quotes from other sellers of similar set ups are deliberately nebulous about the components provided. One went as far as to state that you don't know until you buy. I'd love to take that guys order at a restaurant.

It's pretty clear they charge a craftsman's wage for factory work and their pricing won't stand up to much scrutiny.
I can assemble it better myself and have control over the components used.
I'd rather spend on a good heat source.

 

[86turbodsl]

If you are having trouble making the flow rates work with glycol, you can use methanol as antifreeze too, it pumps easier. I bumped up my flow rates using it.

 

[Firebrick43]

Mixing valves should not be used for a system your proposing. They are more for multiple temp system such as 110 floor heat in combination with 130 degree DHW or 160 degree air handlers.

Having a simple one zone system with a small boiler with high turn down ration 5:1 or 10:1 should get you there with 1 pump.

Most manufactures will "suggest" a primary/secondary loop system with two pumps due to the nature of micro zoning some do. These small zones have issues absorbing the produced heat leading to short cycling.

You set up the single zone with high mass should not have this issue. It will operate most efficiently buy heating only to the temp needed and as cold as temps possible on return.

You are a little light on tubing, another loop would have been nice.

I would recommend a text book named modern hydronic heating. This is my knowledge base, and other than it and designing my system and it is my only experience. I would not feel comfortable designing your system personally.

 

[koditten]

Are you married to the use of a condensing boiler and closed combustion?

I did the math seven ways to Sunday to find out what the difference in cost would be to use one or the other. It will take me 35 years to break even in the savings of gas using an 85% efficient boiler vs a 96% condensing boiler.

I saw no reason to have closed combustion. I'm a welder/fabricator/cigar smoker. I already have ignition sources present. A pilot light on the boiler isn't going to make any difference in my shop.

With that said, I wanted a boiler with a standing pilot light. This type of boiler has 4 components. A gas valve, thermo couple, pilot light and a relay. Dead simple and the parts are cheap and very obtainable.

Boilers are what you should be looking at for a heat source. That is what they do. Use the close spaced tee's method of plumbing your system to reduce cost. It will save a bid on construction cost. do yourself a favor and install flow meters (sight glasses with little windmills or similar) in your primary and secondary loops. It makes it so much easier to balance those loops. My primary loop around the boiler spins 10 times as fast as the secondary loop feeding the tube headers

 

[Innovate1]

When I did a basement floor and garage 14 years ago I used a Polaris 135kBTU condensing water heater for both domestic hot water and, through a flat plate heat exchanger, the floor heat. It requires two pumps but has had no issues. I did have to make an interlock for the master shower that shuts down the floor heat when using the shower because the floor heat can pull down the water temp. I installed return line and pump from the shower area back to the tank and a push button to run it for 45 seconds. It also locks out the floor heat for 1 hour which isn't long enough to be noticed. Probably didn't need antifreeze but used RV antifreeze that is non toxic and didn't have any issue with viscosity.

Now doing a new house and considering just 2 car garage heat which would be very similar to yours. 50 or 60F for temp will be plenty as it is mostly for car storage not primarily a workshop.

I need to check but I think Missouri requires dual wall heat exchangers for heating even with non-toxic antifreeze, maybe even just with water. Have considered an open system - much simpler but not sure it is allowed here.

A small gas furnace hung from the rafters would be much simpler but the warm floor is nice. Debating whether it is worth the extra cost and effort.