Radiant Heat -- Switching Relay Options

[bimmer1980]

I'm in the midst of installing my radiant heat boiler system in my garage. I will have a pump for the floor, one pump for a fan coil heater system and one pump for a small snow melt area outside one garage door and man door.

Which pump relay system are you using?

I've been looking these two:

Tekmar 306P
https://www.supplyhouse.com/Tekmar-306P-306P-Switching-Relay-6-Zones-w-Priority

or

Taco SR506-4
https://www.supplyhouse.com/Taco-SR506-4-6-Zone-Switching-Relay

I will have multiple of the fan coil units that I want to independently control, however, they will all be on the same circulator pump. I basically want the various thermostats to parallel control one circulator pump.

The logic is that the radiant floor heat will be set at around 50 to 55 degrees and the fan coil units will be used in the main workshop or the attic workshop to quickly bring the air temperature up as necessary.

 

[Firebrick43]

With what your wanting to do you would want a zone valve controller such as

https://www.supplyhouse.com/Taco-ZVC406-4-6-Zone-Valve-Control-Module-with-Priority

The controllers you have listed use a pump for each zone. Your going to figure what type of "boiler" you want.

I would highly suggest the text book modern hydronic heating. If your willing to do the studying of the book it will help you design the system. It has it all from pipe size calculation, manual J (heat load), pump placement, boiler types and their pro/cons.

I have the first edition and it is still pertinent. It worth the 120$ new or get a used one of eBay.

 

[bimmer1980]

Firebrick--Thanks for the book suggestion. I looked it up on Amazon and could read the preview. It seems well written and easy to understand. The heat load calculations take me back to my ME college days. I actually enjoyed doing the heat loss calculations. I did do a set of calcs for my garage which helped me chose a boiler.

I have the Triangle Tube Challenger CC125H boiler for this system.

I'm using individual pumps for the three different zones: Primary floor, snow melt slab and the fan coil units. The fan coil units will all be on one loop is the current plan....

 

[finn]

I have three zones, each with a Taco pump, and one Taco relay in the shop.

Other relays and pumps are out there, and probably of similar quality and price, but I live in a rural area and all the local guys stock Taco.

When it’s below zero and a pump or relay goes out, you really don’t want to wait for Amazon Prime.

 

[Firebrick43]

If your air handlers are all going to be on (1) pump and operate together as (1) zone then the controllers you listed first will work. I assumed you wanted to zone the air handlers.

You probably should use balancing valves on the air handlers as you don't want one (probably with shortest run of pipe) to short circuit the others.

You are going to have to put a temperature mixing vavle on the radiant side to keep the temps at 110 ish and the air handler will need 140-160 degree water which will kill some of the efficientcy of a condensing boiler.

 

[bimmer1980]

Interesting......

I did order the book....

I'll have to think a bit more on how I want to handle the air handlers. I would like to be able to control them individually.... One will be on the main level of the garage and the other one or two will be in the attic work shop....

I was going to just use some monoflow t's (I think is what they are called) to divide up the flow... Then I could independently turn on the fans to blow heat. I think the fan coil units are designed to only put out heat when the fan is turning... While it may dissipate a small amount of heat with just the water flowing thru them, I'm ok with that....

Per your point, it may make sense to use a manifold with some flow valves.... hmmm...

The Triangle Tube uses a primary and secondary pump system....

 

[Firebrick43]

Interesting......

I did order the book....

I'll have to think a bit more on how I want to handle the air handlers. I would like to be able to control them individually.... One will be on the main level of the garage and the other one or two will be in the attic work shop....

I was going to just use some monoflow t's (I think is what they are called) to divide up the flow... Then I could independently turn on the fans to blow heat. I think the fan coil units are designed to only put out heat when the fan is turning... While it may dissipate a small amount of heat with just the water flowing thru them, I'm ok with that....

Per your point, it may make sense to use a manifold with some flow valves.... hmmm...

The Triangle Tube uses a primary and secondary pump system....

Monoflo tees are in the book. Be honest other than reading how/why the tee worked I didn't read anymore on them because I didn't use them. If you left the pump on all the time on that circuit and used the thermostats to control the fan units themselves and not thru the controller then yea that could work in my mind. No idea how multiple thermostats would control a single pump other than the main/secondary designated pumps, although I am sure there would be a way?

Are you against radiant panels or baseboards? If you used them you could use 1 variable speed constant pressure pump such as a grundfos alpha and zone valves/zone valve controller. It would allow one temperature water (120 ish) and much simpler. If you put sufficient baseboard or panels the heat output for quick rise could be similar to air handlers.

 

[yeldogt]

Typically the fan coils are going to want high temp water -- the floor and snow melt will require lower temp ... but, this will all depend on design.

Controlling the various temps is what adds to the complexities ----

Due to the heat loss calculations my two earliest projects could not be fully heated using radiant (floor) only ... solution was a combination of panel radiators and floor heat. I used the main outdoor reset control of the boiler to control the panel radiators as they required the highest heat ... the second boiler curve to control a mixing value for the lower per in-floor heat. This way the panel radiators acted as the primary loop of the boiler w/ constant circulation.

You can't do this unless you have hot water flowing in the pipe to all the fan coils --- you could have the fan coils set up as an indirect -- but this would shut off the floor.

What you want to do is a great idea -- I have done it but I used the floor temp water with a larger fan coil .. it still did not produce the heat as it would with 180 degree water.