High temp and low temp heating on one system

ambercontractors

Hello to all.
I was wondering if anyone has a preference on how to mix temp down within one system.
I have some high temp radiators in one area, however the remainder of the house is being heated by radiant. I see there are several options of mixing the temp down, thermostatic, motorized 3 ways, then there is injection. can someone weigh in with preferences and why that specific way would be better. Thanks in advance.

hot_rod

$$, accuracy, complexity. A manual 3 way valve is simple, and if the boiler runs on outdoor reset, it tracks along. If the low temperature is a single zone. A motor could be added for more control.

Thermostatic is next, it will keep the temperature you dial in within a few degrees. The hot supply needs to be at least 20 degrees hotter than the mix to be accurate.

Injection mix cost another pump and a controller. Viega and others have modules all built with control and operator.

4 way valves were used with conventional boilers as you get mixing and boiler return protection from one device. It so common anymore.

With any motorized option you could have outdoor reset.

EdTheHeaterMan

I have some high temp radiators in one area, however the remainder of the house is being heated by radiant.

This sounds like your major heating system is Radiant. Although the Some could mean as little as 2 or as many as 200 or more. (depending on the size of your home). The rest of the house could be a 50 square foot laundry room on a slab with one loop of 3/8" PEX. So being this vague, will not get you a specific answer.

My NJ home has 2 Forced air duct coils. and one small room, that was formerly a garage, with 3 loops of radiant tubing. Each air handler and the radiant are on separate zone thermostats. I chose the mixing valve option for such a small area.

In your situation, there is a greater need for comfort control for the majority of the living space. Based solely on that larger area, I might select a series of 3 way modulating, motorized valves to control separate zones based on room use and/or Floor covering... Tile v. Hardwood, or living v. sleeping.

My inexpensive mixing valve had performed flawlessly for about 12 years now. I even have a NEST thermostat, working flawlessly for 6 years, controlling that zone.

ambercontractors

Thank you for info
Sorry for lack of specificity 
I have a hallway being heated with 4 radiators there is also a mikvah coil (ritual pool)
The remainder of the home is staple up radiant I would say about 30 loops in 4 zones

hot_rod

So a heat exchanger in the mikvah? If so you probably want to run 180F for the fastest recovery?

Depending on the size of the radiators and heat load of that space, they could run anywhere from 120- 180. 180 gives the most output, but could cause some overshoot due to the mass. I think TRVs are the best control for cast radiators.

Here is a mikvah coil that Kal and Moses built for a large project in Brooklyn. Intended to recover the pool in minutes, not hours. Fits under the stairs into the pool. Maybe 10 pools under roof in one building.

Water was "burped" from a deep well with air pressure.

ambercontractors

Yes I know Moshe Fischer I've seen some of his work reverse return mikvah coils higantic storage tsnks etc. His son lives few min away from my house very nice guy.
The mikvahs he designs are for an enormous populous, the one you're referring to is Satmar in Boro Park, this is a much much smaller situation it's just a private mikvah for a single family dont need super recovery cuz they aren't changing the water that often and when they do it can be done ahead of schedule so that there is time to recover. The large ones he designs are used every day by thousands of ppl.

ambercontractors

But yes we have a heat exchanger custom designed by 3rd party steel flat plate fits under steps. These days thats how they all do it

SKYPAINTER

Well, I like simple and relatively inexpensive. System should be primary/secondary piping between boiler and system, on the low-temp system use a Taco 2-way/set-point i-valve and pipe it exactly per instructions, you will need to install temp gauges and a small circulator to complete the system. Works like a charm. Taco also offers a 3-way i-valve if you prefer that piping arrangement. I recommend you visit the Taco website and see how easy these valves are to use.

Paul Pollets

I've always used Viessmann boilers. They don't require primary/secondary piping; as many as 3 mixing valves and motors can be used with their control, and a low temp mix doesn't require a mixing valve if it's the only temperature. A low loss header is required if flow rates exceed 10gpm. I prefer the advance control platform that allows many options for different zone temps. The platform is reliable and robust. And user friendly

jbjb

I always shudder a bit with houses with mixed radiators and underfloor. Always feels like a compromise. It’s happening more and more in the UK as people convert ground floor to UFH.

It would be great if both halves were sized so you could feed the radiator return as the UFH flow, with minimum of mix down, but I guess that’s unlikely.

hot_rod

jbjb said:

I always shudder a bit with houses with mixed radiators and underfloor. Always feels like a compromise. It’s happening more and more in the UK as people convert ground floor to UFH.

It would be great if both halves were sized so you could feed the radiator return as the UFH flow, with minimum of mix down, but I guess that’s unlikely.

Why shutter?

Its very easy to build/ pipe a two temperature systems. Many of the new boilers and combis even have control logic in them to run the mixers, no additional electronics needed.

The UFH is more comfortable, uses much lower supply temperature, and properly installed could be less $$ to operate.

Paul Pollets

I've installed more than 500 systems with both radiators and in-floor heating in the same home. Never had an issue.

Smitdy

I did one with radiant and hydro-air, I used two buffer tanks and put an high limit aquistat on the lower temp radiant zones buffer. 

Paul Pollets

Nice work... I tend to use less pumps, no buffer tanks and zone valves, if required. The Viessmann platform and controls makes this easy.