Fondital radiators, what do I need?

Dsisson · December 2

Folks, I'm working to remodel a historic carriage house. This building has an existing Navien 3 zone boiler, but I need to repipe the entire thing and put new radiators. I've settled (I think…) on the Fondital Blitz radiators from Modern Warmth. I've had an engineer friend help me with sizing the radiators. HOWEVER, what I don't know is the accessories I'll need.

My understanding is that I'm best off running 2 pipes to each radiator - a supply and a return, rather than a big loop where the first radiator is hottest and the last radiator is cool.

Regardless, do I need valves at the radiators? I see that Modern Warmth sells a manual valve, and also an automatic valve. Both are kinda pricey. I'm wondering if the pipes can be directly attached to the radiators, or if the valve is important. I understand that the automatic valve would act as kind of a thermostat, but is that necessary?

If I do need a valve, do I need to buy the ones from Modern Warmth, or can I find a cheaper solution? I'm buying 7 radiators, so the valve cost is significant.

PS: a plumber will be doing the install. I'm just working to buy what's required.

hot_rod · December 3

Need to see a pic of the radiators connection

This is what is known as a convertible valve. The white knob allows you to adjust flow and as a result temperature. Its a manual valve

An automatic temperature responding head, know as a TRV could be added. Basically putting a thermostat on the radiator. Set a temperature and walk away

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EBEBRATT-Ed · December 3

Sounds like you are talking about a manifold system. If so the shut offs and control can be done at the manifold. If you can balance the flow at the manifold, you may not need automatic temp control. If your engineer friend knows hydronic systems he can steer you in the right direction and you can pipe the radiators with pex tubing.

He should be able to design the system for you.

If he picked the radiation he must have selected the water flow and temperature needed. Once he knows that you select the pipe or tubing size, and the circulators needed to supply that flow.

You can't just jump into a system and size one aspect of it.

Heat loss #1

Select radiation #2

Select pipe size and layout#3

Select circulators

hot_rod · December 3

Two options for homerun piping

Each radiator gets a supply and return pex. 1/2" sometimes 3/8" can be used.

At the manifold you could add electric actuators which connect to wall thermostats. You may run a series of radiators in one room from a single thermostat, if desired.

Or with the TRVs each radiator could have individual temperature control.

Pros and cons.

I like TRVs as they are non electric, easy to retro fit if you cannot pull wires to thermostats. They are also proportional, so they typically allow some flow until the room gets to the desired set temperature. As such the radiators are always giving off some heat.

If the boiler has outdoor reset, its possible to have nearly constant flow through the radiators. A nice feature for ultimate comfort. The radiators add exactly the correct amount of heat to the space.

With a manifold and electric actuators, those operate like on/ off switches. The radiator warms when it calls for heat, but will cool to room temperature when the thermostat is off. You need an actuator, wiring, thermostat and relay box for this option.

With either choice use an electronic circulator in the delta P mode. This allows to pump speed to ramp up and down as various radiators turn on and off. So you eliminate any potential velocity noise, and they consume 50% or less energy to run. The circulator has "cruise control"

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Dsisson · December 3

https://forum.heatinghelp.com/discussion/comment/1824142#Comment_1824142

I do have a manifold with the electric actuators. There's also a circulator pump that can run in different modes. I think it's in Delta T mode right now (30 deg temp drop from supply to return). There are two thermostats right now, one for each of the two existing circuits. I'm planning on adding the third circuit. I do plan on adding outdoor temp - I have the sensor already but it's not installed. I guess from what you say, I could add the radiators without any sort of valve? Here in the Northeast, we typically see hot water baseboard radiators, no sort of valve except the electric actuator on the manifold.

hot_rod · December 3

So 7 radiators running off of three thermostats? If so you need to wire the actuators to the thermostats for the rooms they serve. A relay box will help with the wiring.

What brand are the manifold and actuators. Most of the new actuators are low current draw, so you could run 7 actuators off of one relay box.

If the manifolds have flowsetters, like the one shown below, you can adjust and balance flow to each radiator to get the output you desire. The clear plastic flow indicators turn to adjust gpm to each branch

I prefer delta P operation with zone valves. Let the delta vary based on the room loads.

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hot_rod · December 3

It looks like all their radiators are cast or extruded aluminum. So good water quality is important. I would add an aluminum hydronic inhibitor also to further protect the aluminum.

But they are recyclable should they spring a leak :)

Most of the radiators sold globally have a common BSP thread and any brand radiator valve should work. Some US specific radiators have NPT threads. Pretty much all valve manufacturers offer either connection style. But there are some oddballs out there that require an OEM connection.

I suspect Fondital buys valves from a brass manufacturer and private labels them? Looks like they offer more of the designer style valves. In this pic, it is a BSP connection into the radiator, a rubber ring makes the seal, that is the difference between the NPT valves..

All their pictures seem to show a convertible valve. That is a good way to go it give you more adjustment and a way to isolate an individual radiator if needed. It's rare to see pex just screwed into radiators like that. You need a transition fitting either way to go from pex to radiator. Convertible or manual valves typically accept 3/8, 1/2, 5/8, or 3/4 pex or pex al pex.

Caleffi has universal fittings that accept most any pex or PAP tube

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Fondital radiators, what do I need?

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