Manifold for Baseboard heat?

[EricO]

OK so I'm designing my baseboard system, and I'm contemplating several different methods to use. I would like to have a parallel system with 5-6 individual zones. One method uses control valves and balancing valves to control the flow through each zone, but the option I ran across in the idronics magazine was for a manifold system. I really liked that idea. Attached is a picture of the system.

Ideally, this system would be easy to install since i was planning on using pex with oxygen barrier, or pex-al-pex, haven't decided yet. My question is though, how big should the manifold be to keep from running into low flow issues through the baseboards?

Supply line from boiler to manifold is most likely going to be 1"1/4 inch. The supply from the manifold to the baseboards are 3/4 inch. Flows for each zone will be controlled by Thermostatic radiator valves. Basically exactly like the drawing. Just need to figure out sizing for the manifold

Does anyone have a setup like this?

 

[heaterman]

Lot's of 'em. We do all of our panel rad installs home run style via a main manifold. Usually 1 per floor if multi story. Baseboard with TRV's works the same.
The beauty of it is that the TRV's will modulate to match actual load in a given room.

You can also set up multiple manifolds with zone valves in front of them which are managed by a master thermostat in each area. Then using TRV's on the rads or baseboard you can achieve temperature control of each room if wanted or desired.

What you are looking at in that Idronics drawing works great.

 

[EricO]

Lot's of 'em. We do all of our panel rad installs home run style via a main manifold. Usually 1 per floor if multi story. Baseboard with TRV's works the same.
The beauty of it is that the TRV's will modulate to match actual load in a given room.

You can also set up multiple manifolds with zone valves in front of them which are managed by a master thermostat in each area. Then using TRV's on the rads or baseboard you can achieve temperature control of each room if wanted or desired.

What you are looking at in that Idronics drawing works great.

Thanks heaterman. Would you have a suggestion on the size of pipe if i want to have about 6 zones coming off, all 3/4 inch piping? I'm thinking 1"1/4.

 

[heaterman]

What's the total btu load of all 6 zones combined and the total length of BB you'll be supplying?

 

[EricO]

What's the total btu load of all 6 zones combined and the total length of BB you'll be supplying?

The total of all loads is 50742 btu, and the total length is 90 ft. I'm using the Slantfin Multi/Pak 80, and based my length on 160* water temps, hopefully to gain a little bit extra time between burns using my thermal storage.

 

[heaterman]

I don't see any reason to go more than 1" supply to the manifold unless the total length is very long. Like in the neighborhood of 200'+ from boiler out through the BB and back. 1" pex in moderate lengths will flow 6-7 GPM pretty easy. If you have enough emitter out in the rooms to generate a 20* supply-return drop that will give you 60-70,000 btu available.

Assuming that 90' of active baseboard is divided somewhat equally you shouldn't need more than 1 to 1-1/2 GPM through each circuit. You'll gain a few more btu output with increased flow but not much using only 160* degree water. That being said.....

You may want to check the output of that SF80 series with 160* water to make sure you are going to generate enough heat with that temp. Most BB factory output ratings are shown at 180* temp so with 160* you'll get a reduced actual btu's to the room.
Maybe you've already done that but I usually figure 500btu/ft of active fin @ 180* for an average. So using taht, 90' would produce about 45,000 btu.
Bearing in mind that your 160* water temp entering each circuit wants to drop about 20* as it travels out and back, you'll have reduced btu output as it goes along. So a little extra BB is probably something to take a look at.

 

[EricO]

Awesome, 1inch sounds good because that seems like the most available for shopping purposes. No just to decide between a pressure regulated circulator, or a differential pressure bypass valve. I'm leaning towards the circulator.

As for the amount of baseboard, I used slantfin's spec sheets, which are really nice by the way, which give btu's for multiple temperature ranges. If i remember right, they show it for 10 degree intervals starting at 190 all the way down to 120. I based my length off the 160* rating, and then rounded UP a little on each calculation.


Thank you for all the input by the way. It's been very helpful!

 

[heaterman]

Go with the circ for sure. Pressure differential bypass valves are a waste of energy and after time, they always stick rendering them useless.

 

[ewdudley]

... a setup like this?

Note that there is a venting tee at each high point.

 

[Bob Rohr]

Awesome, 1inch sounds good because that seems like the most available for shopping purposes. No just to decide between a pressure regulated circulator, or a differential pressure bypass valve. I'm leaning towards the circulator.

As for the amount of baseboard, I used slantfin's spec sheets, which are really nice by the way, which give btu's for multiple temperature ranges. If i remember right, they show it for 10 degree intervals starting at 190 all the way down to 120. I based my length off the 160* rating, and then rounded UP a little on each calculation.


Thank you for all the input by the way. It's been very helpful!

You may be able to use 1/2 or 5/8" pex to the baseboard loops, depending on BTU load and loop length. 3/4" pex can be gnarly to work with on baseboard with connections close to the floor.

If you use TRVs like shown in that drawing , no need for balancing valve. The TRV is a proportional valve that opens and closes based on temperature requirements. TRVs are a bit awkward on low mounted baseboards, consider zone actuators on the manifiold and low voltage t-stats for every zone. Use a manifold with flow setters and adjusters built on.

Either way use a delta P circ for best control and lowest energy consumption.

 

[EricO]

Why are the TRV's awkward? just being able to access them? DO you have to cut a hole in the baseboard cover? I've thought about the zone actuators, but they seem like they would bump the cost of the system up quite a bit, or am i incorrect?

Also would I need the manifold that has flow setters for both system options (TRV or zone actuators) or would I only need it for the zone actuator set up?

 

[Bob Rohr]

Why are the TRV's awkward? just being able to access them? DO you have to cut a hole in the baseboard cover? I've thought about the zone actuators, but they seem like they would bump the cost of the system up quite a bit, or am i incorrect?

Also would I need the manifold that has flow setters for both system options (TRV or zone actuators) or would I only need it for the zone actuator set up?

Exactly, a temperature control at foot level isn't very user friendly and they are prone to damage from vacuum cleaners, furniture shuffling, etc. I have never seen a really clean way to mount and protect them, and bending over to make temperature adjustments is a young mans sport.

I really like the way a TRV controls heat output, it's the most common control used on European systems both panel rads and radiant. They just have not been embraced in the US market.

I did one job with the Oventrop Unibox, if the "looks" work for you it is a great thermostatic, wall mount control. It takes some planning and has some piping limitations, but is a nice smooth, non electric control, and great with Delta P circs.

The flowsetter manifolds are nice for dialing in flow rates and troubleshooting systems, more and more manufacturers are offering them as standard equipment.

 

[EricO]

Ok, so I might have just missed it, but if i went with the TRV's, your saying that the flow setting manifold is still a good idea correct? Just because it can help with dialing the system in? I just wanted to make sure I understood correctly.

Those pics are great. I like how the manifold has the air bleeds build in to them, as well as the shut off valves.

Would the oventrop unit still mount down low? Have you ever used the remote TRV's? The ones that have a capilary tube? I'm assuming the tube would just go up the wall. Maybe not looking the best....

Side question: When people use the TRV's, what do they do for the thermostat for the boiler? I'm trying to figure out how to set that up. I'd like the baseboards to take their heat from the wood boiler, and then storage tank when boilers not running. Then when the storage starts to run low, propane back up. I'm thinking i would just set the propane back up for a lower temp than everything else, so it only kicks on to keep the house "warm" instead of "toasty"

 

[Bob Rohr]

If you use TRVs match them with a delta p pump, like the Grundfos Alpha, Armstrong Compass, or B&G Vario. As the valve opens, the pump wakes up and modulates it's output to the valves requirements. No need for balancing at the manifold. but most quality manifolds come with the flowmeters anyways. Flow setter/ are good to confirm you have flow, or troubleshooting.

A few ways to fire the boiler or heat source. An outdoor reset control would start the boiler when the temperature hits 68F outside, for example.

Or just an outdoor thermostat to turn the boiler or tank on when the temperature drops. A basic thermostat would not modulate the supply temperature like an outdoor rest does. Basically the outdoor reset control ramps up the supply temperature as the outdoor temperature drops, like a cruise control for your system.

The Oventrop would mount at eye level like a typical wall thermostat. I have not tried the remote cap tube TRVs. They are limited to a fairly short cap tube, so the control would need to be fairly close to the heater, not very doable.

Some additional zoning and manifold info here; including piping, wiring, and control examples.

There are dozens of ways to pipe boiler, tank and back up. If the tank is not too large, just have the boiler maintain that temperature. Pull the heat from the tank with a reset control modulating a valve. That allows you to heat with the lowest possible temperature water.

The back up would only fire when the tank temperature drops to a "low" point. Typically the boiler feeds directly to the heating system, no need to heat the storage with fossil fuel. A modulating output boiler works great for that, and most have all this control logic built into the boiler control now a days.

http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_4_0.pdf
http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_5.pdf

 

[EricO]

OK so maybe you can help me, because I've been trying to comprehend the operation of this system, but I'm stuck on what encourages the water to flow through the storage tank in this set up. This diagram is one from the EKO boilers website, and I think it would work well if I emulated something similar to it, but I'm just trying to figure out what encourages the water to flow into the tank.

Also curious about if the system is running on storage water, or propane boiler, what happens if the pump on the wood boiler turns on to keep warm water circulating so it doesn't freeze? will it mess with the flow to the baseboards? What do you think? Ignore the "what does this do". I know now.. they are check valves

 

[Bob Rohr]

OK so maybe you can help me, because I've been trying to comprehend the operation of this system, but I'm stuck on what encourages the water to flow through the storage tank in this set up. This diagram is one from the EKO boilers website, and I think it would work well if I emulated something similar to it, but I'm just trying to figure out what encourages the water to flow into the tank.

Also curious about if the system is running on storage water, or propane boiler, what happens if the pump on the wood boiler turns on to keep warm water circulating so it doesn't freeze? will it mess with the flow to the baseboards? What do you think? Ignore the "what does this do". I know now.. they are check valves

Good question! I have always wondered which way the flow travels in the piping. The flow will find the path of least resistance, and under some conditions it looks like pumps are in series, doubling the head.

I believe those two valves are to change the flow direction for heating the tank, or un-loading the energy.

 

[EricO]

Good question! I have always wondered which way the flow travels in the piping. The flow will find the path of least resistance, and under some conditions it looks like pumps are in series, doubling the head.

I believe those two valves are to change the flow direction for heating the tank, or un-loading the energy.

I was luckily able to ask the guy who designed the system. He said basically that. It uses some weighted check valves to help decide where the flow will go!

I had one other question for you, since I'm trying to figure out pump size. Each zone (there will be 6) will only have a heat loss of around 9000 btu at most. They are all pretty close in size. Should I try and base the flow off of a 20 degree delta T, or would it matter much if the delta t is lower. I'm thinking if I pumped faster, it would be a lower delta T, but may be just wasting electricity since I'm pumping more water... Thoughts?