Adding zone to boiler with built-in circulator
I've just had a Triangle Tube Prestige 110 boiler installed. This is a modulated condensing boiler, and has an internal circulator pump for the hydronic loop.
What is the typical way to add zone to a boiler with an internal circulator? Would I add additional pumps outside the boiler, or just zone valves?
I'm an electrical engineer, so the control logic is easy for me, and I am a pretty good amateur plumber. So I'd like to do this part myself.
The old forced air system only served the first floor, and the second floor stayed pretty warm anyway. We thought we could get away with just heating the first floor for the time being, but it turns out that it's not the case with the new hydronic system.
Re: Adding zone to boiler with built-in circulator
First, congrats on buying such a great boiler---I know you'll be satisfied with it.
Zoning on hydronic systems is done with either circs or zone valves.
Circs require more components & have the advantage of providing heat even if one of the circs dies at 1 a.m. on a sub-zero nite.
Many techs prefer circs because in the past zone valves were not reliable, but that is no longer the case.
I would recommend 2 zone valves supplying the internal Grundfos circ you have now, due to the low cost of zone valves & the relative ease of the diy install.
You didn't mention the sq.footage of the upstairs & downstairs---I assume this is for baseboard---but how many total feet of basebard/rads/radiant??
You would have to separate the piping so that you would have an upstairs zone and a downstairs zone.
A third zone is often used to run an indirect hot water heater--all on the same circulator.
A useful precaution is to install a shutoff ball valve of appropriate size on either side of the Grundfos circ & have a spare circ handy in the event it dies at an unexpected moment.
The two ball valves would allow the dead circ to be isolated & replaced without draining the system---heat could thus be restored within 1/2 hour.
The zone valve works on the concept of 2 separate t-stats---one upstairs, one down.
The t-stats (really a switch) control everything---when the upstairs or downstairs t-stat calls for heat, the t-stat closes, making the electrical connection.
The t-stat wire goes to the zone valve switch for that zone & slowly electrically (1 minute) opens the valve so water can flow.
After the valve is open the "end switch" on the zone valve sends elec. energy via a wire to the TT terminals on the boiler aquastat & the boiler fires, the circ is energized & starts pumping water thru the recently opened zone valve (the other zone, which is not calling for heat) remains closed, so heat is delivered to one zone only.
If the other t-stat calls for heat while this is going on, then it too will open & will remain so until the t-stat on both zones opens as the room heats up, opening the t-stat contacts & shutting down the boiler---the circ often continues pumping hot water (override)for a minute or 2, then the zone valve slowy closes.
The heat anticipator on the t-stat has to be set to .9 to be compatible with most zone valves.
Some diagrams have been included that show how zone valves or circs are piped in the system.
In the most basic diy zone valve project, the system is closed down at the on/off switch & the water drained; the MAIN SUPPLY PIPE coming out of the top of the boiler is cut, & a simple manifold pipe with the 2 zone valves is attached at that point (after the air eliminator and expansion tank, if they are connected at this location).
Some people use a "Y" fitting the same size as the boiler pipe to establish the 2 branches needed for the 2 separate zones.
The low voltage wiring is then attached according to the diagram that is included with the particular zone valve you buy.
A 40VA transformer (120v primary/24 volt secondary) is often needed to power the zone valves.
When soldering the zone valves to the piping, the ZV head is easily removed with a twist to protect the electronics from heat damage.
The system is recharged with water & turned on for testing.
There are many variations, but that's the basic procedure.
I recommend the 570 series Taco **** zone valves---they are quiet, and very reliable.
You have, I believe, a Grundfos 3-speed UP 15-58 internal circ---these are also reliable units---the speed, or amount of water pumped can be increased or decreased to maximize heating capacity & needs on the two zones.
Some people include a control panel (switching relay) and put everything on a piece of plywood bolted to the basement wall with a manifold for the zone valves, etc. for a more elaborate install---this often looks neater, if the boiler room is cramped elsewhere---make sure you leave enough headroom if you install the ZVs near the ceiling sbove the boiler so you don't bang your head on them walking around there.
You have some diagrams in your Triangle Tube installation manual, but I didn't find them that helpful---the manual (and zone valve diagrams at the "Library") is also on line at their site below.
Also Google "zone valve piping diagram" for additional zone valve piping & wiring diagrams.
The "coil" listed in the temco diagrams (2-way zone valve) is the baseboard coil, representing all the baseboard (heat load) or radiators you have connected in the zone.
Last edited by NashuaTech; 11-20-2008 at 02:55 PM.
Re: Adding zone to boiler with built-in circulator
Thanks for the detailed response!
The installer built a sort of manifold for both the supply and return sides with two branches, each with a separate ball valve. One is unused. He knew I planned on a second zone, so the first bit of pipe is there for me.
The house is tiny - less than 1000 ft^2 total. It's a cape. We just don't want to heat the first floor at night.
The radiators are Veha panel type. They are piped in a reverse return arrangement with 3/4" trunks and 1/2" branches (which are all very short). Second floor will be the same arrangement.
Sounds like I just need to buy two valves and another thermostat and I'll be in good shape.
Regarding the manual, the installer didn't like it much either. It took them 5 days (!), and I had already installed and piped the radiators before they started. They eventually had to have the rep come over to get it fired. Luckily, they were hired by my propane provider who sold me the boiler, so I'm not paying them by the hour!