Zone valves or pumps

jim f

Dave_22

Zone valves or pumps??

What are the advantages or disadvantages of having zone valves or circ. pumps? I am planning a 5 zone system (radiant,BB and Indirect HWH) and wondering if I should go with zone valves or pumps. Also on the Veissmann ad for the Vitodens 200 it says "no Secondary pumps needed" but some of there documentation shows secondary pumps. Is that only if there prim. circulator can't handle the load???

Steve_35

In many cases it's a personal preference. I generally choose to go with zone valves for what I like to feel are rational reasons.

1. The pump gets used all year long if you have an indirect w/h.

2. No flow checks to fail and cause "ghost" flows. I hate the darned things.

3. You don't need a realay for each zone.

4. A $5 24vac relay will give you HW prioritization.

5. Uses somewhat less electricity.


That said I'm not sure how you'll do the radiant portion if it's tube w/o a second pump for it. In that case I'd still use a zone valve on that in place of a flow check. Did I mention I hate flow checks?

Dave H_2

Circs

Based on the scenario (Radiant, BB, and Indirect), more likely to be zoned by circulators.

Is it only these three zones you have on the project?
You could always do combinations of zone valves and circs.

The radiant zone(s) will likely need its own pump because of the mixing valve you will need for the lower temp. Whenever using a mixing valve, a circulator MUST be placed after it in order to induce flow to the radiant floor.

Then you can use another circ for your baseboard and possibly use zone valves after that.

Take a look at the attached piping and wiring schematic. Your may be slightly different based upon the boiler, but the idea will remain the same.

Dave H.

Dave_13

Actually..

The plan is 4 radiant zones, 1 HWBB and 1 Indirect HWH. The 1 BB zone is in a finished basement and will probably run once or twice a week (Don't spend a lot of time down there). I posted a thread awhile back about dual setpoints. It seems like a waste to have boiler water set at say 180F for BB that only run once or twice a week and to mix it down for the radiant all week long. Would like boiler water at 120F for radiant and "IF" the BB zone calls for heat I could ramp up the boiler water to 180F. Then have mixing valves on the radiant that would modulate temp. back to 120F. Does this make sense? Anyone do this type of setup?

Roy_2

water temp

Ah the beauty of hydronics- options! If you want to run the boiler at a lower temp and the only radiation causing you to need 180° simply size the baseboard for lower temp. Most manf. give a 180° and a 140° rating.
Of course you could put the boiler on outdoor reset and let it ramp up and down based on demand ( highly recommended for radiant). Controls are more expensive fuel savings are significant, comfort level is dramatic - but if it is just an unused basement with very low demand to begin with saving 20-30% of $200.00 per year demand - well then its really about comfort and if the room is not used who's comfort are we looking at.
Setting the boiler on cold start with lower max temp and "oversizing" baseboard is a simple option but doesn't offer the same savings as outdoor reset nor will it offer the comfort level on the radiant as outdoor reset and really isn't that what radiant floor heat is about?
Most important is the boiler some boilers cannot be used with a return water temp below 140° not a problem if you want to run 160° supply with a 20° delta T but will void all warrenties if you run 140° with a return of 120°. So make sure the boiler can handle lower temps. The two that I've used are Buderus and Veissmann both European.
All that being said there are more options available depending on your house, need, design and budget. Like I said the beauty of Hydronic Heat is the almost unlimited designs available.
Roy

Dave_13

A twist...

Now, how should the radiant temps. be set up for carpet and vinyl????? From what I understand they should be different?? This will be a underfloor install. with aluminum heat plates.

Dave H_2

Well now

this project is starting to get more complicated!

The first thing to do is to perform a heat loss and a radiant design to find the desired water temps based upon the heat loss and the finished floor coverings.

That is my best suggestion to start with now. The question of which is best, circs or zone valves shouldn't even be coming up now. You need to know your water temps, zoning sequence (which doesn't always work out the way you want because of floor choices, heat loss.....)

But your piping with multiple water temps might look a little like this.......

Dave H.

Big Ed

Dave, the only advantage of using zone valves ....

.....is the cheaper price of the install.


P.S. Jim , nice job, you can see the pride...