Valves vs Pumps

Welcome to the Boiler Room, Joe. Nice to have another Tarm in CNY.

The pump/zone valve debate is alive and well. I had to make the same decision when I installed my boiler, and was told by the dealer that you get better results from pumps, vs. zone valves. So that's what I went with, and it works just fine. I don't think the increased electrical usage is enough to notice.

Hopefully somebody in command of some facts and numbers can provide a better analysis of the pros and cons of each approach.

Depending on what circ you are design around, a typical one consumes around 80W. So 6 X 80 = 480W. Plus each one needs a relay and iso flanges when you look at cost difference.

With a single circ you have 80W plus the current draw of the zone valve transformer. A much smaller number.

Consider you are moving a load of about 140,000BTU/hr. (boiler input) at 70% efficiency or 98,000 BTU/hr. This is well within the range of one small 80 W. circulator.

Keep in mind small wet rotor pumps are fairly electrically inefficient. Depending on where on their curve they run, figure a wire to water of mid to high 20% efficiency. Does it make sense to run 6 circs at 20% efficiency, or less?

Often times installer use the same model off the shelf circ on every zone. With your size load they may be running well off their sweet spot in terms of efficiency.

There is a place for circs and zone valves. Personally for typical residential systems one circ and ZV's is my choice. Very soon higher efficiency ECM circs will hit the streets. These consume much less energy and can self adjust to the load as zone valves open and close. I replaced an 80W circ in my shop with one last year and it runs from about 7W to 28W depending on how many zones are calling. pretty sweet technology.

A spare circ would cost you around 80 bucks if you are worried about a failure keep a spare on the shelf

With zone valve proper installation is important and a pressure bypass valve assures quiet efficient operation. If you go with ZVs be sure to use a large bore high Cv valve on the indirect for quick recovery.

hr

In my never-so-humble opinion, both will work fine. Zone valves probably make more sense in a system with a smaller number of zones, and where the zone flow rates are similar. It seems simpler to add additional heat sources (wood, solar, etc) in a valve based system.

If you get heat loads with vastly different flow requirements, or a large enough number of zones so that overall flow rates vary wildly, then a pump based or even primary/secondary gives you finer control of where heat is coming from and going to.

I've been zone valve based and have had no problems at all. Simple and easy to understand what's happening.

I with no fossil I like valves but if your worried about flow you can always put a larger circ in the place of the existing one and keep the zone valve.

I'm building primary/secondary with all pumps. No valves....... As for the plumbing, Primary/Secondary is the simplest setup going..... Gill Carlson wasn't head of Bell & Gossett's technical division because he was stupid.......

Now, the electrical logic for a storage based system can be a bit tough.. I've got some ideas.... Once I figure them out, I'll share with everyone.....

deerefanatic said:

I'm building primary/secondary with all pumps. No valves....... As for the plumbing, Primary/Secondary is the simplest setup going..... Gill Carlson wasn't head of Bell & Gossett's technical division because he was stupid.......

Now, the electrical logic for a storage based system can be a bit tough.. I've got some ideas.... Once I figure them out, I'll share with everyone.....

Click to expand...

Check with Nofo; he's got this ALL figured out...

An engineer I spoke with mentioned that it seemed to be a North vs. South thing. He observed that up THERE, they used more circulators while we down HERE use more valves. Or maybe it was the other way around, I dunno. It would seem to me the circulator would be less reliable, but modern canned rotor circulators seem to be very durable pieces of equipment. Zone valves can be opened manually if there is a problem. For energy efficiency, the single circulator seems to have an advantage and you could always pipe a second one in parallel for redundancy or heavy load situations if desired.

Chris

For me the key here seems to be the OP has a system using zone-valves already installed - since the investment has already been made in that direction, it would seem that one would need a very compelling reason to switch at this point.

Exactly... No reason to jump ship.. If you're already started with zone-valves, then you have a significant financial investment right there that you should not jump ship on.....

As for my electronics.... I've already been in touch with nofo... His solution is great, but is out of reach of the average non-programmer computer geek... I'm going to try and build my system with simple basic electronic logic and some digital temperature controllers I found for cheap on eBay......... All hard-coded and wired.......