How many pumps?

MechTech_2

Your contractor has identified that the pump in the Baxi is undersized for the application, and he's probably right! Every time we install a Baxi we build a primary loop, and the pump in the Baxi becomes the primary pump. We then install a pump for each type of heat emitter, but this is just a mattter of preference. Does your system satisfy the heating requirements on the coldest days of the year?

Steve Goldstein

How many pumps?

I have a Baxi Luna HT 1.33 that was, to put it mildly, poorly installed 1-1/2 yrs ago. I've had numerous problems with it, and the original installing contractor has basically written me off and won't help me correct the problems.

I've since found another technician in the area who knows the Baxi better than the original contractor and is working with me to make the system right. The first thing he figured out is that there wasn't a large enough gas line running to the boiler, so it didn't have enough gas during high fire. As a result, it couldn't be calibrated correctly, which caused numerous problems. He's since installed a larger gas line, and now the Baxi is calibrated to perfection. The system is heating the home and the DHW tank much better now.

To really make the system right, though, the new contractor is recommending that he re-plumb the whole system to create a primary loop, replace all of my zone valves, install a Taco zone control with DHW priority, add an air scoop and extra expansion tank, and install a circulator pump on each zone.

I'm sure this would be a textbook installation that would work really well. But this job is **expensive**, after paying a lot of money 1.5 yrs ago for the original installation. Frankly, I can't afford the job as he quoted it.

Is he proposing a job that's more complex and expensive than necessary? The system is heating well now. Are his recommendations overkill? Is there a compromise that would improve the system without being as over-the-top as he's suggesting? Is it really necessary for **every** zone to have its own pump? (Right now, the only pump on the system is the pump built into the Baxi, which is servicing 5 copper fin baseboard zones, one air handler zone, and one DHW tank zone. The old cast iron boiler the Baxi replaced also only had one pump on the system.)

I trust that this guy is knowledgeable, but at the same time I can't help but wonder if he's making this job bigger than it needs to be.

I look forward to your advice.

Thanks,

Steve

Steve Goldstein

Yes, the comfort level in the home is very good right now with just the Baxi's pump. But I do admit that the Baxi is moving a lot of water when multiple zones are calling for heat at the same time.

So I don't doubt that adding more pumps is a good idea, but do I really need **seven** more pumps?

When you say that you install a pump for each type of heat emitter, does that mean that you would install one pump to handle all of the baseboard zones, one pump for the air handler, and one pump for the DHW tank?

Constantin

Here is what I would suggest...

Take a look at the manual that came with the boiler (or download it) to see what the manufacturer recommends. Not every boiler needs to be plumbed pri-sec.

From a DHW point of view, it is nice to have a priority control on it. That way, your DHW is maximized since the boiler will dedicate itself to making DHW whenever the storage tank goes out of its lower thermal boundary. However, if your DHW is currently OK for your purposes, then this may be a nice-to-have as opposed to a must-have.

So, in summary, do what the manual tells you to do regarding near-boiler piping for heat and DHW. Manufacturers spend a lot of time developing these manuals hoping that most installers won't just use them as knee-pads during the install.

As for replumbing all the zone valves, you have to understand that a lot of contractors prefer pumps since in their past experience pumps were a lot more reliable than zone valves. Many contractors still feel that way, considering the many "pump panel" pictures one sees on the web. However, most pump-only systems feature pumps that are vastly oversized for their application...

Siggy's Hydronic Explorer program does a great job at figuring out what pumps are actually needed in your home. It is very hard to get pumps small enough in this country to actually match the low-volume water requirements... Hence, some contractors use manifolds with several zones on each one and a pump to feed it all.

For a creme-de-la-creme approach, consider using one or two variable-speed pumps that feed your zone valve manifold(s) since such pumps maximize your operational cost savings via very high efficiency and by only pumping as much water as is needed for each zone. However, the specifc savings are very dependent on your home and the payback may not justify them.

tim smith

How many zones?

You state the pump serves 5 baseboards, 1 air handler and 1 indirect water heater. Thats only 3 + boiler pump, how do you come up with 7 pumps? Also post a pic of your boiler and associated boiler piping just for yucks. Tim

Steve Goldstein

The contractor is proposing that each of the 5 baseboard zones has its own dedicated pump, so that's 5 pumps. Then one pump for the air handler and another one pump for the DHW tank, for a total of 7 pumps (not including the Baxi's internal pump).

I've attached some pics.

joel_19

pumps

I believe your contractor is on the ball as he has already solved a problem that most miss. His approach for the piping will most likely work flawlessly as well.

Here is another aproach that may work well and be less exspensive. Have him look at the Wilo Stratos circulator pump,he may not be aware of this type of circulator. The price of the pump will give heart palpatations compared to a regular circulator. However the capabilities of this pump may save from repiping everything,which could be quite a bit cheaper overall.

I won't get into tech details but basically you can dial in it's speed to virtually anything you want. As zones open and close it will AUTOMATICALLY adjust itself to compensate and keep flow rates through the boiler steady. In addition it will use much less electricity than all those other circulators.

i have no idea not having seen your system if this will work but the idea is worth exploring.

tim smith

What size of boiler is that?

3/4" main S&R from boiler?????? WHAT! Just looks offfff.

MechTech_2

4 options

There are basically 4 options available if it is primary/secondary
1) 7 pumps
2) 3 pumps & 5 zone valves
3) Wilo Stratos pump is probably too big, but their Eco pump would fit the bill, but I don't think they are available yet.
4) Maybe, just maybe the internal pump is overcoming all the head pressure, and that's why your house is keeping up to temperature.

Steve Goldstein

Please elaborate on your option #2. When you say "3 pumps & 5 zone valves", what are those three pumps servicing? One pump for the baseboard zones, one pump for the air handler, and one pump for the DHW tank?

MechTech_2

Option 2

One pump for the baseboards, and each zone of baseboard(s) would have it's own zone valve. When a thermostats calls for heat, the corresponding zone valve would open, and the pump would then come on.

hot_rod

What is the load of the baseboard zones?

seems a pump per loop would be a bit overkill. I'd use the pump with 3 zone valves.

hr