New boiler question

[mrojec]

I recently had a new Munchkin 199K BTU boiler installed in my home with radiant floor heating. Slick little unit, by the way. The installation manual shows 2 circulator pumps, one on the supply side and one on the return side, but mine only has a supply side pump. My contractor said the return side pump is unnecessary.
Perhaps this is a redundancy meant as a safety backup. Anybody have an opinion about this? Thanks!
Mark

[crokett]

I wouldn't know but if you don't get an answer here post over on Woodnet. There are a couple guys who do HVAC for a living who frequent Home Improvement over there. I'd also call the manufacturer and see what they say.

[Uncle Cracker]

I don't have a definitive answer for you, but if it's typical of any closed piping system I've dealt with, a second pump would be unnecessary if the first one was of adequate "oomph" to overcome the friction losses in the piping and equipment (and any elevation change) for the whole system.

Simply put, if the water goes in one end at sufficient pressure, it must come out the other end, as there is no place else for it to go. Whether it gets the appropriate volume and pressure to each area of the network is another question altogether, but would be determined more by the design factors of the piping system, rather than by the pump(s), regardless of how many there are.

Bottom line is that whomever has designed your system is probably the most instrumental. Hope this helps.

[TheRic]

I have hot water heat, also work in a building that has hot water heat. All only have one pump, per zone. For example I have 1 for main floor, one for finished basement. I have a feeling it depends on the distance of the pipe run. You will lose so much pressure drop per foot this varies on pipe / hose size, smaller the inside diameter the more pressure drop. I think the one on the return side is to help pull the water pack.

As you know, pictures in manuals do not always show the only way things can be, just one generic example. If you do some reading in the manual you might find something that talks about this. The size of the pumps can also play a major factor. A 1/4 HP pump is not going to have the potential (volume and/or pressure) of a 1 HP pump.

[Hellrazor]

You don't need 2 pumps if the supply side pump is sized correctly for the size of the run.

[steve-norrell]

The length of run for in-floor heating verses peripherial heating must be substantially longer for the in-floor run. Basically, the in-floor line must duplicate twice the length or width of the room several times over to produce an effective grid under the flooring surface. Physics rules.

A longer run requires either a bigger pump or an added return pump. Which way you go may depend on cost of the larger pump, operating costs (electricity) and noise.

Regards, Steve

[siliconbauhaus]

Why not just ask the manufacturer and explain to them the layout you have? The contractor may or may not be right and it doesn't cost anything to ask.

[430752]

I'd say two pumps are better than one, but thinking of a closed-circuit fluid system, couldn't a second pump be potentially bad? I mean, unless the two were closely linked in pumping power, a second pump which sucked more than the first pump pushed could create vacuum problems, etc., no?

[Uncle Cracker]

I'd say two pumps are better than one, but thinking of a closed-circuit fluid system, couldn't a second pump be potentially bad? I mean, unless the two were closely linked in pumping power, a second pump which sucked more than the first pump pushed could create vacuum problems, etc., no?

Not really. Depending somewhat on the kind of pumps involved, a pump that is pulling will "freewheel" if the available supply is less than its capacity. Other than a bit of cavitation, possibly leading to premature impeller wear, this wouldn't be a make-or-break situation. Fact is, most pumps are far less efficient at pulling water than at pushing it, so it would actually take a much bigger suction pump to create such an imbalance, and in a closed system, the flow rates would be the same at either location.

[pelligrini]

The reason for the second pump may be the pressure drop at the heat exchanger. Most all of their installation diagrams have two pumps, even the circulator sizing chart on page 15. I hope this installation doesn't void the Munchkin warantee.