Replacing a one speed Taco 007 pump, switch to variable speed Delta-T pump or not?

Cliffy

We have a Burnham ESC gas fired boiler with a Burnham ODR module installed, and we need to replace a Taco 007 pump which handles a typical heating loop. The pump dates back to the prior boiler and is very aged.

Would there be any benefit to installing a Taco Delta-T pump, specifically the Viridian-VT2218 Delta-T Variable Speed, ECM High-Efficiency Circulator?

It's been recommended, but I don't understand why.

icesailor

If the 007 was working well, and you are willing to spend money to replace something that was working, spend more money.

You will never in your lifetime, recover the additional cost over the 007 that is working fine.

R2.0

If you are already doing ODR, adding a variable speed pump isn't going to give nearly the cost savings as installing it otherwise. Efficiency gains aren't additive, at least not arithmetically.

Cliffy

Well, I know the board does not like to discuss pricing.

There's some kind of a special or something which makes the variable speed Viridian-VT2218 insignificantly more expensive than the fixed speed 007.

So simply given the choice of either pump, which would be preferable?

I don't understand the benefit of one over the other.

icesailor

Maybe some of us don't understand the benefit either.

MikeL_2

There is a rebate program here ( CT ), that brings the cost of ECM circulators below most fixed speed circulators. ECM circulators can help reduce flow erosion & water hammer, and, may help reduce some expansion noise. They consume much less electricity, resulting in measurable savings........

Tom_133

Here in Vt the posted savings on the Efficiency Vt website is 80.00 off the price of the pump that is very good on an alpha bringing it under the price of a 007 but still making the pump you want the delta T pump a bit more.
If I were in your shoes, I would take advantage of the rebate swap that old pump.

I only posted numbers that are known on vermont's website, I believe Dan would be ok with this.

Steve Thompson (Taco)

Variable speed (flow) or not variable speed - that is the question.
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We get asked this a lot - my take is if the zone sees variable flows then it would make sense to install a variable flow circ (like a car with a gas peddle). Electrical savings only might be about $5 to 7$/year so I completely agree the payback doesn't make sense.

But (always a but), we've seen SYSTEM efficiency increase 25 to 30% using variable flow circs so looking at electrical savings on these little guys is only part of the picture.

Variable flow systems will benefit from variable flow circs (less noise, longer zone valve life, less internal pipe erosion caused by high water velocity etc.). Constant flow on/off circuits (zoning with circs for example) would only see a variable flow benefit if the zone differential temp is modulated with the circ to maintain a higher zone efficiency during various outdoor air temps and zone loads.

There is also the "if it ain't broke don't fix it" thing. So replacing a constant speed with variable speed is up to you guys. Only one word of caution - be very careful using variable flow for a boiler circ - just sayin...

Eastman

@Steve regarding boiler circs:

Have you considered optional minimum/max speeds for variable pumps?

Steve Thompson (Taco)

Agreed - an excellent option for constant load (zoning) circs...

Eastman

Your word of caution regarded boiler circ applications. What are the concerns?

SWEI

Sometimes they just don't get along with the onboard controls. My gut feeling is that this is probably caused by the control loop (PI or PID) coefficients in the pump and the boiler being different. They can get out of sync and cause the boiler safeties to trip.

Variable speed boiler circs should really be controlled by the boiler's onboard controls. I'm still hoping for a 0-10V input on the new smaller VT family some day...