Boiler replacement.

luma · April 26

Hello All,

My existing 5 zone Burnham Revolution boiler unfortunately start leaking and I’m planning on replacing it with a Weil-Mclain Evergreen EVG-155. My current setup is one zone a DHW, the rest are being controlled by Taco 555 Zone Valves. I had 3 different companies provide me with estimates and quotes do vary significantly, but obviously they are not really comparable since each company wanted to use different equipment. All of my zones are being controlled by Nest thermostats, neither has C wire nor would I be able to run a different cable to address a missing C wire. When a new boiler is installed, I’d like to install a Taco ZVC panel (I like the clean simplicity of this thing), the question I have is whether I should go with zone valves or circulating pumps. Currently I have a single pump, but for the past 2 and half years I’ve been replacing zone head valves like crazy. My understanding is that newer Taco Sentry Zone Valves don’t work well with Nest, so should I go with the older Taco valves I have or replace them with circulating pumps, thinking using Taco 007e circulating pumps. I know that this seems to be a rather old question, after all most of us have our own preferences, but what would your recommendation be?

Thank you

pedmec · April 26

Why would the zone sentry be an issue with the nest thermostat? The thermostat is going to be wired into your ZVC. The issue you will have is that you need to use the resistors that come with the ZVC. If you install the resistors you should not have a problem. At least in my experience with the nest and the ZVC. Just install the resistor between W and C on each zone in the ZVC.

luma · April 26

Thank you for the advise, will have to give it a try.

pecmsg · April 26

nothing works well with NEST!

EdTheHeaterMan · April 26

Every circulator will add more Gallons Per Minute GPM flow to the system that probably does not need more GPM flow. If the circulator pump can handle the entire system when all the zones for heat call, then there is no reason to add more pumps.

to turn this down to basic rule of thumb we often use in this trade: 1 GPM = 10,000 BTUh

If you have a boiler that has a net output of 124,000 BTUh NET, then you need to move 12.4 GPM when the boiler is at full output capacity. Having 5 zones with 5 pumps is really overkill. Especially when one pump can handle 12.4 GPM with no problem, if needed. I believe Zone Valves are the way to go for you.

And @pecmsg always has very helpful comments regarding Nest Thermostats. I applaud him for his convection on such a controversial topic.

hot_rod · April 26

I agree with Ed, a common residential circ, 1/12 hp, or ECM version can move 8, 10 or more gpm. That is plenty for common 100,000 btu or so.

On multi zoned 100K systems, the circs may only be moving 1 gpm or so on small zones

So a zone valve system with a variable speed ECM delta P circ, the flow adjusts as zones open snd close. Think of it as a cruise control for the distribution

Add ODR to the boiler and now that too is on cruise control

Boiler replacement.

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