Circulator operation

Brad White

Understood, how could one resist? Still, and as you know, we have to respond to these questions on the basis of what is available....

did I say that? <i>"What is available..."</i>

Yes. Yes I did.

:)

Roger Redmond

Circulator operation

Which is the best way to operate circulators?

1. Constant-running circulator, in which the pump is controlled by a manual switch. The pump is usually turned on at the beginning of the heating season and runs constantly until it is turned off at the end of the heating season. The boiler is independently activated by the thermostat as heat is required.


2. Aquastat-controlled circulator, which turns the pump on and off at a preset boiler temperature (normally 120 F. Like the constantly running circulator, the burner is independently activated by the thermostat as heat is required.


3. Thermostat-controlled circulator, in which water is maintained at a constant temperature in the boiler by an aquastat.


4. Relay-controlled circulator, in which the pump is activated (via a relay switch) whenever the boiler is activated by the thermostat.

Thanks for all replys.

Rich L.

??

Hi Roger, what type of emitters are you using? Condensing boiler? Outdoor reset? Trying to get by for the lowest cost or looking for the highest comfort level?

Brad White

Will you accept \"It Depends\", Roger?

In order of your choices:

1) Constant running via manual switch (or outdoor T-stat I will add): Fine if this is the secondary/radiation side of things or if your boiler has low temperature protection or is a condensing boiler.

There is a school of thought that constant circulation with TRV's on the radiators and the boiler fired by the thermostat give a "by-default outdoor reset", with warmer temperatures in cooler weather. A minimum or low boiler limit is usually required unless it is a condensing boiler.

2. Aquastat control: Fine if you have no other boiler low-limit protection. This is a traditional way to control a lot of boilers since the 1940's-50's. Wastes energy as you are firing the boiler while delivering bupkes.

3. Thermostat-control with constant boiler temperature: Best way to control any system if you are a gas or oil company Large cycles in space temperature, arbitrary fuel consumption, one flavor all the time. At least add boiler outdoor reset to keep a range of 140 minimum up to design high temperature.

4. Relay Control in parallel with boiler. Provided you have boiler low limit protection, this is probably the smoothest compared to constant circulation. No big inrush of hot water as with constant temperature.

Best of all worlds in my opinion: Circulator run off of OD temperature below say 65F. 4-way mixing valve with outdoor reset and boiler protection (if a conventional high temperature boiler) or direct modulation (if a gas fired condensing boiler) for a simple one-zone system.

Best combination of indoor temperature comfort and energy savings.

My $0.02

Brad

jp_2

4 way puzzle?

brad why the 4 way mixing valve with OD reset and a modcon?

got a diagram?

Brad White

Not with a Mod-Con

There are so many variables with these hypothetical intances, JP-

I would never use a 4-way with a Mod-Con. A 3-way if I needed a zone mix-down but otherwise straight off the Mod-Con if I could.

For a conventional cast iron or high temperature boiler, I prefer 4-way valves for all the right reasons.

jp_2

welll

I guess if i would read your post closer I wouldn't ask a dumb question now I see the errors of speed reading.

Brad White

Evelyn Wood

never read the word "hydronics", even slowly.

Unknown

Circulator Operation

These are all great comments for standard, constant speed circulators.

The newer technology ECM VFD type of circ controls itself (automatically decreases speed and flow as zones close). Even with a no flow requirement these residential circs draw less than 6 watts - can run at zero flow (deadhead) forever without overheating. These have been available in Europe for quite a while and larger ones are currently available over here - smaller residential types will be available soon.

In saying that, for optimum energy savings it might be a good idea to automatically shut these off during warm weather shut down.

Appologies, couldn't resist.

Rich L.

variable speed pumps

Hi Steve, When do you expect those new residential pumps to be available over here? I'd be happy to have my house be a test bed