delayed-off relay device for pumps?

Chuckles_2

We have P/S pumping, with a boiler pump and two zone pumps, the latter controlled by a Taco SR503 zone relay box. On the boiler, I can change a setting to cause the boiler pump to run for a while after the thermostat ends its heat call and the boiler stops. But this is completely useless, because the zone pumps are not running, so the water goes to the tees and comes right back.

The relays in the Taco SR503 turn the boiler on/off as well as the pump, based on the thermostat signals, so the relays inside cannot be replaced with delayed-off relays (or the boiler would also stay on longer, which defeats the purpose).

What I want is to have the zone pumps run for a few minutes extra after the thermostats have stopped calling for heat and the boiler has stopped, to purge the hot water from the pipes.

I know I can wire something up using a time-delay relay, but I don't want to use homemade gadgets here. I am hoping there is a packaged device that does that, either as a replacement for the Taco SR503, or inline between it and the pumps. I looked at the Tekmar zone controllers, but they are way too fancy for this purpose.

Many thanks for any suggestions,

Boston Boiler

What exactly is it that bothers you about the temp. of the water in the pipes once the call is met and the circ. shuts down? There is a SR503, is there an indirect water heater on priority zone? Maybe I'm not seeing something.

BB

Chuckles_2

No indirect. It bothers me that there is so much hot water left sitting in the pipes when the boiler stops. (The main zone is a converted gravity zone.)

Dave_13

Hmmm

What you need to do is have a time off delay relay that is controlled by your thermostat signal. across it's contacts will be a hot wire that energizes the zone pumps.

Boston Boiler

With the T-Stat telling the burner to stop and the delay relay to run the circ. for a set amount of time removing the hot water in the pipes, what would calculate the temp. of the water being pushed out by what temp. water being returned. How would the anticipator be acurate? Would you have an ambient temp. that was always inconsistant with the T-Stat setting?

BB

Chuckles_2

???

> With the T-Stat telling the burner to stop and

> the delay relay to run the circ. for a set amount

> of time removing the hot water in the pipes, what

> would calculate the temp. of the water being

> pushed out by what temp. water being returned.

> How would the anticipator be acurate?


I don't know what you are asking. No one is looking at the return temperature is the boiler is off, the water will cool off in the pipes anyway. The anticipator is irrelevant once the thermostat has stopped calling for heat.

> Would you

> have an ambient temp. that was always

> inconsistant with the T-Stat setting?


Well, it will get slightly warmer, but it is not like the thermostat is infinitely precise. It always shuts off slightly warmer than the setting and turns on slightly cooler than the setting, that swing will increase (slightly).

Mny boilers already have a setting to purge the hot water. Unfortunately it does not work in a P/S arrangemnt.

Chuckles_2

Tekmars have it

The Tekmar zone controllers have this option for each zone circulator, so it is nothing unusual or weird or problematic. Unfortunately the Tekmars are rather expensive and have lots of options I don't need (they do reset but I already have a reset controller).

lisa

> We have P/S pumping, with a boiler pump and two

> zone pumps, the latter controlled by a Taco SR503

> zone relay box. On the boiler, I can change a

> setting to cause the boiler pump to run for a

> while after the thermostat ends its heat call and

> the boiler stops. But this is completely

> useless, because the zone pumps are not running,

> so the water goes to the tees and comes right

> back.

>

> The relays in the Taco SR503 turn the

> boiler on/off as well as the pump, based on the

> thermostat signals, so the relays inside cannot

> be replaced with delayed-off relays (or the

> boiler would also stay on longer, which defeats

> the purpose).

>

> What I want is to have the zone

> pumps run for a few minutes extra after the

> thermostats have stopped calling for heat and the

> boiler has stopped, to purge the hot water from

> the pipes.

>

> I know I can wire something up

> using a time-delay relay, but I don't want to use

> homemade gadgets here. I am hoping there is a

> packaged device that does that, either as a

> replacement for the Taco SR503, or inline between

> it and the pumps. I looked at the Tekmar zone

> controllers, but they are way too fancy for this

> purpose.

>

> Many thanks for any suggestions,

lisa

Post purge card

Taco makes a post purge card that will plug into the 503 relay box. This purge card will do what you are asking. This card will operate the zone pumps for a set amount of time after the thermostat has been satisfied. This purge card allows the user to program this run time. I will look into my files and find the model # for you.

Chuckles_2

I looked for it with the keywords you gave me. It's the Taco PC600 card. Unfortunately it only works with their expandable (-EXP) relay line, so I'd have to replace the existing relay box plus buy the new card. Still, thank you for finding a solution to the problem!

Steve Eayrs

Just curious, what kind of boiler?

Possibly a cold start boiler, that is trying to purge the hot water out of the boiler?? Is the purge cycle for the boiler pump, capable of also keeping the zone pumps going too? Maybe a simple relay?

Steve

Rudy

post purge card

The boiler set up is a Peerless Pinnacle. The purge card turns on the zone circulator's and the main circulator, but does not fire the boiler, thus you are able to put this hot water into your other zones. Nice feature, but I don't know how much "free heat" it actually puts back into the system. I still like to install them, as it helps me build the most efficient system possible. My thought is every little bit helps.

Tony_8

Why ?

Would you want to increase the swing in room temp ? Doesn't this contradict comfort ? My customers want no perceptible swing, if possible. Adjust your anticipator or go digital and get it to 1 degree or less.

What makes you think that hot or warm water in the bbd piping that isn't "purged" is wasted ? If it's warmer than the air surrounding it, it's heating the room some. Even a bare 3/4" copper pipe loses 50 BTU/ft in 70F air (180F water).

I wouldn't waste the electric to post-purge the zones, and instead of a special "card" I would buy some accurate thermostats.

Chuckles_2

\"the room\"?

> What makes you think that hot

> or warm water in the bbd piping that isn't

> "purged" is wasted ? If it's warmer than the air

> surrounding it, it's heating the room some. Even

> a bare 3/4" copper pipe loses 50 BTU/ft in 70F

> air (180F water).


You have exposed copper pipe in living areas? My pipes are in the basement and in-wall spaces, which I don't want to heat.

By the way, they're radiators, not baseboard, with fat (former gravity) pipes. So there's a lot of hot water in there.

Tony_8

Now that I know more

about your system I will comment more

If you have that much water in your pipes with that much heat in them, why would you want to purge them into the room ? Won't that make the swing even greater ? Why not pony up the cash for pipe insulation for the basement exposures ? It'll last longer than a pump, too

And, I would consider the piping within a bbd enclosure to be within the room and heat-emitting, whether finned or bare. That would make it, in this instance, "exposed".