Easiest Way to Control Pump

dave brode · Post by **dave brode** » Tue. Mar. 20, 2012 10:17 am

Hello All,

I've bragged on my simple air over water system before. Two fan/coil units, seperate duct systems for basment, and living space above. Pump runs 24/7. In cold weather, it works well, as the heat from the piping is "lost" to the conditioned basement. However, I have realized that it is less than ideal when it is not cold outside. When it's warm, like it's been, the basement is warmer than it needs to be. Since the basement ductwork is hot, due to heat rising from the coil, the basement ceiling is warmed, which heats the living space above too. I can valve the living space coil off to stop heat rising from that ductwork into house, but I can't stop the heat "loss" from the basment fan/coil.

I'm looking at pump controllers. The heat pump has a 24v circuit that is closed whevever the fan runs. The basment fan/coil has a 24v t'stat that controls the fan. I need something that will allow turning the single pump on from the two different 24v circuits.

I've looked at these;

http://www.pexsupply.com/Taco-SR502-2-2-Zone-Swit ... -1965000-p

http://www.pexsupply.com/Honeywell-RA832A1066-2-Z ... -4119000-p

Anyone know of better options? I've looked at $10 relays, but I don't know enough to understand the symbols and such.

TIA
Dave

steamup · Post by **steamup** » Tue. Mar. 20, 2012 2:11 pm

Dave.

The situation you describe is not uncommon but requires some relay logic for switching.

Neither control you list will do the job standalone.

The best option would be to put the honeywell control you list to control the pump. This is a transformer-relay in a box. It has only one control connection (T-T) which is hot with 24 vac. When these two terminals are shorted by a relay, switch, thermostat, etc. the relay is activated.

You problem is you have two other sources that are hot also. These must be isolated. One way would to be put a simple relay hooked into each fan coil that closes when you want heat. This created a dry contact and you can parallel as many dry contacts as you want across the T-T terminal. When either fan coil called, the pump then would be started via the honeywell control.

Another way is instead of a simple relay at each fan coil, install a taco hydroair control:
http://www.pexuniverse.com/taco-hydro-air-fan-controls

This has many more options to improve comfort and efficiency of the system, if you choose.

AA130FIREMAN · Post by **AA130FIREMAN** » Tue. Mar. 20, 2012 3:33 pm

Are you using 1 pump for 2 zones ? Do you have zone valves on them ? What controls the 2 different fans ?

AA130FIREMAN · Post by **AA130FIREMAN** » Tue. Mar. 20, 2012 3:52 pm

I read one of your posts, you don't have the aquastat on the boiler but the pipe instead. What will control the boiler temp if the pump does not work ? I have a heat pump also, but I use 2 thermostats, 1 for the heat pump and one for the coal heat. The coal thermostat starts the circulator, an aquastat (green and white wire on my heat pump) to run the fan when the pipe is hot. And I can keep the heat pump thermostat on at a lower temp as a back up. Their is no back feeds of electric with this, only heat tells the fan to run. The green and white wires only run the fan on my a/c heat pump, the thermostat has a switch to run the fan only.

dave brode · Post by **dave brode** » Tue. Mar. 20, 2012 11:21 pm

Hello Gents,

I guess that I didn't describe the system very well;

I pump the water to both coils 24/7, so there is always heat in the two duct systems. In the spring, when the house gets warm, due to gravity heat flow, I close the ball valves on the branches going to the coil for the house living area. If a cold spell comes, I open them back up. Not a big hassle. There are no zone valves, nor do I want to go to that effort. I figured to just run the pump any time the house heatpump OR the basement fan/coil calls. It might sound dumb, but at least I would not be running the pump 24/7.

As of now: 8124 controls the boiler temp, but not the circulator. The circulator is wired from the same circuit supplying the boiler with power. There are add'l aquastats on the piping, but they don't control the boiler. One is near the basement fan/coil unit, and is set to bring it on for a dump zone, at 210*. The boiler has never had an overshoot hot enough to bring it on, although it does work if I set it lower [see note below]. If I cycle the pump, that one would need to move. I have two more near the coil in the living space duct. One locks the heat pump's compressor out with heat in the pipe, and the other brings the fan in the heat pump on for another dump zone at 240* [left over from my day of hand firing with bit]. Setting the system up as such allowed the heat pump's thermostat to control the heat pump's fan, as it would normally do. If I cycle the pump, I would have to move the aquastat that locks out the heat pump too.

Now, what steamup wrote and re-thinking made me realize that I'm pretty sure that I was wrong about the thermostat circuit for the basement fan/coil being 24v. Although the old honeywell control that I used on it does have a 24v transformer, I now believe that the thermostat controlling it sees no current. otherwise, my parallel circuit from the boiler dump aquastat to the TT terminals would not work. I'll test tomorrow to see if there is current there, but I bet not.

I'm showing what a dumb tin banger I am. I'm really weak on the control end of this stuff.

Thanks.
Dave

steamup · Post by **steamup** » Wed. Mar. 21, 2012 8:08 am

Dave,

This is how I would expect to see the system work for most economical operation-

Two space thermostats, one for basement fan coil, one for house heat pump.

1. Make house heat pump - two stage thermostat. Wire first stage heat to relay (lets call this R1) at heat pump, wire second stage to heat pump call for heat (w1). Lockout aquastat on pipe to remain to lockout compressor (w1) if hot water present.
2. Add relay at fan coil in basement (R2). (exact wiring yet to be determined)
3. Set up boiler for typical operation for pump and boiler control using the triple aquastat. Boiler maintains low setting until T-T recieves call, then boiler fires to high setting and pump is activated.
4. Wire R1 and R2 contacts to T-T. This is the call for heat.
5. Dump zone logic will have to be looked at, but using basement as dump zone is easy, maybe add a relay and some low voltage wire.

Leting the boiler idle until call for heat keep the pipes and duct coils cool, preventing heat loss and gravity circulation. This will save a ton(s) of coal.

It sounds like you have most of the basics in place, you just need a few relays and low voltage wire. Hardest part is figuring out the wiring of the existing fan coil and heat pump.

dave brode · Post by **dave brode** » Wed. Mar. 21, 2012 9:36 pm

steamup,

Thanks for the post.

I'm a bit frazzled at present, Wife developed problems with her vision 1.5 weeks ago. Sudden cloudy vision in one eye. It turned out to be a detached retina. The Doc is 1.5 hours away. Actually, today, he found a small tear in the retina in her other eye, which he fixed in the office via laser. We have to return tomorrow for more complicated surgery on the eye with the detached retina, and return again friday for follow up.

She'll be fine, I'm sure, but I'm not in much shape to study the subject. I will asap though.

Thanks again.

Dave

Post by **Rob R.** » Wed. Mar. 21, 2012 9:38 pm

I hope all goes well at the doctor visit. Check back in when things settle down.

whistlenut · Post by **whistlenut** » Wed. Mar. 21, 2012 9:51 pm

Keep that 'special passenger' comfortable during the ride. My mom had the same issue a few years ago and they told her they would use a 'sandbag' to immobilize her head for the ride to the specialist. I was picturing a 'mini foxhole' kind of thing, however it was 2-5 lb bags that caused me to ask: what do REALLY do when you say a 'Sandbag'? She recovered nicely after the surgery, and I'm sure you will share a similar story when this is all over. Sure is nice to have Specialists available, and 90 minutes may seem like forever, but you'll be a good partner to ride with. The pump controls issue will be waiting for your comments. Family comes first...always! Good luck, and best wishes on this journey.

steamup · Post by **steamup** » Thu. Mar. 22, 2012 10:47 am

Dave,

Good luck with the Doctor stuff.

Personally, I would have more time to discuss after Mid April. I could help you more then. I would need a little more info an exactly what you got at the fan coils. I think you can make a few easy modifications and get a more efficiently controlled system.

dave brode · Post by **dave brode** » Sat. Apr. 28, 2012 11:06 am

Hello Gents,

Sorry for not getting back sooner. Too much stuff going on to fool with pump right now.

Wife made out ok, but she would recommend being knocked out during the procedure to repair retina. She was not, and it was pretty gruesome. Worst thing after that was 8 days of laying face down, or sitting/standing with nose pointed straight down. A gas bubble is put in, and needs to float up to push on back of eye. We learned that detatched retina is quite common for near-sighted people, due to their longer eyeball shape.

Thanks for all the well-wishing.

Dave