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[hondaracer2oo4]

I have a 24x24 water to air hx. When the blower is on I get about a 22 degree heat drop from inlet to outlet which is just about perfect. The problem is that I get a 10 degree drop when the blower is off and just the pump is pushing water through the loop. I would to to put an automatic valve that opens and allows water through the exchanger only when the house calls for heat. Anyone know of an electric diverter valve I could use? Two zone valves maybe?

[baldwin racing]

I have a 24x24 water to air hx. When the blower is on I get about a 22 degree heat drop from inlet to outlet which is just about perfect. The problem is that I get a 10 degree drop when the blower is off and just the pump is pushing water through the loop. I would to to put an automatic valve that opens and allows water through the exchanger only when the house calls for heat. Anyone know of an electric diverter valve I could use? Two zone valves maybe?

I believe you would need a Honeywell 24volt 2way zone valve (or 3way cannot remember which one off top of my head.)so when the house do's not call for heat it closes.yu just plum another line to return with t on other end...so it by passes the heat exchanger back over to return line and returns to boiler....
kelly

[muffin]

3-way.  I have these, but after about a year, they started leaking water through the closed side a bit.  Anyone else have issues with these valves?

[slimjim]

2 or 3 way can be used, typically 2 is less expensive but requires a bypass loop that adds a bit of restriction.

[hondaracer2oo4]

How would the bypass loop be activated when the two way valve closes to keep the water from flowing through the hx? Slim, are you the PandM dealer located on 111 in Lyman? If so I drive by you on the way to and from my camp, I stop once in a while just to look at the PandM's. They always look well built.

[slimjim]

Yes I am, stop and say Hello, the bypass would be a simple set of tees just before the rad with a zone valve on the straight through leg to the heat exchanger, remember water takes the path of least resistance and the weight of the moving water wants to go straight ahead, when the zone valve is closed, water flows between the 2 tees and when it is open it flows through the heat exchanger

[RSI]

Is it causing the temperature to get warmer in the house than you want it to be or making the temperature in the house uneven? If not, I would leave it alone. The blower will have to run more if you change it.

[hondaracer2oo4]

Slim, Is your shop up the driveway to the left of where the boilers are down by the road? I was never sure if that was your house up there or you have a shop too. As far as the isolation valve goes, I figured that if I simply did a 2 way valve with a T that sent the water to the return line when closed than when the 2 way valve was in the open postion allowing water through the HX then a majority of the water would still try to bypass the HX because of the resistance encountered in the HX. Am I wrong on that? RSI- My reasoning for exploring this idea is this. When the water passes through the HX I lose approxiametly 10 degrees from the inlet to the outlet of the HX. My pump, a NRF 36 running on speed three pushing through 2 one inch lines each way should be moving in the range of about 15 gpm if I remember what my calculations were. I am running a Hardy H4 that has 130 gallons of water. That means that every 8.6 minutes the water is completely exchanged and 10 degrees lower. My aquastat is 185 off and 175 on. So every 8.6 minutes or so the unit has to fire to bring the water temp back up. I lose 1 degree of heat from the boiler to the house and 1 degree back. That means that it would take about 40 minutes to lower the temp to the point of firing the boiler again to raise it back up. Anyone think see any issues with my thought process so far? Thanks.

[RSI]

The heat is going into the house so if it isn't overshooting the the thermostat set point it will be needed anyway.

If you have nothing else in your system, you could use a smaller bypass or put a valve in it and close it part way. Most pumps use less power when they have more restriction on them so when the zone valve is closed your power usage would also drop some.

There isn't much restriction on a water to air heat exchanger and if you use the straight through side of the tee to the hx and the side for the bypass, most will go through the heat exchanger when the zone valve opens.

If there is anything else in your loop this probably won't work very well.

[hondaracer2oo4]

The only other thing that I have in my loop is a side arm HX on the hot water heater. I don't see how bypassing the water to air hx would hurt the performance of the side arm?

[RSI]

Probably would be fine. With a restricted bypass you would have less flow through the sidearm but they don't need that much.

[hondaracer2oo4]

I am thinking about changing the side arm to a water to water HX and pumping the hotwater side loop with a strap on aquastat. The recovery time for the side arm is pretty dismal coupled with the fact that the top of the tank is piping hot water and the bottom is freezing cold.

[slimjim]

Yes you are correct Hondaracer regarding the shop first and then the house is next, you can't miss it.

[Chas]

I'm trying to figure out why you're losing 10º across your hx with the blower off. After my inlet thermometer in the basement I have over 20' of uninsulated 1" copper, a 2" sidearm, and a 20"x20" hx, running the same pump as you (nrf-36) on the 2nd speed, and I'm only losing 3º at the outlet thermometer. With the blower on I'm losing 23º.

[slimjim]

I wonder if the temp guages were calibrated, the ones that I use can be calibrated with the screw that is on the end of the stem.