Last Minute System Bypass Retrofit Questions

Quercus

Hi,
I am returning to the Wall , with a new name, after many years of leaving my heating system alone.

Painting a bathroom has expanded into powder coating my radiators while the system was empty. Having the system drained has brought back a lot of latent dissatisfaction with my heating system and the plumbing near the boiler.

First, I picked up some Webstone flanges for my circulators that would enable me to address a pump failure or to experiment with different pumps in the system without a complete drain. I also added a purge/shutoff at the supply end of the main circuit to complete the isolation of the main house.

The house is a 1938 colonial with one zone of cast iron radiators(TRV's on most). There are two branches that appear to separate the front and rear of the house and those have 3" iron pipe feeding the radiator branches.

I would like to heat at a lower temp in the radiators to allow longer circ. run times for comfort purposes. The boiler is oversized for my calculated 60k BTU/hr heat loss and only runs for a few minutes at a time, even in cold weather.

While the piping is out, I thought of installing a thermic mix valve (ESBE VTC) on the return line because I have space there and the circ is already plumbed in the return. I bought a Taco bumble bee pump initially to experiment with the flow rates in the cast iron and I would prefer to use 1 circ. for the zone if I can.

Will the VTC protect my boiler and draw out the heating cycles for my radiators as I am thinking? I put sensors in the layout to control the main zone for delta T while not interfering with the baseboard zone and would like comments if I am on the right track or making a serious mistake.

Also, I am willing to go back next summer and make more involved piping changes but would like to button up the system with cold weather around the corner.

Thanks for viewing,
Steve

Quercus

Also, do I need a balancing valve in the bypass section, a strainer to protect the thermovalve? Shall I bypass in 1-1/4 copper or reduce to provide a little resistance in that section?

Your help is appreciated,
Steve

hot_rod

Those thermostatic bypass are fixed temperature devices, so don't allow the delta T circ to return temperature lower that the cartridge temperature or the valve will bypass.

Remember also there is a differential involved in that thermostatic valve. The Caleffi 280 series, for example has an 18 differential.

So if you order the 120F sensor, add 18F and the bypass is fully off at 138F which is ideal for gas or oil fired return temperature.

I don't know about that brand as far as the differential and need for a balance valve. Ideally a properly designed and built thermostatic protection valve should not require a balance valve to force the proper operating condition.

Try it and see, I'm not sure a delta T circ and thermostatic protection valve will get along that well? I'd be interested in hearing how it performs.

There is a better way to protect a boiler for return temperature, properly, with only two delta T circulators, if you prefer pumps to thermostatic valves.

The thermostatic valves cost some pump head, although the Caleffi is a 11 or 14 Cv, plenty of flow for most residential applictions.

Quercus

Thanks for the reply Hot Rod.

When I thought about where to put the delta T sensors, I put the supply sensor between the bypass and the boiler and the return sensor outside the bypass on the return.

My logic in doing that was that a large dT would be present when the boiler started and the pump would run at a higher rate until the mix opened and the warm water ran through the radiator. Then the pumps dT programming would run things.

I am thinking no matter what, the mix valve would maintain return temps to protect the boiler.

I am interested in the valve because it is a passive device with no wiring. I have basic or worse circulator control and would need to add a zone controller in this phase of changes. I think the valve will function with the main circuit in the house and leave the baseboard in the addition alone - not a lot of water there to worry about it.

I would be interested in the circulator because of the adaptability and programability of the pumps.

Would you suggest a pump in the bypass and a second pump in the supply for the main house? If they would both turn on together and ran in dT mode, then the system pump would control heat delivery to the rads and the bypass pump would mix in enough hot water to satisfy the boiler protect. Actually sounds like the bypass pump would be just using the temp returning to the boiler to control itself.

Reliability-wise, would pumps be preferable to mix valve?

Thanks again,
Steve

hot_rod

I think you schematic is fine, I just wonder how the delta T pump will respond when the thermostatic valve is in full bypass?

Also how the pump will respond to the change in temperature that the valve presents. The valve is not a full open full bypass. As the return warms the valve slowly starts opening, I'm not sure how the pump will respond as the flow rate is changing through the thermostatic?

You may need to play around with sensor placement.

I'd be curious to see this system work for a month with a plain ECM in fixed speed mode, then the delta t to see what if anything changes in comfort, boiler cycling or fuel use.

Quercus

I looked some more at my system and figured out a way to go primary-secondary so that is the path I am taking.

I felt that I would be back tinkering in there and may need to add panel radiators in an electrically heated sunroom and perhaps an indirect. The P/S gives me that flexibility. The thermo valve was too expensive to toss when I repiped in the future.

I will have an ECM pump on the primary and the main house with all the CI radiators and look forward to experimenting with that.

I think the smart motors will open up a lot of control opportunity as retrofits in older systems. I opened a new discussion on my P/S loop since I am considering something unorthodox in my implementation - it may interest you.

Steve