Circulator pump

Sophie

I am installing a wood furnace which comes with a hot water loop.  I would like to cycle to my electric hot water heater, horizontally about 12'. Can anyone recommend a pump to slowly circulate the water? The planned piping layout is out of the bottom of the water heater, pump, to the bottom of the loop, out the top, relief valve and T' ed into the top of the water heater hot side.



Thank you, Richard

Charlie from wmass

You need a heat exchanger

Does the boiler have a coil or are you pumping boiler water from an outdoor unit. Taco 007 in bronze or a stainless Grundfos. Your boiler manufacturer should have schematics for this.

Sophie

circulator pump

I failed to provide enough info. The furnace is a warm air unit with the option of adding a stainless hot water loop inside the firebox. So, I gather it would be a closed loop. Other questions or thoughts? Thank you.

Charlie from wmass

Same pumps I suggested

make sure you have a domestic water expansion tank and I would add another pressure relief valve near the coil inlet. I think you will need to pump that faster than you think to keep it from boiling when the fire is high.

Charlie from wmass

Also use a Sparco

mixing valve on the outlet of the hot water heater to keep a steady and safe water temp to the fixtures. Do not go cheap with the mixing valve as it will simply keep failing and need replacing.

Sophie

circulator pump

Thank you for the thoughts.

Do you recommend the relief valve on the inlet side of the loop, not the outlet?

I did not plan on another expansion tank. This is a well water house, submersible pump to an Extrol, then to fixtures. Should I have another expansion tank between the hot water loop and the existing water heater?



I did plan on a tempering valve and will get a Sparco.

icesailor

Pumps:

You can't do it like that. Or, you can do whatever you want. But you must return the hot water from the wood heater through the cold inlet of the water heater. The heated water will go down the dip tube and mix with the cooler water in the tank. You can not put it in the top. You don't need a Extrol tank as long as you don't install any check valves that would affect pressure.

Charlie from wmass

My concern with using the cold water inlet

was the water from the coil could get quite hot and could damage the dip tube leading to other issues. If he has the outlet going to a mixing valve and the circulator is fed off the bottom of the tank the water will circulate across the tank with out going through the plastic dip tube.

Charlie from wmass

one concern I was thinking about

How do we keep the water in the tank from over heating? What is the hourly rating of the coil and what is the tank size you are heating? At some point you will need to use and aquastat to stop the pump and leave provisions for the relief valve on the inlet of the coil to dump if the water in the coil reaches boiling temp. I actually think a reverse indirect water heater would work nice here. What pressure is your water system running?

World Plumber

Heat dump

You may need to consider a bypass and some kind of heat dump. Maybe a modine heater in the basement or garage that the water can be diverted through when the water tank reaches temperature. Make sure you get the relief valve and expansion tank in there. If you don't your house might find it's way to the next county. It's not pretty when a system over heats and the safeties aren't there.

icesailor

Dip Tubes:

Charlie, the dip tube in it's normal operation is as hot as you can get in a water heater. The dip tube starts in the top of the tank where it is the hottest. There are other issues with this bad idea and as I understand what he is trying to do, in Massachusetts, I don't believe that this is legal because of that provision in the code about domestic water heating equipment being in direct contact with the heat generating source of the building. Most MA inspectors should fail this installation.

Sophie

circulator pump

Thank you to all for the input. Such a fun and simple little project obviously is significantly deeper than  what originally met my eye. I do want it to work properly and safely; I have no love for county politics, but do not want to leave via air, involuntarily. I do not have to install the loop, however the furnace is on from October (Maine) and it seems a shame not to gather a little hot water.

House water is set @ 30/50 #, hot water heater is 40 gal., temp setting about 105+-, not scalding, the loop is 3/4" stainless about 6' and is designed to mount inside the firebox tucked against the sidewall

Digesting the responses, my thoughts are:

out the bottom of the tank, pump  to the loop, relief valve at the loop, back to the inlet side of the tank, relief valve on the tank, mixing valve at the hot outlet to cool things down.

I did consider that it may require a heat dump if it produces too much hot water and I certainly would not mind a little extra heat by my work bench.

Other critiques?