Hydronic Heat Pump Piping with Boiler

Rich L.

I saw the new Climate Master Tranquility THW water to water heat pump at the Iowa Heat Pump's annual conference. It's an interesting machine that they claim will produce 145 degree LWT. It's only available right now in a 32,600 btu size. It also does not produce chilled water.

It has some other neat features but without chilled water it won't work for me.

Jim_161

Piping a hydronic heat pump with a boiler

Hello I am wondering if anyone has an idea how to control the following scenerio. I have a three ton air to water heat pump which will operate down to 5 degrees F. The heat pump and boiler will provide domestic hot water, in floor heating and supply water to fan coils. The heat pump will be installed with a backup in line electric boiler. The electric boiler will come on to help the heat pump when it cannot handle the load. The boiler may start helping out at 20F and will take over 100% below 5F I am looking for a few different ideas on how to control this. Notes: The heat pumps output water temperature is 132F and I cannot let the return water to the heat pump ever go above this or the heat pump will shut off on high head. So I need heat pump protection. The heat pump must operate as long as possible as it is very efficient. In summer the heat pump will switch to cooling mode producing chilled water and the boiler shall provide domestic hot water all year round. Thank You for thinking about this one Jim

hot_rod

primary secondary piping

is one good way. pipe it so the back up boiler or heat source never heats the buffer tank for the geo. This keeps that "load" at the best condition for the heat pump.

I think a bit more buffer capacity than what the geo folks have been suggesting can help. It lessens the cycling of the geo.

Problem is large insulated buffer tanks get pricey. 50 and 80 gallon electric tanks are common. Aboove that the price goes up.

Be sure to upsize the connections if you use a basic HW tank with 3/4" openings. I use both top connections and up size them to 1 or 1-1/4".

Here is a conceptual drawing. A differential control would bring on the buffer circ at the ideal temperature range and drop it off as the tank cools below a useable temperature.

I believe tekmar and maybe HBX, Honeywell and others have a control to handle all of these functions in one "box"

hr

Mike Dunn

buffer tank and geo

I do not understand this drawing. Please explain how when the buffer tank circ is on, the buffer tank supply water ever gets to the load. It seems that it would just move back to the buffer tank. And let's say it does get to the load, how does it get back to the buffer tank.

Sorry but I'm confused.

hot_rod

The buffer

tank circ would run when there is a call for heat, along with the system pump. The geo HX module could charge the tank regardless of any loads calling. And it would not cause flow in any of the heating zones or piping.

The buffer is tied in via primary secondary connections to keep the system hydraulics apart from the buffer and geo hydraulics.

The buffer tank acts as a large hydro separator, storage space, and an air eliminator. It keeps the typical high head circ used in the geo module hydraulically apart from the buffer tank and system circ.

Here is a more complete drawing.

hr

Mike Dunn

P - S

OK
Thanks for helping me on this HR

I thought I knew exactly how primary secondary worked but you drawing is contradicting with what I thought I knew. Please explain in detail what is going on at the prim/sec connection where the buffer tank piping connects into the system piping. You know that whole what goes into a tee has to come out of a tee.

Thanks again HR

hot_rod

nothing or everything

is going on at that connection Depending on flow rates from the various circs. If the buffer is at a useable temperature a setpoint control would turn on that circ. probably interface it with a heating call. No reason to move heat from the buffer to that heating point if there is no need.

So with both the heating circ and the buffer circ running the temperature moves from the buffer tank into the heating zone. the amount and temperature would depend on the flow rate of the buffer circ and the heating loop flow. There may be some mixing going on if the heating flow is larger than the buffer "injection" flow.

Dan and Siggy both have excellent books that show that formula. Or Siggy's HDS software can calc it for you.

Remember the max. output temperature from the geo when you design and calculate. Typically around that 105- 110F number. But there seem to be some new geo units coming from ClimateMaster with claims of 140F??

3 way diverting zone valves would be another way to go for an either or selection from buffer or back up source. Be sure the valve has a Cv in BOTH directions to handle the flow rate. A motorized ball valve may be a good choice. From Caleffi, of course

hr

Ted_5

for controling this

check out HBX ECO-1000. This control was made for Geo and can do what you are asking

Ted

Blackoakbob

What is....

the name of the heat pump that is air to water? I just had someone ask if that was available. Thanks for your reply.
Best regards, Jim.

Jim_161

Heat Pump Name

Aermec, you may see it on our website at http://www.mitsair.com

Josh_10

Another is Simple Comfort Reverse Cycle Chiller by Aqua Products. We have had good success with them. They make a good packaged unit that requires no refrigerant piping.

DennisU

Sorry, I agree with Mr. Dunn

I have to agree with Mr. Dunn on this one... I don't think the system, as drawn, will properly inject the buffer tank water into the system. Maybe in an ideal world you could turn the buffer tank circulator around and it would work.