Grundfos Alpha "fighting" a Honeywell SmartResponse?

ecky

Looking to set up a primary / secondary heating system. Primary loop comes from an outdoor "boiler" (i.e. GARN). Secondary loops feed upstairs and downstairs radiant loops. I was going to have a thermostat (Honeywell) make the call for heat and turn on the pump (one thermostat / pump for each secondary loop). The primary loop was going to be a Grundfos Alpha 15-55. My question is whether the AutoAdapt feature of the Grundfos will conflict with the SmartResponse feature of the Honeywell? Both features "learn" about your heating requirements and make adjustments. My concern is that they are both trying to hit a moving target as they are constantly trying to adjust based on the adjustments made by the other system. Throw in the variable heat output of the GARN (different temp of water coming out) and my system may never stabilize. Any suggestions? Disable SmartResponse (if you can) or get a thermostat without that feature? Looking for a programmable 7-day thermostat.

Thanks.

furnacefigher15

Good question

The pump and thermostat compatibility is not an issue.



How ever the unknown heat output might be.



Can you estimate how many btu the wood boiler is?

ecky

BTU's

Hi Furnacefigher15



Well - based on the manual, water stores 12,476 BTU'S / degree of water temperature change. This unit (GARN WHS-1500) holds 1,500 US gallons. Assuming a temperature rise of about 80 degrees, that equates to over 950,000 BTU's. It can put out 250,000 BTU's per hour. I only need about 50,000.



ecky

furnacefigher15

Those numbers seem high.

Water stores energy, but not that much.



Definition of a btu is the amount of heat energy required to cause a rise 1 pound of water one degree Fahrenheit.



8.33 pounds per gallon * 1500 = 12495 pounds of water. =



so that means it will take 12495 btu to raise 1500 gallons of water 1 degree. so the typical 20 degree rise we deal with in the heating world would be 249,900 btu



A water tank that large will have a fairly stable temperature output.



But if all you need is 50,000 then you need to deliver 5 gpm to the house from the tank to maintain that.



So in short the alpha will work fine.

ecky

High numbers

Hi Furnacefigher15



Can't really comment on the numbers I gave you. Got them right out of the GARN manual. At any rate, my calcs have shown around 5 gpm so we do concur on that. Thank you very much for verifying that the pump will work fine. Always reassuring. However, I would just like to verify that you don't think the AutoAdapt feature of the Alpha will conflict with the SmartResponse of the Honeywell? It just seems to me that if the Honeywell starts calling for heat 1/2 hour earlier so that the temp reaches the required setting, but the pump is trying to AutoAdapt to this earlier call for heat - that they will be constantly trying to "outguess" each other? Add this to the fact that one morning the tank may contain water at 180 degrees and the next morning the temperature in the GARN may by 110 degrees. I can't get my head around how this all would work. Any further thoughts / comments would be greatly appreciated.

furnacefigher15

fighting algorythms

I don't see an issue with the pump and thermostats getting along, Heating systems of any kind are dynamic in nature. Loads change all day every day. The thermostats will cycle though out the day and during setback, and not just when they go into morning warm up.



Regardless, since each zone will have a secondary loop with a pump, the flow will not very through the primary, only the temperature.



I would set the alpha pump to maintain 6 or 7 gpm to be on the safe side and leave it there.



You may have to tweak the setting dependent on how much fire is in the boiler. The more boiler output the more pumping is required.

ecky

RE: fighting algorithms

Thanks for your input. I was surprised to hear that the flow through the primary loop would not vary. I thought the idea was that gpm would change depending upon demand. Shows you what I know! Sheesh. I really appreciate your time and advice. Thanks for your help! Merry Christmas!

furnacefigher15

Alpha pumps and variable flow

The variable flow would come into play with zoning with valves instead of pumps.



Unless you have a different meaning of primary / secondary then I do.



A drawing is worth a thousand words.

ecky

RE: Alpha pumps and variable flow

I guess that is always possible. I am defining primary / secondary based on Dan Holohan's definition in "Pumping Away". Clearly you are dealing with an amateur. I do not currently have a drawing currently. I am attempting to integrate solar with the GARN and was supposed to have this all drawn out by my cousin (an engineer) but that hasn't materialized so I am forced to plug away at this. Not complaining. Have learned lots. Lots more to learn obviously. Basically the primary loop goes from the GARN to the house and back. I will have a manifold off of it with 3 secondary loops. One for DWH, one for the upstairs radiant floor, one for the downstairs radiant. 1 thermostat on each floor to control the corresponding loop for the floor. That's it in the most basic of terms. Sorry I could not give you more. However you have already been more then generous with your time. I trust we are on the same page as for our definitions of primary / secondary.

SWEI

primary loop

You may want to consider keeping the primary loop in the outbuilding with the Garn.  Keeping the HX next to the Garn will allow you to keep all ferrous materials (water treatment required) together and if you use a bronze circulator in the house and have no steel radiators you can forget about oxygen issues for that portion of the system.

Less heat loss moving tempered water in those underground pipes than 180F+ directly from the Garn.  PEX will handle 180F but it really is happier at lower temps.

ecky

RE: primary loop

That makes total sense. I guess my only concern is that I bought the HX after talking to GARN about running the water from the GARN directly through the radiant flooring loops. The HX may not be capable of handling our DHW and the radiant flooring. Have to look into that. But thanks so much yet again!

SWEI

radiant flooring

Can't see how that could possibly work with a Garn.  Return temp requirements to prevent condensation are incompatible with radiant floors.  You could make it work with a mixing valve, but most Garns installs I've seen use a HX to isolate the required water chemistry (Garn is an open system) from the rest of the system.

ecky

RE: radiant flooring

Well I was going to use a mixing valve. The open system (or treated water) are not a problem according to GARN. The idea was that I could get by with a smaller HX.

SWEI

mixing valve

Take a look at the Taco iSeries http://www.taco-hvac.com/uploads/FileLibrary/100-19.pdf



How were you planning to heat the DHW?  If you used a tank indirect like the SMART, it could be fed directly by the open system.

ecky

RE: Mixing valve

Before your idea, I was going to take off the manifold (located in the house) to a HX to the DHW. The other 2 loops were going to go through a mixing valve to each of the radiant floor secondary loops. They were going to get water directly from the GARN (after the mixing valve). This looks like it will change. I will put everything through the HX in the GARN barn, then pipe that water to the manifold in the house. I will get an outdoor reset control and put it where it needs to be. Need to look into that.

NRT_Rob

couple things

1. autoadapt sucks if you're doing any reset control. use a constant pressure mode on the alpha if you're doing a multizone system.



2. use a variable speed injection reset control from HE through the trench... turns the whole trench into an injection loop. large delta-T means you have one hotter leg and one colder leg, so you cut overall trench heat load and you can dramatically reduce the size of the pipes as well in most cases. also, you drop the need for a mixing valve.

croydoncorgi

Stat drives pump!

What no-one has yet pointed out (?? - not sure I fully understand the setup...) is that the stat in the original question will be driving the electrical circuit that includes the pump, so they can't 'fight'.  Until the stat calls for heat, the pump will / should be off.  The auto-adapt (or whatever mode you select) will only apply once it's powered.



The other issue (getting the temperatures for the furnace and the various demands correct and compatible) sounds like more design work is needed!



...I also lack any experience of the Garn machine - but I get edgy when people discuss  connecting an 'uncontrollable' heat source such as a wood burner to anything including valves or thermostats.  Point being that some wood burners will overheat and boil in no-flow situations.  Garn seems not to do this, since it's said to have enough water volume in its own tank to keep from boiling in every situation(??).  Design seems to require 'batch firing' - each wood charge has to burn through completely before any refilling of the combustion chamber.

ecky

RE: stat drives pump

Thanks for the response croydoncorgi. Agreed that the thermostat has to call for the heat. But I was under the belief that variable speed pumps run continuously - albeit at a very slow rate when there is no demand. I would agree that more design work is needed. That is another story unto itself.

You are right that the GARN does do batch boils. It is virtually indestructible because one firing could not possible boil off 1500 gallons. (There is also a low water shut-off.)

ecky

RE: Couple of things

Thanks NRT_Rob for the warning on the AutoAdapt feature. I appreciate the warning. Dumb question but who is HE? I clearly need to look into this variable speed injection reset control. I have never heard of such a beast. Thanks NRT_Rob.

ecky

RE: Couple of things

Thanks NRT_Rob for the warning on the AutoAdapt feature. I appreciate the warning. Dumb question but who is HE? I clearly need to look into this variable speed injection reset control. I have never heard of such a beast. Thanks NRT_Rob.

NRT_Rob

HE

is "heat exchanger".

ecky

RE: HE

Apparently I was right - it was a dumb question.  Thanks NRT - again.

ecky

Re: Variable speed injection reset control

Read the PDF for this product (from Taco) and have copied the following:

"The supply water temperature from a boiler can be controlled by cycling the boiler on and off." Don't see how this will work with a GARN given that it works on a batch boil and does not cycle on and off. Am I missing something?