Posted By Boontucky-girl on 15 Nov 2013 09:43 PM
Jonr - so what is outdoor reset setup? Tech guy did lower the setting so that basically the water going into the zones has to get down to 65 degrees before the boiler will kick on to supplement. As it was before, the water in the tank would get cold enough (below 80) that it would trigger the boiler to run. When you say it should be wired to read air temp, do you mean it should be run by the thermostat? Which one?

FBBP - The buffer tank water heater doesn't have the heating elements in it, that's where the two pipes go in and out of it. I'm not sure if the t-stat is still in. So

I did learn that A-stat 1 does runs the geo.
I think pump 1 is set to turn on at the same time as existing pump (existing pump is a variable speed type, Pump 1 and 2 I'm not sure, they just have a little switch at hi med low)
A-stat 2 turns on pump 2.

Thanks.

Jon - I don't think the boiler can run on air temps. It needs to sense secondary loop temps and come on when the water drops below design temp by probably 5 degrees. The problem is that if the a-stat 2 calls for heat turning on the boiler and the primary loop pump (P1) is running the water is circ'ing through the buffer tank. I think it would be more efficient to just reheat the slab returns and send it back out. This system is not set up as a true primary/secondary loop so doing that would require some changes. I don't know what is controlling the original pump and why it is variable.
The ODR should just run the secondary temps but that would require real primary/secondary separation.

Boontucky-girl - I assume that the piping to the buffer looks like the attached pic. I my case I took out the element but left in the stat. I also assume the geo is looking for just a dry switch closing to fire it. If that is the case, there is no need for power. Just the stat closing will fire the geo to bring up the temp of the buffer tank. If the geo is using the two element holes, then the primary could run off the actual hot and cold tapping, allowing the tank to stratify a bit. With the way it is piped now the complete flow of the system has to run through the tank so probably the 3/4" taping will restrict flow.

http://welserver.com/WEL0545/

The purpose of the buffer tank is to disconnect the flow needed for the heatpump from the variable flow requirements of the zones. The way your system is piped violates this principle and will result in short cycling.
1) The water should flow from the heat pump to the buffer tank and back.
2) Thermostat controlling the heatpump must have the sensor in the buffer tank. If possible with an outdoor reset to increase efficiency.
3) Piping to the zones comes from the buffer tank, and goes back to the buffer tank after flow went through the zones/air handler.
4) Water to the zones should the controlled by your room thermostats, which either open a zone valve or starts a pump

Posted By docjenser on 17 Nov 2013 12:09 AM

http://www.welserver.com/WEL0545

...

Nice job with the write-up on the 3500 SF house that is radiant heated using a water-to-water geo heat pump and a backup emergency heat source ( http://www.welserver.com/WEL0545 ).

I think this is an excellent tutorial on the fundamentals of heating a structure with radiant heating and providing Domestic Hot Water.

My question is: Are you missing showing a pump on the diagram, in the water loop circuit out to the earth and back, controlled by the temp inside the buffer tank?

Thank you.

Best regards,

Bill

Nope, I hate parasitic pumping loss.
There is a pump for the source side (the diagramm shows a 2 pumps flowcenter, but I do all my systems with 1 pump flowcenters now for greater efficiency, and 1 pump on the load side. One pump for the loop, one pump for the load, used the old boiler as backup, but I don't think it ever turned on since we installed it a couple years ago. Keeping it simple.

Doc Do you have a zone valve on the load side of the HP that opens when it is running? One load side pump sure makes the Wilo Stratos more affordable.

Doc, thanks.  I didn't realize that the item in your WEL diagram, between the W-W HP and the earth, is a pump.  That's the pump I was looking for.

Thanks for clarification that it's one pump, not two.

Question: is W-W HP / pump thermostatically controlled by the temp in the buffer tank?

Many thanks.

Best regards,

Bill

Yep, sorry the diagram does not show it. There is a high CV Belimo valve which closes when the heatpump is not running, causing the Wilo Stratos the rev down to save pumping power.

Posted By Bill Neukranz on 17 Nov 2013 08:49 PM
Doc, thanks.  I didn't realize that the item in your WEL diagram, between the W-W HP and the earth, is a pump.  That's the pump I was looking for.

Thanks for clarification that it's one pump, not two.

Question: is W-W HP / pump thermostatically controlled by the temp in the buffer tank?

Many thanks.

Best regards,

Bill

Yes, in this case we used a tekmar 261 to have an outdoor reset. It does control the heatpump based on buffertank temp and outside temps.

http://welserver.com/WEL0545/
Beautifully done. Sometimes it hard to justify saving an old beauty when she costs so much to heat so its nice to see someone went to the effort.

Couple of questions if I may?
Which way is the water flowing in the hot water heaters?
Why is the return temps on the radiant higher than the supply?
Is there checks in the pump flanges?
Is there a reason to use the boiler to heat the BT rather then just the radiant?

Thanks Jonr. I'm reading through that climatemaster pdf.

FBBP - Yes, the piping in to the buffer tank goes where the elements are. I have not taken the cover off to see if the sensors are still in place. I'm not having luck getting a response from the installer to my questions. Since we've been home tonight, the geo has kicked on and off 21 times in 3 hrs, running no more than a few minutes (not counting the times that it ran when forced air called for heat). Make that now 22. I obviously don't want to have to fix/change anything ourselves. We're not installers and I don't feel we should have to do anything ourselves. But it's driving me crazy that geo running on demand of the each zone call for heat!
Good question on why the original pump is variable. That's how the original system was designed and that's the pump that came in the box.
I'm going to go take some covers off and draw up what I see as far as wiring and include all system components and share (more for my knowledge and understanding).

Supposedly if pump 1 and original pump are running, the majority of the water won't go to the tank; it's supposed to go to the floor. The copper t's are so close together that I wonder if the cold return off the floor some doesn't just go back into the floor.

Is there any hope of making this setup run without having to re-pipe? We're currently not in a position to pay for major changes. I can't get get the installer to get back to my questions, how likely am I to come re-do any of it? Do I get a second opinion from another hydron installer? Call Hydron and ask if it's ok my system is shortcycling so bad?

Docjenser - thank you. The points you made are how I thought the system was supposed to function. Now that I'm getting to understand better how it's running, I can see it's not at all like that.
I like the system on your webpage. Reading about the Wel makes me want to add it to my christmas wishlist. Maybe for next year.

Thanks for the discussion and advise. I'll come back with a complete diagram.

(Make that now 23 times that geo kicked on) >:S

"Which way is the water flowing in the hot water heaters?" See arrows
"Why is the return temps on the radiant higher than the supply?" Although the sensors were calibrated, the supply temps seem to more influenced by the ambient temp, thus when the HP is off, supply seems to be lower than return. I might have to go back to recalibrate, too.
"Is there checks in the pump flanges?" No.
"Is there a reason to use the boiler to heat the BT rather then just the radiant?" Boiler is the old oil burner, which is still functioning. And we only used for backup heat. The purpose is to inject heat when needed. Each radiator has a thermostatic zone valve, which means that if only or or two zones are on, or calling for flow, the minimum flow requirements of the boiler would not be met. Thus the flow had to go through the buffer tank. Not needed if the system would not have been zoned.

"Good question on why the original pump is variable."

Because with 5 zones the pump can change speed depending on how many zones are calling.

"I'm not having luck getting a response from the installer to my questions."

Very tough to convince someone they are wrong.

"The copper t's are so close together that I wonder if the cold return off the floor some doesn't just go back into the floor."

Should have a check valve between the tee's to keep that from happening. That's probably why both pumps come on at the same time. Pump 1 moves the water around the big loop, the original pump pulls water out of that loop to send it to the zone/ zones, then back to the big loop.

I think I see how it's suppose to work, but the sensor for A-stat 1 is getting tripped by cooler water sitting in the pipe. When everything turns on it takes a minute or two for the warm water from the buffer tank to reach that sensor, then the heat pump shuts off. That's why A-stat 1 needs to sense the temp in the buffer tank.

Of course non of that addresses why the zones call and then are satisfiied so quickly. Are the tstats slab sensored or air sensored or both? I think some Tekmar's can do both. Almost seems like a wiring issue Tstat turns everything on, Astat 1 turns everything off.

I am just a homeowner with a combo unit, when my radiant was first plumbed I could be seen in the utility room holding different pipes, trying to "see" the flow of warm water. That's how I figured out we needed a check valve. I also have just an electric tank not powered as a buffer.

The floor supply could be plumbed to the hot out at the top of the tank and the floor return plumbed to the cold in at the top of the tank. That is how mine is done and probably how it is shown in the installation manual.

Chris

Don't overestimate what it would take to do it right. Move the zones cold water return line to a T on the blue side of the buffer tank and move aquastat1 to the buffer tank and then you have a non OR buffered system. In mild weather, you can turn down aquastat1 and turn aquastat2 off. Also check that aquastat2 is sensing a point between the two Ts (not just to the right as drawn).