1) Where you live: Iowa
2) Heat loss/gain calculations for your home: 28471 heating load, 20094 cooling
3) Brand, size (model), age and type of heat pump: Hydron Module, 4 ton (HTC048)
4) Type of loop field (open/closed/vertical/horizontal) size and design parameters: closed loop, 4 vertical wells, don't have size or parameters
5) Average cost/Kwh of electricity and consumption: $.05/KWH, don't know consumption but I don't have the bills in front of me right now. I think last two months cost of heat has been around $160/mo.
6) Entering and leaving air temperatures (EAT, LAT) measured immediately upstream and downstream of the heatpump: I don't have that
7) Entering and leaving water temperatures (EWT, LWT) measured at the geo system: I don't have that
8) Percent of load to be covered by geo and balance point: Where do I look for this?
9) Installer's assessment of your systems operation: It's working fine.
10) Projected operating costs, actual operating cost and previous heating and cooling costs: I don' t have this
11) Aux heat for the forced air is electric coil, aux heat for the radiant is the old electric boiler.

My set-up is we had an existing 5 zone hydronic radiant in the bsmt that was run by boiler, now it is run by this new combo unit geo. Main floor is forced air.
The geo seems to be shortcycling to us. Radiant zone will call for heat, geo kicks on, runs for 1 or 2 minutes, shuts off. 20 minutes later, radiant zone calls for hear (could be same one or different zone), geo kicks on runs for a minute or two, zone quicks calling for heat and geo shuts off.

Entering water temp into the radiant zones sometimes measures at 80 degrees, sometimes goes up to 110 degrees. Returning water temp is normally 20 degrees lower, but sometimes it can be a 30 degree delta. I don't think that's working right. I need to get back to radiant designer and ask for re-eval of basement radiant since I know that electric boiler water temp was 120 or so, so I'm assuming the flow rates I have on my radiant loops are probably all wrong for geo (plus we got new carpet in areas where there was none before).

I had the installer come look at it, but he said it is because of the transition season that I should just shut off the radiant and do forced air. He said geo is working fine. But I don't like the cold and I like the more comfortable heat in the basement and like to keep the radiant on until end of April since May 1st is when my seasonal heat rate goes up for the summer.

I don't like the short cycling since it seems like it's running a lot, and to me it does not make sense that the geo should kick on and off with the zones calling for heat. There's a water tank between geo and radiant floors that I thought was supposed to be some sort of buffer between the geo and the radiant floor. Unit will run sometimes 4-5 times in an hour just for the radiant, so that's not counting any run time to do forced air upstairs. There are 2 aquastats. 1 controls the pipes that come from the geo/tank, the other kicks on the boiler when the water temp gets too low to supplement.

Any advise?

Is there a buffer tank for the radiant zones?

Definitely need to confirm that buffer tank

Maybe an outdoor reset control scheme has reduced the on / off gap for the buffer tank. I'm not a radiant expert, but it seems to me that the temperature in a buffer tank should be allowed to vary 5-10 degrees either side of a temperature setpoint; with the base setpoint adjusted by outdoor air temperature.

Second that you need to make sure you have a buffer tank. Also carpet on radiant floors is like wrapping your radiators in a blanket. It is an isolator, decreasing performance.

Sounds like there is a buffer tank. Make sure that you have outdoor reset plumbed correctly. Then make sure all the zones are reasonably balanced and the OR is adjusted properly such that all the zones are on almost all of the time. This maximizes the available thermal mass exposed to the running heat pump.

As Curt suggests, you can increase the hysteresis (aka differential) on the tank thermostat with practically no change in room comfort (but some efficiency loss). Or increase the tank size (another way to increase mass).

Maybe someone else can comment as to whether "sometimes 4-5 times in an hour" is really a problem that needs to be fixed.

There is a tank that was added, that's basically an electric water heater (but no power goes to it). So I think that is the buffer tank. There are 2 aquastats. One of them "runs" the tank since it turns on the pump that runs the loop of copper pipes coming from it.

I thought the set-up I have was so that the geo would keep the water in the tank at a certain temp and it really wouldn't kick on until the water coming from that tank dropped enough, so that it would run for a while to warm that back up. Then the floor would call for heat on and off and heat from that buffer tank and geo wouldn't necessarily turn on just because the floor is calling for heat.

Could the problem be that the aquastat is run off the taco controller for the radiant zones? This aquastat is off until a zone calls for heat, which turns on the circuit, so the aquastat turns on, then when zone stops calling for heat, the taco shuts off, so does the aquastat?

Wouldn't that mean that if the tank water is too cool, technically the geo should stay on warming that water up to satisfy the set point on the aquastat, but it doesn't because the aquastat shuts off? So next zone calls for heat, taco turns on the pump that runs the radiant zones, so aquastat turns on again, geo sees water is too cold, so it turns on, but zone gets satisfied, so taco shuts off the aquastat and geo has to shut off because it thinks tank is satisfied? Or am I getting this wrong?

I'm pretty sure I do not have an outdoor reset set up, though I do have a nice sensor outside that tells me what the temps are outside (I'm pretty sure nothing really uses that outdoor temp to do anything with it).

My thermostats are Tekmar for the radiant zones, but I have a taco controller that runs the main pump and used to run the electric boiler. When the geo was installed in January, there was a second pump added that is on the copper pipes coming from the buffer tank. There's a 3rd pump run off the second aquastat, but that one only kicks on when the geo can't keep up so the water temp drops too low whichs then uses the electric boiler to supplement heating the radiant.

Jonr, How do I make sure zones are reasonably balanced? Maybe 4 -5 times is normal, what I don't like is that zone 1 calls for heat, geo kicks on immediately, runs for 1 minute, zone stops calling for heat, geo shuts off. Sometimes not even 5 minutes go by when a different zone calls for heat, then again geo kicks on immediately, runs for a minute or 2, zone stops calling for heat, geo shuts off. Not to mention that the geo is extremely noisy when running the radiant floor (it sounds like like a grinder that stuck). When it switches to forced air, it's still pretty noisy, but it's more of a hum.

We just moved back to the house a week ago, so we're gone during the day at work, but today being home all day I noticed that the on/off didn't happen as much during the middle of day, but early morning and as we got towards evening, it started doing it again, and it's been at it again.

Docjenser, I know adding carpet is insulating the floor, so I should have mentioned that the radiant was orginally designed for carpet in most of the bsmt rooms. The main change is that the hallway and bath and bar area were supposed to be stained concrete, but now hallway was carpeted and the other two ended up with tile. We did keep the carpet+pad around R2 since the bedrooms were designed for R2. But, initial design was based on a boiler at 120 degrees. Looking at the water from the geo, it seems like the highest it runs is around 105-110, so need to have that looked at and make sure our flow rates for each loop are still appropriate. I'm pretty sure they are not because the delta between water going into the floor and coming back is 30-35 degrees, and I'm pretty sure the design was for a much smaller deltaT.

Thanks!

How well did you insulate under the basement floor?  R-10?

Wouldn't that mean that if the tank water is too cool, technically the geo should stay on warming that water up

Definitely, if it's set up correctly. You might have to diagram the system so we can understand what you have.

Posted By Boontucky-girl on 20 Apr 2013 09:47 PM
Docjenser, I know adding carpet is insulating the floor, so I should have mentioned that the radiant was orginally designed for carpet in most of the bsmt rooms. The main change is that the hallway and bath and bar area were supposed to be stained concrete, but now hallway was carpeted and the other two ended up with tile. We did keep the carpet+pad around R2 since the bedrooms were designed for R2. But, initial design was based on a boiler at 120 degrees. Looking at the water from the geo, it seems like the highest it runs is around 105-110, so need to have that looked at and make sure our flow rates for each loop are still appropriate. I'm pretty sure they are not because the delta between water going into the floor and coming back is 30-35 degrees, and I'm pretty sure the design was for a much smaller deltaT.

Thanks!

OK, sounds like you have a buffer tank. If you have 35 F degrees when a zone is calling, your flow is way too low. We are shooting for a delta T of 5-10F in low temp floors. If it is going in at 110F, and coming back at 75F, how is 75F water heating up the concrete at the end of your circuit? If that is really the case, not many BTUs are leaving the tank, and the heatpump satisfies the tank very quickly, thus shutting off quickly again. Check you zone pumps. IS your house warm where you want it? Do you have a pump for each zone? Or zone valves? Maybe you just need a bigger pump to pump your water through the zones.

Where is the aquastat located(attached)? Almost sounds like it is on a pipe, not attached to the tank itself.

1 or 2 minites of running water through the pipe satisfies the aqustat, shuts off HP.

I have a similar set up, slid the aquastat under the tank insulation, making good contact with the metal tank.

Chris

Digital boiler controls with small probes you can slide behind the tank insulation work very well. We use Tekmar 150. Chris makes a good point, the tank temp is important, not the temp in the pipes.
Still, your radiator design/flow seems to be off.

Alton, We have R10 under the slab.

Jonr, Thanks for confirming that at least I have the right idea in mind. Whether it's set up right or not, I hope I can figure it out. I'll work up a diagram and post.

docjenser - Our setup is one single pump (which I think is variable type) for the whole floor, and each loop has a zone valve. Your comment that the flows are too low is probably right. Maybe now that we have geo we may need a bigger pump, but floor worked great on a boiler with current pump. DeltaT was 20 degrees at worst with boiler, normally 10 to 15 (which if I remember correctly, that was original design. I don't remember delta of 5 being the design number)

Main floor upstairs is ok, for forced air type of heat (not my favorite, but couldn't afford to add radiant on the floors). We haven't lived in the house while it was under reconstruction and just moved back last week. (doors seemed to be always open when crews were here, so it was hard to tell if it was not as comfy because it wasn't keeping up or because we were trying to heat the outside).
But since moving back, I don't think the basement is as comfy as I remember it (specially our 2 zones that had the largest heat loss numbers. Those two keep calling for heat all the time).

Chris J - Both aquastat sensors are taped to the copper pipe right before the water enters the main manifold. I'm not sure if it is the aquastat that gets satisfied, so the HP shuts off. What I see is the aquastat stays off unless a zone calls for heat. I actually think the aquastat power is coming from the same switch/outlet box that turns on the main pump. So pump circuit off because no zone calling heat = no power to aquastat. I'll go take the covers off and see where the aquastats are wired.

Docjenser - I'll contact Rob since they are the ones that designed the original boiler system to check parameters since things have changed to a geo.

Thanks!

Geo works better with lower supply temperatures, lower supply temps means lesser BTUs to the zones, but this can be compensated to a certain degree with more flow to the zones. More flow means lesser delta T.

May came and our heat rates switched for the summer, so we shut off the radiant floors. Also, the response I got from geo installer is that it was the swing season, shortcycling with radiant floors is normal, so I didn't think about it much.

But winter is coming back and having issues still with the shortcycling. I asked the geo installer again about it, and the response I got again is that it's the swing season, shortcycling with radiant floors is normal, and that really it's too soon to have the radiant floor on and I should just turn it off and heat the basement with the forced air and wait until it gets much colder to turn on the floors. But the basement floor was already getting too cold for my taste. Also, we have zoned each room so that if I need to keep one room warmer for guests (like my long term visiting parents) we can.

So I'm still looking to understand what we have and I'm concerned about a lot of things, but don't know enough to know if I should be concerned or not.
I've got the piping layout all drawn up, and I'm studying the system to see how it runs, since I'm still not clear how it's working and not sure how it's wired.

If you see on the diagram, I'm concerned that essentially when a radiant zone calls for heat, the geo kicks in, the hot from geo goes directly to the zones, thermostat gets satisfied, and basically that buffer tank fills up with cold water since the system never stays on long enough to cycle that water on the tank and get it to temp. As soon as t-stat is satisfied, the controller box shuts off, there's no power to the aquastats, and no power to the pumps. I am also concerned that the layout we have does not look like the "suggested layout" for combo piping in the Hydron installation guide.

Also, both sensors to the aquastats are taped to the pipe right after the boiler loop is connected. I've noticed the boiler kicks on too sometimes and I think it's way to soon for the "back-up" to be assisting the geo.
I can see in theory how our piping is supposed to work (I think), but I've never seen that pump 1 run by it-self. And even if that loop did run the geo to just keep the buffer tank satisfied, It doesn't do any good if a zone calls for heat because there's no way for that tank water to get to the floor without going through the geo. I'm assuming if the geo isn't running then water isn't running through it?
To me it looks like the geo is running on demand of each zone and that buffer tank is just pre-heating the water going back to the geo. Am I completely off-track?

Any help or insight would be greatly appreciated. I'd like to know what questions to ask the installer too.

I have the geo installer coming tomorrow, and I'd like to discuss things in more detail, but I don't want to sound like I know what I'm talking about when I only know enough to grasp the concepts, since am not an expert or installer/designer.

Also, we keep having the issue that when the geo is running the hydronic zones, if the upstairs forced air calls for heat, the geo just quits working and the heating element turns on and it won't heat either with forced air or the hydronic. I have to manually set the upstairs thermostat to below room temp so it will quit calling for heat, wait a few minutes, set it back up to desired temp (70) and geo starts to work again. It will run for a day or a week. Sometimes we have this happen 3-4 times in a day, and I'm suspecting the radiant is going to be blamed for it since I "shouldn't" have it on just yet. I'm hoping it's just a setting. I think it was supposed to be set up that main floor is priority, geo will run for 20 mins, check to see if radiant calling for heat, if not keep on forced aid till satisfied, if yes, run hydronic for 20 minutes and switch back and forth until all tstat satisfieds. At least that's what I thought the setting was last year.

Thanks.

I'm pretty sure I do not have an outdoor reset set up

Probably not - you could tell him that you want it re-plumbed for buffered OR which is standard and what most installers understand. Your non-OR design could work efficiently, but it would require bypasses and balancing on the zones so that it wouldn't short cycle. Ie, even if only a single, small zone is calling for heat, there still needs to be enough flow and load to absorb the full output of the HP for say 10+ min. Always allowing some flow to most other zones can provide this.

The electric boiler should be wired to only come on if the house AIR temp falls a couple degrees below the set point. Ie, if the geo system truly can't keep up.

Bt-girl - Since I believe all our geo experts are on the east side and probably in bed already and you want answers for tomorrow, I'll weigh in.

As per this spring's conversation, the buffer tank is the problem. I think your piping should work the way you have diagramed it but the buffer tank must control the geo. You can use the existing aqua stat in the buffer tank (water heater) If it has two element use the bottom one. I believe they are about 20º f deltas so that should work for you. The geo should come on independently of any heat demand from the radiant. It should just keep the tank hot.

The end switch from the radiant zone valves should trigger both the original pump and the new pump one when they cause a heat demand or they could trigger the original pump and A stat two. A-stat two would fire new pump one when the secondary loop drops below preset temps. In this case a-stat two would be powered through the original pump.
(is original pump a variable speed injection pump?)

A-stat one should be set to somewhat below a-stat two so that it brings on the boiler when the buffer tank cannot meet the demand.

I don't see where the forced air is tie in or the taco controller so that might change things. There are different strategies that give better performance or efficiencies but what I have described should run the system without the issues you are describing. The issue of the force air locking out the geo sounds like a controller issue.

May tends to make all heating issues disappear ;-)

No reason for short cycling with a buffer tank, something is obviously not set-up correctly.

Aquastat1 needs to be reading temp at buffer tank period and should have power without a call for heat.

Look at it as 2 systems: 1 is "original" pump circulates water from buffer to floor and back again, just happens to go through HP. 2nd is "pump1" circlulates water from buffer through HP and back to buffer, should by-pass floor.

There is a few ways the priority's can be set up, Shared priority sounds like what you think it is. Can be adjust 20,30 or 40 minutes of air then the same of water, has to stop for 5 minutes in between for pressures within the compessor to equalize. Shouldn't have to reset tstat.

Chris

Thanks for replies.

Technician came out and spent a couple of hours deciphering my setup. To his credit, he said he just started on Monday with this company. I got the impression that what he found was not what he was expecting and me following him around and pestering him with questions probably didn't help. He did take the time to study what he saw and try to understand it. He said he was more familiar with the buffer tank being piped more like it was on the installation manual.

After checking several settings, nothing much changed, other than we discussed at length about the priority setting and he did change some dip-switches on the geo so that the main floor is on priority call now.
Chris, yes, he said it was set to 20 min, shared priority, so if w-w busy with floor, electric heat would kick in for main floor and vice versa. I'm still not convinced it will do what I expect it to do, but he said give that a try.

The technician could see very well that I'm not convinced this will "fix" the way the radiant is running, but it should help with keeping things more consistent, rather. I tried to be very undestanding since he was not the one that installed it or designed it, and I know how it sucks to start a new job.

So now I'm going to ask the company owner about my setup since I now have more questions than I got answers. The technician said he was not familiar with a buffer tank the way I have mine plumbed, so that I needed to check with designer/owner to explain better what is supposed to happen. He called it more of a collector, and that's when he explained that he was new with the company so was not familiar too much with they way this was done. He seemed very knowledgeable about geothermal setup, but not sure if he's done many radiant setups with zones, at least that was the impression I got.

He also said that my t-stats in the basement (tekmar 241,242 I think) must be very sensitive, like if the room temp is set to 72, the t-stat will call for heat if temp drops a half of degree or one degree, so that may be a reason why zones calling for heat for such a short period of time. What we saw was that a zone called for heat, but the room temp said 73, and the set temp was 73, so he said must be very short temp difference (can't remember what he called it). He was not familiar enough with tekmar, but he did peruse through the manual quickly. He said he wasn't sure he could change this sensitivity on the slaves, but maybe in the master one, but he had another call to get to.

When I asked why couldn't the tank run like a buffer tank, with the A-stat having power all the time and just keeping track of the tank, he said it should if it's supposed to be buffer tank, but he didn't believe it was set up to run that way. So I continue to seek answers to my questions.

I haven't sent an e-mail to the designer, but will do so this weekend and see what I learn. I figure I don't want to go doing anything on our own yet since I don't want to mess up any sort of warranty just yet.

Thanks.

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.

Search for "Applications of Water-to-Water Heat Pumps - Climatemaster". The document shows a single zone (multi-zone with some bypass would be similar) and a buffered multi-zone system with outdoor reset. Pages 44 and 45. I'd use one of these standard designs (probably the latter although the lines to the HP should be from Ts on the zone lines - using the coldest water available increases HP efficiency. Page 50 shows this technique).