Tekmar 260/Revolution compatibility and feedback on my setup?

Well, I have been reading posts here and educating myself around the internet for a few weeks trying to work out why exactly my heating is setup the way it is and what I may be able to improve.

I have a Revolution boiler with radiant floors on 3 switched zones and an indirect WH. I am almost positive the boiler was quite a bit oversized for the house based on the % of time its running when it was really cold this winter and how short it appears to run on a call from the water heater. If I can get around replacing the boiler and still make some improvements to the system that would be great.

I would love to know if the tekmar (260) will work well with the system as it is currently plumbed and/or what I can change to optimize its integration and the systems efficiency. I do not understand why a heat exchanger was used in the system (to protect against cold shock?) It sure looks to me like it was plumbed wrong since it doesn't counterflow. Should I keep it in the system? Also I am curious about the mixing valve and whether that will inhibit efectiveness of the ODR or if it needs to be changed?

I'm sure you will have all sorts of other observations or ideas and I would really appreciate them. I made a schematic to clarify the plumbing but can try to get a good picture to post as well. Thanks!

 

For the HX, is there anti-freeze in the radiant zone? Or that possibly there is PEX in use without an O2 barrier?

Al.

 

I have been running a Revolution with a tekmar 260 for three years. Works great. It serves two space heating zones and an indirect.

A quick glance at the schematic suggests you could control your system with a 260 and probably an additional relay or two. There might be other controls that would be a better match.

But first please answer Al's questions regarding why there's a heat exchanger. That's important in figuring out how to proceed.

 

Ok, I looked up about the oxygen barrier stuff and checked out my system... no antifreeze in the radiant circuit but the tubing is PEX. It's definitely not the aluminum sandwiched variety and may not have any oxygen barrier at all. So I would assume the heat exchanger is necessary, but it still appears to be plumbed incorrectly?

 

Sahale, is the circulator pump for the radiant a BRONZE model? If the tubing is NON O2 barrier it should be...

 

Let's see some pictures of the boiler room. That will help a bit.

Depending on your goals to improve the system, and the reasons behind it being set up the way it is, it may or may not be worth it to start hacking away and adding stuff.

What is pretty clear is that the mixing valve is rather unnecessary if you were to use an outdoor reset control like the 260 or similar. The installer was probably unfamiliar with what the Revolution can really do and thus set this up pretty much like a standard boiler.

Meanwhile, some questions.

What model/size Revolution is this? What is the heat load on the house? What kind of radiant installation? What range of supply temperatures? Does the radiant have a reset control or does it simply supply one maximum water temperature? What size indirect?

 

I would run a two stage OD reset on the revolution. The revolution can and will short cycle on the radiant zones especially if you do OD reset.
Two stage OD reset does two things. First it will utilize the heat already in the boiler before firing the burners. Secondly it will increase the run time due to firing the burners at a lower water temp as the circ is stage one. Turn off auto rotate. I prefer an OD reset that will fire both stages on a call for HW.
The second option if all your radiant is running on the same water temp as yours is. You can install an L4006A on the supply line and set it as the high limit needed for the radiant.
Have the higher water temp for the HW tank. Yes, two water temps from just using an inexpensive aquastat. It will not give you OD reset but lowers the system water temp. This would require a minor piping change.

 

ok, i'll have the picture up soon and in the meantime answer those questions as best I can...

The circulator on the radiant circuit does appear to be bronze.

The model number on the boiler is RV4PSL-L2 and it appears to be rated at 96,000btu

The heat loss calc on slantfin seems to be down, is there another program like it?

Radiant installation is 3 switched zones, one per floor with pex in masonry, on seperate thermostats, one circulator on supply from heat x-changer. Only temperature gauges are those shown in the diagram. The one after the mixing valve seems to get up to 160-170 fairly quickly and stay in that range. The gauge on the supply to radiant side of the heat x-changer gets up to around 140 towards the end of a cycle. I do not believe there is any kind of reset on the radiant and the temperature swings in the house support this. The supply temperatures seem to be the same everytime it runs.

Indirect is 80 gallons and house has circ hot water on a timer.

Thats most of what I know, but let me know what else I can track down that would be helpful. Thanks!

 

It does sound like the radiant side has non-barrier PEX in place. Thus the HX'er.

What I would also do is to get the Revolution boiler I&O manual. It may be on-line. Also download the Handbook of Modern Hydronics. This can be found on the Ipex site:

IPEX USA

In the Tech Library. Click on Tech Center first. I tried to get a direct link but they now want an e-card filled out first.

Anyway, between that and the boiler I&O you should be able to get a better understanding of how this system can be put together.

Of course still listen to what the folks here have for input. They have been at this for quite a while.

Al.

 

Please verify that the PEX is non-barrier. It probably is non-barrier, but let's be sure. No reason to keep an exchanger here if it's not needed.

I too have an RV4.... The I&O is linked off this page:

:: Burnham ::

Slant/Fin seems to finally have taken their wonderful software off-line, at least for the moment. Bummer.

Heat exchanger or not, there are other and better options to control this system using outdoor reset so that the radiant gets the water temperature it needs to meet the heat loss, indoor temperature swings are minimized, etc.

 

 

Ipex seems to have taken that manual offline as well. All I could find was a faxable request form for it. Will look around the net for another source.

I finally found some tubing with legible print on it. The 3/4 is wirsbo aquapex which the company describes as non-barrier. And the 3/8 is Infloor brand PEX shown on their site to be non-barrier.

 

rbeck, what/whose control would you use?

Would this require minor wiring changes inside the boiler?

Can you explain a little bit of the details please? I'm curious...

(I bet Xiphias knows this, and I think we talked about it, but my memory is a fog...)

 

p.s. why didja delete the pics?

 

I have no idea what happened to that post.

[my bad - NJT]

 

I had deleted the post when I saw that the pictures were gone... and it says you last edited it at 2:26 ... so I assumed that you had deleted the pics for some reason, and I deleted the post...

I just put it back, so you can see that the pics are gone!

 

Something bizzare going on with my browser or something!

I couldn't see the pics, so I went back to your message and cut and pasted the URL into another tab... then the pics showed up... strange!

anyway... I'm gonna delete them outta yer last message cuz they don't need to be here twice...

 

Is there an expansion tank, air vent, fill valve, etc on the radiant side of the HX?

 

The simplest 2-stage control would be the Taco PC705, which would require an -EXP zone valve control or switching relay (sounds like in this case, the ZVC).

The tekmar 262 would also work, but the minimum firing delay between stage 1 and stage 2 is 2 minutes. That would not be good for DHW recovery (it does not allow both stages to fire simultaneously for DHW calls). In my experience with the RV4 on my fairly low-volume fin-tube system, it would also result in an unnecessarily long delay before firing stage 2. I can see this sometimes when there is a load change and the boiler core water is purged out to the system. It's only good for about 30 seconds of runtime before the boiler should fire and start heating due to supply temperature fall.

Waiting another 90 seconds wouldn't hurt too bad for the space heating, but it would probably have a discernible negative impact on DHW recovery.

So we gonna get those pictures back?

 

Components on the radiant side are limited to a purge valve on the return to the H-X and T in for make up water after the circulator on the supply from the H-X.

I have been studying the following threads and am wondering if it wouldn't be fairly simple to modify my existing system for full odr with a thermic valve or something similar? Am I right in thinking I essentially have primary-secondary piping?

I am curious which side of the heat-xch the supply temp sensor would be placed for the 260?

Also after reading through the IO for the revoultion I was wondering why the integrated mixing control is not capable of the same type of protection as variable injection on a P-S setup for full ODR?

 

The Revolution has built in primary secondary piping and you can do full ODR right out of the box. The internal variable speed circulator (controlled by a tekmar-built VS3000) takes care of everything. No need for thermic valves, etc. etc.

You could (I think, not thinking hard) control this system acceptably with a 260. You'd probably want to get rid of the mixing valve and associated piping. The supply sensor would go before the DHW takeoff. The reset curve would have to be set up such that it would account for the temperature difference between the heat exchanger and the radiant loops. If you have reasonably uniform heating loads in the zones, pick one for the indoor sensor and the whole thing will be automagically tweaked to hold setpoint.

Note there are other tekmar controls that also allow for floor sensor input. That might be preferred for a fully radiant space heating setup.

You should also move the circ on the supply to a point after the DHW takeoff. No point in running two circs for DHW, or having the DHW circ pumping through the other circ.

 

The Taco PC-702 will bring both stages on when a DHW demand is needed. With radiant it is good to use the two stage control as we get lower return water temp on start-up for a longer run time.
Trooper,
Yes, there are some internal wiring changes but very little. We have to move the VS3000 wiring from C1 and use a 24v coil SPST relay.
I agree move the indirect piping with the supply on the supply side if the boiler and the return on the retun side of the boiler keeping both close to the boiler and only run the DHW circ on a call for h/w.
With just a few rooms of radiant is he going to save enough buying an ODR control over just limiting the boiler to say 130º. I'm not sure he will ever re-coup the money.He will probably only run water temps between say 100º -130º or 135º.

Here is what I would do.
www.comfort-calc.net/picture.html Thoughts?

If the boiler is oversized he may want to try the ES2 or wait for the new SCG or Revolution which should be here shortly.

 

That's a clean, simple approach. If not going with ODR, looks like it would work fine and clean things up a lot.

The original poster did make it sound like temperature swings in the house were undesirable, which might argue for ODR.

What's an ES2? What will be in the new Revolution?

 

So I could just set the aquastat on the boiler to 130? There is no risk to the boiler in doing this? Maybe I read the incorrectly but in that scenario how does this work with the indirect recovery?

 

That's not what they're saying...

You won't be able to heat your domestic if you do that.

There's been a couple options put forth. Both have common elements... there's no choice there.

1. rbeck's drawing showing an ADDITIONAL AQUASTAT controlling the boiler, and losing the unnecessary mixing valve setup. Repipe the indirect so the supply and return are direct in/out of the boiler.

2. Run the ODR and set it up so that the MAX temp going to the radiant floors is limited to say 130 or so... and still lose the mixing valve. Repipe the indirect so the supply and return are direct in/out of the boiler.

The Revolution has a BUILT-IN primary/secondary setup with a VARIABLE SPEED circulator inside it... the boiler protects itself, it don't need any help from us.

 

NO. Do not set the Revolution aquastat to less than the specified 210F value. It needs that in order to properly control the internal circulator and provide boiler protection. rbeck is talking about adding a separate aquastat that would serve as a high limit to the hx supplying the radiant loops.

The advantage to this approach is it's simple. The disadvantage -- if I'm interpreting rbeck's aquastat suggestion correctly -- is that you would still have a one-temperature radiant system and thus still have the space temperature swings you have in the house. To address the latter you need outdoor reset.

 

What kind of pressure you seeing on the radiant side? It looks like there's a 'tridicator' on that side? I'd be surprised if you aren't building a good head of pressure out there...

 

If you take note to the drawing there is an indirect. You can get 2 different temperatures for use in your system.I have done a few of these and have gotten quite a few to do it. The boiler aquastat is still set where it needs to be but the L4006 is set at a lower temperature, what ever you want in the radiant system. The indirect gets plenty of hot water (up to 200f) and the radiant only gets what it is set for.
The key is too keep the L4006 at least 2 feet away horizontally from the indirect piping. A call for DHW will let the boiler run to limit. When the indirect satisfies it shuts down and the call for heat takes over. As soon as any temp above the L4006 aquastat setting is sensed by the control it shuts the burner down. When the boilers cools down (quickly due to return water temperature) it only fires to meet the setting on the L4006. Works well for a lot less money. Again, how much of a fuel savings with ODR in small area of radiant. By the original drawing I do not think it is the whole home.

 

Ok, rbecks setup makes perfect sense to me now. I really like the idea of simplifying the existing plumbing... My setup does supply radiant for the entire house and I am still very interested in the 260 or the dual stage setup mentioned.

I will check out the pressure on the radiant side the next few runs and see whats happening there. If I will be simplifying the plumbing on the boiler side I would also like to optimize the placement of any other components in the system or add in anything I may be missing. Any suggestions on that would be great.

Is this the correct placement for the supply temp sensor with an odr control. And what is the reasoning for not just placing it on the supply from h-x to radiant if you will have to adjust reset curves to correct for the h-x?

 

Hmm. can't see my pictures again. Let me know if others can't see them and I will try to post them differently. Heres a link to them as backup.

Click here for album

 

Pressure in the radiant system seems hover in the 25-35 psi range.

I read through the manuals for the taco 2 stage and both of the tekmar units. These controls are so cool! I think I am still aimed towards the 260 for price and for use of the indoor sensor which seems like it might help the system work optimally with the heat exchanger. I had a few questions after reading the manuals...

What would the sepoint minimum be with the revolution (off?)

Is my circulator(grundfos UP 15-42) sufficient for the priority setting on the 260 that utilizes only the ind circ? That was the reason for adding the check valves (as shown in the 260 IO) Is there a particular type of valve that would work best in these spots?

Here is a draft of changes to my system, anything that should be moved, added or replaced?



Picasa Web Albums - Andrew - heating

 

I think you should have an expansion tank out on the radiant side, probably an air separator and auto vent also...

You are showing a 'check valve' and manual valve on your water make-up line... there should be a 'pressure reducing valve' (regulator) and a 'backflow preventer' in place of the check valve. Backflow preventer is pretty much a fancy name for a check valve, but it's more than that...

The reason for the check valves in the boiler loop and indirect piping is to prevent flow through the indirect when there is a heat call, and vice versa...

I wonder if perhaps the sensor should go on the 'other' side of the HX ... on the supply side out to the floors?

 

I will plan on putting in the expansion tank/air seperation on the radiant side. I looked at the current setup and it does have the pressure reducer and and backflow preventer in place on the makeup line. Is there an ideal place to T this line into the boiler loop or does it not really matter?

I was wondering about the sensor placement on the radiant loop as well, but reading through how the controls operate it seems like it would create too much delay or buffer in the feedback and result in the boiler target temperature often running at close to the max setpoint and reduce the effectiveness of having the odr?

 

The 'best' place to plumb it in would probably be between the expansion tank and the air separator...



As shown, with this valve arrangement, the expansion tank and feed water components are very easy to isolate for service.

I'm hoping someone else will weigh in on the sensor placement. I don't think there will be much of a 'delay', but there may be a slight 'difference'... the sensor is easy enough to move around, so you could experiment with the location.

 

I came I saw and decided you were well beyond my experience level

Best of luck