high return temp error

ryanwc

I have a Peerless Purefire mod/con boiler, roughly 12 years old, installed by previous owners, which worked fine for 7.5 years. It has a primary pump at the boiler, and 3 pumps serving different zones of the CH system.

I noticed a problem a while ago, and when I looked into it, realized the control panel was dead. The system was still running, but there was water on the floor under the relief valve. An HVAC company that I found on the Peerless website replaced control panel in summer 2020, but when the boiler returned to operation in the fall, I still found water on the floor at the pressure relief valve.

The company tried replacing the valve, which didn't stop the problem, and seemed to cause two new issues - leaks at two dielectric unions, which they quickly fixed, and significant vibration in the system.

Through a variety of attempts, (replacing expansion tank twice, relief valve twice, pressure reducing valve once; cleaning of heat exchanger and use of some sort of solvent in the piping), the company still hasn't returned the system to proper working order.

The pressure relief valve is no longer releasing water onto the floor, but these symptoms continue:
1) significant vibration which rattles the zone 2 baseboard emitters.
2) frequent "high return temp" blocking errors that turn things off for a few minutes, then allow it to start up again.
3) Not sure this is relevant, but a very low delta between supply and return temps -- 5 degrees, with return temps rising rapidly as supply temp goes up.

It does seem to me like a pump issue or flow issue in the secondary loop feeding the CH is consistent with the high return temp blocking error and the low delta.

I'm not remotely able to do this myself. But I'd like to understand it well enough to choose a new repair company with confidence that they know what they're doing.

Can anyone give suggestions about what may be the issue? Or about how to choose a company? Do they need experience with Peerless Purefire, or is mod/con experience enough? Whether the cause is in the boiler, a pump, or via a flow restriction creating turbulence, it must start somewhere. Shouldn't they be able to figure out where?

My gut is that the guy who initially replaced the valve was inexperienced, and was really yanking on pipes, causing the failure of the dielectric unions which they fixed, but also causing some sort of pump issue that they don't want to acknowledge and address. Is that plausible, or am I just casting about blindly for reasons?

Thanks.
Ryan

JUGHNE

Where are you located? Look above for "Find a Contractor" possibly in your area.

Can you post pictures of the boiler and piping, back up from a few angles.

Pictures will generate more interest for advice.

ryanwc

Thanks for the suggestion. Here are some pics.:

ryanwc

I just left a message for a contractor in the area from the Find a Contractor link above. Their website mentions hydronics and a particular relationship with Carrier. It seems to me this problem is might not be specific to the Peerless brand, so maybe a Carrier contractor will be able to diagnose and correct it?

ryanwc

I just turned the zone 1 thermostat up and watched the heater control panel for much of the last hour. I discovered that the low delta may mostly be an issue after a fault. What I saw was a fairly slow rise in temp for both supply and return, with return lagging about 19 degrees behind supply. I noticed that in addition to the deep, consistent thrum, there is also a bit of a rattle at the elbow just beyond the Zone 1 pump.

About 50 minutes after I bumped the thermostat to get things rolling, temps had risen gradually and consistently, to this point:
Set Pt - 180
Supply - 169
Return - 151

But 6 minutes later, while I was focused on something else, the system experienced a High Return Temp blocking error, and the boiler shut down and purged. I looked, and Supply was at 200 and the Return at 198.

So over 50 minutes, supply rose about 80 degrees to 169.
And then in 5-6 minutes, it rose another 31 degrees!

The control panel at that point said that both General Circ. and CH Circ. were still ON, which I believe should mean that both the main pump and the zone pump were still on. However, the rattle near the zone 1 pump was gone. I could definitely still feel the vibration, meaning something was on (and I'd guess it was the main pump.)

The temperature declined very slowly, to 185 for both Supply and Return roughly 10 minutes later. But 2 minutes after that, I heard a click, the control released the blocking error, and the temps very rapidly fell to 147, and notably, I once again heard the rattle near the Zone 1 pump.

To me, this seems like a situation where the zone 1 pump is failing/going off, which causes temps in the primary loop to rise suddenly and rapidly, triggering the fault. And then temps decline slowly with the main pump driving water primarily through the primary loop, which only has a few feet of piping and can't emit much heat rapidly. But at some point, the system resets, which turns the zone 1 pump back on, and then with water feeding through the long secondary loop, temps fall rapidly.

Anyone have any thoughts on this? Could the pumps be wired incorrectly? Or what?

EBEBRATT-Ed

Try the contractor you found on "find a contractor" Also post your location, someone may have a recommendation.

Talk with the "find a contractor" contractor. If he isn't comfortable with Peerless he may be able to recommend someone.

Sounds to me like the boiler is hitting high limit causing the high return temp fault.

It looks like you have 3 zones with 1 pump is that correct?

It looks like a control valve near the the zone pump. What does that do? Take a few more pictures from farther back and from different angles


Have you had this boiler serviced in the last few years?

JUGHNE

What does the pressure gauge on the boiler indicate in PSI?
Can't tell from the picture for sure but it looks low.

You need to have at least 12-15 PSI pressure when cold and not running. This is necessary to lift the water up to a second floor.

ryanwc

JHUGHNE,

I believe the tech may have caused a problem with the pressure/temp gauge. It read 30 psi at the peak temp today, but it also reads 30 psi now, 2 hours later with the system completely cool. Temps on that gauge have been showing 30 degrees lower than the readings given by the display board. This was not true a month ago, and the gauge is now twisted about 20 degrees from level. Another knock against the contractor I used.

But ... at the point the system gave an error, the 30 psi relief valve released about a tablespoon of water, so it had to hit 30 at that point. And couldn't have been at 30 up till then, since the valve wasn't releasing.

I'm in north suburban Chicago, and the message I left for the contractor was non-emergency, so I expect they'll reply Monday.

ryanwc

EBEBRAT Ed,

You're right that those are valves. Here are pics of the pumps and valves for zones 2 and 3, and then for zone 1 (edited bc pics came up in backwards order.)

ryanwc

On the side I could easily see, the label is in French, and I didn't know a vanne d'eau was a valve. Didn't know what those were.

So it has zone valves AND zone pumps. Could the valve be malfunctioning at heat, and shutting down flow on that side? I remember the contractor people being surprised by the valves.

EBEBRATT-Ed

Normally no reason to have pumps and valves on each zone unless they had gost flow issues. Is every zone heating? If something is wrong with an end switch inside a valve and a pump runs with a closed valve that would account for a noise issue and if the controls are calling for the boiler to run but a valve isn't open or a pump isn't running that could cause error codes.

You need someone to verify pump, valve and control operation. I think then they will find the problems

For Mod Cons to be reliable they need regular service. One reason some will not install them

JUGHNE

The zone valves have arrows on them, do the arrows on the back side of the pumps point in the same direction?
The main boiler pump should pump into the inlet of the boiler.

You can manually open the zone valves with the thumbwheel under the arrow.
If you manually open all the zones and have a call for heat does that change the delta T?

If you have a zone vale not opening but it's pump comes on then it is called "dead heading" and will create some noise.

You can hear a pump running with a screwdriver tip placed on the pump and the handle stuck against your ear. If you can control just one pump at a time that would be best.

ryanwc

The zone valve arrows are pointing in the same direction, (except the main pump doesn't seem to have an arrow. Can't believe that's backwards, since the system runs for significant time before triggering the fault, and does heat the house. I more think a pump or valve may not be functioning properly, rather than being backwards.

I may look into further diagnostics, but more likely will simply pursue it with a new contractor. I did leave an email for the previous, but mentioned that I wasn't interested in paying (them) more. At this point, it's more "do you want to take another shot at avoiding a yelp review that mentions that you seemed to try, but don't really understand these systems." I mean, they didn't even consider the idea of a valve or pump issue, including after I suggested it might be a pump issue. I feel like they did no proper logical, checklist troubleshooting. They simply changed a few things they thought it might be. And then weirdly, when that failed, they changed a couple of those things a second time.

EDITED: As I think about this, I expect to talk to the contractor about the existence of both valves and pumps. If they recognize that's not normal, but can give at least a coherent theory on why a system might need this, or a reasoned position on why it should not, it'll give me confidence they know enough to solve the problem.

Jamie Hall

You do need a contractor who is willing to spend some time figuring out your system -- since it is nowhere near a normal setup, and unless you get the person who installed it the contractor will have to essentially reverse engineer it.

Then figure out what isn't doing what it's supposed to do, and fix it. Chances are the fix will be straightforward enough, but I certainly wouldn't venture a guess without taking a couple of hours to study the system.

Which you will have to be willing to pay for. I might point out that a negative Yelp review may satisfy your annoyance, but will almost guarantee that getting another reliable contractor to turn up -- particularly if it looks like it's a payment issue -- will be close to impossible. Yelp reviews can be used to rate reviewers...

ryanwc

I won't write a negative Yelp review till after I know what did happen, and how serious the negligence of my contractor was. Maybe this will turn out to be so obscure that most people couldn't have solved it. But I would point out that I'm a couple thousand dollars in, lost a whole heating season, and the initial problem (high return temps leading to pressure, water blowing through the relief valve) hasn't been solved, and they seem to have created a new problem (vibration) which they haven't been able to solve.

And while who knows what the cause will be, people here and in another forum have already suggested that a pump/valve issue is something that has to be considered, given the symptoms, but when I suggested that two months and $1,100 ago, they blew it off as ridiculous.

I'm willing to pay someone. But I'm not willing to pay them any more. Thus far, they've made the system worse.

And if their approach is as haphazard as it would seem, other customers deserve to know it. I have a business. We get loads of good reviews on yelp. And a few bad. When I read a bad review, I take it to heart. I would never think to blackball someone who wrote a bad review. That's unconscionable. You may be right that there are contractors so gross as to do that, but I have to assume most are decent people.

Jamie Hall

The only comment further I will make on customer reviews on Yelp -- or Angie's List, or Facebook, or any other social medium -- or even a product review on, say Amazon or whatever -- is this. If you do write a negative review, make very sure that your allegations can be backed up with legally acceptable documentation. A written review is a publication, and as such is subject to the laws regarding libel. Not often invoked, it is true, since demonstrating actual damage can be difficult, but the option exists -- and has been invoked, successfully.

unclejohn

I would get rid of the old white Rogers zone valves.

Grallert

You could try and manually lock open one of those zone valves, run that zone and see your results. This will potentially start pointing fingers. Of course you will need to close the valve when this experiment is done or you will get ghost flow.
Also, with a meter you can check to see if you're getting power to those pumps.

ryanwc

New contractor today - replaced main pump. Throbbing gone, along with the annoying rattle in the baseboard heaters caused by throbbing! Clearly there was something wrong there.

But as he was cleaning up, the system threw another "high return temp" blocking code while Zone 1 was on. He went back, took some time looking at wiring related to the valves, but ultimately decided the problem was the Zone 1 pump, perhaps stressed by the problem in the main pump. So he replaced that.

We had the first floor up to 79 trying to keep it running to test things, so Zone 1 hasn't been on since.

But after he left, Zone 2 threw a "high return temp" blocking code. Truly frustrating. One thing I want to confirm is whether it still happens with Zone 1.

The blocking error just temporarily shuts the system down for five minutes till the return temp goes down. But I have to assume this is indicative of something not functioning properly, that needs to be put in good order, right?

Am I wrong in thinking it almost has to consist of something slowing flow in the secondary loop, so that there's not enough true return water feeding the main pump, and the pressure instead pulls very hot water that just came out of the boiler across the 'bridge' if that's the term, and right back in? Or at least, some mismatch of flow?

I guess a sensor could have gone bad, but the contractor did believe things felt very hot. The temp readings seem accurate.

I'm hoping he didn't put in a main pump that is somehow mismatched to the needed flow in the zones. On the other hand, if I discover that the new 1st zone pump solved the issue there, that might imply that the final solution will be a new 2nd zone pump that ensures that flow in the that loop is sufficient to dilute the boiler water "crossing the bridge".

hot_rod

The boiler circulator, is it sized properly? The manual should tell you which pump is required.
Is the boiler pump wired to the boiler or a zone control box, it could be shutting down while the boiler is still firing. On some pump controls you can post purge, run the pump for a period of time after the burner is off to prevent a high temperature lock out.
Ideally that boiler should be piped and pumped to run without any zone pumps running, the boiler should reach setpoint and shut down. That is the main reason for the primary secondary piping, hydraulically isolate the boiler from the distribution.

It sounds like the boiler is not getting adequate flow, pump bad, impeller plugged or broken, or the boiler heat exchanger is partially blocked, not getting adequate flow. I wonder about the boiler HX cleaning? Did they use a descaler, run it through the boiler only for a period of time?

With all that large diameter piping it would take a lot of cleaner and some long run time to assure everything was flowing, mainly the boiler. If possible I would run a cleaner around the boiler loop without running any zones.

SuperTech

You need to get rid of the White Rodgers zone valves.  Integral flow check valves can easily be installed in your existing circulator pumps to prevent ghost flow. They are very inexpensive. Zone valves and circulators don't belong together on each zone. 

ryanwc

Mr. Rohr,

Thanks for the suggestions. The initial contractor did run a solvent through the system for some significant amount of time. I remember them saying that by the end, it was coming back much cleaner, for what that's worth.

I've had to focus on other things for a week. But the update is that the noise was definitely fixed.

However, the high return temp errors keep recurring. I followed a few cycles, and saw it happen with Zone 1 and Zone 2.

To describe performance with Zone 1, a cycle began with the Supply at 109 and Return at 90ish. (I noticed maybe a minute after it started.) The temps climbed over the course of maybe 40 minutes, but the delta remained at about 22 degrees. At some point I began recording every 3 minutes. My last two recordings were 179/156 (Supply/Return), and then 182/160 3 minutes later. I noticed modulation was still at 94% input at this point, which seems very high, since 180 is the setting.

Before the 3 minutes were up, I got Blocking Error - High Return Temp. By the time I looked, the temps were at 197/197. But I'm not certain what the temps were at the moment the error was triggered. The Blocking Error seems to turn off the Zone Circulator (though the control panel still reads CH Circ - On.

Because of that fact, one theory is that a relatively high temp is triggering the pump's internal fuse, which stops it, with that pump stopped, the main circulator then rapidly pumps water 'across the bridge' and right back to the boiler, so naturally return temps skyrocket. But I don't know that that true.

Within 5 minutes, it comes back on.

One thought I have -- the control is set to a default which is not the high efficiency setting for this boiler. And, I know that the boiler is oversized for the house, because we have always had an 7-degree setback overnight, and even during the polar vortext 2 years ago, the house came back to daytime temps quickly in the morning.

I'm wondering - could I simply set it up to run in the outdoor reset mode (we do have a functioning outdoor temp sensor) and use a lower maximum - perhaps 170, so that it would be unlikely to reach the High Return Temp that triggers the error? I don't think the system would have trouble heating the house even if it never reached 180.

But would that simply be papering over a significant flaw with the system that needs to be diagnosed? I'm about $3,000 in here, with no diagnosis yet. I'd love to cut my losses if this would do it.

icy78

@ryanwc

It looks like the boiler pump is in backwards. Isnt it pumping into the "out" of the boiler? At least,  it looks like its pumping INTO the relief valve side. Haed to see on my phone tho. It would explain high return temp.

ryanwc

The boiler pump, the main circulator, is the strongest pump. It was in place for 12 years. It's possible the December repair of the dielectric valves involved taking it off and reinstalling it, but I doubt it. Even if so, the system ran *fairly well* most of the time over the winter, giving normal deltas, until it would suddenly have a high return temp. It's hard to believe that pump could have been backwards during normal operation. It seems like it would almost immediately create a serious problem.

At any rate, the new contractor that came last week installed a new main pump. And a new Zone 1 pump. The noise issue is solved, but we continue to experience high return rate errors.

ryanwc

I think I just figured something out. I asked that they put the system into an outdoor reset mode, which they did, using Mode 1 - Outdoor Reset with Thermostat.

The way the curve is set up, the Supply temp target today is 136. I watched the system, and it performed well. The Supply was at 142, and it was modulating down rapidly.

But then suddenly, it went off. Was Zone 1 already warm enough?

On Peerless, Mode 1 allows various ancillary settings, and one of them is that the pumps continue to run "post purge" for a few minutes. But the pump wasn't running! Why would that be?

I came upstairs, and discovered that the thermostat was not showing a call for heat, despite the fact that the setting was higher than the room temp. I turned the thermostat down and back up, and everything came on again immediately.

The thermostat is a "Honeywell Chronotherm III". I don't know when it was purchased, but looking at it, the esthetics... um... they don't scream 21st Century. I find a manual for this thermostat online, and it's from 1989.

I think what's been happening is that the thermostat is so old that it has started to fail.

When that happens, I think with no call for heat, the boiler control immediately shuts the zone pump and valve. When this happens, the supply water rapidly rushes across the bridge. If the supply water is at 186 (as it often is when running full blast, which was almost all the time under the previous "Mode"), then that blast of supply water running into the return catchment is way too hot, and blows the High Return Temp blocking error.

So I suspect I have a thermostat failure. GAAAHHHH. This is like the old joke about the guy who kept buying more and more expensive speakers for his stereo, and it would sound better, but never quite right, till he realized he had a bad needle on his record player.

If not the t-stat, I think it'll be in the wiring from t-stat to boiler. Sigh.

If this is true, then it seems to me that the system could still trigger a blocking error if the boiler was operating at 186 degrees or above, at the point the thermostat naturally tripped. That would rarely happen in Outdoor Reset mode, because the boiler target temp would rarely be high enough.

In the Peerless "Mode 7 - Internal Reset", which was the factory default my controller had been left in, the boiler essentially ramps up rapidly to the design temp default of 180. In Mode 1 - Outdoor reset w/ T-stat, they can set the design temp, and I had them set it to 170. I think that will mean that instead of rarely throwing a High Return Temp blocking error, it will never happen, because the supply will only go to 180, so the return would never be at the boiler max of 185.

EBEBRATT-Ed

You need to ask your contractor why you have pumps and zone valves. Just because something has been that way for 12 years means nothing. It could be wrong for 12 years

ryanwc

Sure. You may well be right about the pump & valve set-up.

One trick is that neither of the two contractors I've tried seems to have much understanding of Peerless Purefire generally, nor of the installation in my house. I could roll the dice again and try for a third contractor.

I would note also that the installation manual has a schematic showing an "isolation valve" and a CH circulator on each zone. Which makes me think this is standard for Peerless Purefire set-ups.

Someone above had mentioned that it looked like the pump was installed wrong because it's right above the pressure relief valve. Well, the pump is correct, but when I look at the schematic, it shows the pressure relief valve coming off the supply pipe. But the valve on my system is on the return pipe.

SuperTech

An isolation valve is just a simple on/off ball valve that is only closed to isolate the boiler or a component for service.  
Your boiler is piped incorrectly.  The motorized zone valves do not belong on each zone that is pumped by its own circulator.  I promise you that no installation instructions for any boiler will show the piping configuration of your boiler.  I'm pretty sure you will continue to experience the same thing after you replace the thermostat.  

ryanwc

All right. Thanks.

Maybe I'll have the zone valves removed. I wonder if the system had been throwing High Return Temp errors for years, and I had just never known to look. It does make a certain amount of sense.

After the system was reset to Mode 1 - Outdoor Reset with a lower boiler supply temp target, I've now gone two days without a High Return Temp for the first time since I started looking.

Maybe the issue causing that was the zone valve closing, leading to supply water rushing across the bridge. And it would happen again if the boiler target temp were back at 180.

Irritatingly, the control panel is now showing a new Blocking Error - "E 26 blocked condensate drain". Is there any chance this relates to the external condensate pump, and not the internal tanks? I just had the system cleaned a month ago. I would have thought part of the point was to clear out corrosion that among other things could block the condensate drain. I can't believe it.

This error was triggered yesterday morning, and doesn't seem to have been triggered again during subsequent cycles. Is it possible that whatever briefly blocked the drain was cleared?

ryanwc

The more I think about things, the more this makes sense. The unnecessary zone valves were causing the fault. The fault probably did not occur for years, because the original installers surely set the system to a normal efficiency mode with a peak supply temp below 180. Or possibly it would reach that peak occasionally, when outdoor temps neared design temp.

When the control panel went out, the 1st contractor installed the new panel, but they were too unfamiliar with these systems to understand the modes. They threw it into Mode 7, which I describe as "You paid for a condensing boiler, but we're not going to let it condense" mode, in which the boiler starts with a low supply target, but rapidly increases it to 180 within about 20 minutes.

Since the system allows a 10-degree margin, a target of 180 means the water can reach 190. A return temp of 194 triggers the High Return Temp. I never actually witness return temps higher than 185 or so, even when a High Return Temp error occurred a moment later. The best way to explain what was happening is that a zone valve would close. Suddenly, the boiler is only receiving the water it just heated a moment before, right across the bridge. With such rapid return, it quickly heated that water above 194, shutting the system down. But this tiny bit of hot water would quickly cool and dissipate, so by the time I realize what's going on and press the buttons to see the return temps, everything is back at 190 (the hottest I believe I witnessed.)

If the valve weren't there, as several of you suggest, some water would continue to flow through the zone, piping even after the end of the zone's call for heat, keeping the return temp normal for the brief period before the boiler shuts down since the call for heat has ended.

The first contractor made other necessary repairs; and also some unnecessary ones. Ultimately they couldn't figure out the vibration issue, nor the High Return Temp issue, both of which I believe they caused. (The original issues were a dead control panel, and leaks at the pressure valve, which I think the expansion tank replacement fixed.)

The 2nd contractor solved the vibration by replacing the main pump. Still seeing the High Return Temp error, they unnecessarily replaced the zone pump. But the error returned.

The error only went away when the mode was changed so that it doesn't reach the peak of 180. However, I observed similar temp changes (at a lower level, nowhere near the boiler danger zone of 194) when the zone valve tripped because a call for heat ended. This was the clue allowing me to understand that the zone valve closure is the cause of the High Return Temp error, and that it is only truly problematic if the system is near the maximum allowable supply temp.

icy78

Well relief valves are always on the boiler outlet. That pump is pumping into the relief...so backwards, unless ,as you say, the relief is on the wrong side of the boiler.  But why leave it there?
. Kinda wondering if the boiler was installed backazwards ?
(Just curious about this.)

ryanwc

I'm starting to realize the installation wasn't done well. It was several years before we bought the house. Not that I would have known better if I'd been around.

The installer was actually contractor 0. I called them first. They came, said it required a new control panel, and then didn't call back or respond to emails or calls. After about 6 weeks, I gave up on them and called contractor 1. About 4 months later contractor 0 sent an invoice.

I haven't had good luck with HVAC contractors. At least the last one solved more problems than he caused. But also added an $800 zone pump just cause he didn't know what else to try.

icy78

@ryanwc
I know a really good guy in Chicago.
I'll send you a PM.

ryanwc

Thanks for that, Icy.