Joined on January 19, 2012
Last Post on June 17, 2013
@ May 24, 2013 1:15 AM in Issues with coal fired hydronic heating systemHydronic System Issues
The following is a list of issues that I have found.
• The electricity consumptions appears to be excessive. Pumps P3 and P4 operate all the
time. The fan operates when the boiler thermostat calls for heating. The auger runs 3mins
on, 2mins off while the fan is on. Pumps P1 and P2 run when M1 and M2 are on. These are
time-clock controlled. (This is not a major concern at present as it needs further
The boiler and pumps being always on is killing your efficiency. A large buffer tank and controls will solve this. You could use it as a DHW reverse indirect and put it where your proposing closely spaced tees
• Should the pressure vessel be located on the HP side of the pump (to prevent cavitation).
It will work better on the hot side with the circ "pumping away"
• Should the connection to the distribution system be via closely spaced Tees. (The present
arrangement forces all of the returning water into the boiler via the three port valve
meaning that the boiler inlet temperature will not reach minimum temperature to prevent
condensation at times of high load – i.e. no boiler protection.
Agreed, the piping is suspect
• How closely spaced do the tees need to be. Would a pipe from the return side to the hot
side suffice (as shown on the schematic).
If you are going to do it over, do it right. The tees should be in a straight pipe not on ells
• I have not used the in-slab heating for some time. I can’t remember why I have switched it
off but I think it was because the return water to the boiler was too low. The mixer for the
in-slab heating was set to a water temperature of 30°C, and the return water was at about
20°C. If correct mixing was occurring the return water to the boiler should have been much
higher than that, because the return water from other devices would have been higher.
Fixing the boiler protection piping should resolve this. Consider outdoor reset for the floors.
• Check valve CV2 was added because hot was circulating from the hot port to the cold port of
the three port valve when motorized valve M2 was closed. Initially, I could not explain why
this was happening – my theory now is that both hot and cold ports would open to try to
maintain the required temperature at the outlet port. But because there was no flow,
(because M2 was closed) the hot water was bypassing to the return line via the cold port. Is
I think P3 is deadheading and forcing the zone valve open.
• If all the thermostatic valves on the radiators close, pump P1 will be deadheaded. Pumps P3
and P4 could also be deadheaded (if no other circuits were calling for heat). Is this damaging
for the pumps. How can this be avoided.
Replace P3 with a ECM circulator I think a delta P like grundfos alpha would work well
• If the radiator circuits are on, there appears to be no flow to the water heater. I suspect that
this is because there is no pump in this circuit and the radiator circuit hogs all of the
available flow. The way I have deduced this is a bit convoluted. I have a thermometer on
the inlet and the outlet to the water heater heat exchanger. When the water in the hot
water tank is cold, I noticed that the heat exchanger inlet water temperature was at the
same temperature as the water in the hot water tank (around 20°C) . The inlet temperature
should be something like 70°C. This could only occur if there was no or low flow in the heat
exchanger circuit – the cold water in the tank was cooling down the near stationary water at
the inlet. When the house and day warmed up and the radiators cycled off, I saw the inlet
temperature rise back up to 70°C. From this I deduced that the radiator circuit was hogging
the flow. This causes the water heating recovery to be delayed in the mornings, and we run
out of hot water. This is a major issue for us.
On second thought, why does P3 exist? If each of the branches off the main had it's own circ, and check valve there would be no need for P3
• Are there too many pumps?
• The pumps appear to effectively be in series – is this good? My understanding is that you
use series pumps to increase the head, but there is no indication that increased head is
• Am I correct in my belief that the piping arrangement at the boiler will not provide boiler
protection. (see attached drawing). It is not piped like the drawings in your book (John
• The return water temperature is often around 40°C when the outlet temperature is 70°C.
This suggests that correct mixing is not occurring or the flow is too low. With the piping
arrangement at the boiler, this temperature does not rise much before entering the boiler.
• I am constantly adding make-up water. Perhaps a litre per day. Is that common – how often
Is it coming from the prv?
should you have to add make-up water? There is no evidence of leaks.
• I also have a feeling that the precharge in the pressure vessel is insufficient or leaking. What
should the precharge be?
The precharge should be the same as the system pressure. It needs to be sized correctly. The manufacture has a calculator.
• The boiler is lower than the floor level of the house. Much of the piping is in the ceiling
space of the house. Should there be a air-purging valve in the ceiling at the high point?
It depends, do you have an air problem? If the pipe velocities are sized correctly you shoild not need it
• The maximum flow in the in-slab circuits is about 2l/min or less when all in-slab systems are
What size and how long are the loops.
calling for heat. At these flows the heating in most rooms is barely perceptible. Maybe if
the distribution system was improved I could get the flow rate up a bit?
These are some of the issues that I am having. Some of them might be inter-related. I have taken
these to my installer and he believes that all of the problems stem from the fact that the boiler is not
achieving its rated output of 30kW. However, I often see the boiler switched off on its thermostat,
even when the water heater or the radiators are calling for heat. This suggests to me that it is not a
heat issue but a distribution issue. That is, the boiler is producing the heat, but the distribution
system is not circulating the heat effectively. Unfortunately my installer believes the system is
performing as optimally as possible so is not prepared to do much more. He has offered to install an
additional boiler at a good price, but I am reluctant to do that until I am convinced that the
distribution system is working properly. So I am faced with the problem of fixing it myself. That is
why I am trying to learn as much as I can about hydronic heating.
I feel that the system should be able to cope with at least the water heating and the radiators going
together or with the water heating and the in-slab heating operating together. I am prepared to
accept that there might not be enough capacity in the system for all three at once. I suspect the
installer has not carried out any design calculations, but merely scaled a system that he might have
got working for another client. Our house is a modern one with double glazing and thermal wall and
ceiling insulation. There is also 50mm thick polystyrene under the concrete slab. It is hard to believe
that 30kW is insufficient, even 20kW should be sufficient based on what other homes of a similar
construction and size are using.
The way to figure this out is to do a heat loss calc on the building and compare it to the output rating on the boiler. 30KW is a sizable boiler. It would likely heat a house twice your size in your climate. It is absolutely not undersized.
Personally, I would use a reverse indirect as a buffer, hydrolic separator and DHW source. I would give each branch it's own circ and reset controls. Problems solved.
@ May 22, 2013 12:03 AM in Inspections needed on condensing boilers!The boilers at the Triangle Tube Training facility in Denver have 3/4" pex instead of the flexy crap. You have to expand the tubing a bit to get it on the trap. If you strap the pex securely to the wall or some strut it stabilizes it pretty well. Kind of ironic that they don't even use the stuff they pack with the boiler.
I have no idea about the SAN TEE on it's back (pointed the wrong way). Where is the trap? I think this install has other problems as well.
Good post Tim
@ May 21, 2013 8:58 PM in low water cut-offDoes a mod/com located in a basement need one? You generally have a water pressure safety. Supply and return sensor plus a high limit on the boiler and a T&P.
Is that enough?
An old school cast Iron is a different animal.
@ May 21, 2013 8:29 AM in TT110 Trimax control questionIt looks like it would be easiest to put the the check valves on both the heating and dhw circs. I would then just cut in the tees to make it primary/secondary on the heating side, just like the manual. You can install that boiler with a diff bypass. Why would you? Having the circ in the boiler cabinet working in series with the zone circ is a bad idea for countless reasons.
@ May 20, 2013 5:57 PM in Propane as fuelMost natural gas models are available in propane versions. For radiant heating, high efficiency units work very well as they love the low water temps.
If you insulate well and install good windows, a 500 gallon tank should be plenty.
This site has tons of good info.
@ May 20, 2013 5:52 PM in low water cut-offThere are plenty of places where LWCO's are not required on residential jobs.
Both 120 volt and 24volt accomplish the same thing. Unless code dictates, use whichever is easier for your install.
@ May 20, 2013 5:43 PM in Gas Boiler Pump and Zone LocationsThe boiler circ being flipped would have much less effect on the expansion tank than the 2 zone circs presently have. There just isn't enough resistance between the tees to create a problem.
For my money, I would flip the circ and be done with it.
@ May 20, 2013 5:38 PM in I have noticed more and more shotty workI'm still stuck on the letter box. How about A to H or E to I?
It is important to give the guys something to joke about.
The rest of the list is the making of a first class job.
Can it go from I to C to G?
@ May 20, 2013 5:33 PM in Reverse IndirectMy suggestion on the stainless was to stay away from tanks that have steel or other materials that are not suitable for potable water. The triangle tube smart for example would be a bad choice due to the steel in the outer tank.
@ May 20, 2013 10:21 AM in Reverse IndirectJohn Siegenthaler has written some good stuff on these. You should be able to google some articles.
I think for it to work well it needs to be a high temp heat system and the indirect needs to be stainless on both sides and have plenty of surface area. The heat flow models look like would work well.
@ May 20, 2013 9:59 AM in Gas Boiler Pump and Zone LocationsIf you are looking for a quick solution, there is nothing wrong with flipping the circ.
If you want to make it "really right", your zone circs should "pump away" from the expansion tank as well.
@ May 20, 2013 9:46 AM in is it a problem connecting a larger gas pipe to a smaller gas pipe?Sort of,
The system will have the restriction of 1" but only over the 6" of pipe. If you look on the chart, 6" of 1" pipe can carry lots of gas. If you were to restrict it for 60' that would be a different story
@ May 19, 2013 1:00 PM in Gas Boiler Pump and Zone LocationsThat is what I thought. I do see the primary loop being piped backwards as a big deal.
I have know idea why the boiler has not faulted being as the return must be hotter than the supply. I think they either switched the sensors or the flow rate is so fast, the boiler did not pick up the error.
Personally, I would forgive the other flaws in the system. The reverse piping on the boiler loop is not OK. Just flip the circ and double check the sensor wiring.
@ May 19, 2013 11:07 AM in New kitchen cabinets over existing baseboard heat?A dead post that someone revived by asking what color the cabinets are. I am sure this job was completed long ago and the OP long gone.
@ May 19, 2013 10:39 AM in Gas Boiler Pump and Zone LocationsIn an earlier post, He indicated the arrow was pointed toward the photographer. Now he is confirming that it it pumping toward the boiler (backwards). I think it is important to get all the facts before advising "If it ain't broke, don't fix it". There are many really dangerous systems out there that "work"
@ May 19, 2013 8:06 AM in TT110 Trimax control questionMake sure your sketch is accurate. It looks like the he has the circs is series. Where does this bipass valve fit in? It makes it so much easier when it is installed per the manual. Once it is determined exactly how it is piped, I think we can help you get it set up right.
@ May 19, 2013 12:08 AM in TT110 Trimax control questionCould you confirm the piping under the boiler. The TT110 would normally be piped primarily/secondary using the factory circ. Is the factory circ still installed (inside the cabinet)? A picture of that piping would be helpful.
@ May 18, 2013 11:46 PM in Gas Boiler Pump and Zone LocationsYour system has tons of misdemeanors. Pumping into the expansion tank, lack of isolation valves, how about support for the pipes and wires. I agree with heatpro on these. It is ugly but not worth fixing. Pumping backwards through a boiler, especially a Mod Con is a felony.It will absolutely wrong and is will reduce the life and efficiency of the boiler. The closely spaced Tees are also backwards. The good news is that the fix is to flip the circulator.
It could be an optical illusion, based on the pics, it looks backwards.
@ May 18, 2013 8:18 PM in Gas Boiler Pump and Zone LocationsIt looks like the supply and return on the primary (boiler ) loop is backwards. I am surprised the boiler controller would allow this as the temp sensors would not read correctly.
Ideally the zone circs should be pumping away from the expansions tank.
You said it runs fine? No air or velocity noise issues?
@ May 18, 2013 6:25 PM in is it a problem connecting a larger gas pipe to a smaller gas pipe?Gas line should be sized based on the allowable pressure drop in your system. I think the standard chart allows 1/2" total drop.
As previously posted you start with bigger pipes and reduce the size as the load decreases.
To do your system right, you need to map out what size and length pipe you have and compare that to the ratings of the attached appliances. It may be that you can easily add the additional heater using 1/2" line and have no problems. If you don't do the math you will likely end up with appliances malfunctioning due to pressure fluctuations.
As far as increasing the the pipe size, it won't hurt anything. It doesn't make the job look very professional. Is there a reason for not hiring a pro and doing it right?
@ May 18, 2013 2:15 PM in Gas Boiler Pump and Zone LocationsIf you could post some more pics. Farther away and from different angles. Also note which way the arrows on the circs are pointed.
It is definitely wrong, it is a question of how wrong.