Boilers - Steam and Hot Water Systems - help with boiler system!

Firstly, a fantastic site and forum. Much help has been gleened from these forums over the last several weeks. However, I am stuck...
I have a Utica MBG175 gas fired boiler and 2 zones seperated by plumbing with circulators on each zone's return line and not valves. The secondary zone is currently wired as a 'slave' off the primary zone in that if the primary is calling for heat when the secondary does, it's all good. The system is comprised of 2 ritetemp digital programmable thermostats, an argo ar822 relay, a white rodgers 829a relay, a dayton 1/6 circulator for the main zone, a grundfos 15-42 for the secondary and a honeywell l8148e aquastat. Everything functions well and heats well except ... based on my calculations the grundfos is undersized and I'm looking to replace it with a Taco 00 series VDT circulator (007). Any feedback? I have reworked the wiring of the relays so that each zone can be independently run based on a call for heat, my question is . . . can the 8148E have two thermostat inputs on the T/TV inputs ? Either zone should fire the boiler upon a call for heat that way, but if the boiler is already running and the other zone calls for heat, closing the relay to energize the circulator, does that create a problem for the 8148E in that it's switches will already be closed ?

Firstly, a fantastic site and forum. Much help has been gleened from these forums over the last several weeks. However, I am stuck...
I have a Utica MBG175 gas fired boiler and 2 zones seperated by plumbing with circulators on each zone's return line and not valves. The secondary zone is currently wired as a 'slave' off the primary zone in that if the primary is calling for heat when the secondary does, it's all good. The system is comprised of 2 ritetemp digital programmable thermostats, an argo ar822 relay, a white rodgers 829a relay, a dayton 1/6 circulator for the main zone, a grundfos 15-42 for the secondary and a honeywell l8148e aquastat. Everything functions well and heats well except ... based on my calculations the grundfos is undersized and I'm looking to replace it with a Taco 00 series VDT circulator (007). Any feedback? I have reworked the wiring of the relays so that each zone can be independently run based on a call for heat, my question is . . . can the 8148E have two thermostat inputs on the T/TV inputs ? Either zone should fire the boiler upon a call for heat that way, but if the boiler is already running and the other zone calls for heat, closing the relay to energize the circulator, does that create a problem for the 8148E in that it's switches will already be closed ?

Normally I would highly recommend a VDT circ, but are you sure that it will pay for itself... they are not cheap.

the secondary loop is long and while the little grundfos does work, the heat output of the radiators is nowhere near the output of the main zone with the big circ. I had entertained a 3 speed circ, but in an effort to tinker as little as possible, decided that the VDT is more patient and accurate and will control the circ flow in that zone much more efficiently and patiently than I would assuming a reasonable delta T is used. Any thoughts on the aquastat and two thermostat issue ?

IR "heat" detecting guns are often on sale at automotive/hardware stores (IIRC, I got mine for $40). You can point it onto the supply and return lines (with that zone solo, or both zones flowing) and see what your delta is like.
I dont think there is a way to compare your existing delta to the current pumps spec graph.. and then compare it to a different pump's flow graph. But at least with an (somewhat) accurate reading on your typical delta, you can figure if you need to go upslope or downslope on the flowrate.

I dont know about that Utica boiler.. is it a cold-start boiler ? I dont have a cold-start boiler, so I just strap the TT terminals at the aquastat and let the boiler maintain its own high-low limits. I use zone valves and slaved pumps, but they just call when they need the heat.. the boiler operates simply as a supply maintained between high and low.. even if you dont need it (the disadvantage of a non cold-start unit).

thanks for the tip, I think I'll do that. With a head of about 6 in a 140' loop, what would be a reasonable Delta? That's the motivation for the VDT circ - set it and forget it.

The Utica MBG is a cold start boiler and the Honeywell L8148E is a high limit aquastat. The Utica heats/holds just over 7 gallons and the high limit temp is set at about 180.

The 2 circs are energized independently with a cfh on the thermostats and then energized by their own relays, with the aquastat operating only the boiler. The 2nd zone is slaved to the first currently so a call for heat from the main closes the relay loop for the second thermostat, powering the circ. But if the second TT has a call for heat and the first doesn't - no heat.

I can seperate the loops with the current configuration, but can the aquastat have both thermostat inputs ? ? ?

In other words, if the boiler is running already and another zone relay closes, powering that zones circ, and voltage is again sent to the aquastat while the relays are already closed - does this present any issues or risks to the aquastat ?

There may be times when both zones need heat, but not simultaneously. Currently to heat downstairs, the upstairs has to be hot enough to put you out of the rooms !

I have looked at zone relays like the Taco SR502, but this looks like it powers zones independently as well and not simultaneously should the need arise.

I have looked at zone relays like the Taco SR502, but this looks like it powers zones independently as well and not simultaneously should the need arise.

I scanned your thread, didn't read closely... but, I think the 502 would do what you want...

T'stats connect to the panel, as do the circs. When EITHER OR BOTH call for heat, the respective circs will run, and the ENDSWITCH on the 502 panel will call the boiler for heat demand. Is that what you are looking for?

my question is . . . can the 8148E have two thermostat inputs on the T/TV inputs ?

Yes, as long as they are BOTH 'DRY CONTACTS', in other words a simple contact closure with no source of power on their own.

Take a look at some zone valve wiring schematics. It's a good example of what you are asking about. The ENDSWITCHES that fire the boiler are all wired in parallel to the T/TV terminals on the aquastat. Multiple DRY CONTACT closures feeding one relay.

a 140' loop, what would be a reasonable Delta?

140' ? that's not ALL emitter, right? you are including the non-radiating piping in that length?

Did you say what type of emitters you have? fin-tube baseboard? standing cast iron rads?

If you have a loop that is 140' long, it's probably around 8' of head. But the bigger question, how much of that is radiating?

If you have 140' of baseboard on one loop, I would recommend splitting that loop into two parallel loops... I'm sure if it's all emitter, you will see a DT of around 40-50°, and you probably won't be able to pump enough water through the loop to drop that much...

In other words, if say your talking about a 3/4" pipe, you want to flow not much more than 4 GPM in that pipe for an acceptable water VELOCITY (2-4 FPS). If you are shooting for a 20° DT, then you are talking about 40K BTU. If you are using fin-tube baseboard, at say 550-600 BTU/FT, in order to achieve a 20° DT, you can't have more than say 70' of fin-tube installed on that loop. 70' X 550 = ~40K ... so, given all that mumbo-jumbo, if you have 140' of emitter installed, you would need to almost double your flow rate to get close to a 20° DT, and you really don't want to flow that much.

Are the two zones similar configuration?

that length includes non-radiating piping as well.
The emitters are cast iron rads, 6 of them on the main floor in various sizes all with decorative/functional covers.
I have measured the delta on the supply and return lines and it averages 38. I'm going to try for 35 with the Taco VDT and see how that goes.

The relay problem is solved. The second zone relay (hte 829a) does not have the appropriate dry contact switch the layout should have. I will isolate the zones with a new relay on the slave zone and keep the circs independent on the relays as the zones are plumbed entirely seperately up to the return on the boiler.

So... making progress and very appreciative for the help and feedback. Learning a lot about this hydronic heating (first time) and getting ready for a long NY winter.

Another issue, pressure relief valve is blowing off some water ?
idle pressure is about 12, near high limit temp is 25. No water from valve on exp tank, no air blowoff, tank sounds hollow, pressure measured ok at tank . . . . fill valve seems fine, bad pr valve ?

a new relay

Take a look at the R8845...

Honeywell-R8845U1003-Universal-Switching-Relay (https://www.pexsupply.com/Honeywell-R8845U1003-Universal-Switching-Relay-w-Internal-Transformer-11013000-p)

Another issue, pressure relief valve is blowing off some water ?
idle pressure is about 12, near high limit temp is 25. No water from valve on exp tank, no air blowoff, tank sounds hollow, pressure measured ok at tank . . . . fill valve seems fine, bad pr valve ?

If the pressure gauge is to be believed, and the relief valve is dripping at 25, then I would say replace the valve. If the relief valve is more than 5 years old, replace it in ANY case, leaking or not.

Pressure gauge could be inaccurate... should verify.

"tank sounds hollow" really doesn't mean anything.

Your exp tank, what type? Sounds like you are talking about the bladder type tank? What do you mean "no air blowoff" ?

"Pressure measured OK at tank" ? again, must be bladder tank, presuming so, and leads me to ask: When you measured the pressure at the tank, did you have pressure in the system? If so, you won't get an accurate reading. You need to have ZERO or very close to it on the water side of the tank in order to get an accurate reading on the air side.

Also, what SIZE tank do you have? Since you have standing rads, you might have a larger volume of water in the system, and might require a larger tank...

thanks again for everyone's help and advice, not only with my own post but many, many others as well.

here's where I've gone so far:
i will replace the grundfos with a Taco VDT
I have removed the old relays and replaced with a Taco SR502
I have new prv that I will install tomorrow
Checked expansion tank (drained air, no water at all) and all appears well with it but . . .

idle/cold system pressure is right at 12psi. with return line valve closed, still hows 12. if I close the supply line and the return, and drain the exp tank - pressure drops accordingly. - drain water from boiler and recharge tank to 14'ish psi. No problem, when heating pressure rises to 30 and rv discharges.
I have drained water, bled the rads (all are good with very little or no air - all are hot bottom to top).

There are flow control valves (manual B&G's) behind the exp tank going to the main lines. I can isolate the boiler from gravity pressure via the return line valve and close the supply line. Will the flow control valves stop system water from flowing backwards if I remove the exp tank and simply replace it ? I have a new Amtrol Extrol 60 that I can install ?

Confused and concerned. Any thoughts ?

I think you are doing something wrong there... you said:

Checked expansion tank (drained air, no water at all) and all appears well with it but . . .

idle/cold system pressure is right at 12psi. with return line valve closed, still hows 12. if I close the supply line and the return, and drain the exp tank - pressure drops accordingly. - drain water from boiler and recharge tank to 14'ish psi. No problem, when heating pressure rises to 30 and rv discharges.

It sounds to me that you have a 'bladder type' expansion tank, and if you DRAINED AIR, you did the absolute wrong thing... there MUST be air in the tank in order for it to function!

The air charge in the tank must be equal to the system pressure when the system is cold. So if you have 12 PSI on a cold system, there must be 12 PSI of air in the tank.

Can you please confirm the type of expansion tank that is connected to your system? MAKE / MODEL etc...

After I am SURE of what you have I will tell you how to recharge the tank that you let the air out of.

I isolated the expansion tank as well as the boiler. drained the boiler of any residual water. the gauge still read 12'ish. I released the pressure in the exp tank. the boiler gauge dropped also to 1, which I think is what should happen if everything is properly isolated - is it not? Then using a small compressor I recharged the tank to 12 psi, opened the fill line slowly and then opened the return line to the boiler. Some water fill occurred (very little). All reads a good solid 12. During heat cycle pressure rises to 30, and prv vents some water.

Exp tank is an Amtrol Extrol Model 60, 7.6 gallon 'bladder' type with diaphragm.

OK... first off, don't isolate anything. Leave all the valve as they should be for normal operation, EXCEPT for the one valve that feeds water into the system from the domestic supply. Close ONLY this valve to the domestic supply. Leave all other valves in 'normal' position.

Turn OFF the electric supply to the boiler.

Allow the boiler to cool to 100°F or less.

Open a drain valve on the boiler and let out ONLY ENOUGH WATER TO DROP THE PRESSURE IN THE BOILER TO NEAR ZERO.

Do NOT 'drain' the boiler completely. I repeat, do NOT 'drain' any more water from the boiler than is necessary to drop the pressure to zero.

When the boiler system pressure is at ZERO, put a tire gauge on the expansion tank air fitting and measure. If it is less than 15 PSI, add air pressure to the tank until it is at 15 PSI.

Recheck the gauge on the boiler. If that gauge has risen from zero, open the drain again, and drop the pressure back to ZERO.

Put the tire gauge on the air fitting on the tank again. If it is less than 15 PSI, add more air to the tank.

Repeat the above two steps until you have ZERO PSI in the boiler, and 12-15 PSI air charge on the tank.

When you have ZERO in the boiler, and 12-15 PSI in the tank, reopen the water feed valve into the boiler, and allow the boiler to fill the pressure back to the cold fill pressure.

Turn the power back on to the boiler.

NJ, thanks. I will do exactly as you suggest.
In the event that I need to replace the tank, will the B&G flow control valves contain the backflow of the system water and prevent draining of the system through the expansion tank fitting while I put the new one in place ? Then I assume I would again follow your instructions again.

I doubt that just the flow control valves will be enough to hold back the water... it will come from both directions in the pipe.

I could look and see which valves you might be able to close if you wanted to post pictures. If you do wish to post pictures, you can set up a free account at Image hosting, free photo sharing & video sharing at Photobucket (http://www.photobucket.com) and upload the pictures there, come back here and leave a link for us to view the album.

I am confident that once you do these steps, the pressure will be under control again, and you won't have to change the tank.

If you DO have to change the tank, check the air pressure in the tank BEFORE you install it. Then you won't have to do all this, because you will know the air in the tank is correct.

The object of all this is that in order to accurately charge this type of tank with air, you have to have ZERO PSI on the water side of the tank. Otherwise you will get a false reading on the air side. That's why we have to go through all this procedure when the tank is already connected to the system...

I happened on this sight by accident. It seems like your going through torture. I hope this helps a little bit. First off generally when you have any cast iron rads. in the system go from a 30 to a 60 extrol. Second, if you isolated the tank from the system, discharging the tank should have had no effect on the pressure gauge unless somthing wasn't holding. What you might want to try is to close your supply and return valves to the system if you have them. This will prevent any system water from coming back to the boiler. If you have a valve between the system and the tank that works you can isolate that and you wouldn't have to shut the others off but it won't hurt anyway. Next, shut off your supply water line to your feed valve. Put a buckett under your relief valve and open it up. This will relieve the pressure in the boiler instead of draining it. When the water stops coming out thats all you need because now the water is below the tank and there should be no pressure. Unscrew the tank and replace with the 60. Open up your feed valve and your valve to the tank if you have one and then slowly open the system valves and you should be good to go. By the way when you tap your expansion tank it should be hollow on the top and solid on the bottom where the water is. If the whole tank is solid be careful when you unscrew it because it will be under pressure if the bladder let go. Drain the water first for saftey.

spot8, I have done the process as you suggest several times without avail. While there is no shutoff before the expansion tank, there are flow control valves that (thankfully) held back all but a slight trickle. I did release the pressure and water to 0 pressure on the gauge. Initially, pressure reads 12 bu then rises uder heating conditions. I will install valves in the spring for sure after this ordeal!

NJ, followed your steps EXACTLY - twice! Initially, I was excited - pressure spot on at 12 once reopening system fill . . . heat cycle started and pressure slowly rose to 20. Next cycle crept up to 25. And then next to >30 and some venting of water from the prv. Both times.

I also checked all the rads for air and found 2 of the 14 had only slight air discharge, the rest were good to go. Other than the discharge (I will replace the valve) there is no system demand for water.

Have I overlooked the obvious? What about the supply line fill regulator valve ? What if it is not functioning properly and overfilling the system ? Since there is no demand for water, can this be closed instead of open to test it out ? For that matter can it be closed altogether without harming the system ?

Everything else tests ok and functions as designed/intended so this valve is really the last variable ?

NJ & spot8,

BTW, there is no valve between the boiler outlet and the expansion tank - that's why I think with the boiler isolated via the fill and return vlaves (without the vent open) the gauge also would indicate the exp tank pressure.

And, the tank (original and replacement) is an Amtrol Extrol model 60.

Thanks again for the help.

At this point I would have the tank off, and ensure it holds pressure while off.
If the fill pressure reg was toast, the pressure would build no matter what state the boiler was in (on or off).

Where is the water feed in relation to the expansion tank ?

Maybe time to post a pic or two of the near boiler pipework

First, it will not hurt to run the boiler with the feed valve off to check it. Next, I see you have 14 cast iron radiators and a 175,000 BTU boiler. Because you have cast iron rads. your extrol tank is too small. If you had baseboard the 60 would be fine, but with cast iron rads. the system calls for an SX-30V TANK. The 60 has a tank volume of 7.6 gal. and the SX has a volume of 14 gal. This info came from an extrol sizing chart. What I did on a job because of space limitations when I needed a 60 instead of a 30 was twin them together to get the capacity I needed. That was about 15 years ago and never had to go back. Since you have the two 60's already if you want to try that to get the capacity you need without getting the other tank it should work. The SX tank is also a standup tank. The're not cheap.

My opinion is that the 60 is more than likely fine for the system. If the tank was too small, the same symptoms would appear EACH TIME the boiler was fired, not have the pressure increasing in 5 PSI steps each time.

The thing to understand is that water expands at a fixed rate when it's heated. If you heat water from around room temp to 180F, it will expand just under 4% by volume. This means that if you had 100 gallons! *(you won't, that's HUGE)* after it was heated you would have 104 gallons. That 4 gallons would need to go into the expansion tank, and compress the air bubble inside that tank. Air can be compressed, water cain't!

If you had the SAME amount of water in the system each time it heated, it would produce the SAME pressure each time it was heated.

NJ, followed your steps EXACTLY - twice! Initially, I was excited - pressure spot on at 12 once reopening system fill . . . heat cycle started and pressure slowly rose to 20. Next cycle crept up to 25. And then next to >30 and some venting of water from the prv. Both times.

Was the 20 PSI, 25 PSI, 30 PSI all at the same TEMPERATURE? If so, you are almost definitely adding water to the system somehow.

Also, after you fire the boiler, get it hot, and let it cool again, the pressure should return to where it was... does it?

It does sound as though you have a problem with the fill valve, but as TO said, the pressure would increase regardless of whether the boiler was firing or not.

If you fill the boiler to 12 PSI, and DON'T fire it, and just let it sit for a few hours... what happens to the pressure?

So, let the boiler cool. Adjust the cool pressure to 12 PSI, and as you are thinking CLOSE the water feed valve. Run the boiler and tell us what the pressure does.

that's why I think with the boiler isolated via the fill and return vlaves (without the vent open) the gauge also would indicate the exp tank pressure.

It might come close, but doing that does not ensure that you have the correct air pressure on the air side of the bladder, with ZERO on the other side. The tank could still be partially full of water also... it would still pressurize, but with a volume of water in the tank, which would naturally reduce it's capacity to absorb the expansion of the water... In other words, the tank has to be EMPTY of WATER, and FULL of AIR when you pressurize it. That's why I said to repeat those two steps... because if there was water still in the tank, you may have seen the boiler pressure rise a little after you first charged the tank. Theoretically anyway... but...

A 60 is fine.
I have done a bunch of jobs like that with 60's
More never hurts, and a 90 would be ok too.

Just relaying what I got right from the Amtrol book. They require the 60 with finned baseboard but the SX with the cast iron radiators and because of the boiler size. As far as the feed valve goes, you can isolate it and see what happens. Good Luck, don't give up. NJ, I see your point and your right if it's fired for the same amount of time each time. It just sounds like the longer it runs the hotter it gets the higher the pressure goes which would indicate to me an expansion problem and since the tank is new and working that doesn't leave many options.

Sizing guide (http://www.amtrol.com/sizing.htm)

Understood...

Thing is though, the sizing based on boiler size and type of radiation is more of an 'estimate' than if you base the sizing on the volume of water in the system.

The online guide figures it both ways.

If you plug in 85 gallons, 180°F, 175,000 BTU, cast iron rads, you will get two recommendations. The first based on water volume calls for a 60. The second, based on boiler size and cast iron calls for the model you selected.

Sometimes it's difficult to estimate the volume of water in the system, so a 'play it safe' selection should be made. I'd bet there's not more than 50 gallons in that system...

But, it leads me to ask more questions:

Is this a brand new installation?

Or, has this system been in operation with the 60 for many years and only now having troubles?

If the latter, and it worked fine with the 60, there's no reason to believe it won't work again with the 60.

I was wonderng the same thing. That is why I suggested maybe trying the double 60's before getting the SX. I would assume that the old boiler would have more water content than the new one so what you say makes sense. Good brain teaser.

Yeah, the twin 60's would make more sense especially since they are both on site already! and the $$$ for the SX ...

What you said about perhaps the boiler getting a bit hotter each firing also makes sense, but my gut is telling me there's a problem with the pressure reducing valve 'leaking through'... I guess we'll know soon!

Awesome feedback and assistance guys, I really appreciate it. The system has been in use for many years. The home was built in 1840, but obviously the boiler system was not. It has been retrofitted and upgraded and at one point was an oil fired boiler that was gravity fed I'm sure. It is a large system with some large rads. Using this forum I estimate that it's about 45 gallons in capacity.

Here's the latest: I put everything back together last night and monitored the system through 3 heat and cool down cycles. After so much emphasis on the exp tank, I began to ponder elsewhere . . .During a heat cycle where the temp gauge read almost 160, I decided to conduct an extremely thorough and complex test of the fill valve - I touched it. It should have been warm, but it was cold! A-ha! Onto something . . . I decided to close the fill valve. System idle pressure remained at 14-15, and at cutoff temp was 20 ish. No discharge. Same on next cycle. The balance of the night and all day today the system seemed to function normally and not a drop of water in the bucket from the prv!

Faulty fill valve. It appears that the valve was simply overfilling the system all this time.

How long can I run the system closed, safely until I can replace the valve?

How long can I run the system closed, safely until I can replace the valve?

As long as you have no leaks you may leave the make-up water off forever. Truth is, I prefer running closed systems without automatic make-up. Check the pressure on a regular basis and if it starts to drop then add some water manually.

I run mine closed... but I walk past the boiler every day and glance at the gauges as I go by... which I would recommend you do on a periodic basis.

Older boilers often do not have a low-water cutoff. I would be leery of running such a system with the makeup valve isolated for any length of time. But I know that some feel it's OK.

I wouldn't recommend it to _most_ homeowners... because they simply would not take the time to do due diligence and keep an eye on the pressure gauge... and that is the important thing here. You do NOT want to destroy your boiler and possibly burn your house down by dry firing the boiler! And neither do we!