Hello,

I live in Michigan, and with winter on the way, I'm trying to get prepared for the cold months ahead. I bought my first house in May, and this house is also my first experience with hydronic heating.

My problem is, the temperate gauge on the boiler never seems to go above 145 degrees F. The aquastat is set to 180F as far as I can tell (I temporarily set it to 200F for the picture below), but the burners shut off at 140F.

I don't know how old the boiler is, but here's what I do know: American Standard G-211, 300k BTU/h input, 240k BUT/h output, cast iron. I don't believe it has an outdoor temperature reset.

I don't know how old it is, but it looks pretty old. A lot of the rust is due to the fact that the basement flooded on the previous owners. We had a repair tech come in and replace some parts and get it firing again. I know one thing he replaced was the temperature/pressure gauge.

I was a bit suspicious that the gauge might be inaccurate, but I don't know how to confirm that. I just know what when the system was cold, I had the pressure at 16-18PSI, but when I had the aquastat adjusted to 200F, the temperature was still showing 140F, but the pressure shot up to 38PSI (way too high, right?).

Any suggestions? Here are some pics:



Aquastat (I think):


Aquastat and on/off switch:


Gauges:


If you need to see bigger pics: Boiler pictures by nathanbedford00 - Photobucket

I'd be happy to gather any info I can if it'll help. I'm wondering if I need to replace the aquastat, the gauge, or the boiler itself...

 

The gauge may be off, but since it was recently replaced, it's probably calibrated - but maybe still not reading right. It appears that the gauge is just screwed into a pipe nipple, perhaps 8" or so, rather than into a port extending into the boiler volume itself - if so, the temp will always read low. Was the original gauge mounted in the same place and in the same way as the current gauge?

You can buy an inexpensive strap-on temp gauge. Put it on the boiler outlet pipe - it'll give you an idea of the temp: MP748 - Mr. PEX MP748 - Strap-On Pipe Thermometer for 1/2"-4" Pipe (70-200F)

I suspect that your aquastat is seeing the correct temp - if so, 200 deg is too high. If in doubt between the two, it would be easier to replace the aquastat than the gauge - the 'stat can be replaced without draining the boiler.

Overall, your boiler looks rather neglected, even making allowance for the flood. The burners need cleaning and there is rust piled up beneath the burners. Also, I'm not real wild about the gas valve being mounted inside the boiler enclosure - but if the boiler came than way, I guess it's OK.

I assume the front is removed just for photogenic purposes?

 

It will also be lower if it is on the return.

That boiler is huge!. How big is your house?

 

I want to see more pictures! Is this a pumped system? Assuming it is, I want to see the pump and the control for the pump with the cover off the control.

It appears that you have a "Powerpile" gas valve and that this boiler maintains a heated temperature at all times regardless of whether or not the house is calling for heat. If you have a kitchen oven thermometer with a probe you can clamp the probe onto the water outlet pipe and wrap some insulation around it (or an old rag) and get a pretty good check on the temperature of the leaving water when the circulating pump is running. This temperature should be fairly close to the aquastat setting.

I doubt very much if the new thermometer was "calibrated" but it shouldn't have a huge error. It may indeed be reading several degrees different than the aquastat simply because it is placed in a different location. The aquastat calibration could easily be off by several degrees from the dial setting.

Your system is old enough that it may not have a boiler-mounted safety valve but only a cold-water pressure relief valve mounted in combination with the "automatic fill valve" or as it is more properly described the make-up water pressure reducing valve.



This combination would be mounted in the cold water supply to the system and was common some fifty years ago but it does NOT meet current standards for a boiler safety valve. If you have this please post a picture.

The 38 psi pressure would normally be considered dangerous but it depends upon what the maximum pressure for the boiler was when it was made. Today most heating boilers have a maximum pressure of 30 psi but it is possible that your particular boiler could have a rating of 40, 50 or even 60 psi. You need to find the nameplate and it will state the Maximum Allowable Working Pressure or MAWP with a number.

I can tell you right now that boiler does not have any outside temperature reset and it is doubtful that one could be installed. Quite honestly the ONLY possible up side to that boiler is that it will continue to fire even during a power outage but without power for the circulator pump you would have to manually open a flow-control valve and the heat would be slow reacting.

So let's see a whole bunch more pictures and get some that include the overall piping arrangement.

 

Unless this is a milivolt system, how would the gas valve open without AC power?

 

Judging by what we can see in the pics, it probably IS a millivolt gas valve...

As for the flooded basement, how deep WAS the water? was the gas valve underwater? If so, replace it. Period...

I hope the tech removed and cleaned the burners before leaving... but I bet he didn't even take them out, did he?

How about the expansion tank? was it full of water? was it drained? If the pressure gauge is even reasonably accurate, the 38 PSI you saw could well be caused by a waterlogged expansion tank.

Furd mentioned the pressure relief valve... where is it? What is it's rating?

Yes, more pics... show us everything.

Honestly, my opinion, replace it as soon as you can afford it.

 

Thanks for all the replies. I'll post more pics as soon as I can today (should be up by 3PM EST). I'll post a diagram of my whole system, too if it would help.

 

Yes, the more info we have, the better. Don't forget to answer the questions in my previous post... but maybe the pics will do that for you! What is it they say? "A picture is worth 768 inflation adjusted words"

 

Sorry for the late replies, everyone.

Here are my replies to the questions:

Mike Speed 30:
- Original gauge was mounted in the same place
- I agree that the boiler has been neglected. I'd love to know how I can properly clean those burners. I can easily start with just removing the loose rust...
- Yes, the cover was just removed for the pictures

Drooplug:
- That's a good point...from what I can see, the temperature gauge is at the return end of the tank
- Yes, it's seemed pretty large to me too. The house is 4000 sq ft, and I haven't done a manual J calc yet, but I'm pretty sure the boiler is oversized.

Furd:
- Yes, it's a pumped system. I have two B&G Series 100 pumps. One controls 5 zones, and the other controls 3 zones.
- I tried measuring the outgoing temperature of the water as suggested, and I came up with temperature of 145F when the temp gauge showed 130F. I also measures the temperature of the water coming out of the drain, and it came up at 160F when the gauge showed 140F. So I'm suspecting my gauge, but I'm still not sure why I'm not getting temperatures closer to the 180F that my aquastat is set to.
- I'm pretty sure you're right...I don't see a boiler-mounted safely valve, but I do have a cold-water relief valve (I think). Pics are included at the end.
- I checked the nameplate on the boiler, and it lists 30PSI as the MAWP. I should re-iterate that I had the pressure at 16-18 when it was cold, and it was normally below 25 when hot. As soon as I saw it at 38 I drained water from the boiler

NJ Trooper:
- The water was at least 13 inches for a while...long enough to leave rust marks on the hot water heaters. That does seem to be deep enough to partially cover the gas valve.
- The tech definitely didn't remove and clean the burners. Didn't even take them out. Now I'm really wondering what he DID do. My wife is digging up the reciept so I can see exactly what he replaced besides the tempature/pressure gauge.
- The expansion tank was leaking, so I replaced that several months ago. I found a replacement that matched the old one spec-for-spec.
- I've found a relief valve on the cold supply in, and it looks like it's rated at 30PSI.



Some background on the house:
Originally, it was a ranch-style house, about 65 feet long. Built in the 50s we think. Then, a colonial addition was added (in the 60s we think). The colonial is about 35 feet long, and the boiler is at the far end of that, so our longest heating run is the length of the house (~100 feet).

There are 8 zones, split into two groups. Group 1 is run to the colonial, and it has 5 zones. Each zone has it's own supply and return pipes leading out of the boiler room.

Group 2 is the long run to the ranch, and it has 3 runs. Each zones has a pipe running out, but all three merge together for one run back, so I guess they have a common return. Two of the zones use a series system between their radiators, so there is a big 1 1/4" iron pipe, and the heat is branches out from mono-flow tees to 1/2 copper.

Here are some pretty lame (I tried :-/) sketches:




You can see larger images at Boiler, Sketches - a set on Flickr

 

More pictures (you can see the set in Flickr here):

 

And more pics:

 

Much better.

In your drawing the in and out labels are backwards. The flow is out the top of the boiler, to the various zones and then back through the zone valves, the pump(s) and into the boiler. This is a typical arrangement for the time it was installed.

It does seem that the system was pieced together or at least had parts from several different manufacturers added/changed over the years. The safety valve (green) is by Thrush, the zone valves appear to be White-Rogers and the make-up water valve (pressure regulating valve on the incoming water) is a Bell and Gossett as are the pumps. The relays operating the zone pumps each have their own transformer with one set by Honeywell and the other appearing to have the Sears brand.

Those B&G pumps are almost bullet proof as long as you keep the bearing assembly oiled, that's the oil reservoir nearest the piping. It is almost impossible to over oil this rat as any excess will simply run out. The oil chamber is filled with a cotton wicking that holds oil and feeds it slowly to the bronze oillite bearing. Each end of the motor also has an oiling port but these CAN be over oiled and the excess will run over the rubber mounting rings causing deterioration of the rubber. When this happens the motor will tilt and this usually ends up destroying the flexible coupling between the motor and the pump. The one downside to these pumps is the large motor is an electricity hog.

The zone valves, if the White-Rogers models I am thinking of are good valves that have a low pressure drop across the valves. They require a three-wire thermostat, something not that common so if you desire to change any of the thermostats let us know and we can detail an intervening relay to allow a two-wire thermostat to interface to the three-wire zone valve. One feature that I really like about these valves is that they only require power when changing position, they power the valve open and then the motor stops until the thermostat is satisfied and then they power the valve closed. They also have a manual feature that operates both the valve and the end switches that control the circulating pumps.

You should change out the safety valve sooner rather than later. You could try to lift the test handle but I suspect that if you do the valve either won't open or it won't close tightly. You already know that it doesn't open at the proper pressure of 30 psi.

Definitely remove at least one of the burners for inspection and take a few pictures. I think they are solid cast iron burners and if so you can try wire-brushing the heck out of them or, if available, a shot peening or sand blasting will clean them up. Ideally you should try to clean the inside passages and each "jet" spud on the burner itself. Do NOT get carried away with the sheet metal "shutter on the inlet end and try not to disturb the position of the shutter or at least try to put it back in the same position it was originally. Do not get carried away cleaning the orifice spuds that insert through the shutter. You can CAREFULLY try the butt end of several different number size drills until you find the proper size and then use this to carefully clean the orifices if necessary. You may want to remove the orifice spuds and clean the manifold to remove any rust.

Your aquastat may just be shot. Try jumpering the two wire connected or simply removing both wires and connecting them together. This will need to be a solid connection as you only have about 1/2 to 3/4 of a volt to control the gas valve. This will, of course, put the burners in a "runaway" condition so don't leave the boiler while doing this test. The temperature should continue to rise well above the 145 degrees you are getting now. If it does, reconnect the wires to the aquastat and if that takes you back to a maximum of 145 degrees then you know the aquastat is toast and needs to be replaced.

 

What kind of heat emitters are in the house?

Although you matched the expansion tank when replacing, it's possible that it's too small. Particularly if you have any cast-iron radiators. Expansion tanks are sized based on water volume of the system. Amtrol has a sizing guide on one of their web pages. Best way to determine water volume is to drain the system into five-gallon buckets, but let's not do that until the burner/aquastat/whatever issue is resolved, or we find that this may be an expansion tank issue, too. This system may be problematic to refill and get the air out. (Which you may have discovered when doing the exp tank....)

Find a new heating tech. Not replacing the gas valve was a major boo-boo. Looking at the height of the stain on the water heater and the rust line on the inside of the boiler jacket, it's pretty clear the valve got very wet. That gas valve is almost certainly not something he would have had on the truck, but it should have been slated for replacement on a return visit.

240k output boiler (if running correctly) is probably at least twice as big as needed, and shouldn't have a problem getting your water up to temperature.

If this system is ultimately slated for complete replacement, here are some suggestions. (But first know that the other guys here have made some great suggestions to get this thing through the winter. Never replace a boiler during heating season if you can help it.)

1) do a heat loss for the building. I'll just guess that you come in around 120-140k BTU/hr at design.

2) spend this winter getting a blower door test and thermal IR imagery to identify insulation and air sealing needs.

3) insulate and air seal as much as you can based on your blower door and IR results. Three are good tax credits and often utility rebates for this stuff. Unless the windows are truly shot (e.g., rotting), don't worry about replacing them. They are about the least cost-effective energy upgrade. Air seal around them and air seal and insulate the rest of the house. For old houses like this, you can often cut the heat loss nearly in half. Forever. Improving the building envelope is the most cost-effective and best thing you can do to reduce fuel costs and increase comfort. Use your post-project heat loss to size a new boiler.

4) in late winter to early spring, start thinking new boiler. Tons of options. Lots of advice here. If the water heaters are getting old, and/or have water damage, you might also consider replacing them with an indirect water heater fired by the boiler. It's a very efficient way to heat domestic hot water.

5) longer-term, you might look into whether all that roof space is a candidate for solar thermal domestic hot water and/or photovoltaics. There are excellent tax credits, state programs, etc. that can put the payback for either/both into 4-5 year range. See dsireusa.org for list of incentives in your area as well as federal.