Amateur DIY hot water boiler install on old gravity system with steam boiler attached (long story..)

gchrisman

I hope it's a bit better now - I haven't put up any more photos, but I did get new gaskets for the flanged connectors so I could turn those in the right directions, and I even was able to remove one of them completely to simplify the routing. Plus I got everything secured with unistrut, clamps, and threaded rods.

gchrisman

It has been running reliably now for a week, and doing pretty well. I've balanced the valves on the radiators until the heat is pretty even throughout the house. However, it is not getting the radiators very warm. I have a temp/pressure gauge about 4 feet from the boiler, and when the boiler is producing water at 170 degrees, the temp there (just after the main circulator) reads about 110 degrees. The return temp coming back from the radiator system is around 90 degrees. I've tried changing the setting on the Taco 0015 pump (lo, med, or hi) with no real change to these temps. Since this is piped primary/secondary, is the hot water mostly recirculating right back through the boiler? It makes me wish I had a valve right between the closely-spaced Ts so I could throttle that back a bit, if that is the case.

mattmia2

Is the house getting warm? The emitters shouldn't need to get that hot to heat the house other than when you get near the worst case heat loss and even then it is probably oversized and doesn't need to get that hot.

mattmia2

Oh, right this is a mod con. If it is heating the house then you probably just need to turn the boiler temp down. You might need more pump or bigger pipes to the emitters if it isn't keeping up.

Is there anything that could be clogged from all the crap that is in the old iron radiators and piping?

What is the supply and return temp in the menu of the boiler? Where is the 110 degree reading, is that in the boiler loop or the system loop?

gchrisman

Yes, the house is staying fairly warm. It is in the low teens outside, and the house is around 62 degrees inside. The boiler is operating at its third firing level (of five). When I did my heat loss calc, I used numbers that reflect my plans for the near future, including insulation I plan to add to the attic (but isn't there yet) and two storm windows that need to have panes replaced.

gchrisman

It's possible there is a clog somewhere, but the pressure readings are very even, and I did flush the heck out of the system - partly because every time I tried filling it I found more leaks, and had to drain it again to fix them.

I like your idea of turning the boiler temp down and seeing if it can produce this level of heat even more efficiently. A bigger pump would be another easy option, if I can find a bigger one that will fit the Taco isolation flanges I installed for the 0015.

WMno57

Bump for a hard working homeowner who is 99 percent recovered from a knucklehead professional contractor (the guy who saw big pipes, and installed the steam boiler in a HW system).
@gchrisman if you post some more pictures of your primary secondary piping @hotrod and @ironman may have some suggestions for you.
Neat piping layouts are nice to look at, but Chrome Don't Get You Home.

gchrisman

Thanks, @WMno57 ! I appreciate the understanding and the help. I'll post some updated photos of the piping when I get home from work. Last night I tried turning my current pump (0015 3-speed) up to hi, and lowered the boiler max water temp to 140, but that ended up cooling the house down too much overnight (the supply pipes and radiators were at 90 degrees, the return was 85 degrees, and the house was around 53 degrees this morning - it was 11 degrees outside), so this morning I set the water temp back to 170, and the radiators are starting their slow climb back towards what seems to be their current maximum of 110 degrees.

gchrisman

For clarification, the 110 degrees is in the system loop, and it takes quite a while to get there. The boiler is set to a minimum temp of 96 and a maximum of 170. The boiler seems to burn for a while at level three, and then turn off once it goes over the target temp plus the allowable margin (around 180 degrees). The temperature in the boiler then rapidly decreases, until it is low enough (and the minimum time between cycles has elapsed), then lights up again and repeats. When I have it set to 170, the radiator loop seems to be steady at 110 degrees or so (90 degrees at the return) while the boiler repeats that cycle. The one thermostat I have set to 68 degrees, and the house has only reached that temp in the middle of the day, so at night there is a constant demand for heat at the boiler. It seems like the hot water from the boiler is not being pumped out into the system very effectively. The circulator pump is a Taco 0015 3-speed, and I currently have it set to hi on that theory. The HTP EFTU-110WBN boiler has its own internal pump as well, and I'm wondering if maybe the boiler pump on its very short primary loop is outperforming the 0015 working against the much higher friction of the entire radiator loop, so that the hot water is mostly just cycling through the primary and back into the boiler.

gchrisman

Some current photos.

The primary/secondary piping:

The return gauge:

Automatic fill valve:

Circulator and supply gauge:

Supply gauge:

Boiler display:


If anyone has any suggestions about how to get more of that hot water into the secondary loop and out to the radiators, I would appreciate it! Different circulation pump? Different boiler settings?

mattmia2

what is the return temp of the boiler?
what is the firing rate of the boiler? i believe that is in the menu (or the fan speed percentage)

what is the order of the supply and return tee vs the flow in the system loop?

you may need bigger piping or that may be all the output that boiler has. if it is firing 100% then all the heat is getting in to the system and it is just the mass of the system isn't getting heated above 90 degrees before the t-stat is satisfied.

gchrisman

@mattmia2 The boiler is modulating between level 1 and 3 of 5, so this is not the maximum output - it is just that the primary loop reaches the set max temp and that hot water doesn't seem to make it to the secondary loop. The return temp is about 90 degrees, but that is being measured about 4 feet from the boiler. Let me see if I can find a return temp in the boiler readouts to confirm what I think is happening.

I'm not sure I understand what you are asking about the order of the supply and return T - can you please clarify?

@MikeAmann The returns from each side of the house get reduced from the original 2" and 2 1/2" steel piping to 1" PEX, then these two 1" PEX pipes come together into a copper 1 1/4" T, and it is 1 1/4" copper from there through the dirtmag back to the boiler. (This is an older photo of that T, so the pipe support and the gauge readings aren't accurate anymore)

gchrisman

Actual boiler return temp from the internal diagnostics is 95 degrees. It seems a little low to support my primary re-circulation theory, so I'm not sure what is happening.

gchrisman

Maybe all the 1" PEX is just too small? Too restrictive? However, if I feel the copper pipes, they are only really hot for a few inches after the closely-spaced T towards the supply side, then they cool down before the air separator.

Is there possibly cold water mixing in from the automatic filler valve? Should I try turning that off? I have eliminated all the leaks in the system.

mattmia2

The flow through the boiler is restricted somehow. Even at 5 gpm at a 90 degree rise it should be transferring over 200,000 btu so if it were getting reasonable flow with 90 in and 180 out it should be firing at 100%(assuming it is set for a 180 setpoint).

Are you sure the 3 way valve is fully in the right position and all the air is out of the boiler?

Edit: 1 in pipe is good for around 10 gpm so it isnt the pipe size.

You will want a lower set point once you figure the flow issue out, it is likely you will never want to get the system that hot, it will overshoot if you do. It also reduces or eliminates the amount the boiler condenses reducing efficiency. You will ultimately want to install the outdoor sensor and set up outdoor reset to take advantage of the efficiency and comfort of the modcon. But that is after we figure out the flow.

gchrisman

Thanks for reassuring me that my pipe sizes are OK. I confirmed the 3-way valve position - it is fully in the CH mode, and the controller is unplugged, so it can't be changed back.

Feeling the pipes, they are very hot right up to the top of the closely-spaced T on the supply side. Then they get abruptly cooler. That is also where I found a pinhole leak in my soldering when I was testing the system at pressure, and since it was so close to the boiler resoldering it didn't seem like a good move, so I glued and taped over the leak - which has held. However, it is seeming like too much of a coincidence that it is right there that the heat is being blocked. Where the full boiler heat ends must be where the restriction is - right?

Is there an easier way to replace this copper T, or will I have to do what I think I have to do - cut it all out far enough back that I have room to cut and rejoin the pipes after redoing this section? This would also be the time to reconsider primary/secondary piping, but if that isn't the issue it seems to make sense to use that with the mod con (from everything I've read).

I'll definitely set the temp lower once the flow is worked out, because it isn't doing a terrible job of heating the house even with 100 degree radiators. I also spent some time today insulating the attic - 1/3 done now!

mattmia2

gchrisman said:

Feeling the pipes, they are very hot right up to the top of the closely-spaced T on the supply side. Then they get abruptly cooler. That is also where I found a pinhole leak in my soldering when I was testing the system at pressure, and since it was so close to the boiler resoldering it didn't seem like a good move, so I glued and taped over the leak - which has held. However, it is seeming like too much of a coincidence that it is right there that the heat is being blocked. Where the full boiler heat ends must be where the restriction is - right?

Not necessarily and it is not likely that a piece of copper pipe or ordinary fitting is blocked.

We need to explain how primary secondary works. The purpose is to hydraulically separate the action of the pumps in each loop.

The loop with the radiators in it has its own flow.

The boiler loop pumps in to and out of that loop through the tees simultaneously as the flow from the radiators goes by. So what is happening is the boiler pump is putting a little bit of water in to that cooler stream that is flowing by from the radiators and the 2 streams mix together and make a cooler temp past the boiler supply tee in the radiator loop.

If there were more flow through the piping in the boiler then the radiator loop would be hotter past the boiler supply tee.

We know how much heat the boiler is putting in to the water from the firing rate of the boiler.

We know the temp rise is 90 degrees from the supply and return temp sensors in the boiler.

I don't think you gave us the model of the boiler so I don't know the output of the boiler but let's so it is a 100,000 btu/hr output boiler and it is firing at 50% so it is putting 50,000 btu/hr of heat in to the water.

The formula for heat transfer through water is:

btu/hr = 500 * gallons per minute * Fahrenheit degrees of temperature rise

so

50,000 = 500 * gallons per minute * 90 Fahrenheit degrees

solving for GPM

50,000 / (500 *90 Fahrenheit degrees) = 1.1 GPM

You would have to plug in the actual firing rate to figure out your flow, but it is clearly restricted somehow. You might contact HTP to find out where to look, but if there is a strainer in there it is very likely plugged from debris from the old system or pipe dope and similar materials. It could also be air bound.

mattmia2

Digging deeply in the manual, it says there is a CH filter. Make sure that is clean

gchrisman

I do hope I don't have to cut apart my piping, as crude as it is. It does seem unlikely that an 1 1/4" T could be blocked that severely.

I've bled the system as thoroughly as I can, so I don't think there is any air in there. I'll investigate the dirt mag strainer and the CH filter tomorrow and see if I can drain anything out of either one. The boiler is a HTP EFTU-110WBN, and it is burning at roughly half power, so your calculations look pretty close.

Still trying to understand about the flow - your calculations are for the secondary loop if I understand correctly. So the low flow just means that the blockage is somewhere in the secondary loop, and that even with both pumps going, we're only getting 1.1gpm or so through the radiators, which is why they aren't able to pick up enough hot water from the boiler primary loop. Correct?

@MikeAmann - I read that whole gravity conversion post as well! I've replaced all the radiator valves, and didn't see any of those restrictor washers.

mattmia2

gchrisman said:

Still trying to understand about the flow - your calculations are for the secondary loop if I understand correctly. So the low flow just means that the blockage is somewhere in the secondary loop, and that even with both pumps going, we're only getting 1.1gpm or so through the radiators, which is why they aren't able to pick up enough hot water from the boiler primary loop. Correct?

No. My calculation is for the flow through the boiler. The boiler is restricted somewhere and my bet is on the CH filter.

You are reading 90 return and 180 supply in the boiler menus, correct?

gchrisman

I got 90 return, and the supply is set to 170, but it seems to go over by 10 degrees before the modulation kicks in. Those are internal numbers from the boiler diagnostic menu.

I did also just turn the system off briefly to drain some water from the Dirt Mag, and got some fine black powder in the first few cups, then it ran clear. I removed around a gallon and it ran clear for almost all of it. You may be right about that CH filter - I'll have to find the maintenance procedure in the manual.

mattmia2

Looks like it is on page 88 or 90 depending on which version of the boiler you have. since you have isolation valves at the boiler it should be easy.

gchrisman

In the manual which came with my boiler, page 88 is a notes page and page 90 is a blank page at the end. I did find instructions for replacing the DHW filter on page 82, along with a tantalizing mention of the CH filter ("Ensure the boiler and CH and DHW heating systems have been drained following the instructions in this manual before attempting to remove the CH or DHW water filters."). However, there are no instructions for the CH filter, and I don't see it in their diagram in the front of the manual either. I'm going to email HTP with that question...

gchrisman

One things I did notice in the boiler diagram at the front of my manual is that there is a bypass that goes between the return and the supply, below the 3-way switch. There is some sort of valve on it in the diagram. Perhaps that valve is set incorrectly?

gchrisman

I think I have it working! Even though the diagnostic menu reported that the 3-way valve was set to CH, I ran back through the manual settings again, and this time I cycled the valve a few times before leaving it in the CH position and then unplugging the connector. When I restarted the boiler, the air separator hissed a little, and the temperature is now going up - much more slowly than it was before. I think it is now actually heating the water in the secondary loop! The boiler is running on 100% to try and reach the target temp I set of 150 degrees, and we'll see if it works. So, it seems that the 3-way valve was initially sticky, and didn't seat into position until it had cycled a few times - or something like that.

mattmia2

This is the manual where I was looking at the dh filter on page 99. i might be looking at a different model:
https://htproducts.com/literature/lp-700.pdf

You should be seeing a bigger delta t between the tridicators on the radiator loop now too.

gchrisman

Yeah, that's the ELU, I have an EFTU. In any case, it is heating up now. It is up to 150 degrees at the boiler and on the supply loop tridicator, and I have my circulator on low. The return loop temperature is showing 128 - probably not ideal for efficiency. In any case, the house is now at 68 degrees!

gchrisman

I've been fiddling with the supply water temp manually to get a feel for what the house requires. I figure once I work out roughly what works, I'll set the ODR curve (definitely needs to be flatter than the default 1.3) and let it run automatically from that point. Right now it is doing pretty well with a supply temp of 120 degrees, with the return at 105 or so! While I was worried about going with a BTU output significantly less than the boiler it replaced, it seems like the sizing is correct for the EDR and the heat loss. It'll be even better once I get the insulation finished in the attic...

JakeCK

A steady supply temp of 120 isn't bad and that 15 degree drop is decent too. Should be condensing at those temperatures.

gchrisman

Yup, there is condensate dripping steadily down the drain. I'm really curious to see how efficient this ends up being.