Can I delay my zone pump to give the boiler a head start?

Quercus

This may not be a huge issue during the heating system but I noticed on initial start from cold that the system pump had all the cold water from the house being added into it's flow from the zone pump. I repiped for boiler protection but noticed it took forever for even the supply temp to hit 140*.

Is there a way to fire the boiler and primary pump for either a period of time or to a temp and then turn on the zone pump to draw from the already hot water? I have a Taco SR503 connected to all the pumps at the moment.

Thanks,
Steve

STEVEusaPA

What kind of boiler. You really don't want a lot of cold water returning to the boiler. Can we see a pic of the boiler piping for the bypass protection?

Quercus

It's a Weil Mclain CG4. I understand the problem with cold water but there has always been a lot of cold in the system. It's converted gravity so big pipes. Having the primary and secondary start together seems to still tie the boiler closely to the water mass.

hot_rod

Wouldn't you be adding energy at exactly the same rate in both cases? Preheating the boiler first, slows the amount going to the cold distribution.

Unless you add more hp, the energy exchange is the same.

Quercus

I am not concerned with the heat call taking too long. Starting the two circs together showed a long period of cold water in the primary loop.

So yes, the energy exchange is the same but the rate is different. I am willing to have a longer heat cycle in exchange for the warmer return.

I may get a nasty surprise in my gas bill, like when I tried deep setbacks twice a day with a vision pro t-stat, but would like to pursue this if possible.

I am thinking if the primary loop were 150 or 160, then the secondary began circulating cold back into that then I could minimize the time the boiler operates with cold return.

Was primary / secondary a bad choice for a CI boiler? I am surprised that P/S is considered a means of boiler protection and provides for hydraulic separation but there is no obvious of providing time separation.

By the way, Bob, you have been following my project and commenting and I appreciate that. Thanks.

FranklinD

I considered P/S for my cast iron boiler and decided (for now) to go with a simple boiler bypass. I adjusted it so that the boiler is pretty much always 30* ahead of the system temp. Basically just slows the flow down through the boiler, giving it a wider delta T...so maybe half the water that used to flow directly through the boiler now bypasses it and heads back out to the system. I too have a converted gravity system.

My boiler is rated to accept 110* return water and has a minimum 130* supply rating (Burnham). But without the bypass it spent a LOT of time sitting around the 100* mark (lots of big radiators in this house, and 100* heats it pretty well as long as we're above 30*f outside). Now the system will stay around 100-110 and the boiler temp is 130-140. Not perfect but good enough for this winter. I too just recently got the piping done. It's not perfect because my return temp, at 90-95, is still low...but given the larger delta T across the boiler, and slower flow rate, the average temp across the boiler is about 120 or so. Keeping in mind that this is during the shoulder season, I'm okay with it. We will see what the readings are during a -25* cold snap.

It's interesting to me because I have now piped it exactly as shown in the boiler's install guide (they show it with a boiler bypass for high water content systems, or systems with cast iron radiation). I guess if it's good enough for them...

Quercus

Hatterasguy, here is a pic from the end. There is a loop of white wire around the elbow where the return goes down.

Quercus

yes to a boiler pump. it's a bumble bee at 140 setpoint operation. it's a tight area for pics.

Gordy

What about a 4 way mixer? P/s is no guarantees for boiler protection.

Quercus

I made the assumption that using setpoint on the return pump would cause the flow to slow down if the temp was below the target. That behavior would be the opposite on a zone (duh) where you are below target - then you would increase flow to reach your goal.

Taco's documentation doesn't make this distinction and should be clarified. Perhaps I could get someone from Taco to verify this.

Your explanation makes perfect sense and is the reason I didn't commit to replacing all the pumps up front. Now I know more about the bee I can see it is not properly applied.

Hatterasguy said:

You could actually vary this temperature throughout the season and obtain a poor man's outdoor reset if you wish.

I cannot recommend any of this to a poor person. I have dropped serious coin on this system but I think I am near the finish line. I have had a lot of resistance from heating guys in the past about improvements like ODR or piping and I think they are reluctant to quote such an expensive change without a real boiler plant. It would also send someone out of the ballpark in a competitive bid unless a lot of educating was done for the customer.

For sure, when I check out peoples new boilers (I always ask to see) the plumbing is no frills, no protection. This setup would have to add a hefty percent to a basic CI boiler install if it wasn't already there. I imagine it would be a challenge to explain the value of the fancy pipes to a typical homeowner.

Steve

Quercus

So back in the day, before sensor pumps, what was done? Just a manual system bypass if anything?

FranklinD

Pretty much seems like it. They show a few manual bypass options in the Weil McLain install manuals.

And yes, Hatt, it's not perfect, but it does work. As mine is piped now, it is 'as per the I&O manual' exactly. And it works. As good as a modcon with ODR? Nope. As good as a Taco I-valve? Doubtful. But the house is comfortable, there are very few parts to break down, the boiler isn't condensing, and (the most important factor in my situation, and a factor mentioned by the OP) it was inexpensive....the cost of 2 tee's, 2 ells, a ball valve, and 3' of pipe.

Quercus

FranklinD said:

Pretty much seems like it. They show a few manual bypass options in the Weil McLain install manuals.




it was inexpensive....the cost of 2 tee's, 2 ells, a ball valve, and 3' of pipe.

The manual for my boiler has changed quite a bit in the 23 years I have owned it. I can't fault the installers because it was installed to the manual at the time. Current manual has more sophisticated schemes listed to account for varying system types.

I never said this was inexpensive. 2 pumps going on 3. Zone controller, 20' of 1-1/4, gauges, flanges, uni-strut, shutoffs, bunch of fittings to turn the loops around a tight space ran up a tab. I am mostly pleased with the results and I think I have good advice to get done. The flanges will be welcome if I take Hatteras' advice. As I said before, I think this would be a tough sell to get someone to pay for all the materials and wage and overhead for a heating pro. It was a lot more work and money than I expected but comfort wise it seems to be working (on one zone) and reasonable value.

Quercus

Gordy said:

What about a 4 way mixer? P/s is no guarantees for boiler protection.

Hi Gordy,

I have 2 zones with different emitter types. Would the 4 way vs 3 way require the addition of a controller? The simplicity of the 3 way appeals to me and it does seem like a very positive protection method.

What would be the benefits of going with the 4 way over the 3 way? If there is a boiler loop and an emitter loop with the 4 way, will controlling one of the loops tightly (boiler protection OR circuit temp) mean the other gets what it gets?

I've learned enough to get into trouble. Now I need to learn enough to get out of it. Many thanks to all who have responded.

Steve

Gordy

In rereading the thread I'm with HotRod. The key is not having a hot start boiler. If everything is cold during the heat call boiler shock to the HX is not an issue.

Now boiler condensing is an issue. But so long as the boiler reaches above 130 at the end of the heat call so condensation on the HX burns off it should be okay.

It's when you have a hot boiler, and a cold zone calls which creates an issue of thermal shock. Is this the case?

Quercus

So far the boiler is heating up by the end of the call. I have a 45* delta T on the main house so it is slow to satisfy the thermostat. The longer run time allows the boiler to hit the high limit which is currently at 180*. The boiler will go off for a minute or two while the pumps consume the hot water.

Because of the iron radiators, I would expect the return to be somewhat warm on return in the colder weather. The old layout had direct pipe from the zone to the boiler so I have improved it with the two pump rates on two loops. Since boiler protection was one of my goals I am trying to see what is left for me to do.

From your comment, it sounds like I am OK as long as I finish the cycle hot. The boiler is 23 years old so I am thinking the previous piping wasn't a huge problem.

I like the comfort level with the new setup - it's very even without the hot to cold sensation I used to get. It will be interesting to see how things go through the season with comfort levels and fuel consumption. Next summer I plan to swap some in-wall cast iron for panel radiators and add a couple of panels in an electrically heated room.

How much temp difference will cause a thermal shock? I think flow rate will matter for that question. I have a VT2218 on order to be the system pump and I believe that starts slow and speeds up. The Bee starts at high speed and collects its info to determine its operating point. That behavior would minimize the risk of a shock.

Steve

Gordy

I think your fine as is. What is really a thermal shock scenario is boiler is 180 and a 55-60 degree high mass zone calls and dumps all that cool water at the boiler.

Jason_13

I do not understand the cost concern. It does not cost much more to pipe p/s than a manifold system. I would not have piped the p/s as you did unless you needed different temperature water temperature. By building a 1-1/4" boiler loop is more expensive but just tying the supply and return manifold together with a set of closely spaced tees. Cost next to nothing more than two tees and 4" of pipe. Tie the boiler into the tees. Have a valve on the supply and return of the boiler and just reduce the flow through the boiler by reducing the flow to get your delta-T. No need for a bypass pipe. Your piping called a boiler primary loop will cool the water from zone one to zone two if both zones are running.
Thermal stress is due to rapid temperature changes of the cast iron sections. More damage is done to cast iron boilers by over sized boilers and too many zones which create micro-zones that return water temperature. You need gradual water temperature changes with cast iron boilers.

hot_rod

A few concerns with non-con boilers.

Thermal shock, which is more associated with cold radiant slabs coming on with a hot boiler. Consider a garage slab for example, lots of mass there to keep the boiler running cold for extended periods. Usually heat emitters in the room at 65 degrees do not shock a high mass, large water content boiler.

The other part is return temperature protection. Anytime the boiler fires you want to warm the boiler and flue venting above the fuels dew point within 10 minutes. Depending on the fuel type, humidity, temperature dew point somewhere around 130 is a rule of thumb.
ONLY a smart valve or VS pump can adequately protect boiler returns. Bypass piping or a bypass pump might, but it is not assured without a temperature sensor and a device that responds.

Also you want to avoid short on/ off cycles that are often caused by micro-zones and low load, mild weather conditions.

Modulating the burner, or adding a buffer solves all the above if properly applied and adjusted, and allows simple ODR control. boiler.

Gordy

Jason said:

Thermal stress is due to rapid temperature changes of the cast iron sections. More damage is done to cast iron boilers by over sized boilers and too many zones which create micro-zones that return water temperature. You need gradual water temperature changes with cast iron boilers.

Actually I believe an oversized boiler is more likely to take better to a thermal shock scenario than a closely matched one. Mass would be its friend. Both water content, and cast iron. But then we all know it's taboo to do such a thing.

Constant circulation can actually allow a boiler to take higher deltas across the HX also. Speaking cast iron. It eliminates a boiler that may shut down at high limit, and have a cold zone call, and dump into that already hot boiler HX.

Quercus

hot rod said:

ONLY a smart valve or VS pump can adequately protect boiler returns. Bypass piping or a bypass pump might, but it is not assured without a temperature sensor and a device that responds.

Just to be clear, a 3-way thermostatic valve would qualify as an assured boiler protection method?

Mark Eatherton

Having had seen the application of every means of protection known to mankind, I can honestly say that THE best means of boiler protection, bar none, is the thermostatic non electric anti sweat mixing valve located on the return. It is a proportional valve and does a perfect job of controlling the return water temperatures back to the source, and the slowly bleeds excess energy into the distribution loop.

BTW, boiler protection is now a part of the UMC and USEHC codes.

I believe Caleffi makes one of these anti sweat valves.

Don't forget to incorporate a bypass around the valve for fill and purge requirements. Once filled and purged, close bypass valve , remove handle, and hide it under the jacket of the boiler. No one EVER looks there :-)

I also agree with the comments about the contractors not really watching out for their customers best interests as it pertains to the deployment of these devices. Their competition doesn't, why should they? It is a race to the bottom, and most of the good contractors who frequent this site know how to overcome it, but the consumer is also looking for the best price, and unlike the wary consumers that come here for advice, really don't know what they are looking at or for, and make decisions that really don't make sense.

Our job of education will never end.

ME

Mark Eatherton

Like this http://www.rev2.org/store/Termovar-Mixing-Valve-Wood-Boiler_151841941629.html

ME

Jason_13

Since we are talking residential here a simple bypass is enough. If this conversation was commercial I would totally agree. How many boilers have you seen or heard of fail from flue gas condensation with and without a simple bypass. Once adjusted the delta-T will always be the same due to no change in flow or input. The idea is just get the boiler above flue gas condensing within a reasonable amount of time.
We all have seen CI boilers with no bypass pipes and low water temp due to radiant or CI radiation jobs and these boilers lasted a long time.
Do all the products work, yes but many times overkill on residential products.
I no way always want the old style items or the cheap way out but sometimes simple makes more sense and unfortunately by adding more expensive bits and pieces although they may make a bit of a difference adds more maintenance to the job within the life of the boiler.
BTW that is why I usually suggest the Burnham water boilers if I do cast iron due to being able to return 110f right out of the box without boiler protection, although I usually suggest mod/con's.