reversing circulater pumps

Gary Usa

please would you be so kind to help me with the following,on a gas boiler when the thermostat is satisfied do you install a circulator that will then in turn reverse to prevent condensation being produced within the boiler,is it better for a timed or temperature pump over run of the pump when the boiler turns off to get the residual heat out of the boiler,please would you also tell me how best to adjust the anticipater in the boiler for the thermostat,i am trying to learn different systems and as i progress through new situations try to understand all the best aspects and how to best control and install them.
many thanks as always being able to come here and find the answers i am seeking.

hope you are all keeping well and life is treating you good.

all the best

gary usa

Unknown

Hot Water Boilers

On conventional Hot Water boilers when the thermostat calls the circulator comes on and runs until the call for heat ends. There is usually no need to reverse the flow on standard Forced Hot Water boilers. It is okay to keep the water at final temperature in the boiler waiting for the next call for heat.

Setting of the anticpator on systems including Forced Hot Water systems is to find the amperage draw of the primary control.

Primary control could be one of the following depending on the system.

1. Relay

2. Zone Valve

3. Vent Damper

4. Gas Valve

5. Electronic Ignition Module

6. Integrated Boiler Control

The easiest way to identify the primary control is that it is the control the thermostat controls directly.

Universal Enterprises sells a meter that you can put across the thermostat contacts and get an accurate current draw and set the anticpator to that draw. E-mail me and I will give you info to order it. You can also do that with an Amprobe current tester with a multiplier.

Some new mid efficiency systems and high efficiency systems require a factor to be multiplied times the actual draw in order to control the number of cycles per hour.

Unknown

Another question about gas boilers

Hey Gary , how are you doing ? Still busy , I hope .

My question is - we always protect an oil boiler from condensation problems by installing a bypass to make sure the return water doesnt come back too cool and condense or shock the boiler , but how come there is not a problem with cold-starting a gas boiler ?

Bill Clinton

wondering the same

Having honestly earned loads of trouble from condensation in boilers (not just that Buderus biggie) I have begun to wonder myself. Used to be I could throw in a TD Laars copper boiler and just pump away with no thought of return temperatures. Never a problem. (Almost never, one did soot up after 11 years). So when the instructions started blatting about a bypass, I shined it on thinking that was just a CYA addition and it wouldn't apply in a moderate climate like N. California. After all, I'd been doing this for more than a decade and I knew better than them marshmallows writin' the instructions.

Oh what a difference a couple of percentage points makes! TD Laars along with just about everybody else got on the efficiency bandwagon and boosted combustion efficiency as far as they dared, it seems. Now, I can't get away with those shenanigans anymore. Hell, even a bypass isn't enough: If the floor is suckin up all the output a bypass ain't gonna stop it. You've got to have a means of modulating the output. I now use a strategically placed thermostatic valve which solves the problem and makes the sooty blues (blacks?)go away.

Now how about those cold starts? That improved efficiency should have an effect there too. Grist for the worry machine.

Bill

hr

Good questions Gary



A radiant floor heat system with a ramdomly used zone, say a radiant garage slab, can really hold a boiler in a condensing mode for a dangerously long time.

Proper piping and controls can handle this, learn some options.

Also there are some controls available, Taco for one, that have post purge features. This would allow the pump to purge the residual heat from the boiler into a zone or indirect tank.

Purging into an indirect tank would be another reason to include a good thermostatic valve on the DHW output as you may over run a safe temperature in the tank when you post purge.

Keep in mind this will cause the boiler to start from a cooler temperature on the next "call" possibly so the boiler return protection becomes an essential part of the system.

Damage to boilers from running at too low of temperatures sneek up on you over a period of time, generally. Unless that system is checked on a regular basis you will not be aware of the problem. Another good reason to sell those clean and check contracts

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Boilerpro

Cold starts

> Having honestly earned loads of trouble from

> condensation in boilers (not just that Buderus

> biggie) I have begun to wonder myself. Used to

> be I could throw in a TD Laars copper boiler and

> just pump away with no thought of return

> temperatures. Never a problem. (Almost never, one

> did soot up after 11 years). So when the

> instructions started blatting about a bypass, I

> shined it on thinking that was just a CYA

> addition and it wouldn't apply in a moderate

> climate like N. California. After all, I'd been

> doing this for more than a decade and I knew

> better than them marshmallows writin' the

> instructions.

>

> Oh what a difference a couple of

> percentage points makes! TD Laars along with

> just about everybody else got on the efficiency

> bandwagon and boosted combustion efficiency as

> far as they dared, it seems. Now, I can't get

> away with those shenanigans anymore. Hell, even

> a bypass isn't enough: If the floor is suckin up

> all the output a bypass ain't gonna stop it.

> You've got to have a means of modulating the

> output. I now use a strategically placed

> thermostatic valve which solves the problem and

> makes the sooty blues (blacks?)go away.

>

> Now

> how about those cold starts? That improved

> efficiency should have an effect there too.

> Grist for the worry machine.

>

> Bill

Boilerpro

Cold starts

I think you have hit a nail right on the head that the cast iron boiler manufacturers don't want anyone to think about. When a typical new cast iron vertical section boiler is in a single zone copper fin tube baseboard system, and has a stack damper, and maybe a pilot light, it ussally sits there at about 120F. When there is a call for heat and the pump comes on, that tyically less than 5 gallons of 120F water in the boiler is replaced with 70F water from the baseboard in about 30 seconds. Can you say Thermal shock. And, of course if the boiler is still hot from the last heating cycle and at about 170F (since the damper is helping lock in the heat), You get a 100F delta tee acrooss the boiler at full flow. I think this is why bypass piping is starting to crop up in many installation manuals even for the simplest of systems. Another strike against low water content boilers, especially of the cast iron design in modern single zone systems.

Boilerpro

Unknown

Gas Boilers

The truth is when you get away from the old conventional hot water systems and go to higher efficiencies you have to deal with the same problem on gas. It is required or at least recommended in many boiler books to have a bypass on gas boilers. If you get a chance start looking at the burner section on the return side of gas boilers if it seems to be more rusty or have more scale or is a little more corroded than the other sections then your return water temperatue is too low and is causing this to happen. In years past before we cared about efficiency we oversized boilers, you could put your hand on the supply and then a few minutes later on the return and they would be about the same temperature not very efficient but easier on the boiler. Back then everyone in the gas business was afraid that when we replaced oil or coal that we could not match them for BTU so we oversized. Today with all the sophisticated systems we have to be concerned about return water temeprature. It is my opinion that on all modern FHW installations a provision to protect the boiler from any kind of shock or rapid temperature change is necessary. That is unless the boiler manufacturer has made provision through design to compensate. I always like to see a temperature gauge on the return as close to the boiler as possible. That way we can nkow what is happening with return water.

Gary Usa

thanks

for the kind input on circulating pumps,another thought i had was instead of using a check valve after the heating pumps to use a 2 port motorized valve from honeywell for example,so that when the zone was satisfied the end switch could then turn on a shunt pump on the return to keep the water circulating until the boiler slowley cooled down,then when a thermostat called the zones would not open until the boiler was up to 120 degree temperature then for the zones to open,just a thought,

I know back in the uk low water content boilers we always used a over run on the boiler to prevent kettling and to remove residual heat from the boiler.

hope that you are all well

thanks again

all the best

gary usa