A few years back, my Dad and I replaced the boiler at my home. What I would like to do now is install a time delay relay to keep the circulation pump running for a few minutes or so after the boiler has shut off. I think that since the water is already been heated, and then the pump shuts off when the flame shuts off, the heat could be used better.
My real question, I know these relays exist, but I am not sure how to determine what I need. I have all the paperwork for the boiler, and the panel that is connected to the unit. Can anyone help me to determine the type of relay I need so I can do what I want to do? What info do I need from the unit?

Thanks!!!

 

Make/model of boiler.

What controls are on it? i.e. make/model of the aquastat.

Tell us if you have multiple zones.

Read through this thread:

http://www.doityourself.com/forum/bo...-run-time.html

 

Hi, Thanks for the other information. My system seems fairly simple compared to others I have spoken to with boiler heating systems.
It is a single zone system.
The boiler is a peerless boiler - MI/MIH the manual states
The control module on the side is by Honeywell - L8148A,E Aquastat
I have taken some photos, hopefully they are each worth 1000 words.

I have no limit switches to set from what I know, my old boiler did, however it was also about 80 yrs old and about as big as a small size car. From what I can tell the temp is set to 170*F for the hot water temp. When the thermostat clicks on, flame on, pump goes, chimney valve opens and radiators get warm. Everything is working great, other then the fact that the house is old, and this heat doesn't seem to keep it warm. I'd like to try keeping the pump circulation for a few minutes after the water has been heated.

 

I don't think a few minutes will buy you anything really...

My experience with my temperature controlled setup is that it takes a good 15-20 minutes to drop the temp from about 140 down to the 90° shutoff setting that I use.

With a few extra minutes of run time on the circ you wouldn't have to be concerned with the temp in the home over-shooting much... if you've read the other thread, you know that is a concern. My concern solved itself by the thermostat adjusting it's 'anticipator' and cutting off the boiler earlier than it did before I added the control.

Reading the other thread, you've also learned that with a single zone system you don't have the problem of figuring out how to keep a zone valve open... so that's a plus for you.

I'll poke around in the next few days and see if I can come up with a suitable time delay relay for you... but honestly, I would look into the temperature control idea first.

 

Riello makes an adjustable timer relay to allow their burner to post purge.It has two power wires one to operate the control and one to keep fan running which is time adjustable.

 

So the pipe strap sensor will intercept the standard signal and control the pipe by the temps I set on it? How do the pump turn on then? Does the signal from the burner get re-routed? In a sense it seem like rather than a time delay relay it is a thermal controlled relay.

I’m not up on all the terms, what is post purge of the burner?

 

The term post purge refers to the burner flame being shut down while the burner motor and fan continue to run to remove spent gases from heat exchanger.

 

Gotcha, thanks for that. Mine does not have a blower motor or fan though, just the water pump.

 

Hello Saves,
It also refers to a "post purge" of the latent heat in a boiler by running the circulator pumps to a heat zone in order to purge the heat out of the boiler.

Peter

 

Grainger has an assortment of time delay relays. Maybe one of these would help? Good luck, Steve

Search time delay relay - Grainger Industrial Supply

 

Hello,
Yes is is like a thermally controlled switch. When the temperature is above a certain limit, power is sent to the circulator.
When it drops below the set temperature, the switch opens and power is cut off to the circulator.
It would be wired parallel to the existing circulator control.
It does not interrupt powewr to the circulator. It is a separate power source.
If you decude to go this route, then i'm sure NJT will guide you thru the wiring details.

Peterr

 

The term could apply to a lot off different situations , did not mean to lead anyone astray.

 

Let's try to stay focused please!

Inside your aquastat control there is a relay switch that turn the pump on and off when the thermostat calls for heat.

By installing a strap-on auxiliary aquastat onto the hot supply pipe out of the boiler, one can use this control to allow the circulator to continue to run after the thermostat stops calling for heat.

One would need to wire the contacts in the strap-on that 'MAKE ON TEMP RISE' in PARALLEL with the relay contacts in the operating aquastat.

Once the pipe heats up, the contacts in the strap-on close in parallel with the relay in the operating aquastat and will STAY CLOSED until the pipe cools again.

There are only two wires that need to be run from the strap-on to the 8148 a'stat. These will carry 120VAC so they need to be rated for that purpose.

Looking at those time delay relays, they are PRICEY! There will be 'significant' wiring changes to be made. For around the same average price you can pick up an L6006 Honeywell a'stat and it will be easier to install.

This 4008B model has a 'remote bulb' with a long capillary. You can mount the bulb on the pipe with zip ties, insulate the bulb on the pipe and a foot on either side, mount the a'stat on the wall and run the wires to the 8148.

Patriot Supply -

 

The best situation is a pump that shuts off on temperature but starts as soon as the thermostat calls instead of waiting for the boiler to build temp. As an industry we realize that moving water as soon as the thermostat calls and moving btu's immediately is best. Waiting for the boiler to heat to a setpoint then bring on the pump dependent on water volume, boiler sizing etc can cause the pump to short cycle at the beginning of the heat demand. It can also cause un-necessary strain on the iron to heat up and cool down a few times at the beginning of the cycle. Unfortunately this idea would be much harder to do.
Maybe consider constant run pump and just start and stop the burner as needed. This is simple.

 

No, not at all! That's exactly how this idea operates.

The pump remains connected to C1 / C2 on the aquastat and starts as soon as the relay in the 8148 pulls in. The strap-on a'stat is OPEN circuit at the start of a heat call.

Remember that this strap-on is wired in parallel with the 8148 circ relay, from L1 to C1.

So, the pump starts as it should, and always has... but when the system heats up, and the strap-on MAKES across the 8148 circ relay, the pump will remain running after the heat call has ended and continue to run until the strap-on senses that the system has cooled to the setpoint-diff of the strap-on.

The main thing to keep in mind here is that this will NOT WORK for a system that is zoned with zone valves unless a method is devised which will hold at least one zone valve open until the system cools again. For systems with no zoning (1 zone), it's a cheap and easy way to get that heat out of the boiler and into the home. And also remember that to keep the home from over-shooting the thermostat setpoint, the t'stat must be able to adjust it's anticipator to prevent the over-shoot!

 

Post #13
Did I mis-understand this statement or am I confused now?
Can you supply me with a diagram? Maybe my hard head would understand better. Either post here or e-mail.
Do you actually have 2 hot lines to the pump from the same power source? I see you reference L1 and C1. If so this is genius!

 

rbeck, you flatter me!

I read your mind, here is a diagram. This is for a SINGLE CIRCUIT, NOT ZONED SYSTEM:

 

For standard boilers this is the best of both worlds. Cold start, move heat immediately and post purge heat produced after the demand ends to reduce standby losses. I bow to the wiring God!
As a reminder to viewers this is single zone systems only.

 

Can it be done with zone valves? I would consider something like this on my own system if it makes sense.

Mike NJ

 

Hi Mike,
I almost have a design for a set up with zone valves using 2 relays.
I need to finish it and then run it by that NJT wiring god fella.
I'll try and get to it in the next few days.

Peterr

 

Oh man, I'm never gonna live this one down!

I'm not gonna give away the store until I see Peterr's idea... but I've got one too...

Here's the down side... my design will only hold open one zone... and the choice of zone is fixed, hardwired to that particular zone valve. It isn't the 'last zone called', you have to choose one when you wire it.

It would seem that the best choice would be the largest and/or coolest zone. Maybe setting the chosen zones' thermostat a degree or two lower would ease any overshoot problems that might arise.

My idea involves a double pole relay, the relay would be triggered by the strap-on aquastat, the first pole would shunt the circ relay in the operating a'stat, and the second pole would be wired ACROSS the thermostat wires for that zone.

1. Boiler fires on heat call from any zone.

2. Boiler heats up as it delivers flow to the calling zone.

3. Strap-on a'stat reaches setpoint and closes, triggering DPST relay.

4. Circ relay in operating a'stat is shunted by one pole of relay.

5. THERMOSTAT for chosen purge zone is shunted by second pole of relay.

6. Purge zone valve opens, and gets heat until heat call from calling zone ends, AND the boiler cools to setpoint minus diff of strap-on a'stat.

The DPST relay could be an SR501, R8845, or equiv, OR could be a discretely wired R8222 relay... or one you have in your junque boxe.

Now, if Peterr can come up with a way to keep the LAST ZONE CALLING open to receive the purge heat, I will step down from my lofty office chair.

 

Same as my plan.

Agree this. Qualify by adding the zone with the largest load in btu's per hour/day.

I'm still working on this aspect of my plan.
What's missing is if a different zone is firing now, it would trigger the fixed purge zone.
I have an idea how to get around this.



I believe this will result in an endless loop.
shunting the T'stat will call the boiler and keep the a'stat closed...
never ending.
My plan opens the end switch of the chosen zone valve. As long as the T'stat for the chosen zone is not calling for heat.
Opening the end switch keeps the boiler from firing. Parallel the power to the circulator from elsewhere on my plan. My plan also makes sure the z valve is fully open before the circulator is started.

I think i could do it NJT, but it would take a bucket load of relays.
Probably not worth the effort or expense.
But the real question is..Should it be the last zone that called or the zone that callled the longest time ago??


More later,
Peter

 

I actually just realized this flaw myself, thanks for catching it!

 

Good thought... I think the answer would depend on how large that zone is... if it happened to be a small zone there would likely be problems with overshoot.

With a bucketload of relays, you could open them ALL to purge the heat!

A much more complicated approach might use electronics and a micro-P monitoring room temp sensors and intelligently opening (and closing!) valves based on zone temp. Strategy might be room farthest from it's setpoint first... and if that room gets satisfied, open the next farthest... etc... for this approach I might choose triacs over relays.

Going that far though is definite overkill... no benefit for the time or money expended in developing the idea.

 

How about if one were to use a THREE pole relay... the first two poles as in my previous post, with the third pole wired to OPEN the ENDSWITCH wiring from the selected valve?

Nope... this won't work either because if the selected purge zone also happens to be the zone calling for heat, then when the endswitch is opened, the heat call will end. This will act as a 'reset' on the boiler and it won't get any hotter than the temp on the strap-on aquastat.

 

Hello Friends,
I haven't forgot about this thread.
Having a bit of a rough spot taking care of my 94 year old mom.
Makes it hard to focus.
I'll get back to it as soon as possible.

Peter

 

Do what ya gotta do Peter, we understand...