Wiring the circulator pump to an everhot tankless water heater

paulp

Hi,

I recently connected an everhot tankless water heater to my Weil-McLain steam boiler to supply heat to my basement and a room in my home that previously had no heat via 2 hot water loops. Everything went very well as I followed the guide on this site, "How to run a hot-water zone off a steam boiler"

As I said, everything went very well and the rooms in question maintained a comfortable 70 degrees all winter. However, now that the weather is warming up, the circulator between the boiler and the tankless heater is running constantly because the tankless heater's thermostat is set to pull water from the boiler when the internal temperature drops below 160, however now that the boiler hasn't run for several hours, the water in the boiler is under 160 and thus the tankless heater's internal temperature can never be reached. During the winter this wasn't an issue because the boiler would run every hour or so, so the boiler water was always way above 160.

What I would like to do is have it so that the circulator pump between the boiler and the tankless heater only runs when the either of the two hot water zones call for heat.

I'm not very worried about the boiler being asked to fire when the hot water zone thermostats call for heat because when they do, the boiler is on anyway heating the rest of the house.

I am attaching an image of my switching relay - it is a Taco SR503-EXP. If anyone can give me some pointers as to how to make this happen, I would be very grateful.

Thanks,
Paul

BobC

Having the pump run only run during a heat call might be ok in the heating season but you'll have to go to the normal running scheme in the non heating months.

Remember: Happy wife happy life, I strongly suggest not testing the other side of that.

Bob

paulp

Lol - can't argue with that logic!
However, today was was a nice day by us, so the whole house was at 70-72 without the boiler having to come on at all. But the circulator between the boiler and the TWH has been running non stop. I can't imagine that being good for the pump. What would be the best way to handle this?

paulp

I think I may not have been clear in my original post - the everhot is not being used for domestic hot water - it's being used to heat a separate hot water zone, i.e baseboard radiators (see the link in the original post).

I have a separate 75 gallon hot water tank for domestic hot water.

Hatterasguy said:

Aside from the control problem, what is your current plan for the summer?

In the summer, the plan is to turn the boiler off :-) DHW is being supplied from my 75 gallon HW tank. I don't need to heat the main house (from the steam boiler) nor the addition/basement (from the Tankless WH). I may need to install A/C, though, but that's for another discussion :-)

Mark N

Paul,

Why not post a wiring diagram of how this is actually wired. Do you have an aquastat to turn off the boiler on high limit so you don't make steam when the steam zone is not calling for heat? When either hot water zone calls for heat the circulator for that zone and the circulator for the everhot should come on.

Mark N

Also go to Noel Mudough's site at:
sites.google.com/site/steamheating/home

there is a wiring diagram for a single zone under "Zone Heating with Condensate"

paulp

Mark N said:

Paul,
Why not post a wiring diagram of how this is actually wired.

Hi Mark,

I posted a photo of the actual relay in my first post, and I am attaching here an image of the wiring diagram from the relay's manual (the wiring diagram attached to this comment is not the actual wiring diagram of my installation - please see the photo in the original post to see how my system is actually wired.

Mark N said:

Also go to Noel Mudough's site at:
sites.google.com/site/steamheating/home

there is a wiring diagram for a single zone under "Zone Heating with Condensate"

Thanks Mark. I just took a look at that. I'll have to take a longer look for it to make sense to me :-)

Hatterasguy said:

Get a Taco SR-501.
http://www.supplyhouse.com/Taco-SR501-4-1-Zone-Switching-Relay

Thanks Hatterasguy - this seems like a good option unless (as you said) someone can think of a clever way to wire the 503 on its own.

wogpa67

He could just break the hot to the boiler circ through the 503 x-x terminals that he has. If the relay is rated for the current draw. Which I think it is.

paulp

wogpa67 said:

He could just break the hot to the boiler circ through the 503 x-x terminals that he has. If the relay is rated for the current draw. Which I think it is.

I'm sorry wogpa76 - could you elaborate? Thanks.

wogpa67

the x-x terminals on your existing 503 may be able to be used for the boiler side circulator.
Check the rating of the ice cube relay to see if that is possible. You most likely have a taco 007 which only draws .65 amp

wogpa67

I am not sure if you are using an aquastat to maintain temp in the buffer.
So this may not be ideal. If you are using an aquastat. You would overheat the steam zone with this setup.

wogpa67

Ok so he is maintaining temp in the buffer tank. Didn't see that.
Let me ponder.

wogpa67

Then why not just add a Rib?

wogpa67

Not questioning your suggestion Hat but a Rib would be quick and easy.
And why would you want to maintain temp in a buffer tank? I never have used that strategy and it has worked out fine.
Just my opinion. I very well could be wrong.
Always willing to learn more.

paulp

Sorry - what's a rib?

Tim Potter

RIB = Relay in Box
http://www.functionaldevices.com/building-automation/

michalmarsh

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New England SteamWorks

What you want: When either (or both) of your hot water heating zones call for heat the boiler fires, the appropriate zone circulator comes on, as well as the EverHot circulator. When the call for heat ends, all circulators and boiler shut off (unless steam TT is calling)

To accomplish:

1. Run a thermostat wire from XX Isolated End Switch to TT on the boiler.
2. Remove the TT wire from The EverHot aquastat. Not needed.
3. Remove the hot wire for the EverHot circulator, splice in a second wire using a wire nut, and connect one of the wires together with the hot on the zone one circulator terminal, and the other together on the zone 2 hot terminal.

You might have a problem on cold days with the hot water zones if the water temperature gets too hot, so normally there is a way to control this, either with an aquastat that breaks on temperature rise or (better) a mixing valve that allows the blending of the zone return water with the supply water to temper the temperature. But you don't have that now, and sometimes with small zones you can get away without it.

EBEBRATT-Ed

How do these old posts pop up?

ethicalpaul

thesumppumpguides said:

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thesumppumpguides

From this possibly spammy post (apologies to thesumppumpguides if it's not spammy)

I assume @Erin Holohan Haskell is constantly fighting these

Erin Holohan Haskell

@ethicalpaul - I sure am! Good catch. Thanks!

ethicalpaul

Ironically this post had links to a bunch of great info I hadn’t found before, so thanks, spammer!