Use Tekmar reset control with MZ boiler?

pch

I am a DIYer. Twenty years ago we purchased a home built in 1898. In the 50s it was turned into 4 apartments, then not much was changed until we started to turn in back into a single-family home.

Prior to our second winter in the house, I removed the ancient, inefficient, 50-year-old beast of a furnace and its ducting, and installed a Monitor MZ 25 (which ran on propane that year. I didn't update the gas service until the following summer). For the past 18 years the MZ has faithfully provided hot water and single high-temp zone heat, supplying a fan coil (SpacePak) in the attic. I am now in the process of installing radiant floor heat on the first floor, old houses can be a bit drafty, which will require a second temperature zone.

Eventually I will need a new boiler, but would like to put that off for now.

OK, large preamble, here comes the question... It's a two-parter.
1. I know that MPI came out with a boiler reset control a couple of years after we installed, but we did not need it because of the single heating zone. The addition of the in-floor heat changes that. I have a Tekmar 422 Reset control. Can that be used in place of the Monitor reset control? How? Specifically, the control wiring: the MPI reset comes with a wiring harness, I have not seen anything in the MZ manual related to connecting a reset. Maybe my manual is too old?
2. Since, at some point, I will need to replace the MZ, I would like to set up the system so that I can swap in the new boiler without making (major) changes.

Thanks for any help.

Ironman

I’m not familiar with that particular boiler, but any control strategy MUST have a matching piping strategy.

We frequency use injection mixing with a Tekmar 356 when two separate SWTs are required. And that will generally work with any type of boiler. I think that the 422 functions similarly. You can also use a smart mixing valve, but again, the piping will have to be made to match the controls.

hot_rod

It was, is a basic on off boiler, one of the very first condenser, not much control logic. A MZ still operating has to be a very rare case

Your next boiler may come with all the control functions, so might not be a good investment to buy a stand alone tekmar?

If you need two temperatures a 3 way valve would be the least expensive option, requiring some piping changes.

pch

I gather from the comments that the MZ does not respond to reset commands? I am a bit confused. What then does the MPI 9110 MZ OUTDOOR RESET CONTROL do?

As for piping, I believe I have a reasonable plan for that. I will install a 30g Boiler Buddy to provide hydraulic separation and some mass to help limit short-cycling. I also will install a 3-way valve with a circulator for the in-floor zone. I was hoping that I could get a lower boiler temp when only the in-floor calls for heat and therefor a bit more efficiency.

Thanks for the comments!

hot_rod

Sounds like you have the optional module. Which, to me, looks suspiciously like a tekmar component

Are you piped primary secondary? I think you need that to get a two temperature system.

Know when you direct pipe the boiler needs 3.5- 4 gpm minimum. So a small zone may not be workable without primary secondary.

The manual has some suggested multi temperature piping options.

Alan (California Radiant) Forbes

Surprisingly, we have 3, maybe 4 still going; parts are still available. They were all installed in 2000. If I had one, I’d be replacing it next summer. 

High temperature systems lasted longer as the condensate from radiant systems eventually compromised the HX. 

Don’t throw a lot of money for ODR on your new radiant. Maybe just a 3-way mixing valve. And you may have to tie it into an existing zone to keep the flow rate high enough to keep the boiler happy. 

MarkRad

Alan (California Radiant) Forbes said:

Surprisingly, we have 3, maybe 4 still going; parts are still available. They were all installed in 2000. If I had one, I’d be replacing it next summer. 

High temperature systems lasted longer as the condensate from radiant systems eventually compromised the HX. 

Don’t throw a lot of money for ODR on your new radiant. Maybe just a 3-way mixing valve. And you may have to tie it into an existing zone to keep the flow rate high enough to keep the boiler happy. 

You mentioned parts are still available…. I’m looking for a PN 9011 over-pressure relief valve (3 Bar valve). Can you tell me where I can get any parts for my MZ (MZ25C)?

hot_rod

Got a pic of that relief valve. Probably just a BSP straight thread standard relief. It would not need to be a MZ part. Find them online once you know the size. It should have a manufacturers name and model number on the valve

If it is dripping or seeping, check the expansion tank. That too could be a different brand or type, it doesn’t need to be inside the cabinet.

Teemok

When the time comes for a boiler look at an IBC SL They have a clever multi temperature demand option. The boiler will split run times to different zone at different temperatures. Zone are given priority numbers to split the run times up right. It has ODR and will keep piping simple. I recommend talking to a dealer or them to find out if the feature would be a good match for you.

pch

I probably will preempt any boiler outage by replacing the MZ next summer. From the online brochure, this is an interesting sounding system. Have you installed any; do you have experience with it?

Teemok

Yes I've installed more than 10 sl IBC. I like them. I've never programed for multi heating temp. but I've gone through the control enough to know how it's done. A radiant floor and fan coil, I would think would work well. The cycle for the fan coil call is short enough that the radiant floor zone would never know it wasn't top priority. Room for a DHW tank?

pch

Yeah, the MZ supports priority DHW, so I am piped for that. Ball park $ for the 115?

Teemok

Whole house cold start times would be elongate some. If that's a concern for you it might not be the best. IBC will be able to tell you more than I can.