Monitor boiler

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Old 04-26-06, 12:38 PM
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Monitor boiler

I have a friend that is considering a Monitor MZ25-S boiler for hydronic heat and DHW. I have not come across Monitor products before but it looks like a nice package that's easy to install.

If anyone has had experience with these, good or bad, I'd like to hear about it.

Thanks in advance.

http://mzboiler.com/products/mz/mz25s.html
 
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Old 04-26-06, 02:10 PM
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This is all second hand, but everything I have heard about it (the C model not the combi S unit that you are referring to) is that it is a great boiler.... well-built, reliable etc. but the big however is that it doesn't modulate. The 40 model is at least a 2 stage boiler, but if you are spending that coin on a gas wall-hung getting one that modulates will pay you back with better comfort and effiency.

The lack of modulation would be a show stopper for me. If it was only 70 or 0 outside that wouldn't be an issue.

I also wouldn't get a combi unit unless I had a really small house and absolutely no place for a hot water tank. The heat exchanger on combi units and the flow controls seem far more troublesome than an indirect. They also don't work if people plan to shower and use hot water for something else concurrently.
 
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Old 04-27-06, 04:28 PM
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If I dont ask the following dumb question, I may never find the answer:

I believe that a modulating boiler probably a good thing, *but* if it's 0F outside, and a non-modulating boiler fires & heats the water to, say 190F, it will satisfy the thermostat in a certain period of time. If it 65F outside, the same boiler will fire to the same temp & satisfy the thermostat that much quicker, no? If it were a modulating boiler that took the water to say, 150F, wouldn't it take proportionally longer to satisfy the thermostat?
 
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Old 04-28-06, 08:01 AM
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You may be thinking about outdoor reset, where the boiler heats the water up to a traget temperature that is based on the outside temperature. The Monitor does that (although I think the kit is an option).

With modulation, it's more like the accelerator on your car. It tries to open the gas valve just far enough so that it can hold your house at the desired temperature. This is done instead of the control saying FIRE.... (until it gets to target) wait..... (until it falls under the target) FIRE.... (until it again gets to target temps) wait (until it needs to refire) at whatever intervals it does. Short cycling is a big problem for boilers that cannot modulate and rather than try to have buffer tanks to extend the burning cycles, it's nice to have a boiler that can match its heat to the heatloss.
 
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Old 04-29-06, 04:28 PM
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Thanks for the replies. I'll pass it along to my friend & we'll see what he decides.
 
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