Heating Help

Boiler Controls

I have a client with a 10 year old cast Iron boiler serving  in floor radiant heat 8 zones and a side arm tank.
I want offer some state of the art controls but not sure which?

Thanks

Zoning

Are the zones controlled by pumps or zone valves?

HW

sounds like a canidate for a honeywell aq252 with a 4 zone expansion port. look up the features on their website. This control offers a lot of functionality for the price.

Boiler Controls

Zone Valves

tekmar control option for Boiler, DHW and 8 Mix temp zones

One control option you could look at would be a tekmar 402 House Control with a 313 Wiring Center and eight 527 Thermostats.
It would be an easy retrofit as the thermostats use only two wires. You get a nice digital LCD display and they are very simple to operate.
The 402 House Control would operate the Boiler, DHW, Mixing and four of eight Zone valves. The 313 Wiring Center would operate the other four Zone valves.
Your radaint floors would require the use of some form of Mixing. Either Variable Speed Injection using a pump or Floating Action using a 3 or 4Way Mixing valve & motor.
The 402 supports either method. This would allow you to run the boiler hotter for DHW and to prevent condensing, while running full outdoor reset to the radiant zones.
Here is  link to a promo document for the House Control system.
http://www.tekmarcontrols.com/literature/acrobat/p523web.pdf

Keep It Simple

I like to keep systems as simple as possible. How about a Taco RMB (Radiant Mixing Block). Would provide outdoor reset for the radiant, give you both your injection and system pump along with boiler protection in one nice litttle package. You can then zone off that.

water not getting as hot as it should w/ 5yr old AQ475A

I have an old boiler that I installed a AQ475A outdoor air reset control on 10/30/05. It's worked fine up to this winter. The water doesn't seem to get anywhere near as hot as it used to when it gets down to 10 degF At that outdoor temp, the boiler water should get to around 160F, but this year it only gets to 140 at best. Has the outdoor sensor gone bad? Is there a way to check it? Is there a resistance curve available for the sensor so I can tell if the sensor is bad by using a ohmmeter? The spec sheet states that the sensors should be 10K ohms at 77F, but what should the resistance be at 20F, or 10F? The boiler hi temp is set at 190F, the low at 120F and the outdoor low is set at -20F The system has worked fine until this winter. Any help will be greatly appreciated. Thanks- Henry Z

Henry...

You should start a new thread for your question, your not going to get as many answers to your question off someone elses topic.